Rosemount ROX GT and GP O2 Analyzers-Rev C Manuals & Guides

Rosemount Analytical

ROX GT
ROX

O

XYGEN ANALYZERS

I

NSTRUCTION MANUAL

748375-C

GP

OTICE

N

The information contained in this document is subject to change without notice.

Swagelok® is a registered trademark of Crawford Fitting Co.

Manual Part Number 748375-C
August 2000
Printed in U.S.A.

Rosemount Analytical Inc.

4125 East La Palma Avenue
Anaheim, California 92807-1802

C

PREFACE

PURPOSE/SAFETY SUMMARY........................................................................1

SPECIFICATIONS - ROX GT TRACE OXYGEN ANALYZER............................ 3

SPECIFICATIONS - ROX GP PERCENT OXYGEN ANALYZER......................4

CUSTOMER SERVICE, TECHNICAL ASSISTANCE AND FIELD SERVICE............5

RETURNING PARTS TO THE FACTORY.........................................................5

TRAINING ......................................................................................................5

DOCUMENTATION............................................................................................5

COMPLIANCES .................................................................................................6

ONTENTS

SECTION 1. INTRODUCTION

1.1 OVERVIEW.................................................................................................1

1.2 TYPICAL APPLICATIONS ..........................................................................1

1.3 THEORY OF TECHNOLOGY......................................................................2

SECTION 2. INSTALLATION

2.1 UNPACKING...............................................................................................5

2.2 ASSEMBLY................................................................................................. 5

2.3 LOCATION..................................................................................................6

2.4 GASES ......................................................................................................6

2.4.1 Connections...................................................................................6

2.4.2 Gas Specifications.........................................................................7

2.5 ELECTRICAL CONNECTIONS...................................................................9

2.5.1 Line Power Connection..................................................................9

2.5.1.1 115/230 VAC Operation.................................................9

2.5.1.2 24 VDC Operation..........................................................9

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

i

ONTENTS

C

2.5.2 Interconnections............................................................................ 10

2.5.3 Signal Output Connections............................................................ 11

2.5.4 Concentration Alarms.................................................................... 11

2.5.5 Off Range Contact ....................................................................... 11

2.6 INSTALLATION GUIDELINES.................................................................... 12

SECTION 3. STARTUP AND OPERATION

3.1 STARTUP................................................................................................... 13

3.2 CALIBRATION............................................................................................ 13

3.3 OPERATION............................................................................................... 14

3.4 ALARM SETPOINTS .................................................................................. 14

SECTION 4. MAINTENANCE AND TROUBLESHOOTING

4.1 MAINTENANCE OVERVIEW .................................................................... 17

4.2 OXYGEN SENSOR REPLACEMENT......................................................... 17

4.3 POWER FUSE REPLACEMENT................................................................ 20

4.3.1 115/230V AC................................................................................. 20

4.3.2 24V DC ..................................................................................... 20

4.4 PRINTED CIRCUIT BOARDS..................................................................... 21

4.5 ALARM CONFIGURATION......................................................................... 21

4.6 TROUBLESHOOTING................................................................................ 22

S

ECTION

5.1 ROX REPLACEMENT PARTS ................................................................... 25

5. R

5.1.1 Replacement Sensors................................................................... 25

5.1.2 Replacement Parts List.................................................................25

EPLACEMENT PARTS

APPENDIX A. MATERIAL SAFETY DATA SHEETS

MATERIAL SAFETY DATA SHEET (PN 748378)
MATERIAL SAFETY DATA SHEET (PN 748380)
MATERIAL SAFETY DATA SHEET (PN 748381)

ii

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

ONTENTS

C

ENERAL PRECAUTIONS FOR HANDLING AND STORING HIGH PRESSURE GAS CYLINDERS

G

ARRA NTY

W

IELD SERVICE AND REP A IR FACILIT IES

F

FIGURES

1-1. Electrochemical Sensor Technology..........................................................2

1-2. ROX GT Front View....................................................................................3

1-3. ROX GP Front View...................................................................................3

2-1. ROX Top View (cover removed..................................................................5

2-2. Back Panel Connections............................................................................7

2-3. Recommended Sample Handling Diagram -

Positive Pressure Sample.............................................................8

2-4. Recommended Sample Handling Diagram -

Insufficient Pressure or Flow........................................................8

2-5. Rear Panel Electrical Input Connection.....................................................10

4-1. Sensor Installation......................................................................................19

4-2. ROX GT, GP 115/230V AC Fuse Location.................................................20

4-3. ROX GT 24V DC Fuse Location.................................................................21

4-4. Alarm Switch Location...............................................................................22

TABLES

4-1. Alarm Setting Configuration........................................................................ 22

A-1. Sensor Reference Guide ............................................................................A1

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

iii

ONTENTS

C

NOTES

iv

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

I

NTRODUCTION

1

1.1 OVERVIEW

This manual describes the ROX GT trace oxygen analyzer and the ROX GP percent
oxygen analyzer of the ROX Series of oxygen analysis instruments.

The ROX GT is designed to determine continuously the concentration of trace oxygen
in a flowing gaseous mixture. The concentration is expressed in parts-per-million by
volume. The ROX GP is designed to measure continuously the concentration of
percent oxygen in a flowing gaseous mixture.

The ROX GT / GP is designed for panel mount or 1/2 19” rack mount, with gas
connections made from the rear. All electronic connections are also made from the
rear including the AC power input.

1.2 TYPICAL APPLICATIONS

Typical applications for the ROX GT include:

• Monitoring trace oxygen contamination in pure nitrogen or argon streams from
air separation facilities.

• Determination of trace oxygen content of inerting atmospheres in heat treat
furnaces.

• Monitoring inert atmosphere glove boxes for oxygen impurity

Typical applications for the ROX GP include:

• Measuring percent impurities in pure gases

• Controlling inerting atmospheres in heat treat applications

• Monitoring oxygen enriching or deficient operations

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

1

NTRODUCTION

I

1.3 THEORY OF TECHNOLOGY

The ROX GT / GP uses an electrochemical sensor technology to achieve the
measurement of oxygen. See Figure 1-1. The sensor is a self contained disposable
unit which requires no maintenance. The sensor utilizes the principle of
electrochemical reaction to generate a signal proportional to the oxygen concentration
in the sample.

The sensor consists of a cathode and anode which are in contact via a suitable
electrolyte. The sensor has a gas permeable membrane which covers the cathode
allowing gas to pass into the sensor while preventing liquid electrolyte from leaking
out.

As the sample diffuses into the sensor, any oxygen present will dissolve in the
electrolyte solution and migrate to the surface of the cathode. The oxygen is reduced
at the cathode. Simultaneously, an oxidation reaction is occurring at the anode
generating four electrons. These electrons flow to the cathode to reduce the oxygen.

The representative half cell reactions are:
Cathode:

4e- + 2H2O + O2 → 4OH

-

Anode:

4OH- + 2Pb → 2PbO + 2H2O + 4e

-

The resultant overall cell reaction is:

2Pb + O2 → 2PbO

This flow of electrons constitutes an electric current which is directly proportional to
the concentration of oxygen present in the sample. In the absence of oxygen, no
oxidation / reduction reaction occurs and therefore no current is generated. This
allows the sensor to have an absolute zero.

Oxygen

Gas PermeableMembrane

Thin Electrolyte Layer

Electrolyte

Anode

OH

-

-

e

Cathode

F

IGURE

2

1-1. E

Current Signal

Contact Plates

LECTROCHEMICAL SENSOR TECHNOLOGY

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

ALARM SETPOINT ADJUSTMENT

NTRODUCTION

I

F

IGURE

ALARM
SETPOINT
BUTTON

1-2. ROX GT F

CELL BLOCK
COVER

RANGE SELECTOR SWITCH

RONT VIEW

ALARM SETPOINT ADJUSTMENT

LARM
ETPOINT
UTTON

F

IGURE

748375-C Rosemount Analytical August 2000

1-3. ROX GP F

RONT VIEW

CELL BLOCK
COVER

RANGE SELECTOR SWITCH

ROX GT/ROX GP Oxygen Analyzers

3

NTRODUCTION

I

N

OTES

4

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

I

NSTALLATION

2

2.1 UNPACKING

Carefully examine the shipping carton and contents for signs of damage. Immediately
notify the shipping carrier if the carton or contents is damaged. Retain the carton and
packing material until all components associated with the instrument are operational.

2.2 ASSEMBLY

The ROX GT comes fully assembled with sensor installed. Please note that the gas
inlet and outlet connections are sealed to prevent exposure of the sensor to air.
Prolonged exposure of the sensor to air can cause extended start up time, reduction
of performance or damage to the sensor. Do not remove the sealing caps until all

associated sample handling components are installed and the instrument is
fully ready for installation.

The ROX GP requires that the sensor be installed after the analyzer has been
installed and gas connections made.

F

IGURE

Cell Block

2-1. ROX T

Meter Display Alarm Setting

Power Board

OP VIEW (COVER REMOVED

)

Switch

Signal Board

Power Entry Module

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

5

NSTALLATION

I

2.3 LOCATION

Install the ROX GT/GP in a clean, weather-protected, non-hazardous, vibration-free
location free from extreme temperature variations. For best results, install the analyzer
near the sample take off point to minimize sample transport time.

Operating ambient temperature is 5 °C to 45 °C, limited to temperature changes of
less than 10 °C/hr. Acceptable dew point range is less than 95% relative humidity, but
not in excess of 45 °C wet bulb temperature.

2.4 GASES

During normal operation, the analyzer requires no support gases. Calibration gases of
air or an appropriate mixture of oxygen in nitrogen are recommended (ppm level for
ROX GT, % level for ROX GP).

After initial startup or startup following a prolonged shutdown, the analyzer may
require extended time to recover to the range of measurement. Commonly, this is
caused by the introduction of ambient air into the sample and/or vent lines to the
sensor. The presence of higher than normal levels of oxygen at the sensor will cause
the sensor electrolyte to become saturated with dissolved oxygen. When the
instrument is placed in operation, the sensor must now consume all excess dissolved
oxygen above the desired measuring level. This recovery period is required only for
the ROX GT.

All new external gas tubing is strongly recommended, preferably pre-cleaned,
stainless steel or copper tubing.

Note
Do not use plastic tubing for trace oxygen measurements as it can permeate
oxygen from the ambient air and cause higher than expected oxygen readings.

ROX GT gas line connections are compression fittings. Do not use pipe thread tape.
ROX GP gas line connections are female NPT and the use of pipe thread tape is
recommended.

2.4.1 C

ONNECTIONS

See Figure 2-2. Connect sample inlet and outlet lines to appropriately labeled fittings
on the rear panel. All connections are 1/4-inch ferrule-type compression fittings on the
ROX GT. The ROX GP has 1/8-inch female NPT connections.

If sample is available at positive pressure and flow between .1 and 2 SCFH we
recommend following the sample handling configuration shown in Figure 2.3.

If sample is available at ambient pressure or flow is insufficient to meet minimum flow
requirements, we recommend following the sample handling configuration shown in

6

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

NSTALLATION

A

I

Figure 2.4. The inclusion of fast loop bypass, particulate filtration and moisture
removal are not shown in these drawings and are the responsibility of the customer to
include as required.

F

IGURE

2.4.2 G

ALIBRATION GASES

C

VENT
(ROX GT)
1/4" SWAGELOK
(ROX GP)
1/8" FPT

SAMPLE IN
(ROX GT)
1/4" SWAGELOK
(ROX GP)
1/8" FPT

2-2. B

ACK PANEL CONNECTIONS

AS SPECIFICATIONS

1 2

+ -

3 4

C NO

5 6
+ -

7 8 9

C NC NO

10 11 12

C NC NO

LARM CONTACT #1

0 - 1VDC OUTPUT
OFF RANGE CONTACT

4-20mA ISOLATED OUTPUT

FUSE

POWER
SWITCH

Calibration method and gases depends on the desired operating range, and speed of
calibration recovery. Due to the characteristics of the sensor, no zero gas is required.
In the absence of oxygen, the sensor has an absolute zero.

Span gas can be either air or a certified blend of known ppm concentration of oxygen
in nitrogen. All calibration gases are introduced through the sample inlet at the rear of
the module

AMPLE GAS

S

Sample gas should be nonflammable (below 100% of the sample's LEL) and inert.
Consult factory if sample gas contains CO2, CO, acid gases, or halogen gases. These
samples may not be suitable for use with this analyzer.

LOW RATE

F

The sample flow rate can set be between .1 SCFH and 2.0 SCFH (50 - 1000 cc/min)
without effecting the accuracy of the sensor. Sample flow should be set at a constant
value within these limits which provides the desired response time and sample
conservation.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

7

NSTALLATION

I

RESSURE/FILTRATION

P

Sample pressure at the inlet should be within the range of 0 to 15 psig (1013 to
2048 hPa).

The analyzer does not contain any integral sample filtration. Sample should be
filtered for particulates down to five microns to reduce the risk of internal sample line
blockage.

Sample
Vent

F

IGURE

2-3. R

S

Flowmeter

Sample
Inlet

Air or Span

Gas

Sensor

Isolation

Valve

Flow Control

Valve

ECOMMENDED SAMPLE HANDLING DIAGRAM

AMPLE

Vacuum
Breaker

Eductor

ROX GT

(back)

- P

OSITIVE PRESSURE

Nitrogen or
Air In

F

IGURE

8

2-4. R

P

Flowmeter

Sample

Vent

Sample
Inlet

Ambient Air or

Span Gas

Flow Contr ol

Valve

Sensor

Isolation

Valve

ECOMMENDED SAMPLE HANDLING DIAGRAM

RESSURE OR FLOW

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

ROX GT

(back)

- I

NSUFFICIENT

2.5 ELECTRICAL CONNECTIONS

All electrical connections can be found on the back of the analyzer (Refer to Figure

2.2).

NSTALLATION

I

2.5.1 L

INE POWER CONNECTION

2.5.1.1 115/230 VAC O

The ROX GT/GP is designed to operate on 115 or 230 VAC 50/60 Hz power. The
power entry module is located on the right rear panel of the instrument. The power
entry module utilizes a standard IEC 320 connector allowing universal connection in all
countries by selecting the appropriate line cord at installation. A standard North
American power cord is provided with the analyzer.

The analyzer comes configured from the factory for operation on 115 VAC power. If
you need to operate the unit on 230 VAC, check to make sure that the unit is
disconnected from line power, open the cover door on the power entry module and
extract the fuse-block as explained in Section 4.3. Turn the fuse-block over and
reinstall so that the “230V” is now visible through the window in the cover door. Close
the cover door prior to connecting power.

2.5.1.2 24 VDC O

The ROX GT 24 VDC Analyzer (PN 658301-24) is designed to operate on 24 VDC
input.

PERATION

PERATION

Prior to making electrical connections to the analyzer, verify that the power rating on
the instrument name-rating label is correct.

The 24 VDC electrical connection is located on the right rear panel of the instrument,
see Figure 2-5. The terminal strip is labeled:

+

-

+24 VDC

-24 VDC
Ground

WARNING: POSSIBLE ELECTRICAL DAMAGE

Connection of AC voltage to the power input connections will result in serious
damage to the analyzer. Verify all electrical input connections for correct
voltage and power before powering up analyzer.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

9

NSTALLATION

I

F1A - 24V

FUSE

+

-

24 VDC POWER CONNECTION

F

IGURE

2.5.2 I

2-5. R

NTERCONNECTIONS

EAR PANEL ELECTRICAL INPUT CONNECTION

The analyzer has two kinds of output connections, a signal output and a set of relay
contacts. The contacts are rated at 115 VAC, but with the following provisos:

There is only "basic insulation (within the meaning of IEC 1010-1) provided between
the contacts and the rest of the circuitry. This means that in the event of a single fault,
it is possible that 115 VAC connected to the relay contacts would be connected to the
output connections as well. Any equipment connected to the analyzer output may
potentially see this 115 VAC.

10

WARNING: ELECTRICAL SHOCK HAZARD

The output connection is for use only with equipment which has no live parts
which are accessible.

The connecting cable and the equipment to which the output is connected must
have insulation rated for at least 150 VAC, since under fault condition the output
may be connected to the relay contacts witch themselves may be connected to
150 VAC.

The connection used at the remote end of the output circuit must be such as to
be suitable for 150 VAC and must have no accessible live parts.

The equipment connected to the output must either be approved to IEC 1010-1
or equivalent or must be suitable for use with an input that may potentially be
connected to 150 VAC, and must not catch fire in this circumstance.

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

NSTALLATION

I

Note
The interconnection terminal strip on the rear of the analyzer is designed to be

unplugged for easier connection. It is polarized so that you cannot plug it in
backwards. Make the connections with plenty of service loop and then plug it
in. Double check that you have used the correct terminals, and do not apply a
high voltage (e.g. 115 V) to the relay contacts before you have verified that the
output connections are correct - putting AC on the signal output will destroy the
analyzer.

2.5.3 S

IGNAL OUTPUT CONNECTIONS

The analyzer comes standard with both 4-20 mA DC isolated and 0-1 VDC outputs.
For ease of installation, the signal output connections are made via a removable
terminal strip connector which is shared with the alarm connections (Refer to Figure

2.2).

WARNING: POSSIBLE EXPLOSION HAZARD

Check all wiring connections prior to reconnection of the terminal strip. The
application of AC power to the signal output terminals will damage the analyzer.

2.5.4 C

ONCENTRATION ALARMS

The analyzer comes standard with two concentration alarms both configured high and
normally energized. For ease of installation, the alarm connections are made via a
removable terminal strip connector which is shared with the signal output connections
(Refer to Figure 2.2). Each set of alarm connections are labeled for easy identification
to the associated alarm. The connections labeled NO (normally open), NC (normally
closed), and C (common) refer to relay positions with the power removed (de­energized) .

Both alarms are configured from the factory for fail-safe mode (normally energized,
and loss of power will cause a change in relay status) and high oxygen setpoint (relay
status change above setpoint). To change the alarm configuration, refer to Section

4.5.

2.5.5 O

FF RANGE CONTACT

Additionally, there is an off range contact available. This contact provides the user
with a contact that changes status when the range switch is moved out of the desired
range. This contact comes from the factory configured normally energized on the 0-10
ppm range. In the event of a loss of power or the range switch is moved to a different
position, the contact will open.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

11

NSTALLATION

I

2.6 INSTALLATION GUIDELINES

• Is the analyzer’s location clean, weather-protected, non-hazardous, vibration-free,
and with a stable ambient temperature?

• Are gas supply cylinders equipped with a clean, metal diaphragm, hydrocarbon free,
two stage regulator with shut off valve?

• Are external tubing, regulators, valves, pumps, fittings etc. clean?

• Is the oxygen content of the supply gases compatible with the analysis range?

• Is the sample non-flammable?

• Have all the external gas connections been leaked checked?

• Has clean stainless steel or other appropriate metal tubing been used for sample

lines?

• Are all electrical connections secure and correct?

• Has the sensor been installed in the ROX GP?

• Is the proper line input power displayed on the power entry module?

12

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

S

TARTUP AND OPERATION

3

3.1 STARTUP

After completion of the installation procedure in Section Two, proceed as follows:

1. Set range switch to the 25% position (full counterclockwise)

2. Turn on power by placing the switch on the power entry module to the “-” position.

3.2 CALIBRATION

See Section 2.4.2 for a description of the method for choosing calibration zero and
span gases.

To calibrate the ROX GT/GP, introduce air or span gas into the SAMPLE INLET, and
do the following:

1. Set range switch to the 25% range setting (full counterclockwise) or the appropriate
range for the span gas used. It is recommended to use the highest concentration
span gas which provides you with the best fit for your requirements. The use of air
for calibration provides the least chance of span gas error, but does require
extended recovery time down to low ppm level measurement.

2. If you have followed the recommended sample handling diagram in Section 2.4.1.
open the sensor isolation valve first to avoid exposing the sensor to excessive
sample pressure or vacuum. Flow span gas or air at a floweret between 0.1 and

1.0 L/min. Be careful to not obstruct the outlet as this will cause an increase in
sample pressure and a consequent increase in oxygen reading.

Note
Alarm setpoints are not defeated during calibration. Take appropriate

precautions during calibration.

3. Wait f o r reading to stabilize. This should only take a few minutes.

4. Locate the SPAN ADJUST potentiometer on the front panel and adjust
appropriately to make the display correspond with the span gas concentration.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

13

TARTUP AND OPERATION

S

Turning the potentiometer clockwise will increase the display reading while
counterclockwise will decrease the reading.

5. If you have used air to span the instrument, switch to zero gas or sample as soon
as possible to avoid prolonged exposure of the sensor to high concentrations of
oxygen. The longer the sensor is exposed to air, the longer it will take for the
sensor to recover to low ppm levels. W hen installing a new sensor or starting the
instrument for the first time, it may take as long as eight hours for the analyzer to
purge down to the lowest operating range.

6. Allow the unit to stabilize at the final reading on zero gas or sample. The unit is
now ready for operation.

Unit should be calibrated once a week until familiarity is achieved in required
calibration frequency. Calibration intervals as long as once a month are possible on
stable installations. Processes which have large changes in environmental conditions
and sample composition may require more frequent calibrations.

3.3 OPERATION

After calibration, proceed as follows:
Supply sample gas to the SAMPLE INLET. Adjust external flow controller or throttle

valve so that flow discharged from the outlet is between 0.1 and 1.0 L/min.

Note
Flow indication is not provided with the instrument and must be provided

external to the analyzer. Refer to installation section for proper location.

When shutting down the instrument, always close the sensor isolation valve last to
avoid exposing the sensor to excessive pressure or vacuum.

3.4 ALARM SETPOINTS

The ROX GT/GP come standard with two fully adjustable alarms with relay contacts.
These alarm setpoints are designed to operate as percent of range as opposed to
discrete concentration value. The alarms are configured from the factory as high and
failsafe.

To view the alarm setpoints, turn the range switch to the desired measuring range and
press the “SET LO ALARM” or “SET HI ALARM” button. The alarm setpoint will be
displayed in actual concentration units. Since the alarms are configured as percent of
scale, changing ranges will also change the value of the alarm setpoint. For example,
if the LO alarm is set for 5 ppm on the 10 ppm range (50% of range), it will read 50
ppm on the 100 ppm range (50% of range).

14

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

TARTUP AND OPERATION

S

To adjust the alarm setpoint, press the appropriate alarm setpoint button, then locate
and adjust the associated alarm setpoint adjustment potentiometer as indicated in
Figure 1-1. Turning the potentiometer clockwise will increase the setpoint while
turning the potentiometer counterclockwise will decrease the setpoint. You must keep
the alarm setpoint button depressed during the adjustment procedure to continuously
view the alarm setpoint value. Always adjust the “LO” alarm for the lowest setpoint
value and the “HI” alarm for the higher value.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

15

TARTUP AND OPERATION

S

N

OTES

16

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

M

AINTENANCE AND TROUBLESHOOTING

4

CAUTION: QUALIFIED PERSONNEL

This equipment should not be adjusted or repaired by anyone except properly
qualified personnel.

WARNING: PARTS INTEGRITY

Tampering with or unauthorized substitution of components may adversely
affect the safety and performance of this product. Use only factory approved
components for repair.

4.1 MAINTENANCE OVERVIEW

The ROX GT/GP analyzer components which may require replacement include:

• Oxygen sensor

• Power fuse

• Printed circuit boards

4.2 OXYGEN SENSOR REPLACEMENT

CAUTION: CAUS TIC MATERIAL

The sensor contains electrolyte which is caustic and can cause serious burns to
skin. Do not ingest contents of sensor. Read and understand the Material
Safety Data Sheet in the rear of this manual before handling sensor.

The oxygen sensor used in the ROX GT/GP analyzers is a consumable item and does
require replacement periodically. To determine if the sensor requires replacement,
see the troubleshooting portion of this section.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

17

AINTENANCE AND TROUBLESHOOTING

M

ENSOR INSTALLATION

S

To install a new sensor follow the procedures exactly in the order listed below. Failure
to follow the procedure in order may result is extended exposure of the sensor to air
causing greater delays in returning to on-line monitoring:

1. Turn off power to unit and turn off sample flow to analyzer.

2. Locate cellblock cover and remove using the key tool provided with instrument.
Rotate cover counterclockwise to remove.

3. Inspect cellblock cavity for signs of liquid. If liquid is present, use protective
equipment as described in the material safety data sheet in the rear of this manual
before proceeding. Extreme care should be used and the liquid should be treated
as a caustic substance.

4. Remove existing sensor and dispose of in accordance with national, federal, state,
and local regulations. Use the existing pull-tab on the sensor to remove from the
cellblock.

5. Inspect inside of cellblock for signs of residual liquid or deposits on the contact
pins. If liquid is present, use appropriate protective equipment and follow the
cleanup procedure as described in the material safety data sheet in the rear of this
manual. Deposits on the contact pins can be removed by wiping with a damp cloth
or using the eraser from a pencil. Do not use abrasives (i.e. sandpaper) as this will
damage the contact pins.

6. If sample is inert (e.g., nitrogen) a low flow of sample (50 cc/min) can be
introduced to the analyzer to purge out the internal volume of the cellblock prior to
installation of the new sensor. This procedure is not required and is recommended
as a step to reduce the purge down time of the new sensor.

CAUTION: MAXIMUM FLOW

Do not flow a volume in excess of 50 cc/min. Exceeding this level may produce
an oxygen deficient breathing environment to the technician conducting sensor
replacement. Do not flow sample if it is flammable or toxic. Do not use this
procedure if the sample handling configuration is for insufficient pressure or
flow.

18

7. Inspect the package containing the replacement sensor. Do not open the bag.
Make sure that it is the correct model type and that there is not visible liquid in the
bag. If the bag contains liquid, do not open and contact the factory for a
replacement.

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

AINTENANCE AND TROUBLESHOOTING

M

8. Locate the shorting tab on the back of the sensor. The tab is designed to maintain
contact between the two contact plates of the sensor while it is stored in the bag.
This contact allows the sensor to continuously consume dissolved oxygen inside
the sensor. This clip will need to be removed prior to installing the sensor in the
analyzer.

9. Locate the pull-tab portion of the sensor label. W hen installing the sensor in the
cellblock, make sure that this tab faces forward for easy sensor removal later.

10. Cut open the bag being careful not to damage the sensing face of the sensor.
Quickly remove the sensor from the bag, remove the shorting clip and install in the
cellblock with the contact plates on top and the sensing face on the bottom. Make
sure that the pull-tab is facing forward and the writing on the label is right side up
(see Figure 4-1).

11. Reinstall the cellblock cover turning clockwise until the O-ring just makes contact.
Turn no more than 1/4 turn additional.

Note
Do not overtighten. Doing so may damage the cover.

12. T urn on power and check reading.

13. Calibrate as described in Section 3.2

Key Slot

Cell Block
Cover

Contact Plates

Cell Block (with
cover removed)

Oxygen Sensor

Sensing Face

F

IGURE

748375-C Rosemount Analytical August 2000

4-1. S

ENSOR INSTALLATION

Sensor Pull Tab

ROX GT/ROX GP Oxygen Analyzers

19

AINTENANCE AND TROUBLESHOOTING

M

4.3 POWER FUSE REPLACEMENT

4.3.1 115/230 V AC

The ROX GT/GP has the main power fuses located in the power entry module. No
other fuses are located inside the instrument.

Before replacing the main power fuse, turn off the analyzer and disconnect the power
cord from the power entry module.

Using a small blade slotted screwdriver, carefully pry open the f ront door of the power
entry module. There is a access slot on the top of the module and the door opens
downward (see Figure 4-2). Once the door is opened, you can remove the red power
selector / fuseholder by inserting the screwdriver into the slot on top of the fuseholder
and carefully prying the fuseholder out. The fuseholder contains two 1A fuses.
Replace as required.

Reinstall the fuseholder so that the correct voltage is visible through the small window
in the door of the power entry module.

Access slot

Fuseholder
(Red)

Power Entry Module

(with front door open)

Rear Panel

F

IGURE

4-2. ROX GT, GP 115/230V AC F

USE LOCATION

4.3.2 24V DC

The ROX GT 24V DC Analyzer has the main power fuse located directly above the
electrical power input terminal strip on the rear panel, Figure 4-3. No other fuses are
located in the analyzer.

20

Before replacing the main power fuse, turn off and disconnect electrical power to the
analyzer.

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

AINTENANCE AND TROUBLESHOOTING

M

The fuseholder utilizes a standard twist-off cap. To replace the fuse, rotate the
fuseholder cap counterclockwise until the cap is free from the body. The fuse will
come out with the cap. Replace fuse and re-install cap onto fuseholder.

F1A - 24V

FUSE

+

-

Rear Panel

F

IGURE

4-3. ROX GT 24V DC F

USE LOCATION

4.4 PRINTED CIRCUIT BOARDS

Both printed circuit boards can be replaced if necessary. Refer to Figure 2-1 for the
location of the power and signal boards.

4.5 ALARM CONFIGURATION

The alarm setpoints are factory set for high normally energized. If you wish to change
the configuration of the alarm setpoints you can do so by the following procedure.

1. Verify that the power module is off and the power cord is disconnected from the
analyzer

2. Remove the top cover from the analyzer

3. Locate the signal board as indicated in Figure 2-1

4. Locate the alarm setting dip switches on the signal board

5. To change the alarm setting refer to Figure 4-4 and Table 4-1 for desired
configuration

In all cases, “LO ALARM” should be adjusted for the lowest setpoint value and “HI
ALARM” should be adjusted for the higher setpoint value.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

21

AINTENANCE AND TROUBLESHOOTING

M

F

IGURE

4-4. A

ON OFF

4
3
2
1

EDGE OF SIGNAL BOARD

EDGE OF SIGNAL BOARD

LARM SWITCH LOCATION

LO ALARM SETTING
(S2)

HI ALARM SETTING
(S3)

T

ABLE

TRIP POINT - FS/NFS SWITCH #

(RELAY STATUS) 1 2 3 4

HIGH - FAILSAFE
(NORMALLY ENERGIZED)
HIGH - NON FAILSAFE
(NORMALLY DE-ENERGIZED)
LOW - FAILSAFE
(NORMALLY ENERGIZED)
LOW - NON FAILSAFE
(NORMALLY DE-ENERGIZED)

4-1. A

LARM SETTING CONFIGURATION

OFF ON ON OFF

ON OFF OFF ON

ON OFF OFF ON

OFF ON ON OFF

22

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

AINTENANCE AND TROUBLESHOOTING

M

4.6 TROUBLESHOOTING

The following provides a short list of common troubleshooting tips.

NALYZER DOES NOT POWER UP

A

Check to make sure that the power cord is properly installed and the voltage is
correctly selected. The voltage configuration of the analyzer is visible through the
window of the power entry module. Make sure that the power switch is in the on
position (“-”).

If the unit does not power up, turn off power switch, remove power cord and open door
on power entry module as described in Section 4.4 above. Inspect fuses and replace
as required.

NALYZER FAILS TO PURGE DOWN TO PPM LEVELS

A

The number one problem associated with trace oxygen analyzer installation is the
occurrence of leaks in the sample line plumbing. If the oxygen reading will not come
down to ppm levels or is reading higher than expected, the sample plumbing prior to
the instrument may have a leak. A quick check can be conducted by observing the
oxygen reading at two different flow levels; 0.2 and 2.0 SCFH. If the oxygen reading
drops significantly when the flow is increased from 0.2 to 2.0 SCFH, this is a good
indication that a leak exists.

To check for leaks prior to the sensor, disconnect the analyzer and cap the inlet and
outlet fittings on the analyzer to reduce the amount of oxygen exposure to the sensor.
Cap the inlet line and pressurize the inlet line to 5 - 10 psig and check all connections
with a soapy solution to identify leaks.

WARNING: POSSIBLE SENSOR DAMAGE

Do not pressure check the sample line with the sensor/analyzer connected.
Over-pressurization of the sensor can result in damage.

If the reading increases with an increase in flow, the vent line may be obstructed
causing back pressure on the sensor. Inspect your vent line and remove any devices
which may be causing backpressure.

If the reading slowly decreases over time, the sensor may have been exposed to high
levels of oxygen for extended periods of time. The sensor must consume all of the
dissolved oxygen in the sensor electrolyte before it will accurately measure ppm le vels
of oxygen. In some cases it is not possible for the sensor to recover to low ppm levels
and the sensor must be replaced.

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

23

AINTENANCE AND TROUBLESHOOTING

M

NALYZER IS READING TOO LOW

A

Check to make sure that the sensor has been calibrated properly. Flow an
appropriate span gas through the instrument and follow the calibration procedure in
Section 3.2. If you are unable to achieve span calibration, the sensor has reached the
end of its useful life and needs to be replaced (see Section 4.2).

If calibration is possible, but the reading still appears too low, conduct a span check on
the 25% range with air. Adjust reading as necessary. If the reading requires
adjustment, your bottled span gas may be incorrect or corrupted.

If sensor life seems too short, you may have compounds present in your sample which
are poisoning the sensor. Acid gases, CO2, SO2, or H2S can reduce the life of the
sensor and should be removed from the sample prior to measuring.

NALYZER ALWAYS READS ZERO

A

Check to make sure that the sensor has been installed correctly with the contact
plates on top and the gas permeable membrane facing downward. If the sensor has
been installed incorrectly, carefully remove and check to make sure that the
membrane has not been damaged. If the sensor is leaking, or shows signs of distress
to the membrane, replace with a new sensor. If the sensor is okay quickly reinstall in
the correct position.

Verify that the cellblock contact pins are making good contact with the metal surfaces
of the sensor. If the pins are not making contact, carefully bend the wire down to
reestablish contact. Check that the contact pins are clean and do not show signs of
deposits or oxidation. Clean as necessary.

A good sensor will have an output of 150 to 500 micro amps in air. You can check this
by connecting a digital volt-meter across the contact plates of the sensor while it is
removed from the instrument and measuring the current. If the sensor does not
produce sufficient output, replace the sensor with a new one.

HE READINGS ARE ERRATIC AND DRIFT NOISILY

T

This is normally an indication that the sensor has reached the end of its useful life. If
the analyzer cannot be spanned on a cal gas or air, the sensor must be replaced. If
the sensor spans okay and appears stable at high oxygen concentrations, there may
be a sample line leak or obstruction of the vent line. Follow the procedure described
above in “Analyzer fails to purge down to ppm levels”.

If no sample line problems are found, open the cellblock and inspect the sensor for
signs of damage or leakage. Follow the procedure in Section 4.2. for correct method
of opening cellblock and precautions for handling a leaking sensor.

24

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

R

EPLACEMENT PARTS

5

5.1 ROX REPLACEMENT PARTS

WARNING: PARTS INTEGRITY

Tampering with or unauthorized substitution of components may adversely
affect the safety and performance of this product. Use only factory approved
components for repair.

5.1.1 R

5.1.2 R

EPLACEMENT SENSORS

Refer to Table A-1 in Appendix A for easy cross reference of the correct oxygen
sensor for your specific instrument.

658303 Oxygen Sensor GT1
658304 Oxygen Sensor GT3
658310 Oxygen Sensor GP1
658311 Oxygen Sensor GP3
658312 Oxygen Sensor GP4

EPLACEMENT PARTS LIST

904699 Connector Rear Output
873155 Power Cord
904759 Power Supply Board
904760 Cap. Cell Block
904761 O-Ring, Cell Block Cap
904762 Ribbon Cable
904763 Power Entry Module
099393 Fuse 1A 250V
748375 Instruction Manual

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

25

EPLACEMENT PARTS

R

ROX GT O

NLY

904768 Cell Block Assembly
904769 Amplifier Board (658301) (658302)

ROX GP O

NLY

904764 Cell Block Assembly
904765 Amplifier Board (658307)
904766 Amplifier Board (658308)
904767 Amplifier Board (658309)

26

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers

A

PPENDIX

A. M

ATERIAL SAFETY DATA SHEETS

A

The following section contains important information regarding the characteristics of
the oxygen sensor used in the ROX GT/GP analyzers. Read and understand all
information before attempting any replacement or installation of the oxygen sensor.
The following sensor reference guide will provide a quick reference of the specific
oxygen sensor type used in your specific analyzer model and part number.

T

ABLE

MODEL INSTRUMENT

PART NUMBER

ROX GT 658301 GT1 658303
ROX GT 658302 GT3 658304
ROX GP 658307 GP1 658310
ROX GP 658308 GP3 658311
ROX GP 658309 GP4 658312

A-1. S

ENSOR REFERENCE GUIDE

OXYGEN SENSOR

MODEL

OXYGEN SENSOR

PART NUMBER

748375-C Rosemount Analytical August 2000

ROX GT/ROX GP Oxygen Analyzers

A1

PPENDIX

A

N

OTES

ATERIAL SAFETY DATA SHEETS

A. M

A2

August 2000 Rosemount Analytical 748375-CROX GT/ROX GP Oxygen Analyzers