Senscient ELDS 1000 Series, ELDS 2000 Series Instruction Manual

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Version 1.06 Iss 4 ECR111

INSTRUCTION MANUAL

Baseefa ATEX - Europe

01-01-1865-D

Senscient ELDS™ 1000 / 2000 Series

Open Path Gas Detector including Cross Duct

Read and understand this Instruction Manual before installing,

operating or servicing ELDS 1000 / 2000 Series OPGD systems

Installations

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SAFETY

Ensure that you read and understand these instructions BEFORE operating the equipment. Please pay particular attention to the safety Warnings / Special Conditions of Safe Use.

WARNINGS / SPECIAL CONDITIONS OF SAFE USE

1. The Senscient ELDS™ 1000 / 2000 Series gas detectors are Baseefa ATEX certified for use in Hazardous (Explosive) Atmospheres.

2. For installations in Europe (ATEX Certified) install in accordance with EN60079-14.

3. Elsewhere, the appropriate local or national regulations should be used.

4. ELDS™ 1000 / 2000 Series gas detectors must be properly earthed / grounded to protect against electrical shock and minimise electrical interference. Internal and external equipotential bonding facilities are provided for this purpose. For electrical installation design considerations refer to Section 3.3.

5. Operators must be fully aware of the action to be taken if the gas concentration exceeds an alarm level.

6. ELDS 1000 / 2000 Series gas detectors cannot be repaired or serviced by customers. If units require repair or service they must be safely removed from any hazardous location / area in which they are installed, and returned to Senscient. Other than the rear cover providing access to the terminals for connection purposes the units are not intended to be opened in service. Return to manufacturer for service or r epair.

7. Test gases may be toxic and/or combustible. Refer to Material Safety Sheets for appropriate warnings.

8. Do not drill holes in any housing as this will invalidate the explosion protection.

9. In order to maintain electrical safety, units must not be operated in atmospheres with more than 21% v/v oxygen.

10. Ensure that the bolts which secure the front flameproof enclosure are fully tightened. The securing bolts are stainless steel M5 X 16mm socket head cap screws grade A4-

70. To ensure replacement suitability contact Senscient or their approved agent/distributor.

11. Do not open the enclosure in the presence of an explosive atmosphere. Keep cover tight when energised

12. The apparatus is certified for use in Hazardous Areas at atmospheric pressures not exceeding 1.1 bar (16 psi).

13. Install only in environments with ambient temperature ranges of -40°C to +60°C.

14 For Europe (ATEX), apparatus incorporates an integral threaded cable entry (M25 x

1.5). Terminate cable only with a suitable equipment certified ATEX cable gland (not a component). To maintain water and dust ingress protection seal threads with suitable non-hardening sealant as described in EN 60079-14.

Note: See control drawing for product specification allowing selection of cable g lands.

15. For all installations use cable / conductors rated for service at temperatures >= 85°C

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SAFETY

16. At all times during transit, installation and commissioning protect lens from accidental direct mechanical impact. Use Senscient OEM supplied packaging during transit.

17. The transmitter and receiver units must be mounted horizontally and protected from impact i.e. do not mount at floor le vel or in area s where moving veh icles, person nel or loads may be of concern regarding impact.

CAUTIONS

1. Use only approved parts and accessories with the Senscient ELDS™ 1000 / 2000 Series gas detectors.

2. To maintain safety standards, commissioning and regular maintenance of ELDS™ 1000 / 2000 Series gas detectors should be performed by qualified personnel.

3. Transit cases for the alignment telescope and gassing cell are manufactured from nonantistatic materials, and may, under certain circumstances become an electrostatic risk. It is the users responsibility to take adequate precautions during transportation and use if taken into hazardous areas.

IMPORTANT NOTICES

1. Senscient Inc. can take no responsibility for installation and/or use of its equipment if this is not done in accordance with the appropriate issue and/or amendment of the manual.

2. The user of this manual should ensure that it is appropriate in all details to the exact equipment to be installed and/or operated. If in doubt, the user should contact Senscient Inc. for advice.

3. Effect of explosive atmosphere on materials. The Senscient ELDS™ 1000 / 2000 Series is manufactured from materials which

exhibit good resistance to corrosive substances and solvents. The Ex d enclosures are made from 316L stainless steel (or aluminium, onshore only) and the explosion protected windows are made from robust and chemically inert glass. Senscient are not aware of any significant effects of explosive atmospheres upon these materials. Contact Senscient or one of their agents for specific queries.

4. The final and long term effectiveness of any Open Path Gas Detector depends heavily upon the user, who must be responsible for its proper application, installation and regular maintenance.

Senscient Inc. reserves the right to change or revise the information supplied in this document without notice and without obligation to notify any person or organisation of such revision or change.

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SAFETY

If further details are required that d o not appear in this ma nual, contact S enscient or one of their agents. Senscient Ltd. will supply this manual in other languages of the European Union (countries covered by the ATEX directive) upon request.

HELP US TO HELP YOU

Every effort has been made to ensure the accuracy in the contents of our documents. However, Senscient can assume no responsibility for any errors or omissions in our documents or their consequences.

Senscient would greatly appreciate being informed of any errors or omissions that may be found in our documents. To this end we request that if you believe there are any errors or omissions, please send us an e-mail at info@senscient.com describing the error or omission, so that we may take the appropri ate action.

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CONTENTS

 INTRODUCTION .................................................. ....................................... ..................... 7

2 SYSTEM DESCRIPTION ............................................................................................... 10

2.1 Introduction ........................................... .............................................................. 10

2.2 Transmitter .......................................................................................................... 11

2.3 Receiver .............................................................................................................. 12

2.4 Adjustable Mounting Bracket ........................................... ................................... 13

2.5 Sunshade ............................................................................................................ 14

2.6 Cross Duct Mounting Plate ...................................................................... .... ....... 15

3 INSTALLATION DESIGN & ENGINEERING .......................................... ....................... 16

3.1 Introduction ........................................... .............................................................. 16

3.2 Siting and Mounting ................................................................................. .... .... ... 16

3.2.1 General ......................... .................................... ....................................... ....... 16

3.2.2 Location for Best Coverage ...................... ............................................... ....... 17

3.2.3 Beam Path ........................ .... .... ........ .... .... .... ........ .... .... .... ....... .... .... .... ........ ... 19

3.2.4 Supporting Structure ....................................................................................... 21

3.2.5 Wall Mounting ....................... .... .... .... ........ .... .... .... ........ .... .... ... ........ .... .... .... ... 22

3.2.6 Orientation ........................ .... .... .... ........ .... .... .... ........ .... .... ... ........ .... .... .... ....... 22

3.2.7 Siting and Mounting Cross Duct ELDS Systems ............................................ 23

3.3 ELECTRICAL CONNECTIONS .......................................................................... 24

3.3.1 Electrical Installation Design & Engineering Recommendations .................... 24

3.3.2 Electrical Connections: Terminal Compartment ............................................. 27

3.3.3 Receiver Electrical Connections ..................................................................... 28

3.3.4 Transmitter Electrical Connections ................................................................. 35

3.3.5 Power Supply Connections & Wiring .............................................................. 37

4 INSTA LLATION & COMMISSI ONING ............................................................................ 38

4.1 Unpacking an ELDS 1000 / 2000 Series System ............................................... 38

4.1.1 General ......................... .................................... ....................................... ....... 41

4.1.2 Mechanical Installation ..................... .... ........ .... .... .... ........ ... .... .... .... ........ .... ... 41

4.1.2.1 Wall Mounting ....................................................................................... 41

4.1.2.2 Pole Mounting ...................................................................................... 42

4.1.2.3 Mounting a Transmitter or Receiver ..................................................... 43

4.1.2.4 Mounting a Cross Duct Transmitter or Receiver .................................. 44

4.1.3 Electrical Installation ................................................................................ .... ... 46

4.2 Alignment ............................................................................................................ 46

4.2.1 Initial Pointing .................................................................................................. 46

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 Final Alignment Using Telescope ................................................................... 48

4.2.2

4.2.2.1 Attaching the Alignment Telescope .................................................. ... 48

4.2.2.2 Final Alignment Procedure ................................................................... 54

4.2.2.3 Making Alignment Adjustments ............................................................ 57

4.3 Cross Duct – Alignment Requirements .............................................................. 62

4.4 Commissioning ..................................................... ........................................... ... 62

4.4.1 Configuring SITE - Adding Users .................................................................... 63

4.4.2 Commissioning a System - Transmitter .......................................................... 64

4.4.3 Commissioning a System - Receiver .............................................................. 71

4.5 Installation Checklist ............. .... ........ .... .... ........ .... .... .... ....... .... .... .... ........ .... .... ... 88

5 FUNCTIONAL TESTING ... .... ... .... ........ .... .... ........ .... .... .... ........ .... .... ....... .... .... .... ........ ... 91

5.1 Introduction ........................................... .............................................................. 91

5.2 SimuGasTM Explained ................................................... ...................................... 91

5.2.1 Harmonic FingerprintsTM ................................................................................. 91

5.2.2 Electronically Synthesised Harmonic Fingerprints – SimuGasTM ................... 93

5.3 SimuGas

Auto .................................................................................................. 94

5.4 SimuGasTM Inhibited ........................................................................................... 95

5.5 SimuGasTM Live ........................................................................ .......................... 96

5.6 Testing with the Gassing Cell ............................................................................. 97

5.7 Testing Cross Duct ELDS Systems with the Gas Challenge Cell ....................100

6 MAINTENANCE ............................................................................................................105

6.1 Scheduled Inspection, Cleaning & Testing .......................................................105 

6.2 Cleaning the Lens-Windows of ELDS OPGDs .................................................107

7 PROBLEM SOLVING ....................................... ........ .... .... .... .... ........ ... .... .... .... ........ .... .109

8 SPECIFICATIONS ........................................................................................................114

8.1 SYSTEM ................................................... ........................................................114 

9 CERTIFICATION .............................................. ........................................... .................117

9.1 General ......................................... ........................................................... .........117

9.1.1 ATEX Label Combustible or Combustible and Toxic .................................. 118

9.1.2 Control Drawing CENELEC / ATEX ............................................................ 119

APPENDIX A - i.Roc PDA ....................................................................................................120

10 APPENDIX B - GLOSSARY .........................................................................................121

10.1 Terminology .............................................. ........................................................121

10.2 Measurement Units ...........................................................................................121

10.3 Abbreviations ............................................................ ........................................122

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 APPENDIX C - ACCESSORIES & SPARE PARTS ........................................ .... .... .... .123

11.1 System Units .....................................................................................................123

11.2 General ......................................... ........................................................... .........123

12 MANUFACTURER’S EC DECLARATION ....................................................................125

13 MANUFACTURER’S CONTACT DETAILS ......................................................... .... .... .126

Version 1.06 Iss 4 ECR111 Senscient ELDS™

INTRODUCTION

1 INTRODUCTION

The Senscient ELDS™ 1000 / 2000 Series is a range of open path, flammable and / or toxic gas detectors that is currently available in two versions*.

 Senscient ELDS™ Series 1000 CH  Senscient ELDS™ Series 2000 CH

- Methane Detector

+ H2S - Simultaneous Methane & Hydrogen

Sulfide Detector

The Senscient ELDS™ Series 1000 CH

detector consists of a Transmitter unit that sends

an infrared laser beam to a separate Receiver unit that can be installed on a line-of-sight at a distance of up to 200m. The ELDS 1000 Series CH4 detector can be located where there is a risk that a leak of flammable methane gas may occur, to provide a rapid, early warning of such a hazard. The ELDS™ 2000 version is similar, except that there are two coinciding infrared laser beams, one for the detection of methane and the other for the detection of hydrogen sulfide.

All ELDS

gas detectors operate on the principle of absorption of infrared laser light. Gases absorb light at specific wavelengths depending on their molecular composition. Hydrocarbon gases such as methane and propane absorb in the infrared region of the spectrum. If a cloud of target gas is present, the specific wavelength(s) of the infrared laser light output by the ELDS Fingerprint

onto the signal reaching the Receiver that is proportional to the amount of gas

Transmitter is absorbed by the gas, introducing a Harmonic

in the beam. The Senscient ELDS™ Transmitter unit produces the precisely controlled infrared laser light

required to detect the target gases; whilst the Receiver unit contains an infrared detector and advanced signal processing electronics which look for the Harmonic Fingerprint

produced by the presence of target gas in the beam path. Each unit is housed in a robust 316L stainless steel or aluminium housing. The Receiver includes two 4 - 20mA analogue outputs which are used to signal the quantity of each target gas measured in the beam path, for example 0-1LEL.m CH4 and 0-250ppm.m H

S for the Series 2000 detector. These

outputs provide a linear relationship with the measured gas concentration. Note that this product does not measure point concentration of the target gas(es), rather it

measures the integrated concentration over the whole length of the measurement path between the transmitter and receiver units. This means that some account of the likely scale of any gas cloud being monitored must be considered when attempting to interpret the actual concentration of gas that might be present and must adjust any subsequent alarm levels appropriately. The following figures illustrate this.

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INTRODUCTION

Each of these different gas clouds will produce the same ELDS reading of 1.0 LEL.m, however only the 1 flammable concentration within it.

example where the gas cloud is very small actually has a potentially

*Versions of the ELDS 1000 / 2000 Series for other gases and in different configurations will be made available in the near future.

NOTE: THE INFRARED LASER BEAMS ARE INVISIBLE AND COMPLETELY EYESAFE.

Senscient ELDS™ is designed for use in the most demanding environments/applications and provides a sensitive, fast and reliable response. The sophisticated ELDS

open-path technology provides immunity to sunlight and minimises the effects of environmental factors such as rain, fog, ice, snow and condensation.

The Transmitter and Receiver units incorporate heated optics designed to minimise the build up of humidity, condensation, snow or ice on the glass lens-windows that could obscure the optics in extreme conditions.

Both the Transmitter and the Receiver are microprocessor controlled with advanced selfdiagnostics and fault finding facilities.

Local communication between an operator /technician and the gas detector system is made via SITE (Senscient Installation & Test Environment) running on a laptop or an iRoc PDA, using a communication link to either the transmitter or receiver. SITE provides the user with a menu-style interface to select and invoke commands for commissioning and configuring the system, and for viewing the system state and measurements.

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INTRODUCTION

This manual consists of the following parts:

 Chapter 1 INTRODUCTION  Chapter 2 SYSTEM DESCRIPTION  Chapter 3 INSTALLATION DESIGN & ENGINEERING  Chapter 4 INSTALLATION & COMMISSIONING  Chapter 5 FUNCTIONAL TESTING  Chapter 6 MAINTENANCE  Chapter 7 PROBLEM SOLVING  Chapter 8 SPECIFICATIONS  Chapter 9 CERTIFICATION  Appendix A Handheld Interrogator  Appendix B Glossary  Appendix C Accessories & Spare Parts

Information notices

The types of information notices used throughout this handbook are as follows:

WARNING

Indicates hazardous or unsafe practice which could result in severe injury or death to

personnel.

Caution: Indicates hazardous or unsafe practice which could result in minor injury to

personnel, or product or property damage.

Note: Provides useful/helpful/addi tional information.

If more information beyond the scope of this technical handbook is required please contact Senscient.

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SYSTEM DESCRIPTION

2 SYSTEM DESCRIPTION

2.1 Introduction

Each Senscient ELDS™ 1000 / 2000 Series gas detector consists of two units, a Transmitter and a Receiver. This separate Transmitter / Receiver configuration provides the most reliable basis for open path gas detection. There are no transceiver units or retropanels utilised in the Senscient ELDS™.

Mounting Bracket

Sun Shade

Alignment Adjustment

(horizontal and

vertical)

Tx and Rx Units

Monitored Path

There are several operating ranges of Senscient ELDS™ gas detector, e.g.: Series 1000 CH

, 0 - 1000ppm.m, 0 - 1LEL.m 5 - 40m, 40 - 120m, 120 -

200m

Series 2000 CH Series 2000 CH Series 2000 CH

Series 1000 XD CH

0 - 1LEL.m + H2S 0 - 250ppm.m 5 - 60m

0 - 1LEL.m + H2S 0 - 500ppm.m 5 - 60m

0 - 1LEL.m + H2S 0 -1,000ppm.m 5 - 60m

0 - 10%LEL, 0 - 25%LEL, 0 100%LEL 0.5 - 3.5m

Refer to Senscient for additional ranges and gases.

When designing an installation for Senscient ELDS™ 1000 / 2000 Series it is important that the correct range of the gas detector for each path to be monitored is selected and specified.

Note: In order to avoid the problems associated with gas detectors b eing used beyond

their specified ranges or when incorrectly aligned, a procedure within the Senscient Installation & Test Environment (SITE) checks for correct gas detector

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SYSTEM DESCRIPTION

type, operating range and signal levels before allowing the ELDS OPGD to activate.

The Transmitter and Receiver are each mounted upon robust, adjustable mounting brackets. The design of the mounting and alignment arrangement for the Senscient ELDS™ 1000 / 2000 Series is highly accommodating, making it simpler to realise a good installation in a variety of locations and environments. Installation details are given in section 3.

2.2 Transmitter

The Senscient ELDS™ Transmitter produces up to two controlled-divergence beams of infrared laser light from solid-state laser diodes. The outputs from the laser diodes are partially collimated using a faceted lens, the facets of which introduce the controlleddivergence that is necessary to reduce system alignment sensitivity. The Transmitter operates continuously

NOTE: THE INFRARED BEAM IS INVISIBLE AND EYE-SAFE.

245mm

220mm 300mm

The Transmitter contains a small retained sample of the target gas(es) to be detected by the system, and uses this retained sample as a reference to maintain its laser diode(s) in Harmonic Fingerprint

lock. By continuously maintaining Harmonic Fingerprint lock it is possible to be certain that whenever target gas(es) enter the system’s beam path this will introduce a Harmonic Fingerprint onto the signal which will be seen and measured by the Receiver. The retained target gas sample also enables the Transmitter to know precisely how to simulate the presence of target gas in the beam by means of adding Harmonic Fingerprint components to the drive signal applied to the laser diode(s). This is the basis of the SimuGas on-demand functional test technology incorporated in Senscient’s ELDS OPGDs.

The transmitter also incorporates links which can be used to communicate with a laptop or i.Roc PDA. Using SITE and these communication links, a laptop or i.Roc PDA can be employed to perform alignment checks, commissioning, configuration, functional testing, diagnostic procedures and SimuGas

tests.

The Transmitter window is heated to minimise condensation, frosting and the build up of snow.

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SYSTEM DESCRIPTION

Three connections to the Transmitter are required, +24V, 0V and GND (for electrical safety).

2.3 Receiver

The Senscient ELDS™ Receiver collects infrared laser light from the Transmitter and determines the size of any Ha rmonic Fingerprint

components that have been introduced

onto this signal to establish the quantity of any target gases present in the beam path The Receiver collects and concentrates infrared laser light from the Transmitter onto a

single, infrared detector using an aspheric condensing lens-window. The detector output is amplified and processed by a sophisticated electronic signal processing system which effectively removes any ambient light and extracts Harmonic Fingerprint

information related to the quantity of target gas in the beam path. The detector amplification chain incorporates an advanced Automatic Gain Control (AGC) system that enables it to compensate for the wide range of signal levels that can be received due to effects arising from rain, fog, snow, dirt etc. This enables the ELDS 1000 / 2000 Series to continue operating reliably in the harshest conditions that are likely to be encountered at Oil & Gas installations around the world.

245mm

300mm 220mm

The solid state, InGaAs photodiode detectors used in the Senscient ELDS™ 1000 / 2000 Series provide an exceptional dynamic range and superb temperature and long term stability. These properties contribute significantly to the solar immunity and stability of the Senscient ELDS™ 1000 / 2000 Series.

The primary output(s) of the Receiver are up to two 4 - 20mA loop outputs which can be configured for source, sink or two-wire isolated operation. The outputs are factory calibrated to provide the appropriate full scale range for the measured species and model variant. The output is typically calibrated in units of LEL.m or ppm.m (See section 10 for the explanation of LEL.m and other terms).

The receiver also incorporates links which can be used to communicate with a laptop or i.Roc PDA. Using SITE and these communication links, a laptop or i.Roc PDA can be employed to perform alignment checks, commissioning, configuration, functional testing, diagnostic procedures and SimuGas

The Receiver window is heated to minimise condensation, frosting and the build-up of snow.

tests.

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SYSTEM DESCRIPTION

Between four and eight connections to the Receiver are required, depending upon the number and configuration of the 4-20mA outputs used. These connections are required to provide +24V, 0V, 4-20mA(1), 4-20mA(2) and GND (for electrical safety).

The ELDS system does not have any gas alarm set functions. The 4-20mA signal outputs from the receiver are non-latching. If the ELDS system is intended to indicate a potentially flammable gas concentration then any auxiliary equipment (e.g. control room plc, control unit or monitoring apparatus etc.) shall have an alarm set point that is latching, requiring a deliberate action to reset. If two or more set or alarm functions are provided the lower may be non-latching.

2.4 Adjustable Mounting Bracket

The adjustable mounting brackets for the ELDS 1000 / 2000 Series are:

 Purpose-built for the Transmitter and Receiver.  Provide coarse and fine adjustment for quick, simple system alignment  Rigid, stable and robust.  Made from 316L stainless steel or aluminium (with aluminium units).

The coarse horizontal adjustment facility enables a transmitter or receiver to be quickly pointed in the approximate direction of its counterpart and provides a full 360º of rotation. The fine horizontal adjustment facility enables a transmitter or receiver to be precisely aligned and locked-off with respect to its counterpart, and has an adjustment range of 25º.

The fine vertical adjustment facility enables a transmitter or receiver to be precisely aligned and locked-off with respect to its counterpart and has an adjustment range of 25º.

Alignment details are given in Section 3

Clamp nut

Mounting bracket

adjusting screw (2 off)

Adjustment clamp lock

screw

Mounting Lug (on unit

body)

Pivot block adjusting

screw (2 off)

Clamp nut

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SYSTEM DESCRIPTION

2.5 Sunshade

The sunshade is a standard-fit item provided to ensure that units stay as cool as possible, wherever they are installed and operated, thereby maximizing the service life of the electronics inside. The sunshade is adjustable in order to facilitate use of the alignment telescope and provide easier access to the electrical connections inside the terminal compartment.

Sunshade

Retaining Screw

The sunshade is fixed by a single retaining screw as illustrated. Loosen this in order to allow adjustment of the position of the sunshade. Tighten the retaining screw to ensure that the sunshade remains in the desired position.

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SYSTEM DESCRIPTION

2.6 Cross Duct Mounting Plate

Cross Duct ELDS systems are designed to be mounted on opposite sides of flat, parallelwalled ducts using the Mounting Plate provided for this purpose and shown below.

Note

It is the installers / end users responsibility to ensure that the duct hazardous (classified) location and / or hazardous area is in compliance with ELDS certification (see Section 9 for ELDS certification details).

Additionally, the duct environment shall not exceed the following: Pressure: 80kPa (0.8Ba r) to 110kPa (1.1Bar) Temperature: -40ºC to +60ºC Oxygen Content: less than 21%v/v

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INSTALLATION DESIGN & ENGINEERING

3 INSTALLATION DESIGN & ENGINEERING

3.1 Introduction

WARNING

The applicable National Code of Practice regarding selection, installation and maintenance of electrical apparatus for use in Hazardous Areas/Zones must be complied with at all times

The Senscient ELDS™ 1000 / 2000 Series has been designed engineered and customer tested to be the most robust, reliable Open-Path Gas Detector (OPGD) available to date. The design and ELDS makes it far more resistant to the adverse effects of the operating environment and nonideal installation engineering than previous generations of OPGDs.

With careful consideration of the intended operating environment and the installation design, the installer/operator can maximise the reliability, availability and performance achieved with ELDS™ OPGDs.

technology employed in the Senscient ELDS™ 1000 / 2000 Series

Before designing or specifying an installation for Senscient ELDS™, it is strongly recommended that the installation design authority reads and understands this chapter, and considers how the information and recommendations provided can be applied to their installation(s).

If a design authority has any queries concerning their installation design, they should contact Senscient or their local agents.

Senscient is committed to ensuring that customers achieve reliable operation of their Senscient ELDS™ OPGDs. For this reason, Senscient ELDS™ OPGDs should only be installed by fully trained personnel (trained by Senscient or a Senscient authorised trainer). This training will provide the installer with a clear understanding of the Sensci ent ELDS™ OPGD product and the associated accessories and tools. It will also provide familiarity with the installation, alignment and commissioning procedures, plus installation assessment skills to identify potential problem areas.

For each installation, it is recommended that the installer should check the installation and operating environment against the Check List presented in Section 4.4.

NOTE: THE INFRARED LASER BEAMS ARE INVISIBLE AND EYE SAFE.

3.2 Siting and Mounting

3.2.1 General

When designing an installation for a Senscient ELDS™ OPGD it is important to give consideration to where it is to be located, what potential sources of problems may be encountered in this location and how the unit is to be mounted and supported and protected from accidental impacts.

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INSTALLATION DESIGN & ENGINEERING

3.2.2 Location for Best Coverage

Guidance on the positioning of gas detectors to provide the best detection coverage is contained in national Codes of Practice. It is recommended that the installation designer consults these Codes of Practice. Senscient would advise that the best current methodology for siting all types of fixed gas detectors is based upon the expert use of gas dispersion modelling, performed for the particular area(s) of plant or facility where potential gas leak hazards exist. There are a number of organisations with the gas dispersion modelling tools and expertise necessary to perform this work. In general, for OPGDs the following positions usually provide the best results:

 Running parallel to the physical perimeter of an area of plant or facility

containing potential gas leak hazards.

 Forming a continuous ‘ring-fence’ surrounding an area of plant or facility

containing potential gas leak hazards.

 At sufficient distance from any potential leak sources for dispersion to

produce a gas cloud of a size that will reliably be intercepted by the beampaths of the OPGDs employed.

 Between potential leak sources and any known or likely sources of ignition.  For natural gas: beam-path parallel to the ground / floor and above the height

of most of the valves and flanges in the vicinity.

 For toxic gases: beam-path parallel to the ground / floor at ‘breathing height’ (~

1.4m – 1.7m).

 For gas mixtures significantly denser than air: beam-path parallel to the

ground / floor and below all potential leak sources*.

 For gas mixtures significantly lighter than air: beam-path parallel to the ground

/ floor and above all potential leak sources*.

*NOTE: In mo st instances the hazardous gases leaking from a plant or facility are mixtures

of a number of gases with different chemical and physical properties. In a gas mixture the constituent gases will retain most of their chemical properties, but the physical properties of the gas mixture will be the proportionate sum of the physical properties of the constituent gases.

For sour natural gas, the above principle means that this gas mixture will be both toxic and flammable; whilst the density of this mixture will tend to be dictated by its high methane content.

Only accurate modelling will determine the precise physical properties of a leak of sour natural gas, but typically this mixture’s density will be similar to, or slightly lower than that of air. Only leaks of very cold natural gas or of neat hydrogen sulfide are likely to be slightly denser than air.

Dispersion modelling provides little support for the practice of placing hydrogen sulfide detectors close to the ground. In the majority of instances leaks of sour natural gas or hydrogen sulfide will not sink; whilst the toxicity hazard is greatest at the height where such gas can be breathed in.

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INSTALLATION DESIGN & ENGINEERING

Location to Maximise Reliability and Availability

Care in choosing the location of ELDS™ OPGDs can contribute significantly to the overall reliability and availability.

When locating units, attempt to avoid areas where they may be adversely affected by the following:

Vibration - Angular vibration of the structure to which ELDS™ OPGD units are attached should be kept to less than +/- 0.5. Where possible, avoid locations where high levels of vibration will be directly induced into the mounting structure. If close proximity to significant sources of vibration is unavoidable, take steps to reduce coupling of this vibration and maximise the rigidity of the mounting structure.

Intense Heat - ELDS™ OPGDs are certified and specified for operation in environments up to +60C. If sources of intense heat (flarestacks, intense sunlight, etc.) are present, the effect of these will be reduced by the fitted sunshade. If the sunshade proves insufficient in an extremely hot installation then further shielding should be provided.

Sources of Heavy Contamination - Avoid locations where high levels of contaminants will persistently be blown onto the unit’s lens-windows. Potential sources of heavy contamination include generator/turbine exhausts, flare-stacks, drilling equipment, process vents/chimneys etc. If sources of heavy contamination cannot be avoided, consider fitting extra shielding and/or providing good access for more routine cleaning.

Snow and Ice in Ambients Below -20

melt snow or ice on the lens-windows in ambient temperatures down to approximately

-20C. Below this temperature, snow or ice blown onto the lens-window will not be melted until the ambient temperature rises. If long-term, outdoor operation in very cold climates is intended, it is recommended that extra shielding/covers are employed to prevent snow/ice from being blown onto the windows and building up.

Deluge and Flooding - Senscient ELDS™ OPGDs are rated IP66/67 and as such will not be damaged by occasional deluge or flooding. However, during such instances the unit will completely lose its IR signal and will enter the BEAM -BLOCK/FAULT state. Also, when the deluge/flooding subsides, there is the possibility that contaminants will be left on the windows. Therefore, it is recommended that ELDS™ OPGD units be located away from areas particularly prone to deluge or flooding.

Areas Prone to Subsidence and Settling - Where possible, it is recommended that ELDS™ OPGD units are not mounted on structures located where problems with subsidence, settling or thawing of permafrost are known to cause significant movement. If such locations cannot be avoided, the foundations of the mounting structure should be engineered to minimise any angular movements.

C - The heated optics on ELDS™ OPGD units will

Areas Prone to Earthquakes - In locations prone to earthquakes, there is a chance that during or after an earthquake, the units of an ELDS™ OPGD will become misaligned with respect to each other. Provided that the ELDS™ OPGD units do not suffer from direct mechanical impact damage during an earthquake, they should remain undamaged by such events. Anti-vibration mounts are unlikely to be of any benefit and are not recommended. After an earthquake it is recommended that ELDS™ OPGDs are visited and their alignment be checked.

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Accidental Impact - Mount transmitter and receiver horizontally to protect from impact. Locations where there is a likelihood of equipment, personnel or moving objects accidentally knocking ELDS™ OPGD units out of alignment should be avoided. If such locations cannot be avoided, measures including improved mechanical protection and warning notices should be considered.

Intense Electromagnetic Fields - Senscient ELDS™ OPGDs comply with FM63 25 an d a re designed to comply with EN50270, and as such are well protected from interference by electromagnetic fields. However, locations in close proximity to radio/radar transmitters, heavy electrical plant and high voltage power cables may experience field strengths in excess of those specified in EN50270. Where possible, such locations should be avoided or units should be installed as far as possible from the source of the electromagnetic field. Measures including additional screening, filtering and transient suppression may also be of benefit in such locations.

3.2.3 Beam Path

The Transmitter and Receiver unit lens-windows should directly face each other across the area to be protected and, depending on the range of the Transmitter in use, should be the following distance apart:

Senscient ELDS™ Detector Series Type Path length between units

1000 CH4 0 - 1000ppm.m, 0 - 1LEL.m 5 - 40m, 40-120m, 120 - 200m 2000 CH4 0 - 1LEL.m + H2S 0 - 250ppm.m 5 - 60m 2000 CH4 0 - 1LEL.m + H2S 0 - 500ppm.m 5 - 60m 2000 CH4 0 - 1LEL.m + H2S 0 - 1000ppm.m 5 - 60m 2000 H2S 0 - 100ppm.m 5 - 60m 2000 H2S 0 - 250ppm.m 5 - 60m 2000 H2S 0 - 500ppm.m 5 - 60m 2000 H2S 0 - 1000ppm.m 5 - 60m

The beam path and immediate surrounds should be kept free of obstructions that might hinder the free movement of air in the protected area or block the infrared beam. A clear beam path of 20cm diameter or greater is recommended. In particular, for optimum availability, avoid areas affected by the following.

a. Steam vents and plumes b. Smoke stacks and chimneys c. Walkways and personnel areas d. Splash and spray, e.g. from moving equipment, cooling towers, etc. e. Parking, loading, cranes, vehicle temporary stops, e.g. bus stops, road junctions, etc. f. Vegetation, e.g. shrubs, bushes, branches, etc. - if currently clear, movement due to

weather and future growth or planting must be considered

Note: Where c. and d. cannot be avoided, consider indicating the beam by marking the

walkway or road with paint.

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Beam

clearance arc -

radius more

than 10cm

Telescope clearance arc radius - more than 30cm

Notes:

1. In order to fit the alignment telescope, used during the alignment process, a clear

accessible arc of at least 30cm radius is required close to the unit as shown.

2. A clear beam path of at least 10cm radius or greater is recommended.

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3.2.4 Supporting Structure

The Transmitter and Receiver units should be fixed to a stable supporting structure using the mounting brackets supplied.

Note: The maximum movement of the supporting structure under all anticipated

operating conditions must be

If either unit is unable to be mounted on an existing structure, and the required height above the ground is no more than 3m, then the supporting structure shown is recommended:



0.5º.

100mm to 150mm (4” to 6”) dia.

steel pipe, nominal 6mm wall

thickness 4” to 6”

up to

500mm

minimum

500mm

minimum

500mm

minimum

Concrete foundation

Note: The pipe can be filled with concrete to provide extra stability if necessary

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3.2.5 Wall Mounting

The mounting bracket can be directly attached to a suitable wall or similar structure as is illustrated below:

3.2.6 Orientation

Senscient ELDS™ OPGDs are solar immune and therefore there is no need to take account of the sun’s movement when considering orientation.

When positioning the units do not install them with the optical axis at an angle greater than 45º to the horizontal. This is to avoid dirt/water build-up on the lens-windows.

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3.2.7 Siting and Mounting Cross Duct ELDS Systems

Cross Duct ELDS systems are specifically designed and engineered for installation with their beam-path running across the duct, perpendicular to the direction of flow through the duct. In order to facilitate installation in this manner, the walls of the duct at the location where the Cross Duct ELDS system is to be installed must be flat and parallel to each other. Provided that this requirement is met it is then a simple matter of mounting each half of the Cross Duct ELDS system directly opposite its counterpart. Self-adhesive templates (011389-D) are provided to assist with the location and drilling of suitable holes in the duct wall.

NOTE: The most important requirement for successful installation of a Cross Duct ELDS system is that the optical centre lines, as indicated by the cross-hairs on the self-adhesive templates are directly opposite each other on the duct wall.

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3.3 ELECTRICAL CONNECTIONS

3.3.1 Electrical Installation Design & Engineering Recommendations

All ranges of the Senscient ELDS™ 1000 / 2000 Series comply with the electrical and EMC requirements of EN50270. In order to maintain compliance with the applicable standards it is essential that the electrical installation of ELDS™ 1000 / 2000 Series systems is engineered accordingly.

Electrical installation standards and practices vary between countries, companies and applications. It is the responsibility of the installation design authority to determine the applicable standards and practices, and to ensure compliance with them.

When designing electrical installations for ELDS™ 1000 / 2000 Series systems, it is recommended that the installation design authority takes into account the following:

a. In order to comply with the applicable electrical installation standards and practices,

the metal cases of units must be connected to earth / ground. Care should be taken in the design and engineering of this earth / ground connection to ensure that any electrical noise or voltage introduced onto a unit’s case is no greater than the levels specified in EN50270.

b. The case earth / ground bonding arrangement must ensure that the maximum

transient voltage between a unit’s case and any field cable conductor is less than 1000V. Voltages in excess of this may cause permanent damage to the unit.

c. The entire length of the field cabling connected to each unit should be fully shielded /

screened. This shield / screen should be connected to a low noise (clean) earth / ground, preferably at a single point.

d. The shields / screens of the field cabling should not be connected such that earth /

ground loops are produced, or in a manner that will result in the shields / screens carrying large currents from heavy plant or equipment.

e. Where the shield / screen of field cabling enters the terminal compartment of an

ELDS 1000 / 2000 Series unit, this shield / screen should not be connected to the unit’s earth / ground terminal and should be preve nted from maki ng any contac t with the unit’s case. The unit’s case will be connected to a local earth / ground which will typically be noisy, and this noise should not be allowed to get onto the field cable’s shield / screen.

f. Any electrical interference induced onto the 4-20mA loop conductors by the

installation must be kept below the levels necessary to comply with the general requirements of EN50270. In practice, this means that peak noise currents induced on the current loop should be no greater than 0.2 5mA.

g. The use of ‘two wire 4-20mA' isolated configurations effectively eliminates the

problems associated with field devices being at different potentials to those in the control room and reduces susceptibility to noise and interference pick-up on a 420mA loop. Isolated ‘two wire 4-20mA’ configurations are therefore recommended for applications where there is a long distance between the field device and the control room (e.g. > 750m) or where there are particularly strong sources of electrical noise and interference (e.g. heavy electrical plant) in the vicinity.

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h. When a single wire is used as the primary 4-20mA signal carrying conductor, the

current loop is completed by either the 0V or the +24V conductor running to the unit. In such ‘single wire 4-20mA' configurations, any noise on the 0V or +24V rail is effectively introduced onto one side of the current sensing resistor in the 4-20mA loop. It is therefore beneficial to limit the level of noise and interference present on the system’s 0V and +24V supply rails.

i. The level of noise on the 0V and +24V supply rails of a system can be reduced by

choosing high quality power supplies that are rated for the continuous supply of the system’s maximum calculated power requirement, and that have effective filtering on their outputs. Installation designers should avoid low cost, switched-mode power supplies with minimal output filtering because they are noisy, unreliable and become increasingly noisy as the cheap capacitors inside them degrade.

j. The 24V supply providing power to field devices should be free from large transients

and fluctuations.

k. The earth / ground at industrial facilities is typically very noisy, and therefore the level

of noise on the 0V and +24V rails can be reduced by the use of power supplies that are isolated from earth / ground.

l. The use of a single, screened cable for each field device ensures maximum

screening and minimum crosstalk. This should be the preferred cabling arrangement for field devices forming part of a gas detection system.

m. Cabling arrangements which use a single multicore cable for connecting a large

number of field devices compromise screening and increase the potential for crosstalk. Such arrangements should be avoided wherever possible.

n. The 4-20mA outputs of gas detectors are typically updated no more than a few times

a second; whilst the electrical interference and noise introduced onto the cabling carrying a 4-20mA signal back to the control room can include components with frequencies ranging from 50Hz to 2GHz. In order to reduce false alarms due to electrical interference and noise it is therefore extremely beneficial for the 4-20mA inputs of gas detection control systems to be able to ignore high frequency components. This can be achieved by analogue filtering / conditioning of the 4-20mA input, or by appropriate processing of the digitized 4-20mA signal, or by a combination of the two. The installation designer is advised that failure to address this issue can result in an unacceptably high rate of false alarms in many industrial environme nts and applications.

o. All electrical equipment directly connected to a gas detection system should comply

with applicable EMC standards such as EN50081, EN50270 & IEC 61000.

p. Radio, radar and satellite communication equipment is normally licensed to emit RF

radiation at power levels greatly in excess of those allowed by EN50081, EN50270 & IEC 61000. Field devices should not be installed in close proximity to the antennae of radio, radar or satellite communication equipment; whilst additional filtering / screening measures may be required for reliable operation of field devices within 10 to 20 metres of such antennae.

q. The conductors carrying power to ELDS 1000 / 2000 Series units should have

sufficient cross sectional area to ensure that the minimum supply voltage reaching

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units is 18V when they are drawing their maximum specified power. Refer to section

3.3.5 for information to assist with the selection of suitable cable.

r. The power consumption of each half of an ELDS 1000 / 2000 Series system is

around 10W, which is sufficient to create a significant voltage drop due to the current flowing through the resistance of the field cabling. Where installation designers intend to ‘daisy chain’ the supply of power to an ELDS 1000 / 2000 Series system by running the +24V and 0V connections to one half of a system and from there to the other half, caution is advised. The voltage drop to the first half of the system will be the product of the total system current and the cable resistance to that point; whilst the voltage reaching the second half of the system will be still lower, further increasing the current drawn by this half of the system. A ‘daisy chain’ arrangement should be acceptable for systems installed within a few hundred metres of the control room, but for greater distances the installation designer will need to calculate the voltage drops and necessary cable resistances very carefully. Rather than use the same pair of conductors to carry +24V and 0V to the system it may prove better to use a separate pair of conductors to carry +24V and 0V to each half of the system.

s. All ELDS 1000 / 2000 Series units incorporate a power-up current limiting circuit. This

circuit ensures that even during power-up, the current drawn by a unit never exceeds the maximum current that would be drawn by the unit when operating from the minimum supply voltage (18V). See 3.3.5.

t. All ELDS 1000 / 2000 Series units incorporate a brown-out survival reservoir. Under

normal operating conditions this reservoir should be sufficient to enable the unit to continue operating without being reset by a +24V power brown-out of up to 10mS duration. The installation designer should therefore endeavour to ensure that any battery back-up or similar system should detect a brown-out and restore the +24V power rail within 5mS.

u. Whilst signalling readings using a 4-20mA current loop is considerably more robust

than signalling readings using a voltage (which will normally drop between the field device and the control room) it is not completely immune to cable losses. Where long cable runs are employed between the field device and the control room it is possible for current to leak away through the insulation, reducing the current reaching the control room and therefore the apparent gas reading. (This can be misinterpreted as negative drift or warnings / faults being signalled.) Current leakage is not usually a problem in high quality cables manufactured from durable, resistant materials, but it can be a problem in lesser quality cables, especially after such cables have seen several years of service. The installation designer is advised to ensure that all of the insulation, protection and screening materials used in the construction of the cables employed will resist the effects of chemical attack, corrosion, mechanical wear and solar radiation that the cable is likely to experience over its anticipated service life. (Bear in mind that if the outer insulation perishes, water will get through to any armour and screening below, which will tend to corrode fairly rapidly. Once this has happened, you have field conductors running in a solution of metallic corrosion products surrounded by an earthed conductor. This arrangement is ideal for bleeding current away from a 4-20mA loop, especially in wet conditions.)

v. Where a low noise instrument (clean) earth is employed, this instrument earth should

only be connected to safety earth (usually dirty) at a single point on the site /

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installation. The location and arrangement of this connection should be carefully engineered to minimise the introduction of noise onto the instrument earth.

w. The terminal compartment of each ELDS 1000 / 2000 Series unit incorporates a

single cable entry on the underside of the unit. This arrangement minimizes the potential for water ingress th rough the cable entry and should di scourage use of the terminal compartment for purposes for which it is not well suited. If the installation designer wishes to ‘daisy chain’ units or marshal the connections to several field devices, a separate junction box should be employed.

x. For compliance with ATEX requirements, the Ex d (flameproof) terminal compartment

of ELDS 1000 / 2000 Series units can be entered by cables fitted with any suitable equipment certified ATEX cable gland (not a component).

Note: For further details of installation requirements see ATEX Control Drawings in Section 9.2

3.3.2 Electrical Connections: Terminal Compartment

The Transmitter and Receiver units of the ELDS 1000 / 2000 Series OPGD both feature an integral terminal compartment which is to be used for making all electrical connections to the units. The terminal compartment is an explosionproof design, and in order to comply with the applicable hazardous area protection standards, must be entered by a cable or conduit fitted with a suitable explosionproof cable gland or conduit entry.

Prior to opening the terminal compartment it is recommended to slide forward the sunshade and remove the M6 X 12 screw together with the anti-tamper device using an M6 Allen key (supplied). Retain all components, and refit when installation is complete. Access to the electrical connections inside the terminal compartment can then be gained by unscrewing the threaded rear cover. A 12mm Allen key wrench (supplied) can be used to loosen the rear cover.

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3.3.3 Receiver Electrical Connections

The terminal compartment of the Receiver of an ELDS 1000 / 2000 Series OPGD contains a 12-way terminal block, by means of which most electrical connections to the unit can be made. The terminal block is capable of accepting wires of up to 2.5mm bootlace ferrules. The terminal numbers, connection labels and proper functions of the connections available via the Receiver terminal block are detaile d in the table below:-

or compatible

Terminal

No.

1 +24V Positive connection to system power supply. 2 0V Negative or zero volt connection to system power supply. 3 LOCAL +24V Local connection to +24V to configure 4-20 (1) as source. 4 4-20 (1) SNK Sink + connection for 4-20 (1) 5 4-20 (1) SRC Source - connection for 4-20 (1) 6 LOCAL 0V Local connection to 0V to configure 4-20 (1) as sink. 7 LOCAL +24V Local connection to +24V to configure 4-20 (2) as source. 8 4-20 (2) SNK Sink + connection for 4-20 (2)

9 4-20 (2) SRC Source - connection for 4-20 (2) 10 LOCAL 0V Local connection to 0V to configure 4-20 (1) as sink. 11 RS485 (A) Connection to RS485 (A) Modbus output. 12 RS485 (B) Connection to RS485 (B) Modbus output.

Note: Conductors and insulation should be rated for operation at temperatures >= 85°C

Connection

Label

Function

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Wiring Diagram for ELDS 1000 Receiver with Isolated 4-20mA Output

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Wiring Diagram for ELDS 1000 Receiver with Current Source @ 4-20 (1)

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Wiring Diagram for ELDS 1000 Receiver with Current Sink @ 4-20 (1)

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Wiring Diagram for ELDS 2000 Receiver with Isolated 4-20 (1) & 4-20 (2)

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Wiring Diagram for ELDS 2000 Receiver with Current Sources @ 4-20 (1) & 4-20 (2)

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Wiring Diagram for ELDS 2000 Receiver with Current Sinks @ 4-20 (1) & 4-20 (2)

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3.3.4 Transmitter Electrical Connections

The terminal compartment of the Transmitter of an ELDS 1000 / 2000 Series OPGD contains an 8-way terminal block, by means of which most electrical connections to the unit can be made. The terminal block is capable of accepting wires of up to 2.5mm compatible bootlace ferrules. The terminal numbers, connection labels and proper functions of the connections available via the Transmitter terminal block are detailed in the table below:-

Terminal

No.

1 +24V Positive connection to system power supply.

2 0V Negative or zero volt connection to system power supply.

3 LOCAL +24V Local connection to +24V to configure 4-20 (1) as source.

4 4-20 (1) SNK Sink + connection for 4-20 (1)

5 4-20 (1) SRC Source - connection for 4-20 (1)

6 LOCAL 0V Local connection to 0V to configure 4-20 (1) as sink.

7 RS485 (A) Connection to RS485 (A) Modbus output.

8 RS485 (B) Connection to RS485 (B) Modbus output.

Note: Conductors and insulation should be rated for operation at temperatures >= 85°C

Connection

Label

Function

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Wiring Diagram for ELDS 1000 / 2000 Series Transmitter

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3.3.5 Power Supply Connections & Wiring

The Senscient ELDS™ gas detector is designed to be operated from a nominal 24V DC supply. For correct operation, the supply voltage reaching the terminals must be within the range 18V to 32V.

The unit maximum power consumption and cable lengths are as follows:

Component Maximum Power

Consumption, W

Maximum Cable

Length, m with 1.5mm

Conductors (12Ω/km)

Maximum Cable Length,

m with 2.5mm

Conductors (7.6Ω/km)

Receiver 10W 450 710 Transmitter 12W 375 590

Note: Control room supply voltage assumed to be +24V.

Terminal sizes: Transmitter 0.5mm Receiver 0.5mm

- 2.5mm2 (20AWG - 14AWG)

– 2.5mm2 (20AWG - 14AWG)

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4 INSTALLATION & COMMISSIONING

4.1 Unpacking an ELDS 1000 / 2000 Series System

Each ELDS 1000 / 2000 Series system is shipped inside custom-designed packaging intended to provide substantial protection of the units during shipment and handling. Before unpacking the two boxes that contain a complete ELDS OPGD system, inspect the packaging for any external signs of damage.

1) Carefully unpack the equipment, observing any instructions that may be printed on or contained within the packaging.

2) The first step is to remove the m ounting bra cket and small box con taining Al len keys and documentation etc.

Note: The unit is constrained within the packaging by rotatable retaining parts as

illustrated below, simply rotate these in order to allow the Transmitter or Receiver to be removed.

Rotate retainers prior to

attempting to remove unit

3) Check the contents for damage and against the packing note for deficiencies.

In the event of damage or loss in transit, notify the carrier and Senscient or your local agent immediately.

4) Ensure that the installer/end user of the equipment receives the technical documentation (operating instructions, manuals, etc.) contained in the packaging.

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NOTE: A complete shipment of an ELDS 1000 / 2000 Series OPGD system consists of the following items.

1 x ELDS™ Transmitter Assembly

1 x ELDS™ Receiver

ssembl

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2 x Mounting Brackets

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4.2 Installation Procedure

4.1.1 General

The Senscient ELDS™ 1000 / 2000 Series OPGD is designed to allow installation and alignment to be performed by a single, trained technician.

The installation procedure is split into mechanical installation and electrical installation. Each unit needs to be mounted to a supporting structure before making the electrical connections.

4.1.2 Mechanical Installation

The mechanical installation procedure applies to both the Receiver and the Transmitter.

1) Check that the gas detector equipment supplied is compatible with the required application (i.e. correct gas and operating range for ap plication).

2) Ensure that the Hazardous Area Certification of the equipment supplied is correct for the Hazardous Zone where the equipment is to be installed.

3) Check tha t the locations selected for siting the equipment are suitable - see Section

3.2

4) For each unit (Tx and Rx) fix the mounting bracket using one of the procedures described in the following sections.

4.1.2.1 Wall Mounting

Schematic of Bracket Base-plate showing Slot Positions for Bolts / U Bolt Fixings

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Attach the mounting bracket to the wall or similar vertical surface using suitable fixing bolts as illustrated below. The choice of fixing will depend on the nature of the surface and should take regard of the weight of the unit (~13kg).

4.1.2.2 Pole Mounting

Attach the mounting bracket to the pole using suitable fixings. It is suggested that U bolts are used as illustrated below; however other techniques may also be considered provided the unit is securely attached to the pole and is prevented from slipping or rotating around the pole.

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4.1.2.3 Mounting a Transmitter or Receiver

Mount a Transmitter or Receiver unit onto the bracket as illustrated below. The retaining nut should be tightened to 45Nm (wrench tight) to ensure that the unit is secure.

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4.1.2.4 Mounting a Cross Duct Transmitter or Receiver

Attach the self-adhesive mounting templates to the duct wall in the position identified for mounting of the Cross Duct ELDS system. Using the templates, drill and cut the necessary mounting holes in the opposite sides of the duct.

Cross Duct ELDS Mounting Template 01-01-1089-D

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Bolt Mounting Plates on each side of the duct.

Bolt a Transmitter or Receiver unit to the corresponding Mounting Plate.

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4.1.3 Electrical Installation

Perform electrical installation in accordance with the applicable Codes of Practice or Guidelines for the installation of electrical apparatus in Hazardous Areas/Zones.

CAUTION: Before electrical installation ISOLATE or switch OFF all associated power

supplies and ensure that they remain ISOLATED or OFF during the electrical installation.

The electrical installation process should include the following steps:

1) Removal of the red plastic bungs from the terminal compartment cable entry.

2) Feeding of field cabling or wires through the cable entry into the terminal compartment.

3) Screwing a suitable explosionproof M25 cable gland into the terminal compartment entry and making this off.

4) Connecting the wires required for the field connections to the unit to the appropriate terminals of the terminal block. (See Section 3.3)

5) Connecting the unit’s case to safety earth / ground (equipotential bonding) using one of the internal or external earthing points provided.

6) Verification of correct connectivity back to the control room / gas detection monitoring system.

Note: Detailed information and recommendations relating to the design and engineering of the electrical installation of ELDS OPGDs is presented in Sections 3.3.1-3.3.5.

4.2 Alignment

In order to maximize operational reliability and availability, Senscient recommends that the alignment and commissioning of ELDS™ 1000 / 2000 Series OPGDs should be performed by personnel trained by Senscient or authorised trainers.

Alignment and commissioning of ELDS OPGDs can be performed by a single technician using the alignment telescope and the Senscient Installation & Test Environment (SITE) running on a laptop or iRoc PDA.

WARNING

Do not attempt to view the sun through the optical telescope.

4.2.1 Initial Pointing

The mounting bracket of ELDS OPGDs is designed to enable Transmitter and Receiver units to be initially pointed in the direction of their counterpart without use of the alignment telescope or the precision adjustment mechanisms. Loosening the M12 nut and M6 locking screw on the adjustment block allows the unit hanging below to be quickly pointed in the direction of its counterpart.

Once each unit is pointing in the direction of its counterpart, the M6 locking screw should be tightened, followed by the M12 nut. Further adjustments will then only be possible by use of the precision adjustment mechanisms.

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Adjustment Block

M12 Clamping Nut

M6 Locking Screw

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4.2.2 Final Alignment Using Telescope

Final alignment of ELDS OPGDs can be performed by a single technician using the following equipment:-

 Alignment Telescope (see Appendix C, section 11)  2×M6 hex (Allen) key

Notes:

1. Ideally, final alignment should be performed on a clear, dry day.

2. Get familiar with the workings of the adjustable parts of the mounting bracket before proceeding with the alignment procedure, see section****.

3. To ensure precise field alignment, the alignment telescope makes use of the same mounting datum that was used when the unit was aligned in the factory.

4. The telescope incorporates eye relief adjustment for comfortable viewing. The eyepiece should be rotated to focus the image.

5. Keep the telescope and prism optics clean.

6. Do NOT try to adjust the cross-hairs using the telescope's elevation and windage adjusters. These were precisely set in the factory and CANNOT be adjusted to this precision in field conditions.

7. If the telescope is damaged or misaligned it will need to be returned to the factory for repair and/or realignment.

4.2.2.1 Attaching the Alignment Telescope

The primary objective when attaching the alignment telescope to a unit to be aligned is to get the alignment telescope’s datum sitting correctly on the unit’s alignment datum.

The alignment telescope’s datum is the flat, circular ring inside the three centration fingers on the bottom of the alignment telescope mounting mechanism.

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The unit’s alignment datum is the flat, circular ring on the front of each unit’s telescope mounting ring.

When the alignment telescope is correctly mounted, its datum is sitting flat against the unit’s alignment datum.

The simplest procedure for correctly attaching the alignment telescope is as follows:-

1) Hold the alignment telescope in one hand, with the three centration fingers ready to

locate on the edge of the telescope mounting ring.

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2) With the centration fingers touching the edge of the telescope mounting ring, firmly push

the back surface of the gripping mechanism forwards towards the unit.

3) Push the back surface of the gripping mechanism forward until all three (3) gripping

fingers have clicked into the gripping recess on the telescope mounting ring.

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4) When all three (3) gripping fingers have clipped into the gripping recess on the telescope

mounting ring, carefully release the alignment telescope, allowing it to be pulled against the unit’s mounting datum by the gripping mechanism.

5) Double check that the alignment telescope is correctly mounted by checking that all three

(3) gripping fingers are clicked into the gripping recess and that the alignment telescope’s mounting datum appears to be in contact with th e unit’s alignmen t datu m all the way aroun d the mounting ring.

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6) Once the alignment telescope is correctly mounted on the unit’s alignment datum, gently

rotate the telescope such that the eye-piece is in a convenient position for vie wing.

7) With the eye-piece in a convenient position for viewing and the alignment datum’s in

contact, the alignment telescope is ready for use.

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4.2.2.2 Final Alignment Procedure

Final alignment of Transmitter or Receiver units can be performed using just the alignment telescope and the precision adjustment mechanisms built into the mounting brackets.

The primary objective of the final alignment procedure is to align each unit such that the crosshairs on the alignment telescope is in the centre of the lens-window of the opposing unit as illustrated below:-

Notes:

1) Unlike NDIR OPGDs, Senscient ELDS 1000 / 2000 Series OPGDs are not critically sensitive t o al i g nment.

2) A small improvement in alignment can be achieved by performing alignment adjustments whilst monitoring the received signal levels using SITE running on a laptop or iRoc. However, for ELDS 1000 / 2000 Series OPGDs these small improvements are not important or necessary. ELDS OPGD systems aligned by the correct use of the alignment telescope will perform to full specification with out further alignment tuning

Correct Final Alignment

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3) In order to use the alignment telescope correctly, it is necessary to view the image produced by the telescope correctly. This requires the user to position one of their eyes on the axis of the alignment telescope. When the eye is on axis, the user will see a symmetrical, circular image f ield. See below:-

4) To see the full field-of-view of the alignment telescope, the user should position their eye approximately 3 inches away from the eye-piece (See below). The alignment telescope features an eye-relief adjustment which can be adjusted to make it easier for different individuals to focus on the telescope’s image.

Eye on-axis

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5) If the user’s eye is not on the axis of the alignment telescope, an elliptical image field will be seen, as below. For correct use of the alignment telescope, the user must keep their eye on-axis, which will result in them seeing a sym metrical, circular image field.

Eye off-axis

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4.2.2.3 Making Alignment Adjustments

The Receiver and Transmitter units of ELDS OPGDs ar e mounted on brackets that allow precision alignment adjustments in the horizontal and vertical directions.

Precise adjustments of horizontal and vertical alignment can be made using the opposed pairs of M6 adjustment screws on the mounting bracket assembly. A pair of M6 Allen keys is provided with each unit to enable the adjustment screws to be rotated.

Adjusting screws for horizontal alignment

Adjusting screws for vertical alignment

Tips:

1) Achieving a good alignment is best performed iteratively. Make alignment adjustments in one axis to bring the cross-hairs nearer to the centre of the lens-window, and then make some adjustments on the other axis. Expect to go back and forth between the horizontal and vertical axes a few of times before achieving a good final alignment result.

Tips: continue on following pages.

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2) Initially, it is likely that the alignment will be quite a long way from ideal. When it is necessary to make relatively large alignment adjustments it is best to ident ify which direction needs to be moved in, and to loosen off the adjustment screw that would oppose such a movement. This enables the aligner to drive the adjustm ent in the desired direction without the resistance of the opposing adjustment screw.

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3) If the alignment is a long way from ideal, it might be difficult to see the opposing unit through the alignment telescope. If this is the case, reduce the magnification of the alignment telescope using the magnification adjustment, which will allow a larger field to be seen. Once the opposing unit is more central, the magnification can be increased again to enable the opposing unit to be seen more clearly.

CAUTION: Do NOT try to adjust the cross-hairs using the alignment telescope's

elevation and windage adjusters. These have been factory set.

Unauthorised adjustments of alignment telescopes will lead to systems

being incorrectly aligned. Return an alignment telescope to Senscient if a problem with its alignment is suspected.

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4) When the aligner is getting close to achieving a good alignment, they should screw in both pairs of adjustment screws such that the tips of these screws are in contact with their points of action. Final, precision alignment adjustments should be made against the resistance that arises from the screw tips being in contact with their points of action.

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6) When the aligner is happy that a good, final alignment has been achieved, the alignment

should be locked-off, by simultaneou sly rotating the opposed pair of adjustment screws in the opposite direction against each other. Performed correctly, this locking-off step should not affect the adjustment but should ensure that both adjustment screws are tight and that there is no play in the alignment of the unit.

Correct Final Alignment

Locking-Off

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4.3 Cross Duct – Alignment Requirements

The Cross Duct ELDS system is designed to be installed and ‘aligned’ by simply mounting each half of the system opposite its counterpart on the other side of the duct. Provided that the duct walls where the Cross Duct ELDS system is installed are nominally parallel and the walls are sufficiently rigid that they do not deform significantly when the Cross Duct ELDS system is mounted upon them, no alignment is required.

In order to enable this simplified installation process, the Transmitter and Receiver units of a Cross Duct ELDS system have a wide field-of-view (>= 6), enabling these units to accommodate the out-of-parallel angular errors typically associated with duct walls. All that is necessary is that the optical centre-lines of each half of the system should be opposite each other to within 25mm when mounted on the duct wall. This modest requirement can be met by employing normal constructional methods and tools such that the cross-hairs on the Mounting Plate templates are positioned opposite each other when they are used to guide the drilling and cutting of the required mounting holes.

4.4 Commissioning

The commissioning process can be performed by a single, trained technician using the Senscient Installation and Test Environment (SITE) running on a laptop or an iRoc PDA. The commissioning procedure requires that each receiver is ‘paired’ with the appropriate transmitter unit. Calibration data for each unit is held within each transmitter unit and is copied to the paired receiver as part of the installation process. For this reason it is

necessary to commission the transmitter unit before attempting to commission the

receiver for each system. If multiple systems are to be installed it is possible to install all

the transmitters prior to the receivers; alternatively each system (transmitter/receiver) can be commissioned in turn.

The necessary steps to commission a system are as follows:-

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4.4.1 Configuring SITE - Adding Users

1) Start the SITE software, the initial screen will invite the user to log-in to the program as

the adminis trator.

2) The appropriate password is “S3nsci3nt” (Senscient with each “e” replaced by “3”, note the case sensitivity also). Enter this password and then press the “OK” button, the main SITE screen is then displayed. This contains a series of buttons as illustrated below.

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3) Select the “Admin” button, this generates the following dialogue screen

4) To add a new user, simply fill in the fields for Operator ID Number, Username and the

optional Password (leave this blank to allow access to SITE without password protection). Once the appropriate details have been entered press the “Add Operator” button, the new entry will then appear in the list of operators in the list-box as illustrated above.

5) Once the required entries have been made close the “adminform” dialogue box by using the form close button

(top right).

4.4.2 Commissioning a System - Transmitter

1) Open the transmitter’s terminal compartment and connect the RS485 A & B leads from

the laptop to the corresponding terminals on the transmitter’s terminal block (Positions 7 RS485(A) - Purple lead and 8 RS485(B) - Black lead). Ensure that the transmitter is powered before proceeding.

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Purple - A

2) Start the SITE software, a login screen will be presented, enter the appropriate user

name and password and press OK.

3) From the various button options available select “Commission Unit” as i llustrated.

Select this Button to commence installation

Black - B

4) The first screen presented illustrates the connection of the computer to the transmitter

unit as described above, once the appropriate connections have been made and the unit is

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powered press the “Next” button, SITE will then present the following screen while it interrogates the unit connected.

5) After a short delay SITE will report the type of unit found as illustrated below.

6) Press “Next” to proceed. The following screen is then presented.

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7) Senscient uses the unit serial number as the default Tag. If this is acceptable then select

“Leave Default”, otherwise select “Add Tag”. In this case the following dialogue is presented; edit/change the displayed Tag as required then select “Next” to continue. Note that either a real keyboard or the on-screen virtual keyboard may be used to change the Tag data.

8) A confirmation that the new Tag has been saved will be presented, following this an opportunity to check the operation of the 4-20mA output of the unit is offered.

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9) Select “Next” to proceed past this advisory screen.

10) For transmitter units there is no current requirement to check the operation of the 4-

20mA output (which is available for future feature expansion), so select “Skip” to proceed past this option without undertaking any tests. The following screen is then displayed, tick the option to confirm that the 4-20mA operation is confirmed and then press “Next” to proceed.

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11) The opportunity to change/select the behaviour of the 4-20mA drive is then presented.

Again for transmitter units it is not necessary to consider any configuration of this so select “Leave Defaults” to proceed.

12) SITE will then complete the commission ing of the unit and save various data relating to the transmitter and the appropriate calibration for it, the following screen indicates the successful commissioning of the transmitter.

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13) Select “Next”, the following screen is then presented.

14) Select “Next” to this screen to complete the process, SITE then returns to the main

selection screen. Disconnect the RS485 A and B leads from the transmitter’s terminal block. Carefully replace the terminal compartment lid and screw it down firmly. Caution: Both the explosion proof protection and the ingress protection of the ELDS OPGD

system rely upon the terminal compartment lid being screwed down full y. The lid should be tight and the o-ring compressed when the lid is properly screwed down.

Once the terminal compartment lid is properly screwed down, attach and lock-off the antitamper fixture.

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The transmitter installation is now completed.

4.4.3 Commissioning a System - Receiver

1) Open the receiver’s terminal compartment and connect the RS485 A & B leads from the

laptop to the corresponding terminals on the receiver’s terminal block (Positions 11 (RS485(A) - Purple & 12 (RS485(B) - Black). Ensure that the receiver is powered prior to proceeding with SITE.

Purple - A

2) Enter SITE and the software will check for a connected unit. Screen as below:-

Black - B

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3) If the receiver unit is already powered up, it should be detected and the following screen

will appear. If the receiver unit is not correctly connected or not powered up, rectify the problem and wait for the receiver to be detected.

Note: It can take up to 60 seconds from power up for a receiver unit to begin communicating with SITE.

4) Having reached the above screen successfully, click on Next to continue the commissioning process.

5) It is now necessary to select a transmitter unit to “pair” the receiver with. The following screen is presented which allows the appropriate transmitter to be selected.

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6) SITE will normally select the last transmitter that was installed as the default option. If this

is not correct then select the appropriate unit from the drop-down list. Note that units are identified by the Tag number so it is important that the installer is aware of the appropriate Tag number that was entered on the unit which the receiver is to be paired with.

7) Once the appropriate unit is selected press “Next” to continue. SITE will then transfer the calibration data for the selected transmitter to the receiver unit and confirms this with the following screen.

8) SITE will display the screen below, requesting the operator to enter the range in metres between the transmitter and receiver. This value will be used by SITE to confirm that the signal reaching the receiver from the transmitter is as expec t ed.

9) The range can be adjusted by clicking on the up and down arrows to the right of the box displaying the range. When the correct range has been set, click on Next.

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10) Assuming that the transmitter and receiver units have been satisfactorily aligned with

respect to each other and there is nothing obscuring the beam-path, SITE will display the following screen, indicating that the signals are okay.

11) Move onto the next step in the commissioning process by clicking Next.

12) If SITE displays the following screen then the signals reaching the receiver from the

transmitter are lower than expected. This could either be due to poor alignment of the transmitter or receiver, or due to obscuration of the beam-path.

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13) IF the Signal Low screen is displayed: Check that the lens-windows of both the

transmitter and receiver are clean, and that there is nothing obscuring the beam-path between the transmitter.

14) If the check at 13) does not identify any problem, use the alignment telescope to doublecheck that there is nothing obscuring the beam-path.

15) Finally, using the alignment telescope, double-check the alignment of the transmitter and receiver with respect to each other. (See Section 4.2 for Alignment instructions.)

16) If SITE displays the screen below then there is no signal reaching the receiver from the transmitter. There could be a number of reasons for this:-

 Beam Blocked – There is something in the beam-path which is completely blocking

the beam-path between the transmitter and the receiver.

 No TX Power – The transmitter is not receiving the +24V (nominal) power supply

voltage that it requires to operate.

 System Not Aligned – The transmitter or receiver have not been aligned with respect

to each other, or are so far from correct alignment that no signal is reaching or being seen by the receiver.

 TX Fault – There is a fault condition preventing the transmitter from producing the

expected output.

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17) In order to continue with the commissioning process, the cause of the ‘No Signal’

problem must be identified and corrected. Perform checks to establish which of the reasons listed at 16) is causing the problem experienced and where possible correct this problem.

18) Once the SITE software displays the green ‘Signals OK’ screen you are ready to proceed to the next step in the commissioning process.

19) Upon the successful completion of the signal levels test, SITE will move on to the zeroing process.

20) If the system has not been zeroed before, SITE will display the following screen.

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21) Verify that there is no target gas in the system’s beam-path, and once this has been

verified click Next to zero the system.

Caution: Zeroing a system with target gas in the beam-path will result in a positive offset on the unit’s zero position. This offset will introduce errors in the gas readings output by the system and may give rise to the spurious diagnosis of Fault or Warning conditions. Only zero a system when you are confident that there is either zero target gas or a negligibly small quantity of target gas in the beam-path.

22) If the system has been zeroed before, SITE will display the following screen.

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23) If you do not want to re-zero the unit, click “Leave Zero Data” and then click Next to

move on.

24) If you elect to re-zero the unit then, the following screen will be displayed.

25) SITE will display the above screen throughout the zeroing process, which will normally

take around 30 seconds.

26) Subsequent to satisfactory completion of the zeroing process, SITE will display the following screen.

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27) If you are happy that the zeroing process was performed satisfactorily, click Next to

save the zeros in the system.

28) If any of the events below occurred during the zeroing process, the zero might not be correct. In order to ensure that a good zero is performed, click Previous to return SITE to the zeroing s c r ee n:-

 A release of target gas took place in or near the system.  An object or person moved into or through the beam-path.  A gas challenge cell or gassing cell was mistakenly inserted into the beam-path.

29) Once SITE has successfully saved the zero data on the system, the following screen will be displayed.

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30) Click Next to move onto the next step in the commissioning process.

31) SITE will now ask you if you would like to enter a tag number for the unit. This is

recommended as it will give the unit a recognisable ID when subsequently communicating with the unit using Bluetooth, or downloading event history logs. The tag number should ideally correspond to the position / location of the unit on the site or within the safety system to which it is connected.

32) Select “Add Tag” if you want to enter a tag number and SITE will display the tag number entry screen.

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33) Select “Leave Default” if you do not want to enter a tag number. In this case the

Senscient serial number of the unit will be left as the default tag number, then click Next to move on to the next step in the commissioning process.

34) Using either the touchscreen keyboard displayed by SITE below or a real keyboard, enter the tag number for the unit.

35) When you are happy with the tag number, click Next and this will be stored inside the unit.

36) SITE will now display the following screen, recommending that the 4-20mA output and loop be checked.

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37) When you are ready to check the 4-20mA output and loop, click Next.

38) SITE will now give you the opti on o f per fo rming 4-2 0 mA lo op tests wi th a fo rced 4-20 mA

output.

39) If you want to force a specific test current out on the 4-20mA output to test the loop and / or the control system’s response, click “Force 4-20mA”.

40) If you do not want to force a specific current out on the 4-20mA output, click “Skip”, in this case the output current for loop testing will be 4mA.

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41) If SITE is displaying the screen below, use the up and down arrows to the side of the

current setting box to set the current to be output by the receiver unit and when you are happy with the value click the Set 4-20mA button followed by Next.

42) With the receiver attempting to output the 4-20mA check current on the 4-20mA loop, check that the current flowing through the loop is as expected. This can either be done using a multimeter inserted into the loop or by checking the current or gas reading being displayed for this loop by the control system. Note that both circuits (for a dual gas receiver) will be generating the selected current and both should be checked.

43) Once the operation of the outputs has been tested select “Next” to proceed.

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44) SITE wants to make sure that you have checked the 4-20mA output and lo op before it

allows the system to be fully commissioned. To this end, SITE requires you to click the check box next to the 4-20mA Circuits Checked statement - before you can proceed any further. Only click the check box if you have successfully checked the 4-20mA output and loop.

45) SITE next displays the screen illustrated below to allow the behaviour of the 4-20mA loops to be configured.

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46) The behaviours that can be configured are Inhibit current, Fault current, Beam Block

current, the Time between detecting a beam blocked state and raising the associated warning, the Time between loosing optical signal and detecting/declaring a beam blocked state, the Low Signal state current, the Time between detecting low signal and entering the low signal state and the over-range current. Each of these parameters has default values associated and screens are presented in turn to allow the defaults to be adjusted as required. At the end of this process a summary screen is presented as follo ws:

47) Note that in this example all the values are left at the factory defaults. Note that the “Beam Block to Fault” time is -1 hours by default, this value disables this feature (i.e. BeamBlock does not generate a Fault condition and is just signalled as a warning.).

48) Once the correct parameters are established press “Save Config” to update the unit, if any values remain incorrect the select “Change Config” to allow further changes to be made.

49) Following “Save Config” a confirmation screen is presented declaring that the values are updated

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50) Select “Next” to proceed.

51) SITE will then write a commissioning log, this takes a few seconds to implement and

completes with the following screen

52) Select “Next” to proceed, the following screen is then displayed.

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53) Disconnect the RS485 A and B leads from the receiver’s terminal block.

54) Carefully replace the terminal compartment lid and screw it down firmly. Caution: Both the explosionproof protection and the ingress protection of the ELDS OPGD

system rely upon the terminal compartment lid being screwed down full y. The lid should be tight and the o-ring compressed when the lid is properly screwed down.

55) Once the terminal compartment lid is properly screwed down, attach and lock-off the anti-tamper fixture.

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4.5 Installation Checklist

The following information is for the guidance of personnel carrying out installation checks / tests on Senscient ELDS™ OPGDs. In general it should be noted that:

Installation of ELDS™ 1000 / 2000 Series OPGDs should be performed by personnel trained by Senscient or authorised trainers.

Detailed information concerning installation, alignment and commissioning is provided in this Instruction Manual.

Senscient ELDS™ is explosion protected by a certified, explosionproof enclosure. Carefully read the safety warnings, cautions and certification details in this manual. Ensure that they have been complied with, before and during the installation.

The following is a check list with notes to assist the installer:-

Site/Facility

Check that the unit is being installed at the correct site / facility, e.g.

Hibernia Platform, North Atlantic

Is this the correct site / facility?

Operating Range

Check the di stance (preferably in metres), between the Transmitter and the Re ceiver. Is the unit being installed suitable for this operating range?

Detector Location

Check the location / position of the unit, e.g.

West Walkway, Compressor Skid

Is this the correct location / position for the unit?

Tag No

Check the Tag No, or equivalent, that has been allocated to the ELDS™ Receiver and Transmitter units. Do the Tag No.’s and details for the units all tie up?

Mod State

Check the Mod State of the units as indicated on their certification labels.

Certification

Check the ce rtification of the units, e.g.

Is the Hazardous Area Certification of the unit correct for the Hazardous Area/Zone where it is being installed?

Mount Rigidity

Check that the units have been mounted securely to the supporting structure. Check that the supporting structure is sufficiently rigid to maintain alignment in the anticipated operating conditions. A maximum angular movement of 1º is allowable.

Baseefa ATEX (Europe),

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As an approximate guideline, a sufficiently rigid mount/supporting structure will only move a few millimetres (not more than 6mm) when leaning body weight against it.

When pushed hard and released, the mount/supporting structure should return quickly to its original position and should not wobble or sway. If the mount/ support is unacceptable, take steps to have the mount / supporting structure improved.

Vibration

Check the installation and its close surrounds for potential or existing sources of excessive vibration. Such sources could include heavy plant/machinery, turbines, generators etc.

If there is the possibility that such vibration sources could be or already are causing unacceptable movement, investigate how the effects of this vibration can be mitigated.

Excess Heat

Check the installation and its surrounds for potential sources of excessive heat. The unit is specified for ambients up to +60°C. Potential sources of excessive heat include flare-stacks, generator/turbine exhausts and steam vents. If there is the possibility that such heat sources are causing unacceptable temperatures to be reached, investigate how the effects of these sources can be reduced.

Supply Voltage

Check that the supply voltage applied to the unit is within the specified 18V to 32V range and is stable.

Earthing

Inspect the earth / ground connections to the units.

RFI/EMC

Assess the installation, cabling and its close surrounds for known or potential sources of excessive RFI/Electromagnetic Interference. Such sources could include radio/radar transmission antennae, high voltage switch-gear, large electrical generators/motors etc.

Contaminants

Assess the installation and its surrounds for sources of contaminants that could build up on the unit’s windows. Such contaminants could include oil mist, heavy sea spray, drilling mud, dirty exhaust fumes, wave splash etc.

If there is a realistic possibility that such contaminants could eventually completely obscure the optics, consider how the rate of build-up could be reduced or whether scheduled cleaning might be required.

Beam Obstruction/Blocks

Ideally, a clear path of at least 20cm diameter should be provided between the Transmitter and the Receiver. Assess the installation and the beam path for potential sources of beam blockage. These could include personnel walking in the beam, parking vehicles, moving machinery/plant, growing vegetation etc.

Functional Test

After completing the installation procedure, perform a functional test upon the unit either using a gas challenge cell, a gassing cell or SimuGas.

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4 - 20mA Loop Integrity

Test the 4 - 20mA loop integrity by forcing the unit to output a known current and monitoring this at the control room or with a multimeter inserted into the loop. Update the appropriate box.

Fault/Warning Log

Check the Fault / Warning Log. In order for the unit to complete installation satisfactorily, the ACTIVE FAULTS log must be CLEAR. Use SITE running on a laptop or iRoc interrogator to diagnose and remedy all ACTIVE FAULT conditions.

Wherever possible, it is recommended to CLEAR any ACTIVE WARNINGS, since these may lead to faults in the future.

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5 FUNCTIONAL TESTING

5.1 Introduction

Senscient’s ELDS 1000 / 2000 Series OPGDs feature the most advanced gas detector functional testing technology currently available, enabling the correct function of OPGDs to be tested with far greater ease and frequency than has previously been possible. The key functional testing technology incorporated in Senscient’s ELDS OPGDs is called SimuGas beam-path.

The flexibility afforded by SimuGas testing of ELDS OPGDs in a number of different ways, including SimuGas Auto, SimuGas Inhibited and SimuGas Live, which approaches are described in the following sections.

In addition to the use of SimuGas, it is also possible to test the function of ELDS OPGDs using methodologies that physically introduce target gas into the monitored beam-path. For these purposes, Senscient provides a Gassing Cell that can be used in conjunction with ELDS OPGDs.

and is an on-command, electronic simulation of a quantity of target gas in the

technology makes it possible to perform functional

5.2 SimuGasTM Explained

5.2.1 Harmonic FingerprintsTM

In an ELDS Transmitter the drive current applied to the laser diode(s) comprises two components, a DC bias co mponent which sets the mean operating wavelength of the laser diode(s), and a pure sinusoidal component which modulates the wavelength of the laser diode(s). Continuous registration of the wavelength(s) of the Transmitter’s laser diode(s) is achieved by passing a small fraction of the laser diode output(s) through a retained sample of target gas(es) inside the Transmitter, and measuring the resulting signals from a reference detector (See below).

Transmitter: Gas Reference Channel

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Using the signal reaching the reference detector through the retained gas sample, the transmitter’s microcontroller is capable of determining the precise bias and wavelength modulation components that need to be applied to the laser diode(s) in order to ensure that absorption of the laser diode’s optical radiation by target gas always produces a Harmonic FingerprintTM.

A Harmonic Fingerprint absorption, in which the relative amplitudes and phases of the components are known and specific to the target gas absorption line that is being scanned by the ELDS Transmitter. When the laser diode drive conditions in an ELDS transmitter are maintained such that target gas absorption always produces a Harmonic Fingerprint, the transmitter is said to be maintaining Harmonic Fingerprint Lock.

is a set of harmonic components introduced by target gas

Harmonic Fingerprint for a H

Under conditions of Harmonic Fingerprint Lock, the size of any Harmonic Fingerprint measured is proportional to the amount of target gas in the beam-path. In an ELDS OPGD system, the Receiver detects and measures the size of any Harmonic Fingerprints in the signal reaching it from the Transmitter, and uses this to determine the quantity of target gas in the monitored beam-path.

S Line at 1589.97nm

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5.2.2 Electronically Synthesised Harmonic Fingerprints – SimuGasTM

As described in Section 5.2.1, the transmitter in an ELDS-based OPGD is continuously using the signal from its reference detector channel to maintain Harmonic Fingerprint Lock. The transmitter’s microprocessor controls the electronic synthesis of the drive waveforms that are applied to the laser diode(s) such that the laser diode(s) remain precisely locked to the chosen target gas absorption line(s), and by so doing ensures that the sizes of each Harmonic Fingerprint component produced by target gas absorpti on are precisely known.

Because the transmitter in an ELDS OPGD is electronically synthesising the drive waveforms that are applied to its laser diode(s) and knows the sizes of the Harmonic Fingerprint components produced by target gas, it is possible for a transmitter to electronically synthesise laser diode drive waveforms which include Harmonic Fingerprint components corresponding to a quantity of target gas.

When the laser diodes in an ELDS transmitter are driven by waveforms including Harmonic Fingerprint components corresponding to a quantity of target gas, their optical outputs include the Harmonic Fingerprint components - just as if they had been introduced by genuine optical absorption by the target gas.

This means that an ELDS transmitter can electronically simulate the presence of a

quantity of target gas in the monitored beam-path. Senscient refers to this type of

electronically simulated gas as SimuGas When the receiver of an ELDS OPGD receives signals from the transmitter which include

SimuGas

components, it cannot tell the difference between electronically synthesised Harmonic Fingerprint components and those produced by genuine absorption by target gas. Consequently, the receiver processes the received signal and calculates the amount of target gas believed to be present in the beam-path - based upon the sizes of the Harmonic Fingerprint components.

Comparing the gas quantity calculated by the receiver to the quantity of SimuGas simulated by the transmitter provides a powerful means of verifying the correct function of an ELDS OPGD. Because of the flexibility afforded by the SimuGas perform functional testing of ELDS OPGDs in a number of different ways. The different functional test methodologies made possible by the use of SimuGas Auto, SimuGas Inhibited and SimuGas Live, and are described in the following sections.

SimuGas

OPGD functionality testing offers considerable advantages over conventional OPGD testing methodologies, including the following:-

 There is no need for operators to generate, handle or apply hazardous gases to

detectors in the field.

 There is no need for operators to gain direct physical access to detectors in order

to test them. Commands to perform SimuGas tests can be sent remotely from wherever it is convenient, and the results of tests ca n be monitored remotely too.

 Because SimuGas is simple, quick and convenient it makes it possible to

functionally test gas detectors much more frequently, improving the safety integrity of a fixed gas detection system.

 If desired, the functional testing of gas detectors can be completely automated

(SimuGas Auto).

 The operation and maintenance costs for a fixed gas detection system are

considerably reduced.

technology it is possible to

include SimuGas

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5.3 SimuGas

The simplest way for users to realise the considerable safety integrity benefits provided by SimuGas configured, the transmitter will perform a SimuGas test with a known level every 24 hours; whilst the receiver will check that each test produces acceptable results. In the event that a SimuGas Auto test does not produce acceptable results, the receiver is configured to signal a Warning or Fault to the control system, providing an early warning about a potential problem with the ELDS OPGD affected.

Compared to conventional OPGD testing methodologies or operator-initiated SimuGas tests, SimuGas Auto has the following advantages:-

When configured for SimuGas Auto, an ELDS OPGD system performs the following actions:-

technology is to configure ELDS OPGDs to perform SimuGas Auto. When so

 Testing is performed without the gas detector being visited by operators.  Testing is performed every 24 hours, providing far earlier diagnosis of any problem

than tests relying upon operators visiting gas detectors.

 Requires no additional cabling, software or control system infrastructure. SimuGas

Auto can be employed successfully using the same wiring and control systems that were used with earlier generations of gas detectors.

1) Every 24hours, at a user-set time the transmitter commences the procedure for a SimuGas Auto test.

Auto

2) The transmitter warns the receiver that it is about to perform a SimuGas Auto test.

3) The receiver freezes the gas reading signalled on its 4-20mA output(s) at the value(s) immediately preceding the SimuGas Auto test.

4) The transmitter drives it laser diode(s) such that its output includes a pre-defined quantity of SimuGas, and holds this SimuGas level for 30 seconds duration.

5) The receiver measures the size of the Harmonic Fingerprint components introduced by the SimuGas test and calculates the quantity of gas that this corresponds to.

6) At the end of the SimuGas test, the receiver un-freezes its 4-20mA output(s), enabling a return to the live signalling of the quantity of gas in the monitored beampath.

7) The receiver compares the quantity of gas calculated to be in the monitored beampath during the recent SimuGas test with the quantity of gas known to be simulated during SimuGas Auto tests.

8) The receiver assesses whether the results of the SimuGas Auto test were satisfactory, and if satisfactory continues operating as normal.

9) If the results of the SimuGas Auto test were not satisfactory, the receiver updates its status and outputs the configured Fault or Warning signal on its 4-20mA output(s)

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5.4 SimuGasTM Inhibited

A SimuGas Inhibited test enables a Simu-Gas functional test to be performed without the receiver signalling a gas reading on its 4-20mA output(s). The purpose of the receiver not signalling the gas reading during this test is to avoid unwanted initiation of executive actions by the safety system, such as shut-downs or audible alarms.

A SimuGas Inhibited test can be commanded by using SITE software on a laptop or iRoc handheld that is in communication with a transmitter. Following receipt of a valid SimuGas Inhibited command and an acceptable gas level, the transmitter will calculate the laser drive waveforms necessary to simulate the instructed gas level, and drive its laser diodes with these waveforms for 30 seconds, subsequently returning to the ‘gas-free’ drive waveforms.

During the SimuGas Inhibited test the receiver will calculate the gas level present in the monitored path as normal, and will remember these levels. Immediately following the test, the receiver will calculate the average gas level present during the last 20 seconds of the test and store this reading for later retrieval and assessment using SITE software on a laptop or iRoc handheld communicating with the receiver.

The results of a SimuGas Inhibited test may be determined by comparison of the gas reading(s) stored in the receiver with the gas level(s) that the transmitter was instructed to simulate during the test. Assuming that there were no target gases present in the beampath during the SimuGas Inhibited test, the reading stored by the receiver should be within +/-10%FSD of the level that the transmitter was instructed to simulate.

Example

For a 0-1LEL.m CH4 system, simulating 0.5LEL.m, the reading stored by the receiver should be:-

0.5LEL.m +/- 0.1LEL.m Or between

0.4LEL.m & 0.6LEL.m

Note:

1) In the event that a SimuGas Inhibited test is performed whilst there is real target gas in

the beam-path, the amount of gas seen by the receiver will be the combination of the SimuGas level and the real gas level. Since real gas levels tend to fluctuate rapidly, this could cause problems correctly interpreting the results of a SimuGas Inhibited test.

2) Due to the problem noted at 1) it is preferable to perform SimuGas tests when there is no real gas in the monitored beam-path. This can be established by checking the gas readings from the receiver before performing a SimuGas test. If the gas readings are stable at zero, SimuGas testing results will be simpler to interpret.

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5.5 SimuGasTM Live

A SimuGas Live test enables a Simu-Gas functional test to be performed with the receiver signalling the quantities of gas calculated present in the monitored beam-path on its 4-20mA output(s).

Caution: Unless the purpose of a SimuGas Live test is to confirm correct initiation of executive actions by the connected safety system, before performing SimuGas Live tests the user will have to take steps to ensure that live gas readings being signalled on the 420mA output(s) of ELDS OPGDs are inhibited further up in the system.

A SimuGas Live test can be commanded by using SITE software on a laptop or iRoc handheld that is in communication with a transmitter. Following receipt of a valid SimuGas Live command and an acceptable gas level, the transmitter will calculate the laser drive waveforms necessary to simulate the instructed gas level, and drive its laser diodes with these waveforms for 30 seconds, subsequently returning to the ‘gas-free’ drive waveforms.

During the SimuGas Live test the receiver will calculate the gas level(s) present in the monitored beam-path as normal, and signal these over its 4-20mA outputs .

The results of a SimuGas Inhibited test may be determined by comparison of the gas reading(s) signalled by the receiver during the test with the gas level(s) that the transmitter was instructed to simulate. Assuming that there were no target gases present in the beampath during the SimuGas Live test, the reading stored by the receiver should be within +/10%FSD of the level that the transmitter was instructed to simulate.

Example

For a 0-1LEL.m CH4 system, simulating 0.5LEL.m, the reading stored by the receiver should be:-

0.5LEL.m +/- 0.1LEL.m Or between

0.4LEL.m & 0.6LEL.m

Note:

1) In the event that a SimuGas Live test is performed whilst there is real target gas in the

beam-path, the amount of gas seen by the receiver will be the combination of the SimuGas level and the real gas level. Since real gas levels tend to fluctuate rapidly, this could cause problems correctly interpreting the results of a SimuGas Live test.

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5.6 Testing with the Gassing Cell

Senscient’s ELDS OPGDs are supplied factory calibrated and cannot be re-calibrated in the field because experience has shown that accurate OPGD calibration can only be achieved in a controlled factory environment. Where customers must undertake calibration checks, these can be performed using the Gassing Cell, but users are advised that such checks are far more likely to be in error than the original factory calibration.

Caution: The use of conventional gas cells employing glass windows will lead to

erroneous results with Senscient ELDS™ products because of optical interference fringes generated by cell windows. ONLY the Senscient Gassing Cell should be used with ELDS OPGDs.

The Gassing Cell is designed to allow easy response checking using high concentration test gases. The cell is suitable for both high level (LEL) response ranges such as CH 1LEL.m units or for lower concentration ranges applicable to toxic gases such as H

0 -

The gassing cell is designed to fit to the front of a ELDS™ transmitter or receiver unit. It may be helpful to move the sun shield to the furthest back position to allow better access to the clamping bolts on the cell when fitting the part.

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The integrated LEL.m concentration in the cell can be calculated using the following formula:

Int(lel.m)

ELDS = Lcell * (Concv/v / LELv/v)

where:

Int(lel.m)

cell = Length of cell in metres (0.236 for the Senscient Cali bration Cell),

Conc

LEL

ELDS = Integrated LEL.m reading output by Senscient ELDS™,

v/v = Gas concentration in %v/v and

v/v = Lower Explosion Limit of the gas in %v/v.

The integrated ppm.m concentration in the cell can be calculated from the following formula:

Int(ppm.m)

ELDS = Lcell * Concppm

where:

Int(ppm.m)

ppm = Gas concentration in ppm by volume.

Conc

ELDS = Integrated ppm.m reading output by Senscient ELDS™,

The test gas concentration must be selected to generate a reading from the unit that is between 0.5× and 1× full scale.

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WARNING

Take the necessary precautions to ensure safety when dealing with flammable or toxic gases

The Gassing Cell utilises thin film windows which are relatively fragile. Avoid touching these during use and also ensure that no over-pressure is applied to the cell during the filling process to prevent damage to the windows

To get the very best accuracy when using the gassing cell:

1) Mount the empty Gassing Cell on the ELDS™ OPGD receiver unit.

2) Zero the ELDS™ OPGD with the empty Gassing Cell in place.

3) Apply the test gas to the Gassing Cell and allow sufficient time to fully flush the cell through, without pressurising it and check that the reading output by the ELDS™ OPGD has completely stabilised.

Note: A maximum flow-rate of 1 litre/min is recommended for the Gassing Cell. The cell

must be purged for at least 5 minutes at this flow-rate to ensure the correct burden will be presented to the unit

4) Check the ELDS™ OPGD output is as expected.

5) Remove the Gassing Cell.

6) Re-zero the ELDS™ OPGD.

Note: In common with all optical gas sensors the ELDS™ OPGD respond s to the total

quantity of gas in the beam. When attempting to check calibration accuracy using a Gassing Cell the quantity of gas in the beam will be affected by atmospheric pressure and ambient temperature. Suitable allowance for these factors must be made when assessing the response of the system. Errors of the order of +/-5% of reading should be expecte d; whilst errors as la rge as +/-10% of readin g can and will occur at times.

Senscient ELDS 1000 Series, ELDS 2000 Series Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual