Teledyne 306WA User Manual

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INSTRUCTION MANUAL

MODEL 306WA

TRACE OXYGEN ANALYZER

DANGER

HIGHLY TOXIC AND OR FLAMMABLE LIQUIDS OR GASES MAY BE PRESENT IN THIS MONITORING SYSTEM.

PERSONAL PROTECTIVE EQUIPMENT MAY BE REQUIRED WHEN SERVICING THIS SYSTEM. HAZARDOUS VOLTAGES EXIST ON CERTAIN COMPONENTS INTERNALLY WHICH MAY PERSIST FOR

A TIME EVEN AFTER THE POWER IS TURNED OFF AND DISCONNECTED. ONLY AUTHORIZED PERSONNEL SHOULD CONDUCT MAINTENANCE AND/OR SERVICING. BEFORE

CONDUCTING ANY MAINTENANCE OR SERVICING CONSULT WITH AUTHORIZED SUPERVISOR/ MANAGER.

TELEDYNE ELECTRONIC TECHNOLOGIES

Analytical Instruments

P/N M4624

09/14/99

ECO# 99-0373

Model 306WModel 306W

Model 306W

Model 306WModel 306W

ments

mentsments

All Rights Reserved. No part of this manual may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any other language or computer language in whole or in part, in any form or by any means, whether it be electronic, mechanical, magnetic, optical, manual, or otherwise, without the prior written consent of Teledyne Electronic Technologies/Analytical Instruments, 16830 Chestnut Street, City of Industry, CA 91749-1580.

WarrantyWarranty

Warranty

WarrantyWarranty

This equipment is sold subject to the mutual agreement that it is warranted by us free from defects of material and of construction, and that our liability shall be limited to replacing or repairing at our factory (without charge, except for transportation), or at customer plant at our option, any material or construction in which defects become apparent within one year from the date of sale, except in cases where quotations or acknowledgements provide for a shorter period. Components manufactured by others bear the warranty of their manufacturer. This warranty does not cover defects caused by wear, accident, misuse, or neglect. We assume no liability for direct or indirect damages of any kind and the purchaser by the acceptance of the equipment will assume all liability for any damage which may result from its use or misuse.

We reserve the right to employ any suitable material in the manufacture of our apparatus, and to make any alterations in the dimensions, shape or weight of any parts, in

so far as such alterations do not adversely affect our warranty.

Important NoticeImportant Notice

Important Notice

Important NoticeImportant Notice

This instrument is intended to be used a tool to gather valuable data. The information provided by the instrument may assist the user in eliminating potential hazards caused by the process that the instrument is intended to monitor; however,

that all personnel involved in the use of the instrument or its interface with the processthat all personnel involved in the use of the instrument or its interface with the process

that all personnel involved in the use of the instrument or its interface with the process

that all personnel involved in the use of the instrument or its interface with the processthat all personnel involved in the use of the instrument or its interface with the process being measured be properly trained in the process itself, as well as all instrumentationbeing measured be properly trained in the process itself, as well as all instrumentation

being measured be properly trained in the process itself, as well as all instrumentation

being measured be properly trained in the process itself, as well as all instrumentationbeing measured be properly trained in the process itself, as well as all instrumentation related to it.related to it.

related to it.

related to it.related to it.

The safety of personnel is ultimately the responsibility of those who control process conditions. While this instrument may be able to provide early warning of imminent danger, it has no control over process conditions, and can be misused. In particular, any alarm or control system installed must be tested and understood, both as they operate and as they can be defeated. Any safeguards required such as locks, labels, or redundancy must be provided by the user or specifically requested of Teledyne.

The purchaser must be aware of the hazardous conditions inherent in the process(es) he uses. He is responsible for training his personnel, for providing hazard warning methods and instrumentation per the appropriate standards, and for ensuring that hazard warning devices and instrumentation are maintained and operated properly.

it is essentialit is essential

it is essential

it is essentialit is essential

Teledyne Electronic Technologies/Analytical Instruments, the manufacturer of this instrument, cannot accept responsibility for conditions beyond its knowledge and control.

disseminated by the manufacturer or his agents is to be construed as a warranty ofdisseminated by the manufacturer or his agents is to be construed as a warranty of

disseminated by the manufacturer or his agents is to be construed as a warranty of

disseminated by the manufacturer or his agents is to be construed as a warranty ofdisseminated by the manufacturer or his agents is to be construed as a warranty of adequate safety control under the user's process conditions.adequate safety control under the user's process conditions.

adequate safety control under the user's process conditions.

adequate safety control under the user's process conditions.adequate safety control under the user's process conditions.

No statement expressed or implied by this document or any informationNo statement expressed or implied by this document or any information

No statement expressed or implied by this document or any information

No statement expressed or implied by this document or any informationNo statement expressed or implied by this document or any information

TELEDYNE ELECTRONIC TECHNOLOGIES

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Table of Contents

1 Introduction

1.1 Method of Operation................................................. 1-1

1.2 Required Equipment................................................. 1-2

1.2.1 Sample Conditioning................................... 1-2

1.2.2 Recorder /Meter Readout ........................... 1-2

2 Operational Theory

2.1 Sensor ..................................................................... 2-1

2.2 Humidifier ................................................................ 2-1

2.3 Flow System............................................................ 2-2

2.4 Calibrator................................................................. 2-4

3 Installation

3.1 Location.................................................................... 3-1

3.2 Electrical Connections............................................. 3-1

3.3 Sample Connections ............................................... 3-2

4 Operations

4.1 Filling the Reservoir.................................................. 4-1

4.2 Detector Cell............................................................. 4-1

4.2.1 Cell Packaging ............................................ 4-1

4.2.2 Electrolyte ................................................... 4- 1

4.2.3 Cell Installation............................................ 4-3

4.3 Calibrator.................................................................. 4-5

4.4 Throttle Valve ........................................................... 4 -5

4.5 Humidity Control....................................................... 4-7

4.6 Power ....................................................................... 4 -8

4.7 Warm-Up and Stabilization....................................... 4-8

4.7.1 Calibration................................................... 4-8

Maintenance & Troubleshooting

5.1 Flowmeter and Humidifier ....................................... 5-1

5.2 Cell Electrolyte Level............................................... 5-1

5.3 Reservoir ................................................................. 5-1

TELEDYNE ELECTRONIC TECHNOLOGIES

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5.4 Calibration ............................................................... 5-2

5.5 Cell .......................................................................... 5-4

5.6 Screen Assembly..................................................... 5-5

5.7 Calibrator................................................................. 5-6

5.8 Reservoir and Humidifier Column ........................... 5-6

5.9 Leak Detection ........................................................ 5- 8

Appendix

Specifications ................................................................. A-1

Spare Parts List.............................................................. A-2

Drawing List.................................................................... A-3

Calibration Data..............................................................A-4

Model 306WModel 306W

Model 306W

Model 306WModel 306W

5.4.1 Internal Calibrator ........................................ 5-2

5.4.2 Standard (span) Gas Calibration ................. 5-2

5.5.1 Electrolyte Replacement.............................. 5 -4

5.5.2 Lead Electrode............................................. 5-5

5.9.1 Leak Detection Procedure ........................... 5-8

5.9.2 Cell Leak...................................................... 5-9

TELEDYNE ELECTRONIC TECHNOLOGIES

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The Teledyne Analytical Instruments Model 306WA Trace Oxygen Analyzer is designed to detect trace concentrations of oxygen in process streams. It utilizes Teledyne’s patented electrochemical sensor which requires minimal maintenance and exhibits a 90% response in less than one minute. Cell output is insensitive to flow rate changes within the operating range of the analyzer’s flowmeter.

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IntroductionIntroduction

Introduction

IntroductionIntroduction

Introduction 1.0Introduction 1.0

Introduction 1.0

Introduction 1.0Introduction 1.0

The Model 306WA features a welded stainless sampling system for long-term, leak-free operation.

While the analyzer is offered in several configurations, they are virtually identical with the exception of housing or options such as special meters. For purposes of clarity, this manual will discuss the unit in general, since differences will be minor and will be obvious to the user.

1.11.1

1.1

1.11.1

Gas from the process stream is fed through a sample line to the sample inlet port of the analyzer. The sample is directed through the analyzer’s sample system, where oxygen concentration is detected by the sensor. The sensor generates an output signal which is read out on a suitable recorder or meter.

The analyzer components include a throttle valve and flowmeter to control sample flow, a humidifier to condition the sample, the measuring cell and its associated circuitry, and a calibrator to adjust the sensitivity of the analyzer to the desired measurement range.

Method of OperationMethod of Operation

Method of Operation

Method of OperationMethod of Operation

1.21.2

1.2

1.21.2

For proper operation, the analyzer may require accessory equipment, particularly in the area of sample conditioning. The need for additional equipment is dictated by the conditions of each application.

Required EquipmentRequired Equipment

Required Equipment

Required EquipmentRequired Equipment

TELEDYNE ELECTRONIC TECHNOLOGIES

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1-1

1.0 Introduction1.0 Introduction

1.0 Introduction

1.0 Introduction1.0 Introduction

Model 306WModel 306W

Model 306W

Model 306WModel 306W

1.2.11.2.1

1.2.1

1.2.11.2.1

The sample should be free of entrained solids and condensable vapors, and be at a relatively constant pressure between more efficient operation is obtained with pressures in the range of

psigpsig

psig. Pressure surges can carry fluid from the humidifier into the cell and

psigpsig

impair cell operation. Filters, scrubbers, or pressure regulators are often necessary, depending on local conditions.

1.1.

Filters.Filters.

Filters. If filters are necessary, they should be conveniently

1.1.

Filters.Filters.

located near the analyzer, and installed in a fashion which permits easy removal for periodic cleaning or replacement.

2.2.

Scrubbers.Scrubbers.

Scrubbers. If the sample contains small quantities of acidic

2.2.

Scrubbers.Scrubbers.

anhydrides (SO2, etc.) or mercaptans (H2S, etc.) they will react with the electrolyte or the cathode, and for consistent operation should be removed. A caustic scrubber is usually effective.

3.3.

Pressure regulators.Pressure regulators.

Pressure regulators. While the analyzer will accept pressures to

3.3.

Pressure regulators.Pressure regulators.

100 psig, a range of pressure surges can affect instrument operation. In either case, the use of a pressure regulator is advisable. Install the regulator as close to the sample point as possible to reduce sample travel time to a minimium. The regulator should incorporate a metallic diaphragm to prevent the diffusion of atmospheric oxygen into the sample.

Sample ConditioningSample Conditioning

Sample Conditioning

Sample ConditioningSample Conditioning

5 to 10 psig5 to 10 psig

5 to 10 psig is recommended. In addition,

5 to 10 psig5 to 10 psig

1 and 100 psig1 and 100 psig

1 and 100 psig. However,

1 and 100 psig1 and 100 psig

5 to 105 to 10

5 to 10

5 to 105 to 10

1.2.21.2.2

1.2.2

1.2.21.2.2

The meter installed on the 306WA is either analog or digital. The recorder used for analyzer signal readout is usually of the self-balancing potentiometric type. It should have an input inpedance of for the 0 to 1 VDC (or optionally less than 0-1 VDC) signal output, and 4-20 mADC isolated ground (standard) for maximum load resistance of

1-2

Recorder /Meter ReadoutRecorder /Meter Readout

Recorder /Meter Readout

Recorder /Meter ReadoutRecorder /Meter Readout

20 20

ΚΩΚΩ

ΚΩ or higher

20 20

ΚΩΚΩ

TELEDYNE ELECTRONIC TECHNOLOGIES

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1.0 1.0

1.0

1.0 1.0

ΚΩ.ΚΩ.

ΚΩ.

ΚΩ.ΚΩ.

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The sensor is an open-cathode cell, an electrochemical transducer specific to oxygen. The cathode of the cell is composed of silver screen elements with a large surface area. The screen assembly is mounted in an acrylic block, with the lower edges of the screens immersed in potassium hydroxide electrolyte. A thin layer of electrolyte is maintained on the surfaces of the screens by capillary action. A lead disk is positioned under the screens and serves as the anode.

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Operational TheoryOperational Theory

Operational Theory

Operational TheoryOperational Theory

2.1 Sensor2.1 Sensor

2.1 Sensor

2.1 Sensor2.1 Sensor

Operational Theory 2.0Operational Theory 2.0

Operational Theory 2.0

Operational Theory 2.0Operational Theory 2.0

The sample gas stream is passed directly over the cathode screens, initiating an electrochemical reaction. Four electrons are generated by the oxidation of the lead anode, and are then used to reduce oxygen at the cathode. The flow of electrons between the anode and cathode creates an electric current which is directly proportional to the oxygen concentration in the sample stream. In the absence of oxygen, no oxidation or reduction takes place, and no current is produced.

In simplified form, the reaction may be described as follows: oxygen is reduced at the cathode by the mechanism

4e- +O2 + 2H2O → 4OH

This cathodic half-reaction occurs simultaneously with the anodic halfreaction

Pb + 2OH- → PbO + H2O + 2e

The overall reaction is

O2+ 2Pb → 2PbO

2.2 Humidifier2.2 Humidifier

2.2 Humidifier

2.2 Humidifier2.2 Humidifier

It is necessary to maintain a film of electrolyte on the screens of the electrode assembly. This means that the humidity of the sample as it flows through the cell must be such that the water vapor pressure of the electro-

TELEDYNE ELECTRONIC TECHNOLOGIES

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2-1

2.0 Operational Theory2.0 Operational Theory

2.0 Operational Theory

2.0 Operational Theory2.0 Operational Theory

lyte is equal to the water vapor pressure in the sample gas. If the humidity of the sample is too low, water will evaporate from the electrolyte, drying the cell. If the sample humidity is too high, water will condense out into the electrolyte, flooding the cell.

The sample is humidified by bubbling it through water in the humidifier column just before it enters the cell. The humidifier column is in the same heated compartment as the cell and so is held at the same temperature. The water in the column, however, is cooled by evaporation into the sample gas. Thus, the sample gas will normally have a humidity that is too low for equilibrium with the cell. It is assumed here, of course, that since the cell component is heated above ambient temperature, the sample gas is less than saturated at the compartment temperature when it enters the analyzer.

The humidity of the sample is increased to be in equilibrium with the cell electrolyte by heating the water in the humidifier column. The humidifer heater is in the base of the column, and the amount of heating is adjusted with the humidity control that is located on the panel of the control unit.

Model 306WModel 306W

Model 306W

Model 306WModel 306W

The amount of heating required depends on the sample flow rate, the sample humidity, and the specific heat of the sample. The correct adjustment for the operating conditions of any particular installation is obtained by checking the cell electrolyte level periodically as described in section 4.2.3.

The humidifier column also contains baffles to stop water from splashing up into the line to the sample cell at high flow rates.

2.3 Flow System2.3 Flow System

2.3 Flow System

2.3 Flow System2.3 Flow System

The analyzer flow system is shown schematically in Figure 1. It includes a needle valve for adjusting the sample flow rate, a flowmeter to indicate the sample flow required for calibration, the humidifier, the calibrator, the measuring cell, and an automatic level control system for the water in the humidifier.

As can be seen from Figure 1, the sample enters the humidifier column against the pressure of a water column from the base of the humidifier to the water level in the reservoir, which is approximately 4 inches. This determines the minimum sample pressure at which any sample can flow through the analyzer. In practice, the sample pressure must be somewhat greater than this in order to have an adequate flow rate.

The automatic level control in the humidifier column is accomplished by connecting the sample outflow from the cell to the bottom of the reservoir. The puts a back pressure on the sample in the cell and upper portion of

2-2

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Operational Theory 2.0Operational Theory 2.0

Operational Theory 2.0

Operational Theory 2.0Operational Theory 2.0

Figure 1: Flow System Schematic

TELEDYNE ELECTRONIC TECHNOLOGIES

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2-3

2.0 Operational Theory2.0 Operational Theory

2.0 Operational Theory

2.0 Operational Theory2.0 Operational Theory

the humidifier column equal to the water column from the bottom of the reservoir to the water level in the reservoir. Thus, the water level in the humidifier column is held even with the sample connection at the bottom of the reservoir. There will be a slight additional pressure in the top of the humidifier column depending on the flow rate (the pressure needed to push the sample through the cell and associated tubing), but at normal flow rates this merely slightly lowers the level in the humidifier column.

The sample bubbles through the water in the reservoir on its way to the outlet port. Some of the water vapor will re-condense, so that the sample flows out of the outlet port saturated at the reservoir temperature, which is slightly above ambient. The sample bubbling through the make-up water will scrub out any oxygen which may be dissolved in it. This assures that the sample will not pick up any oxygen as it passes through the humidifier column.

Model 306WModel 306W

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Model 306WModel 306W

2.4 Calibrator2.4 Calibrator

2.4 Calibrator

2.4 Calibrator2.4 Calibrator

The number of electrons flowing through the measuring cell’s load resistance (the output current) is directly proportional to the amount of oxygen that has reacted. If no oxygen is present, no output current flows, giving the analyzer an absolute zero. No zero adjustment is required. The analyzer can be completely calibrated with only one standard sample, instead of the two usually required for process analyzers.

If the oxygen content indicated by the analyzer is plotted as ordinate against the actual oxygen content as abscissa on a simple graph, the condition of proper calibration is represented by a straight line starting at the origin with a slope of 1 (see Figure 2). If the analyzer has a low sensitivity, the slope will be greater than 1. In each case, however, the line passes through the origin because of the absolute zero, and the slope is determined by the sensitivity adjustment. Thus, the analyzer can be completely calibrated by adjusting the slope of this curve; i.e., by adjusting the span so that the change in output indication is equal to a known change in actual oxygen content of the sample. This can be done by adding a known amount of oxygen to the sample flowing through the analyzer, even though the amount of oxygen in the sample is now known. Refer to section

4.7.1: Calibration4.7.1: Calibration

4.7.1: Calibration.

4.7.1: Calibration4.7.1: Calibration

The calibrator provided is an electrolysis cell in which water is converted to hydrogen and oxygen by an electric current.

The concentration of oxygen added to the sample can be calculated from the amount of current passing through the calibrator and the sample flow rate.

2-4

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Operational Theory 2.0Operational Theory 2.0

Operational Theory 2.0

Operational Theory 2.0Operational Theory 2.0

Figure 2: Proper Calibration

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2.0 Operational Theory2.0 Operational Theory

2.0 Operational Theory

2.0 Operational Theory2.0 Operational Theory

The three ranges of the analyzer are intended primarily to make calibration convenient. It is expected that the oxygen content of the sample being analyzed will be within the narrow range (Range No. 1) of the analyzer. Then when the analyzer is switched to Range No. 2, a sufficiently large amount of oxygen can be added by the calibrator to five a reliable calibration. Since the calibration is dependent on adjusting the change in indication, this change should be as large as possible—at least 50% of the wider range.

For example:

Analyzer range: 0-1, 0-100, 0-1000 Sample reading: 18 PPM Check calibration:

Adjust the analyzer calibration potentiometer so that 50 ppm of oxygen is being added to the sample. This is the change in actual oxygen content of the sample.

Model 306WModel 306W

Model 306W

Model 306WModel 306W

Assume that the analyzer changes its output to read 52.

The change in output indications is 52 - 18 = 34 when 50 PPM O2 is added. Therefore, the span potentiometer should be adjusted to give a reading of

(18 x 50) + 50 = 76.5 PPM

NOTE:NOTE:

NOTE:

NOTE:NOTE:

For details, see Appendix: Calibration Considerations.For details, see Appendix: Calibration Considerations.

For details, see Appendix: Calibration Considerations.

For details, see Appendix: Calibration Considerations.For details, see Appendix: Calibration Considerations.

2-6

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InstallationInstallation

Installation

InstallationInstallation

3.1 Location3.1 Location

3.1 Location

3.1 Location3.1 Location

Installation 3.0Installation 3.0

Installation 3.0

Installation 3.0Installation 3.0

With proper shielding of the leads, the analyzer and the readout device can be separated by as much as 1,000 feet. However, they should be placed as close together as possible. For the most convenient operation, the readout recorder or meter should be within view of the controls, particularly when the unit is being calibrated. Other location considerations:

1) The analyzer should be sheltered from the elements.

2) Ambient temperature must be within

30 to 120 °F.30 to 120 °F.

30 to 120 °F.

30 to 120 °F.30 to 120 °F.

3) The unit should not be subject to excessive shock or vibration.

4) It should be as close as possible to the sample point.

5) There must be access to the back and side of the unit for connection or maintenance of sample lines and power.

NOTE:NOTE:

NOTE:

NOTE:NOTE:

Since the level of the electrolyte in the measuring cell is critical andSince the level of the electrolyte in the measuring cell is critical and

Since the level of the electrolyte in the measuring cell is critical and

Since the level of the electrolyte in the measuring cell is critical andSince the level of the electrolyte in the measuring cell is critical and the water level control system for the humidifier is gravity sensitive,the water level control system for the humidifier is gravity sensitive,

the water level control system for the humidifier is gravity sensitive,

the water level control system for the humidifier is gravity sensitive,the water level control system for the humidifier is gravity sensitive, THE ANALYZER MUST BE MOUNTED SO THAT THE BOTTOM OFTHE ANALYZER MUST BE MOUNTED SO THAT THE BOTTOM OF

THE ANALYZER MUST BE MOUNTED SO THAT THE BOTTOM OF

THE ANALYZER MUST BE MOUNTED SO THAT THE BOTTOM OFTHE ANALYZER MUST BE MOUNTED SO THAT THE BOTTOM OF THE CASE IS LEVEL.THE CASE IS LEVEL.

THE CASE IS LEVEL.

THE CASE IS LEVEL.THE CASE IS LEVEL.

Figure 3 depicts a typical system layout.

3.2 Electrical Connections3.2 Electrical Connections

3.2 Electrical Connections

3.2 Electrical Connections3.2 Electrical Connections

A diagram of the necessary electrical connections is shown in Figure 4.

Note: Note:

Note:

Note: Note:

See the Interconnection Diagram (drawing A-21916) included in theSee the Interconnection Diagram (drawing A-21916) included in the

See the Interconnection Diagram (drawing A-21916) included in the

See the Interconnection Diagram (drawing A-21916) included in theSee the Interconnection Diagram (drawing A-21916) included in the back of this manual, as well as any Addenda that may be includedback of this manual, as well as any Addenda that may be included

back of this manual, as well as any Addenda that may be included

back of this manual, as well as any Addenda that may be includedback of this manual, as well as any Addenda that may be included with this manual for information specific to your instrument.with this manual for information specific to your instrument.

with this manual for information specific to your instrument.

with this manual for information specific to your instrument.with this manual for information specific to your instrument.

The connections include a terminal for grounding the analyzer case and chassis in accordance with accepted industrial practices. The maximum power requirement is less than

1½ amperes at 115 VAC1½ amperes at 115 VAC

1½ amperes at 115 VAC.

1½ amperes at 115 VAC1½ amperes at 115 VAC

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3.0 Installation3.0 Installation

3.0 Installation

3.0 Installation3.0 Installation

Model 306WModel 306W

Model 306W

Model 306WModel 306W

Figure 3: Typical System Layout

3.3 Sample Connections3.3 Sample Connections

3.3 Sample Connections

3.3 Sample Connections3.3 Sample Connections

The sample line is connected at the back of the analyzer case as depicted in Figure 5. Use care in assembling any part of the sampling system to avoid leaks. Oxygen can diffuse into the system through small leaks even when sample pressure is much greater than atmospheric pressure.

ConnectorsConnectors

Connectors. Use straight tube connectors where possible.

ConnectorsConnectors

This facilitates removal of the analyzer section from the case during maintenance or service.

LinesLines

Lines. Lines should consist of metallic tubing, since oxygen can

LinesLines

diffuse through plastic. Use continuous tubing where possible.

VentVent

Vent. The analyzed sample is vented through the back of the

VentVent

unit as shown in Figure 5.

The analyzer should have a vent line of ¼" diameter tubing at least two feet long, running air from diffusing into the reservoir and dissolving into the humidifier makeup water.

downwarddownward

downward from the vent connection. This is to prevent

downwarddownward

If it is not desirable to vent the sample into the atmosphere, a vent line to carry the sample to a suitable venting area will be required. The sample leaves the vent connection of the analyzer saturated with water vapor at a temperature somewhat above ambient, so a suitable trap to remove condensate without plugging the vent line will be required. The vent line should also be arranged so that it cannot become plugged by dirt or dust.

3-2

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