Novatech 1638 User Manual
Dew Point Analyser
Model 1638
August 2009
CONTENTS
SPECIFICATIONS .......................................................................................................................... 3
1
2 DESCRIPTION .............................................................................................................................. 13
3 INSTALLING & COMMISSIONING .......................................................................................... 19
4 OPERATOR FUNCTIONS ........................................................................................................... 33
5 SETTING UP THE TRANSMITTER ........................................................................................... 39
6 MAINTENANCE ........................................................................................................................... 57
APPENDICES
APPENDIX 1 PROBE OR SENSOR EMF TABLES ............................................................................. 62
APPENDIX 2 % OXYGEN SCALE TO LOGARITHMIC .................................................................... 65
APPENDIX 3 SAMPLE LOG PRINT OUT ........................................................................................... 66
APPENDIX 4 CIRCUIT SCHEMATICS ................................................................................................ 67
APPENDIX 5 MODBUS™ REGISTER MAP AND APPLICATION NOTES ..................................... 76
Note: This manual includes software modifications up to Version 8.11, May, 2006
© Copyright NOVATECH CONTROLS PTY. LTD. - 1996 - 2008
This manual is part of the product sold by Novatech Controls Pty. Ltd. ("Novatech Controls") and is provided to the
customer subject to Novatech Controls' conditions of sale, a copy of which is set out herein. Novatech Controls'
liability for the product including the contents of this manual is as set out in the conditions of sale.
All maintenance and service of the product should be carried out by Novatech Controls' authorised dealers.
This manual is intended only to assist the reader in the use of the products. This manual is provided in good faith but
Novatech Controls does not warrant or represent that the contents of this manual are correct or accurate. It is the
responsibility of the owner of the product to ensure users take care in familiarising themselves in the use, operation and
performance of the product.
The product, including this manual and products for use with it, are subject to continuous developments and
improvement by Novatech Controls. All information of a technical nature and particulars of the product and its use
(including the information in this manual) may be changed by Novatech Controls at any time without notice and
without incurring any obligation. A list of details of any amendments or revisions to this manual can be obtained upon
request from Novatech Controls. Novatech Controls welcome comments and suggestions relating to the product
including this manual.
Neither the whole nor any part of the information contained in, or the product described in, this manual may be adapted
or reproduced in any material form except with the prior written approval of Novatech Co ntrols Pty. Ltd.
All correspondence should be addressed to:
Technical Enquires
Novatech Controls Pty Ltd
309 Reserve Road
Cheltenham Victoria 3192 Phone: Melbourne +61 3 9585 2833
Australia Fax: Melbourne +61 3 9585 2844
Website:
http://www.novatech.com.au/
August 2009
1638 Dew Point Analyser 1
USING THIS MANUAL
The Novatech 1638 Oxygen Transmitter has a variety of user-selectable functions.
They are simple to use because each selection is menu driven. For options you are not sure about; read the manual on
that particular item.
Please read the safety information below and the ‘Installation’ section before connecting power to the analyser.
CAUTION 1
The probe or sensor heater is supplied with mains voltage. This supply has electrical shock danger to maintenance
personnel. Always isolate the analyser before working with the probe or sensor.
The EARTH wire (green) from a heated probe or sensor must ALWAYS be connected to earth.
CAUTION 2
Combustion or atmosphere control systems can be dangerous. Burners must be mechanically set up so that in the worst
case of equipment failure, the system cannot generate explosive atmospheres. This danger is normally avoided with
flue gas trim systems by adjustment so that in the case of failure the appliance will not generate CO in excess of 400
ppm in the flue. The CO level in the flue should be measured with a separate CO instrument, normally an infrared or
cell type.
CAUTION 3
The oxygen sensor which is heated to over 700°C (1300°F) and is a source of ignition. Since raw fuel leaks can occur
during burner shutdown, the analyser has an interlocking relay that removes power from the probe or sensor heater
when the main fuel shut-off valve power is off. If this configuration does not suit or if it is possible for raw fuel to
come into contact with a hot oxygen probe or sensor then the Model 1638 analyser with a heated probe or sensor will
not be safe in your application.
An unheated probe can be utilised in such applications, however the oxygen readings are valid only above 650°C
(1200°F).
August 2009
2 1638 Dew Point Analyser
1
SPECIFICATIONS
Section
Number
MODEL 1638 OXYGEN & DEW POINT ANALYSER ................................................................. 4
1.1
1.2 SERIES 1230 OXYGEN PROBES & SENSORS ............................................................................ 7
1.3 PURGE & CALIBRATION CHECK ACCESSORIES .................................................................. 11
1.4 FILTER PURGE PRESSURE SWITCH ........................................................................................ 11
August 2009
1638 Dew Point Analyser 3
1.1 MODEL 1638 OXYGEN & DEW POINT ANALYSER
A
p
r
A
DESCRIPTION
The Novatech model 1638 oxygen analyser / transmitter provides in-situ measurement for one or two oxygen probes in
annealing and other furnaces with protective atmospheres of hydrogen / nitrogen. The analyser provides local
indication of oxygen and dew point plus sixteen other selectable variables.
One or two oxygen sensing probes in one process can be controlled from one analyser to providing an average and/or
individual probe signals. Two linearised and isolated 4 to 20 mA output signals are provided for oxygen and for dew
point. Alarms are displayed at the analyser and relay contacts activate remote alarm devices. The analyser, which is
available for heated or unheated zirconia oxygen probes, provides automatic on-line gas calibration check of the probe
and filter purging. The electronics self-calibrates all inputs every minute.
The 1638 has a keyboard for selecting the output range, thermocouple type, etc., as well as maintenance and
commissioning functions. The instrument is microprocessor based and all adjustments are made using the keyboard.
• Used for product quality control to avoid blueing or browning of steel products during the annealing process
• Used for monitoring hydrogen / nitrogen protective atmospheres in applications such as lead holding furnaces
• Automatic selection of second probe on probe failure
• Simple to install
• Linear output of % oxygen and dew point for recording or control
• Built in safety features
• 24 different alarm conditions that warn the operator of oxygen, dew point, probe or analyser problems
• Isolated RS 232-C printer/computer interface and an RS 485 MODBUS network interface
• Safety interlock relay for heated oxygen probes
Zirconia Oxygen Probe
Flowmeter
Reference Ai
Cable
Calibratio
Checking
1638
Oxygen
nalyser
Com
uter and/or Printer
(Optional)
Recorder/
controller
larms
Oxygen Probe and Analyser System
August 2009
4 1638 Dew Point Analyser
SPECIFICATIONS
Inputs
• Zirconia oxygen probe, heated or unheated
• Furnace thermocouple, field selectable as type K or R
• Process purge complete / main flame established safety interlock (for heated probes)
• Purge pressure switch
• Remote alarm accept
Outputs
• Two linearised 4 to 20 mA DC outputs, max. load 1000Ω
• Common alarm relay
• Three other alarm relays with selectable functions
Computer
• RS 232-C or RS 485 for connection of a computer terminal or printer for diagnostics of the analyser, sensing
probe, or process. This connection is suitable for network connection to computers, DCSs or PLCs using
MODBUS protocol.
Range of Output 1
Field selectable from the following:
Output Zero Range Span Range
Dew point -60°C to +20°C -40°C to +40°C
-76°F to +84°F -56°F to +104°F
Linear oxygen 0 to 99 % 1 to 100 %
Oxygen, reducing range 1.0
If 2 probes are used -
Linear oxygen, probe 1 0 to 99 % 1 to 100 %
Reducing oxygen output probe 1 1.0
Dew point, probe 1 -60°C to +20°C -40°C to +40°C
-76°F to +84°F -56°F to +104°F
Linear O
Reducing O
, probe 1 & 2 averaged 0 to 99 % 1 to 100 %
2
, probe 1 & 2 averaged 1.0
2
Dew point, probe 1 & 2 averaged -60°C to +20°C -40°C to +40°C
-76°F to +84°F -56°F to +104°F
Note:
The average dew point, linear O
and Reducing O2 selections will automatically select to the operating probe if one
2
probe fails, or selects probe 1 if both probes fail.
Range of Output 2
Field selectable from the following:
Output Zero Range Span Range
Linear O
0 to 99 % 1 to 100 %
2
Oxygen, reducing range 1.0
Dew point -60°C to +20°C -40°C to +40°C
-76°F to +68°F -40°F to +104°F
Sensor EMF 0 to 1200 mV in 100 mV steps 100 to 1300 mV in 100 mV steps
Aux Temperature 0 to 1300°C in 100°C steps 100 to 1400°C in 100°C steps
If 2 probes are used -
Linear O
, probe 2 0 to 99 % 1 to 100 %
2
Oxygen, reducing range, probe 2 1.0
Dew point, probe 2 -60°C to +20°C -40°C to +40°C
-76°F to +68°F -40°F to +104°F
Probe EMF 1 0 to 1200 mV in 100 mV steps 100 to 1300 mV in 100 mV steps
Probe EMF 2 0 to 1200 mV in 100 mV steps 100 to 1300 mV in 100 mV steps
-16
% oxygen 1.0
-16
% oxygen 1.0
-16
% oxygen 1.0
-16
% oxygen 1.0
-16
% oxygen 1.0
-30
% oxygen
-30
% oxygen
-30
% oxygen
-30
% oxygen
-30
% oxygen
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1638 Dew Point Analyser 5
Range of Indication, Upper Line
• Oxygen auto ranging from 10
-30
to 100 %
• Dew point -60 °C to +40 °C, -76 °F to +104 °F
Indication Choice, Lower Line
Any or all of the following can be selected for lower line display:
• Dew point probe 1
• Dew point probe 2 **
• Dew point probe 1 and 2 averaged **
• Date - time
• Run Hours since last service
• Date of last service
• Oxygen probe 2 **
• Oxygen probe 1 and 2 averaged **
• Probe EMF 1
• Probe EMF 2 **
• Temperature probe 1
• Auxiliary Temperature *
• Temperature probe 2 **
• Impedance probe 1
• Impedance probe 2 **
• Ambient Temperature
• Ambient Relative Humidity
* If the analyser is enabled for 1 probe
** If the analyser is enabled for 2 probes
Accuracy
• ±1% of actual measured oxygen value with a repeatability of ±0.5% of measured value.
Relay Contacts
• 0.5A 24 VAC, 1A 36 VDC
Environmental Rating
• Operating Temperature: -25 to 55°C
• Relative Humidity: 5 to 95% (non-condensing)
• Vibration: 10 to 150Hz (2g peak)
Power Requirements
• 240 or 110V, 50/60 Hz, 105 VA (heated probe)
• 240 or 110V, 50/60 Hz, 5 VA (unheated probe)
Weight
• Analyser, 3.75 kg
Degree of Protection
• IP65 without reference air pump
• IP54 with reference air pump
Mounting
• Suitable for wall or surface mounting.
August 2009
6 1638 Dew Point Analyser
1.2 SERIES 1230 OXYGEN PROBES & SENSORS
DESCRIPTION
Novatech series 1230 oxygen probes and sensors employ state-of-the-art zirconia sensors and advanced materials,
which provide the following benefits:
• Improved control due to fast response time to typically less than four seconds
• Cost-efficient design provides improved reliability
• Longer-life probes with greater resistance to corrosion from sulphur and zinc contaminants in flue gas
• Low cost allows maintenance by replacement
• Reduced probe breakage due to greater resistance to thermal shock and mechanical damage during installation and
start-up
• Series 1230 probes are simple to install and maintain. All models provide direct measurement of oxygen level.
On-line automatic calibration check is available if required. Probes may be used with Novatech combustion
controllers and some analyser models from other manufacturers.
All Novatech oxygen probes are designed and manufactured to exacting standards of performance and reliability.
Series 1230 probes are the result of extensive research and development by Novatech, industry and government
agencies. Novatech Controls provides application and after sales support for oxygen probes, sensors and analysers,
worldwide.
Model 1231 Heated Oxygen Probe
Model 1232 Unheated Oxygen Probe
August 2009
1638 Dew Point Analyser 7
1234OXYGEN
SENSOR
GAS INLET 1/4" TUBE ELBOW
NOVATECH
CONTROLS
EXHAUST
ID LABEL
CABL E GLAND
EXHAUST 1/4" NPT FEM ALE
Model 1234 Oxygen Sensor
STANDARD PROBE ‘U’ LENGTHS
1231 1232
250 mm (10”) 500 mm (20”)
350 mm (14”) 750 mm (30”)
500 mm (20”) 1000 mm (40”)
750 mm (30”) 1500 mm (60”)
1000 mm (40”)
1500 mm (60”)
2000 mm (80”)
Ordering Information
1. Probe insertion length (from process end of mounting thread to probe sensing tip).
2. Mounting thread (process connection), BSP or NPT (for size of thread refer to specifications).
3. Lagging extension length, if required.
4. If model 1232 probe, state preferred thermocouple type (refer to specifications).
August 2009
8 1638 Dew Point Analyser
OXYGEN PROBE SPECIFICATIONS
MODEL 1231 1232
Application Furnaces operating Furnaces operating
below 900°C above 700°C with
refer to note 1 no contaminants.
Temperature Range 0 to 900°C 700 to 1400°C
(0 to 500°C with filter fitted)
Length 250 to 2000 mm 500 to 1000 mm
Process 1 1/2" BSP 3/4" BSP
Connection or NPT or NT
Electrical Weather-proof plug-in connector or optional screw terminals. The plug connector is
Connection supplied with the cable. Ex(e) heads have screw terminals.
Cable Order a specific length with the analyser except for hazardous installations where the
cable is supplied by the customer.
Heater Yes No
Furnace Thermocouple Refer to note 3 R or S, integral
Response Time Typically < 4 secs. Typically < 1 sec
Head Temperature -25 to 100°C with weatherproof connector
-25 to 150°C with screw terminals
Reference Gas Ambient air 50 cc/min approx. Pump supplied with analyser
Ref Air Connection 1/4" Tube Integral air line in probe cable or external ¼” tube.
Optional Filter Sintered titanium alloy
particulate filter, replaceable,
30 or 15 micron.
Calibration Check Gas 1/8" NPT female 1/8" NPT female
Connection
Weight 2 kg plus 165 g / 100 mm 1 kg plus 100 g / 100 mm
Notes:
1. Care must be taken to avoid contact with explosive or inflammable gases with 1231 heated probes. Novatech
analysers have built in safety protection.
2. Please contact factory for corrosives other than sulphur or zinc. We can provide test materials to try in your
atmosphere.
August 2009
1638 Dew Point Analyser 9
OXYGEN PROBE MODEL SELECTION GUIDE
Heated probes-temperature range 0-900°C.
1231 - U Length - Outer - Internal - Mounting
Sheath Thermocouple Thread
Basic model 2. 250mm 1.316 SS max 850°C 1. Type K max 900°C 1. BSP
3. 500mm 2. Inconel *(1) 2. NPT
4. 750mm
5. 1000mm
6. 1500mm
7. 2000mm
*Note:
1. The Inconel option has all inconel wetted parts except for the ceramic sensor and viton ‘O’ rings.
Unheated probes for clean gases-temperature range 700-1400°C.
1232 - U Length - Outer Sheath - Internal Thermocouple - Mounting Thread
Basic model 3. 500mm 1. 253 MA-max 1200°C 1. Nil *(2) 1. 3/4” BSP fixed
4. 750mm 4. Type R max 1400°C 2. 3/4” NPT fixed
5. 1000mm
6. 1500mm
3. High Purity Alumina
max 1300°C Horizontal
max 1400°C Vertical
4. 446 SS max 1000°C
*Note:
1. For applications up to 1200°C it may be more economical to use a separate type “K” or “N” thermocouple than the
internal “R” thermocouple. It is important that a separate thermocouple senses the same temperatures as the oxygen
probe tip.
August 2009
10 1638 Dew Point Analyser
1.3 PURGE & CALIBRATION CHECK ACCESSORIES
Due to the absolute measurement characteristics of zirconia sensors and the self calibration features of Novatech
analysers, probe calibration checks with calibrated gas are not normally required. In some installations however
customers prefer the have a calibration check facility.
Novatech probes and analysers provide a ready method of connecting on-line calibration check gases. They provide
on-line automatic checking of probe and analyser calibration, as well as a probe purge facility.
The absolute characteristics of zirconia sensors require only one calibration check gas to properly check the probe’s
performance. Where required however, the dual gas calibration check facility can be utilised .
Dirty furnace applications often require the back purge facility to keep a probe filter free from blockage. (In these
applications, it is more reliable to install probes pointing vertically dow nwards with no filter). Purge and calibration
check solenoid valves can be operated manually or automatically from a 1638 analyser.
The external components required for automatic / manual gas calibration checking are:
• A calibration check gas flow meter/regulator
• A mains voltage (240 or 110 VAC) solenoid valve for each calibration check gas
The external components required for automatic / manual purging are:
• A mains voltage (240 or 110 VAC) purge solenoid valve
• A purge pressure switch, 0 to 35 kPa (0 to 5 psi), to test for filter blockage.
The user should supply:
• Span gas cylinder(s), typically 2 % oxygen in nitrogen or a similar percentage of 0
gas stream being measured, to ensure fast recovery.
• A 100 kPa (15 psi) clean and dry nitrogen supply when filter purging is required.
close to the normal level in the
2
1.4 FILTER PURGE PRESSURE SWITCH
To automatically sense a blocked probe filter, a pressure sensor should be connected to the ‘purge’ line to the probe
‘cal’ port. It should be adjusted so that it energises just above the purge pressure with a new or clean filter installed.
The switch contacts should be connected to terminals 12 & 13 (PURGE FL SWITCH). If the filter is still blocked or
partly blocked after an auto purge cycle, the pressure switch will energise and cause a ‘Probe Filter Block ed’ alarm.
The contacts must be normally closed.
The pressure switch should have an adjustable range of 0 to 35 kPa (0 to 5 psi).
August 2009
1638 Dew Point Analyser 11
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12 1638 Dew Point Analyser
2
DESCRIPTION
Section
Number
THE ANNEALING PROCESS (OR OTHER SIMILAR APPLICATIONS) ................................ 14
2.1
2.2 THE OBJECTIVE OF ATMOSPHERE MONITORING............................................................... 14
2.3 WHAT DO WE NEED TO MEASURE? ....................................................................................... 14
2.4 ZIRCONIA OXYGEN PROBE MEASUREMENT ....................................................................... 14
2.5 OTHER TYPES OF OXYGEN MEASUREMENT ....................................................................... 14
2.6 DEW POINT MEASUREMENT .................................................................................................... 14
2.7 IN-SITU OXYGEN PROBES ........................................................................................................ 14
2.8 THE ZIRCONIA SENSOR ............................................................................................................. 15
2.9 THE ANALYSER ........................................................................................................................... 16
2.10 ALARMS ........................................................................................................................................ 16
2.11 HEATER ......................................................................................................................................... 16
2.12 APPLICATIONS WHERE SENSING POINT IS NOT AT ATMOSPHERIC PRESSURE ......... 16
2.13 PROBE IMPEDANCE .................................................................................................................... 16
2.14 AUTO CALIBRATION – ELECTRONICS ................................................................................... 16
2.15 AUTO CALIBRATION CHECKING – PROBES ......................................................................... 17
2.16 AUTO PURGE ................................................................................................................................ 17
2.17 RS 485 AND RS 232C PORT ......................................................................................................... 17
2.18 AUXILIARY TEMPERATURE THERMOCOUPLE ................................................................... 17
2.19 WATCHDOG TIMER .................................................................................................................... 17
2.20 BACK-UP BATTERY .................................................................................................................... 17
August 2009
1638 Dew Point Analyser 13
DESCRIPTION
2.1 THE ANNEALING PROCESS (OR OTHER SIMILAR APPLICATIONS)
The annealing process is carried out in an atmosphere of hydrogen and nitrogen to protect the surface of the steel from
oxidising and discolouring during the annealing process. There is usually some air leakage in a furnace and the
hydrogen serves to “mop up” the oxygen by combining with it to form water vapour.
2.2 THE OBJECTIVE OF ATMOSPHERE MONITORING
The primary objective of monitoring the furnace atmosphere is to be able to measure whether the steel product in the
furnace will become oxidised during the process and to raise an alarm to warn the operator that there is a problem.
2.3 WHAT DO WE NEED TO MEASURE?
The variable that we need to measure to monitor the atmosphere to prevent oxidation of the product is the oxygen
partial pressure at the surface of the steel. At any particular furnace temperature, there is a unique oxygen partial
pressure, above which the steel will tend to oxidise and below which no oxidation will occur. The steel acts as a
catalyst in the hydrogen / nitrogen bringing the gas at the surface close to chemical equilibrium. The composition of
the gas at the surface is normally different from that of the gas nearby. For example, trace oxygen is quickly converted
to water vapour.
In the gas, a reaction to form water vapour requires collisions involving two hydrogen molecules and one oxygen
molecule, the probability of which is low. On the surface of the steel, one or the other of the molecules becomes partly
immobilised. This increases the probability of successful collisions to form water vapour. Essentially, gas molecules
are held on the steel surface, waiting for the complementary molecule(s) to arrive.
2.4 ZIRCONIA OXYGEN PROBE MEASUREMENT
The catalytic process which occurs on the surface of the steel also occurs on a zirconia oxygen sensor. This means that
the measurement of the oxygen level with a zirconia oxygen sensor exactly duplicates the equilibrium conditions of the
gas at the surface of the steel. It measures the oxidation potential of the gas or its potential to damage or discolour the
steel.
2.5 OTHER TYPES OF OXYGEN MEASUREMENT
Other types of oxygen analysers such as a paramagnetic analyser measure the unreacted molecular level of oxygen in
the furnace atmosphere, which has no direct thermodynamic relationship with the effect of the gas on the steel. These
analysers are not useful for measuring the oxidation potential in annealing furnace atmospheres.
2.6 DEW POINT MEASUREMENT
Dew point measurement was commonly used in the past because dew point analysers were the only technology
available at the time. Dew point can be related to the oxidation potential of the furnace atmosphere but the relationship
depends on how much hydrogen is available at the surface of the steel. With dew point held constant, if the hydrogen
level varies, so will the oxidation potential of the atmosphere. Dew point measurement is not the best method of
measurement because of this. Also dew point instruments normally have limited reliability in on-line applications on
annealing furnaces.
With a known hydrogen level, the dew point in the furnace can be calculated. This is provided as an output on a
standard Novatech 1638 analyser but we recommend the use of the oxygen output from the same analyser. Both
outputs are available simultaneously for operators who are more used to furnace dew point levels. The dew point
output however is only an approximate guide if the hydrogen level in the furnace varies.
2.7 IN-SITU OXYGEN PROBES
There are very few oxygen probes on the market, which can operate reliably in an annealing furnace atmosphere at
furnace temperatures. Novatech probes have been developed in co-operation with BHP steel for annealing furnace
applications to provide a reliable measurement for monitoring both continuous and batch furnaces. BHP now have 60
Novatech probes and analysers installed to protect their products during the annealing process. These sensing probes
give long life with no need for calibration. The most important feature however is that Novatech oxygen probes
measure the oxygen partial pressure just as it occurs at the surface of the steel.
August 2009
14 1638 Dew Point Analyser
2.8 THE ZIRCONIA SENSOR
(
The analyser input is provided from a solid electrolyte oxygen probe, which contains a zirconia element and
thermocouple. The probe is designed to be inserted into a furnace. Sampling lines and filters are not required for insitu probes. When a sampling line is required, the sample flows to the sensor under process pressure in most
applications. In applications where the process pressure is negative or neutral, a su ction pump will be required. A
reference air pump is provided in the 1638 oxygen analyser. The internal construction of a probe is shown as follows.
Thermocouple
Wires
External Wire
Contact
Internal electrode wire
Four-Bore Thermocouple
Insulating Tubing
Alumina Tube
Heater
(required only
with heated
probes)
Electrode Material
Ziconia Disc
Thermocouple
Junction
Internal Electrode
Schematic View of a Sensor Assembly
The heater control in the 1638 analysers consists of a time proportioning temperature controller and solid state relay so
that the thermocouple junction is controlled to 720°C. Probes operating in a combustion environment above 650°C do
not require a heater. When exposed to different oxygen partial pressures at the outside and inside of the sensor, an
EMF (E) is developed which obeys the Nernst equation:
log
⎛
⎜
e
⎜
⎝
RT
millivoltsE
)(
=
4
F
)
insidePO
2
()
outsidePO
2
Where T is the temperature (K) at the disc (>650°C), R is the gas constant, F is the Faraday constant and (PO
and (PO
) OUTSIDE are the oxygen partial pressures at the inner and outer electrodes, respectively, with the higher
2
⎞
⎟
⎟
⎠
) INSIDE
2
oxygen partial pressure electrode being positive.
If dry air at atmospheric pressure, (21 % oxygen) is used as a reference gas at the inner electrode, the following
equations are obtained:
2
−
×=
log10154.2)(
TmillivotsE
e
()
21.0
outsidePO
2
Transposing this equation
() ( )
2
ATMoutsideO
=
−
exp21.0%
ER
421.46
T
The 1638 transmitter solves this equation which is valid above 650°C. The probe heater, or the process maintains the
sensor temperature at this level.
August 2009
1638 Dew Point Analyser 15
2.9 THE ANALYSER
The 1638 analyser is a transmitter with two 4 to 20 mA outputs. One output is % oxygen or dew point with selectable
zero and span. The second output can be selected as dew point, oxygen, auxiliary temperature or sensor EMF. Four
alarm relays are provided. Refer to the sections 4.2 and 4.3 for more details.
The 1638 analyser is designed to operate with either one or two heated or unheated, zirconia probes in one process. If
two probes are being used, the analyser can average the two oxygen and dew point signals, alarm when there is a high
difference, transmit and display the average and/or individual oxygen signals.
If heated probes are being used, the analyser will maintain the temperature of the sensor(s) at 720°C. The analyser
solves the Nernst equation and will provide accurate oxygen measurements up to 1500°C (2730°F), although most
probes are suitable only to 1400°C (2250°F). 1231 heated probes are limited to 900°C (1650°F).
2.10 ALARMS
Refer to OPERATOR FUNCTIONS Section 4 for details on alarm functions.
2.11 HEATER
CAUTION
The probe heater is supplied with mains voltage. This supply has electrical shock danger to maintenance personnel.
Always isolate the analyser before working with the probe.
The EARTH wire (green) from the probe / sensor must always be connected to earth.
The heater is supplied from the mains power directly, and the temperature is controlled initially at over 700°C (1300°F)
after turn on.
2.12 APPLICATIONS WHERE SENSING POINT IS NOT AT ATMOSPHERIC
PRESSURE
To apply the 1638 analyser to processes, when the pressure at the point of measurement is significantly above or below
atmospheric pressure, then compensation must be applied. (Refer to Set-up Steps 34 and 35 in Section 5.5). If two
sensors are being used, they must be close to the same pressure.
2.13 PROBE IMPEDANCE
The probe impedance is a basic measurement of the reliability of the oxygen reading. A probe with a high impedance
reading will eventually produce erroneous signals. The analyser regularly checks the probe impedance and if the
impedance is above the maximum level for a specific temperature then the impedance alarm will be activated. Typical
probe impedance is 1 KΩ to 8 KΩ at 720° C.
2.14 AUTO CALIBRATION – ELECTRONICS
The analyser input section is self calibrating. There are no adjustments. The analog to digital converter input stages are
checked against a precision reference source and calibrated once every minute. Should the input electronics drift
slightly then the drift will be automatically compensated for within the microprocessor. If a large error occurs due to an
electronic fault then an ‘ADC CAL FAIL’ alarm will occur.
A one-off calibration procedure of the precision reference sources should never need to be repeated for the instrument
life unless the instrument has been repaired. For a description of the calibration procedure, refer to ‘Setting Up The
Analyser’ Section 5.5, items 7, 8 9 and 10.
The digital to analog converters or output section of the analyser are tested for accuracy every minute and if they are
found to have an error then a ‘ADC CAL FAIL’ alarm will occur. The D/A sections are re-calibrated by pressing the
‘AUTO CAL’ button on the keyboard while in 'SET-UP' mode.
All output signals will drop to 0 mA for a one second period. It is suggested that a D/A re-calibration be performed
after the instrument has stabilised, approximately 30 minutes after first switching on and after Setting Up The Analyser
Section 5.5, items 6, 7, 8 and 9 have been completed, and then annually.
August 2009
16 1638 Dew Point Analyser
2.15 AUTO CALIBRATION CHECKING – PROBES
On-line automatic gas calibration check is not normally required. Where it is required however, the probe can be
checked for accuracy in-situ and on-line. Solenoid valves can admit up to two calibrated gas mixtures into the probe
via solenoid valves under microprocessor control on a timed basis. For details on installation refer Section 3.11. For
details on setting up this facility refer to Set-up steps 41 to 53 in Section 5.5.
During probe auto calibration checking, the analyser output will freeze and remain frozen for a further adjustable
period, allowing the probe time to recover and continue reading the furnace oxygen level.
Calibration check gases may be manually admitted by pressing the ‘CAL’ buttons on the keyboard while in ‘RUN’
mode. The analyser output is frozen during the pressing of these buttons and immediately becomes active when the
button is released. If calibration gas checking is enabled in the Set-up menu for either gas, an automatic gas cycle can
be started by pressing the ‘CAL’ buttons in RUN mode. The cycle can be terminated by pressing any other button.
2.16 AUTO PURGE
In steel annealing applications it is expected that the furnace will be gas fired. However, in oil and coal fired plant, it is
possible for the probe sensing filter to become blocked. An automatic purge cycle can be set up so that a blast of air or
nitrogen, maximum 100 kPa., will automatically back-flush the probe filter on a timed basis. Refer to Set-up steps 36
to 40 in Section 5.5. A purge pressure switch will sense if there is insufficien t flow to clear the filter during the purge
cycle. In this case a ‘PROBE FILTER’ alarm will occur. The probe can be manually purged from the keyboard while
in ‘RUN’ mode. The analyser output is not frozen during or after the pressing of this button.
Automatic or manual purge is not available if two probes are being used. However, one of the gas check output could
be used to purge the filter.
2.17 RS 485 AND RS 232C PORT
The serial port is for connecting a printer, a data logger, or any computer with an RS485 MODBUS or 232-C port. It
can be used to monitor the transmitter and process by logging the values of functions selected in step 70 of the Set-up
menu in Section 5.5. The log period may be selected in step 71, and the baud rate may be set in set-up step 72.
Alarms, including the time they occurred, will be transmitted to the printer and computer whenever they are first
initiated, accepted and cleared. The protocol for the serial port is eight data bits, one stop bit, no parity. Please contact
the factory for further details on serial communications with external systems such as computers, DCS’s or PLC’s.
The MODBUS address is set in step 81 of the set-up menu.
2.18 AUXILIARY TEMPERATURE THERMOCOUPLE
A furnace thermocouple should also be connected when an additional temperature display or transmitted signal is
required. This input is not available if two probes are being used.
2.19 WATCHDOG TIMER
The watchdog timer is started if the microprocessor fails to pulse it within any one second period, (ie. fails to run its
normal program). The microprocessor will then be reset up to three times until normal operation is resumed. Reset
cycles are displayed by the POWER light on the keyboard. A steady ‘ON’ light indicates normal operation. If the
program has not resumed normal operation after three attempts to reset, the common alarm relay will be activated. The
reset function will continue repeatedly after the alarm. If a successful reset is achieved, the alarm will be cancelled and
the analyser will continue to run normally.
2.20 BACK-UP BATTERY
The transmitter’s RAM and real-time clock are backed up by a lithium battery in the event of power failure. All set-up
variables are saved and the clock is kept running for approximately ten years with the power off. The battery module
should be replaced every 8 years. (It is the battery shaped device clipped in a socket labelled M1 on the 1630-1 PCB)
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1638 Dew Point Analyser 17
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18 1638 Dew Point Analyser
3
INSTALLING & COMMISSIONING
Section
Number
MOUNTING THE ANALYSER .................................................................................................... 20
3.1
3.2 INSTALLING A 1231 OXYGEN PROBE ..................................................................................... 20
3.3 INSTALLING THE AUXILIARY THERMOCOUPLE ................................................................ 21
3.4 SHIELD CONNECTIONS ............................................................................................................. 21
3.5 ELECTRICAL CONNECTIONS ................................................................................................... 22
3.6 HEATER INTERLOCK RELAYS ................................................................................................. 24
3.7 CONNECTING AN OXYGEN PROBE CABLE .......................................................................... 24
3.8 CONNECTING THE AUXILIARY THERMOCOUPLE (OPTIONAL) ...................................... 26
3.9 CONNECTING THE OUTPUT CHANNELS ............................................................................... 26
3.10 CONNECTING THE ALARMS ..................................................................................................... 26
3.11 CONNECTING THE AUTOMATIC PURGE AND CALIBRATION CHECK SYSTEM .......... 27
3.12 CONNECTING REFERENCE AIR ............................................................................................... 27
3.13 CONNECTING THE DUAL FUEL INPUT .................................................................................. 28
3.14 CONNECTING THE PRINTER ..................................................................................................... 28
3.15 CONNECTING THE ANALYSER TO A MODBUS™ NETWORK ........................................... 29
CONNECTING POWER ................................................................................................................ 30
3.16
3.17 COMMISSIONING – SET-UP MODE .......................................................................................... 30
3.18 COMMISSIONING – RUN MODE ............................................................................................... 30
3.19 BURNER BYPASS SWITCH ........................................................................................................ 30
3.20 CHECKING THE ALARMS .......................................................................................................... 30
3.21 PROBE CALIBRATION ................................................................................................................ 30
3.22 FILTER PURGING ......................................................................................................................... 31
3.23 CALIBRATION GAS CHECK ...................................................................................................... 31
3.24 DUST IN THE FURNACE ............................................................................................................. 31
INSTALLATION
COMMISSIONING
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1638 Dew Point Analyser 19
INSTALLATION
3.1 MOUNTING THE ANALYSER
Surface mount the transmitter case on to a flat surface or bracket, using the four mounting brackets provided.
40mm
1.6"
11"
280mm
Gland Plate
200mm
8"
180mm
7"
REAR VI EW
6"
150mm
Horizontal Mounting Brackets
12.8"
REAR VIEW
Vertical Mounting Brackets
9.8"
250mm325mm
9"
225mm
Case Mounting Dimensions
3.2 INSTALLING A 1231 OXYGEN PROBE
Weld a BSP or NPT socket to the furnace in a suitable position for sensing the furnace atmosphere. For the correct size
of socket refer to probe data in Section 1. The oxygen probe is normally installed pointing vertially upwards in
removable cover, coil annealing furnace. Probes can be mounted at any angle. If there are any particulates in the
furnace, the filter can be omitted by pointing the probe vertically downwards. Otherwise the filters may have to be
replaced periodically.
If installing a probe into a hot environment, slide the pro be in slowly to avoid thermal shock to the internal ceramic
parts. If the furnace is 1000°C, it should take approximately ten minutes to install a 500 mm. probe, moving it in about
20 mm steps.
CAUTION
The oxygen probe should protrude into the furnace at least 25 mm. If the furnace has high velocity fan circulation a
filter should be used on 1231 oxygen probes or, in extreme cases, a flow diverting vane. Without a filter or vane the
fan velocity can cool the 1231 heater.
Although it is rare, occasionally a probe may sense oxygen vastly differently from the average reading in the furnace.
If it occurs, then the probe should be moved, or a longer probe installed. This phenomena is normally caused by
stratification of the furnace atmosphere.
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20 1638 Dew Point Analyser
3.3 INSTALLING THE AUXILIARY THERMOCOUPLE
Weld a 1/2 inch BSP mounting socket to the furnace within about 300 mm, and upstream of the oxygen probe. The
thermocouple should be of similar length to the oxygen probe to prevent furnace temperature distribution errors.
3.4 SHIELD CONNECTIONS
All external wiring to the 1638 analyser should be shielded. Do not connect shields at the field end. Simply clip off
and insulate. An extra terminal strip may be required to connect all shields together. This should be supplied by the
installer.
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1638 Dew Point Analyser 21
3.5 ELECTRICAL CONNECTIONS
All wiring should comply with local electrical codes. The printed circuit boards are fully floating above earth. All
earth and shield connections should be connected to the earth stud on the LHS inside the case. Before connection of
mains power check that the 115 / 230 volt power selector switch is set to the correct voltage.
Burner safety
or if safety
not required
terminals 18 &
4- 20mA Out put s
Selectable
ran g e s
Op t i o na l Alarm
Re l a y Co nt a c t s
Normally Closed
Ora nge
Brown
Black
Blue
Black
Blue
Ora nge
Brown
1
Probe +
2
Probe -
3
Probe TC+
4
Probe TC-
5
Probe TC2 / Aux+
6
Probe TC2 / Aux-
7
+12V
8
RGCI/ P+
RGCI/ P-
9
Sen s # 2 +
10
Sen s # 2 -
11
Purge Flow
12
Purge Flow
13
Fuel 1 / 2
14
Fuel 1 / 2
15
Re mot e Ala rm
16
Re mot e Ala rm
17
18
Bur n e r On I n pu t
19
Bur n e r On I n pu t
20
RS- 2 3 2 Rx
21 RS- 232 Tx
22 Network -
Net wor k +
23
Ser i a l Common
24
Ou t p u t 1 +
25
26 Output 127 Output 2+
28 Output 229 Common Alarm
30 Common Alarm
31 Alarm 2
32 Alarm 2
33 Alarm 3
34 Alarm 3
35 Alarm 4
36 Alarm 4
41
Pur ge Sol
42
Pur ge Sol
43 Cal 1 Sol
44 Cal 1 Sol
45 Cal 2 Sol
46 Cal 2 Sol
Ma i n s Po we r
240/ 115VAC
SENSOR # 2
White
White
White
White
SENSOR # 1
47 Mains E
48
49 Mains N
50 Mains A
51 Heater #1
52 Heater #1
53 Heater #2
54 Heater #2
Connection Diagram for 1638 Analyser and one or two 1231 Heated Sensors
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22 1638 Dew Point Analyser
All wiring should comply with local electrical codes. The printed circuit boards are fully floating above earth. All
earth and shield connections should be connected to the earth stud on the LHS inside the case. Before connection of
mains power check that the 115 / 230 volt power selector switch is set to the correct voltage.
Burner safety lock
or if safety interlock
not required, link
terminals 18 & 19
4- 20mA Out puts
Selectable
ran g e s
Op t i o na l Alarm
Re l a y Co nt a c t s
Normally Closed
Ora nge
Black
Red
Red
Ora nge
Black
1
Probe +
2
Probe -
3
Probe TC+
4
Probe TC-
5
Probe TC2 / Aux+
6
Probe TC2 / Aux-
7
+12V
8
RGCI/ P+
RGCI/ P-
9
Sen s # 2 +
10
Sen s # 2 -
11
Purge Flow Swit ch
12
Purge Flow Swit ch
13
Fuel 1 / 2
14
Fuel 1 / 2
15
Re mot e Alarm Reset
16
Re mot e Alarm Reset
17
Bur n e r On I n pu t
18
Bur n e r On I n pu t
19
RS- 2 3 2 Rx
20
21 RS- 232 Tx
22 Network -
Net wor k +
23
Ser i a l Common
24
Ou t p u t 1 +
25
26 Output 127 Output 2+
28 Output 229 Common Alarm
30 Common Alarm
31 Alarm 2
32 Alarm 2
33 Alarm 3
34 Alarm 3
35 Alarm 4
36 Alarm 4
41
Pur ge Sol
42
Pur ge Sol
43 Cal 1 Sol
44 Cal 1 Sol
45 Cal 2 Sol
46 Cal 2 Sol
47 Mains E
Mai ns Power Suppl y
240/ 115VAC
PROBE #2
PROBE #1
48
49 Mains N
50 Mains A
51 Heater #1
52 Heater #1
53 Heater #2
54 Heater #2
Connection Diagram for 1638 Analyser and one or two 1232 Unheated Sensors
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1638 Dew Point Analyser 23
3.6 HEATER INTERLOCK RELAYS
CAUTION
Explosion protection for heated probes is achieved by switching the power to the probe heater off whenever the main
fuel valve is closed.
The principle of safety is that if the main fuel valve is open then main flame has been established. With this primary
source of ignition on, the probe heater can be safely switched on. The most dangerous situation is if fuel or hydrogen
leaks into the furnace when the fuel valve is closed. When power is removed from the main fuel valve the heater
should be switched off.
To achieve this protection, connect a main fuel valve voltage free contact to the ‘BURNER ON SWITCH’ terminals 18
& 19. When the main fuel valve is open, the voltage free contact should be closed. For installations where there is no
risk of explosion, connect a link between terminals number 18 & 19.
For Safety Interlock
Contact must be closed
when main fuel valve is open
18
Burner on Switch
19
Heater Supply Interlock Connection For Heated Probes
3.7 CONNECTING AN OXYGEN PROBE CABLE
Connect the probe lead as shown in the following drawings. Unheated probe leads have integral reference air tube. An
adaptor has been supplied to connect this tube to quarter inch flexible PVC tubing, from the air pump or reference air
supply.
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24 1638 Dew Point Analyser
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