Rosemount 951C NOx Analyzer-Rev X Manuals & Guides

Model 951C NOx Analyzer

Instruction Manual

748214-X

December 2013

Applies to analyzers with SN# F-09000034 or higher.

TABLE OF CONTENTS

Section 1: Description and specifications

Typical applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Section 2: Installation

Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Voltage requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Operating on 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Connecting cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Connecting the power cord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Connecting the potentiometric recorder cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Connecting the current recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Adjusting the current output to produce a zero of 0 mA . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Gas requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Air (U.S.P. Breathing Grade) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Span Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Sample requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

Connecting gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Leak testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Section 3: Operation

Front panel indicators and controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Range selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Blinking backlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Sample pressure gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Ozone pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Zero and span potentiometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Ozone interlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Starting the analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Setting up remote range switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

Calibrating the analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

Zero calibrating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

Upscale calibrating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

Optimizing the converter temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

Measuring converter efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16

Recommended calibration frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

i

Section 4: Theory

Nitric oxide concentration is determination by chemiluminescence method . . . . . . . . . . . . . . . . . . . 4-1

Analyzer flow system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Flow of sample, standard gas or zero gas to reaction chamber . . . . . . . . . . . . . . . . . . . 4-4

Ozone generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Signal conditioning and display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Circuit functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Analyzer thermal system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Section 5: Routine servicing

System checks and adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Adjusting the display fullscale span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Factors affecting the overall sensitivity of the analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Monitoring ozone output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Finding the cause of excessive background current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Servicing the flow system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Cleaning the sample capillary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Confirming a faulty ozone restrictor fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

Servicing the photomultiplier tube and the reaction chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Removing or replacing the photomultiplier assembly . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Cleaning the reaction chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Reconstructing the photomultiplier assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15

Photomultiplier tube and housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16

Replacing the photomultiplier tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16

Ozone generator assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17

Removing the ultraviolet lamp and lamp housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17

Replacing the ultraviolet lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Removing the power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Converter assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

Removing the glass converter tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

Servicing the electronic circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

Section 6: Replacement parts

Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Circuit board replacement policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Replacement parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Common parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Photomultiplier assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Converter assembly 654070 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Temperature control assembly 654068 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

ii

ESSENTIAL INSTRUCTIONS

READ THIS PAGE BEFORE PROCEEDING!

Rosemount Analytical designs, manufactures, and tests its products to meet many national and
international standards. Because these instruments are sophisticated technical products, you
MUST properly install, use, and maintain them to ensure they continue to operate within their
normal specifications. The following instructions MUST be adhered to and integrated into your
safety program when installing, using, and maintaining Rosemount Analytical products. Failure
to follow the proper instructions may cause any one of the following situations to occur: Loss of
life; personal injury; property damage; damage to this instrument; and warranty invalidation.

• Read all instructions prior to installing, operating, and servicing the product.

• If you do not understand any of the instructions, contact your Rosemount Analytical

representative for clarification.

• Follow all warnings, cautions, and instructions marked on and supplied with the

product.

• Inform and educate your personnel in the proper installation, operation, and

maintenance of the product.

• Install your equipment as specified in the Installation Instructions of the appropriate

Instruction Manual and per applicable local and national codes. Connect all products
to the proper electrical and pressure sources.

• To ensure proper performance, use qualified personnel to install, operate, update,

program, and maintain the product.

• When replacement parts are required, ensure that qualified people use replacement parts

specified by Rosemount. Unauthorized parts and procedures can affect the product's
performance, place the safe operation of your process at risk, and VOID YOUR
WARRANTY. Look-alike substitutions may result in fire, electrical hazards, or improper
operation.

• Ensure that all equipment doors are closed and protective covers are in place,

except when maintenance is being performed by qualified persons, to prevent
electrical shock and personal injury.

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

This page is intentionally left blank.

PREFACE

Highlights the presence of a hazard which will cause severe personal injury, death, or substantial
property damage if the warning is ignored.

DANGER

Highlights an operation or maintenance procedure, practice, condition, statement, etc. If not strictly
observed, could result in injury, death, or long-term health hazards of personnel.

WARNING

Highlights an operation or maintenance procedure, practice, condition, statement, etc. If not strictly
observed, could result in damage to or destruction of equipment, or loss of effectiveness.

CAUTION

Highlights an essential operating procedure, condition or statement.

NOTE

The purpose of this manual is to provide information concerning the components,
functions, installation and maintenance of the 951C NOx analyzer.

Some sections may describe equipment not used in your configuration. The user
should become thoroughly familiar with the operation of this module before operating
it. Read this instruction manual completely.

DEFINITIONS

The following definitions apply to dangers, warnings, cautions and notes found
throughout this publication.

vii

SAFETY SUMMARY

ELECTRICAL SHOCK HAZARD

Do not operate without doors and covers secure. Servicing requires access to live parts which can
cause death or serious injury. Refer servicing to qualified personnel.

This instrument was shipped from factory set up to operate on 115 volt 50/60 Hz. For operation on
230 volt 50/60 Hz, refer to Section 2-3.

For safety and proper performance this instrument must be connected to a properly grounded three­wire source of power.

DANGER

INTERNAL ULTRAVIOLET LIGHT HAZARD

Ultraviolet light from the ozone generator can cause permanent eye damage. Do not look directly at
the ultraviolet source in ozone generator. Use of ultraviolet filtering glasses is recommended.

WARNING

If this equipment is used in a manner not specified in these instructions, protective
systems may be impaired.

AUTHORIZED PERSONNEL

To avoid explosion, loss of life, personal injury and damage to this equipment and on
site property, all personnel authorized to install, operate and service the this
equipment should be thoroughly familiar with and strictly follow the instructions in this
manual. SAVE THESE IN-STRUCTIONS.

viii

TOXIC CHEMICAL HAZARD

This instrument generates ozone which is toxic by inhalation and is a strong irritant to throat and
lungs. Ozone is also a strong oxidizing agent. Its presence is detected by a characteristic pungent
odor.

The instrument exhaust contains both ozone and nitrogen dioxide, both toxic by inhalation, and may
contain other constituents of the sample gas which may be toxic. Such gases include various
oxides of nitrogen, unburned hydrocarbons, carbon monoxide and other products of combustion
reactions. Carbon monoxide is highly toxic and can cause headache, nausea, loss of
consciousness, and death.

Avoid inhalation of the ozone produced within the analyzer and avoid inhalation of the sample and
exhaust products transported within the analyzer. Avoid inhalation of the combined exhaust
products at the exhaust fitting.

WARNING

PARTS INTEGRITY

Tampering or unauthorized substitution of components may adversely affect safety of this product.
Use only factory documented components for repair.

WARNING

HIGH PRESSURE GAS CYLINDERS

This instrument requires periodic calibration with a known standard gas. See Sections 2-5 and 3-3.
See also General Precautions for Handling and Storing High Pressure Gas Cylinders, page P-5.

WARNING

ix

TOXIC AND OXIDIZING GAS HAZARD

The ozone generator lamp contains mercury. Lamp breakage could result in mercury exposure.
Mercury is highly toxic if absorbed through skin or ingested, or if vapors are inhaled.

HANDLE LAMP ASSEMBLY WITH EXTREME CARE

If lamp is broken, avoid skin contact and inhalation in the area of the lamp or the mercury spill.

Immediately clean up and dispose of the mercury spill and lamp residue as follows:

• Wearing rubber gloves and goggles, collect all droplets of mercury by means of a suction pump and
aspirator bottle with long capillary tube. Alternatively, a commercially available mercury spill clean­up kit, such as J. T. Baker product No. 4439-01, is recommended.

• Carefully sweep any remaining mercury and lamp debris into a dust pan. Carefully transfer all
mercury, lamp residue and debris into a plastic bottle which can be tightly capped. Label and return
to hazardous material reclamation center.

• Do not place in trash, incinerate or flush down sewer.

• Cover any fine droplets of mercury in non-accessible crevices with calcium polysulfide and sulfur
dust.

WARNING

TOPPLING HAZARD

This instrument's internal pullout chassis is equipped with a safety stop latch located on the left
side of the chassis.

When extracting the chassis, verify that the safety latch is in its proper (counter-clockwise)
orientation.

If access to the rear of the chassis is required, the safety stop may be overridden by lifting the
latch; however, further extraction must be done very carefully to insure the chassis does not fall
out of its enclosure.

If the instrument is located on top of a table or bench near the edge, and the chassis is extracted, it
must be supported to prevent toppling.

WARNING

x

GENERAL PRECAUTIONS FOR HANDLING AND

STORING HIGH PRESSURE GAS CYLINDERS

• Never drop cylinders or permit them to strike each other violently.

• Cylinders may be stored in the open, but in such cases, should be protected

against extremes of weather and, to prevent rusting, from the dampness of the
ground. Cylinders should be stored in the shade when located in areas where
extreme temperatures are prevalent.

• The valve protection cap should be left on each cylinder until it has been

secured against a wall or bench, or placed in a cylinder stand, and is ready to be
used.

• Avoid dragging, rolling, or sliding cylinders, even for a short distance; they

should be moved by using a suit-able hand-truck.

• Never tamper with safety devices in valves or cylinders.

• Do not store full and empty cylinders together. Serious suck-back can occur

when an empty cylinder is attached to a pressurized system.

• No part of cylinder should be subjected to a temperature higher than 125° F (52°

C). A flame should never be permitted to come in contact with any part of a
compressed gas cylinder.

1

• Do not place cylinders where they may become part of an electric circuit. When

electric arc welding, precautions must be taken to prevent striking an arc against
the cylinder.

1. Compressed Gas Association, Handbook of Compressed Gases, Second Edition, Van Nostrand
Reinhold Company, 135 West 50th Street, New York, NY 10020, © 1981.

xi

CONDENSED STARTUP AND CALIBRATION

PROCEDURE

The following summarized instructions on startup and calibration are intended for
operators already familiar with the analyzer.

For initial startup, refer to detailed instructions provided in “Operation” on page 3-1.

1. Review the Purchase Order and make a note of the range that was purchased—
Low Range, Mid Range, or High Range.

2. Set the Range switch on the Signal Conditioning board to position 4, 250ppm,
500ppm, or 2500 ppm.

3. On the Signal Conditioning board, verify that the correct Hi/Mid/Lo Selection
Jumpers are installed for the range that was purchased.

4. Turn on the analyzer. It will take approximately one to two hours to reach
temperature equilibrium, which is required for calibration.

5. Verify that the air cylinder’s pressure regulator is set to a pressure of 20 to 25
psig.

6. Establish the correct sample gas pressure:

a. Supply sample gas to rear-panel sample inlet at 15 psig.
b. Adjust the sample back pressure regulator so that the sample pressure

gauge indicates 4 psig.

7. Establish the correct zero gas pressure :

a. Supply zero gas to the rear panel sample inlet and set to 15 psig.
b. Note the reading on the sample pressure gauge. It should be the same as

in Step 7b. If not, adjust the output pressure regulator on the zero gas
cylinder as required.

xii

8. Establish the correct upscale standard gas pressure:

Supply pressure for sample, upscale standard gas and zero air must be the same. If not, the
readout will be inaccurate.

NOTE

It is the responsibility of the user to measure the efficiency of the NO2-to-NO converter during the
initial startup, and at intervals thereafter appropriate to the application—normally once a month.

NOTE

a. Supply upscale standard gas to the rear panel sample inlet.
b. Note the reading on the sample pressure gauge. It should be the same as

in Step 7b. If not, adjust the output regulator as required.

9. Do the following to perform a zero calibration:

a. Set the PPM RANGE Switch to the range to be used for sample analysis.
b. Set the front panel Range 1 potentiometer to its normal operating setting, if

known; otherwise, set the potentiometer to the middle setting—that is,

halfway between the left and the right settings.
c. Supply zero gas to the rear panel sample inlet.
d. Adjust the front panel Zero potentiometer to achieve a reading of zero on a

multimeter or recorder.

10. Do the following to perform an upscale calibration:

a. Set PPM RANGE Switch at setting appropriate to the particular span gas.
b. Supply upscale standard gas to the rear panel sample inlet.
c. Adjust front panel the Range 1 potentiometer so that a reading on a

multimeter or recorder is equal to the upscale standard gas’ known NOX

concentration.
d. Adjust R25 on the signal board so that the display value and the recorder

output are equal.

xiii

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xiv

Section 1: Description and specifications

The Model 951C NOx analyzer continuously analyzes a flowing gas
sample for nitric oxide (NO) and nitrogen dioxide (NO2). The sum of
the two concentrations is reported as NOx.

The analyzer is designed to measure NO
ranges designated as Hi, Mid, or Lo.

The analysis is based on the chemiluminescence method of NO
detection. The sample is continuously passed through a heated bed
of vitreous carbon, in which NO

present in the sample passes through the converter unchanged, and
any NO2 initially present in the sample is converted to an

approximately equivalent (95%) amount of NO.

The NO is quantitatively converted to NO2 by gas phase oxidation
with molecular ozone produced within the analyzer from air supplied

by an external cylinder. During this reaction, approximately 10% of the
NO2 molecules are elevated to an electronically excited state,

followed by immediate decay to the non excited state, accompanied
by the emission of photons. These photons are detected by a
photomultiplier tube, which in turn generates a DC current
proportional to the concentration of NOx in the sample stream. The

current is then amplified and used to drive a front panel display and to
provide potentiometric and isolated current outputs.

is reduced to NO. Any NO initially

2

using one of three sets of

x

To minimize system response time, an internal sample bypass feature
provides high velocity sample flow through the analyzer.

The case heater assembly of the Model 951C maintains the internal
temperature at approximately 50° C (122° F).

1 - 1

Instruction Manual Model 951C

748214-X DECEMBER 2013

1.1 Typical applications

The Model 951C analyzer has the following specific applications:

• Oxides of nitrogen (NOx) emissions from the combustion of
fossil fuels in:

• Vehicle engine exhaust

• Incinerators

•Boilers

• Gas appliances

• Turbine exhaust

• Nitric acid plant emissions

• Ammonia in pollution control equipment (with converter)

• Nitric oxide emissions from decaying organic material (i.e.,
landfills).

1 - 2

Model 951C Instruction Manual

DECEMBER 2013 748214-X

1.2 Specifications

Repeatability Within 0.1 ppm or ±1% of fullscale, whichever is greater

Zero/Span Drift Less than ±0.1 ppm or ±1% of fullscale, whichever is greater, in 24

hours at constant temperature

Less than ±0.2 ppm or ±2% of fullscale, whichever is greater, over any
10 C interval from 4 to 40 C (for rate change of 10 C or less per hour)

Response Time
(Electronic + Flow)

Sensitivity Less than 0.1 ppm or 1% of fullscale, whichever is greater

Detector Operating
Pressure

Total Sample Flow
Rate

Sample Pressure 138 kPa (20 psig)

Ozone Generator Gas U.S.P. breathing-grade air

Ambient Temperature
Range

Analog Output

Potentiometric 0 to +5 VDC, 2000 ohm minimum load

Isolated Current Field-selectable 0 to 20 or 4 to 20 mA, 700 ohm max load

Display Digital, 4-1/2 digit LCD, readout in engineering units, back-lighted

Power Requirements 115/230 VAC 10%, 50/60 3 Hz, 570 W maximum

Enclosure General purpose for installation in weather-protected areas

Dimensions 8.7 in. x 19.0 x 19.0 in. (H x W x D)

90% of fullscale in less than 1 minute

Atmospheric

1 Liter per minute at 20 psig

4 to 40 C (40 to 104 F)

22.0 cm x 48.3 cm x 48.3 cm (H x W x D)

Weight 22.2 kg (49 lbs) approximate

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Instruction Manual Model 951C

This page is intentionally left blank.

748214-X DECEMBER 2013

1 - 4

Section 2: Installation

2.1 Unpacking

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

2.2 Location

Install analyzer in a clean area, free from moisture and excessive
vibration, at a stable temperature within 4 to 40° C.

Figure 2-1. Panel Cutout / Installation Drawing

The analyzer should be mounted near the sample source to minimize
sample transport time.

2 - 1

Instruction Manual Model 951C

WARNING

748214-X DECEMBER 2013

A temperature control system maintains the internal analyzer
temperature at 50° C (122° F) to ensure proper operation over an
ambient temperature range of 4 to 40° C (40 to 104° F). Temperatures
outside these limits necessitate the use of special temperature
controlling equipment or environmental protection. Also, the ambient
temperature should not change at a rate exceeding 10° C per hour.

The cylinders of air and span gas should be located in an area of
constant ambient temperature.

2.3 Voltage requirements

ELECTRICAL SHOCK HAZARD
For safety and proper performance this instrument must be connected to a properly
grounded three-wire source of power.

This instrument was shipped from the factory pre-configured to
operate on 115 VAC, 50/60 Hz electric power.

2.3.1 Operating on 230 VAC

To operate the analyzer on 230 VAC, 50/60 Hz, do the following:

1. Set the voltage select switches (S1, S2, S3) on the Power
Supply Board and the voltage select switch (S3) on the
Temperature Control Board to the 230 VAC position.

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Figure 2-2. Power Supply Board voltage select switches

Figure 2-3. Temperature Control board voltage select switch

2. On the rear of the analyzer, replace the 6.25 A fuse with the

3.15 A fuse (P/N 898587) that is provided in the shipping kit.

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Figure 2-4. Rear view of Model 951C (cover removed)

2.4 Connecting cables

The power (PN# 899330) and recorder (PN# 899329) cable glands
are supplied in the shipping kit. To connect the appropriate cable to its
connector or terminal strip on the analyzer, do the following:

1. Remove the analyzer’s rear cover to access the terminals.

2. Route each cable through its cable gland and connect to the
appropriate connector or terminal strip.

Figure 2-5. Cable gland

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3. Tighten the glands.

2.4.1 Connecting the power cord

If this instrument is located on a bench or table top or is installed in a
protected rack, panel or cabinet, power can be connected with a 3­wire flexible power cord.

The power cord must be at least 18 AWG with a maximum outside diameter (OD) of
48 inches.

To connect the power cord to the Model 951C, do the following:

1. Using the cable gland (PN# 899330) that is provided in the
installation kit, insert the power cord through the hole on the
Model 951C that is labeled POWER.

2. Connect the power cord leads to TB1 on the rear panel.

3. Tighten the cable gland adequately to prevent the rotation or
slippage of the power cable. Since the rear terminals do not
slide out with the chassis, no excess power cable slack is
necessary.

The following power cord and/or support feet are available:

• Power cord (PN# 634061), which contains a 10-foot North
American power cord set.

• Enclosure Support Kit (PN# 634958), which contains four
enclosure support feet for bench top use.

• Power Cord/Enclosure Support Kit (PN# 654008), which
contains a 10-foot North American power cord set and four
enclosure support feet.

If the instrument is permanently mounted in an open panel or rack, use electrical
metal tubing or conduit.

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2.4.2 Connecting the potentiometric recorder cables

Potentiometric recorder cables connect to the rear panel. Route the
cable through the cable gland in the hole on the Model 951C that is
labeled RECORDER OUTPUT and connect the cable’s leads to the
VOLT OUTPUT terminals.

Distance from recorder to analyzer: 1000 feet (305 meters) maximum

Input impedance: Greater than 2000 ohms

Cable (user supplied): Two conductor, shielded, min. 20 AWG

Voltage output: 0 to +5 VDC

2.4.3 Connecting the current recorder

Current recorder cables connect to the rear panel. Route the cable
through the cable gland in the hole on the Model 951C that is labeled

RECORDER OUTPUT and connect the cable’s leads to the CUR
OUTPUT terminals.

Distance from recorder to analyzer: 3000 feet (915 meters).maximum

Load resistance: Less than 700 Ohms

Cable (user supplied): Two conductor, shielded, min. 20 AWG

Voltage output: 0 to +5 VDC

2.4.4 Adjusting the current output to produce a zero of 0 mA

Do the following to adjust the current output to produce a zero of 0
mA:

1. Do the following to establish the correct zero gas pressure:

(a.) Supply zero gas to rear panel sample inlet.
(b.) Note the reading on internal sample pressure gauge. It

should be the same as the nominal 4 psig (28 kPa)
sample pressure indicated on the internal sample
pressure gauge.

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(c.) The internal sample pressure should remain constant

when the analyzer input sample is switched from a
calibration gas standard to a zero gas standard. This
can be assured by setting the delivery pressure from the
sample gas cylinder and the zero gas cylinder equal to
the delivery pressure of the span gas cylinder, which is
20 psig (138 kPa). If this cannot be accomplished,
adjust the output pressure regulator on the zero gas
cylinder as required.

2. Adjust R23, the zero adjust potentiometer on the power supply
board, to produce 0 mA current output.

2.5 Gas requirements

The instrument requires two gases normally supplied from cylinders:
air and span gas.

2.5.1 Air (U.S.P. Breathing Grade)

Air is used as both an oxygen source for the generation of the ozone
required for the chemiluminescence reaction, and as a standard gas
for zero calibration. Air for each purpose must be supplied from a
separate cylinder due to the different pressure requirements at the
ozonator and the zero inlets.

2.5.2 Span Gas

Span gas is a standard gas of accurately known composition that is
used to set an upscale calibration point. The usual span gas is NO or
NO

in a background of nitrogen.

2

HIGH PRESSURE GAS CYLINDERS
The Model 951C requires periodic calibration with a span gas. “Calibrating the
analyzer” on page 3-10. See also General Precautions for Handling and Storing
High Pressure Gas Cylinders, page P-5.

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For maximum calibration accuracy, the concentration of nitrogen oxide in the span
gas should be similar to that in the sample gas. Also, the span gas should be
supplied to the Model 951C’s rear panel sample inlet at the same pressure as the
sample gas. To ensure constant pressure, use a pressure regulator immediately
upstream from the sample inlet.

Each span gas used should be supplied from a tank or cylinder
equipped with a clean, noncorrosive, two-stage regulator. In addition,
a shut off valve is recommended.

Install the gas cylinders in an area of relatively constant ambient
temperature.

2.5.3 Sample requirements

The sample gas must be clean and dry before entering the analyzer.
In general, the sample should be filtered to eliminate particles larger
than two microns and should have a dew point below 90° F (32° C).

Proper supply pressure for sample, zero and span gases for the Model 951C is 20
psig (138 kPa).

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2.5.4 Connecting gas

TOXIC AND OXIDIZING GAS HAZARDS
This instrument generates ozone which is toxic by inhalation and is a strong irritant
to throat and lungs. Ozone is also a strong oxidizing agent. Its presence is detected
by a characteristic pungent odor.

The instrument exhaust contains both ozone and nitrogen dioxide, both toxic by
inhalation, and may contain other constituents of the sample gas which may be
toxic. Such gases include various oxides of nitrogen, unburned hydrocarbons,
carbon monoxide and other products of combustion reactions. Carbon monoxide is
highly toxic and can cause headache, nausea, loss of consciousness, and death.

Avoid inhalation of the ozone produced within the analyzer and avoid inhalation of
the sample and exhaust products transported within the analyzer. Avoid inhalation
of the combined exhaust products at the exhaust fitting.

Keep all tube fittings tight to avoid leaks. See Section 2-8 for Leak Test Procedure.

Connect rear exhaust outlet to outside vent by a 1/4 inch (6.3 mm) or larger
stainless steel or Teflon line. Check vent line and connections for leakage.

To connect a gas to the Model 951C, do the following:

1. Remove plugs and caps from all inlet and outlet fittings.

2. Connect the exhaust outlet to the external vent with stainless
steel or teflon tubing that has an outside diameter of at least
.25 inches (6.3 mm).

3. Connect the external lines from the ozonator air and sample
sources to the corresponding rear panel inlet ports. For sample
line, stainless steel tubing is recommended.

4. Adjust the regulator on the ozonator air cylinder to an output
pressure of 20 to 25 psig (138 to 172 kPa). At least 20 psig
should be present at the rear of the analyzer.

5. Supply sample gas to the rear panel sample inlet at
appropriate pressure: 20 psig (138 kPa).

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2.5.5 Leak testing

The following test is designed for sample pressure up to 10 psig (35
kPa).

1. Supply air or an inert gas such as nitrogen to the analyzer’s
sample and air input fittings at 10 psig (35 kPa).

2. Use a tube cap to seal off the analyzer’s exhaust fitting.

3. Cover all fittings, seals, and other possible leak sources with a
liquid leak detector such as Snoop® (PN# 837801).

4. Check for bubbling or foaming, which indicates leakage, and
repair as required. Any leakage must be corrected before
introduction of sample and/or application of electrical power.

To further confirm that the system is free of leaks, perform one of the
tests in Section 5.

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Section 3: Operation

NOTICE

NOTICE

To analyze a sample stream, do the following:

1. Calibrate the analyzer. See “Calibrating the analyzer” on

page 3-12 for more information.

2. Supply sample gas to the sample inlet.

3. Set the PPM RANGE Switch to the appropriate position.

The Model 951C will begin analyzing the sample stream and is
designed for continuous operation. Normally, it is never turned off
except for servicing or for a prolonged shut-down.

During periods of shutdown, turn off the ozone lamp by shutting off the input air
source.

3.1 Front panel indicators and controls

3.1.1 Display

The display is a 4-digit liquid crystal device that always displays NOX
concentration in parts per million.

3.1.2 Range selection

The Model 951C can be configured to perform its analysis within one
of three sets of ranges designated as Hi, Mid, or Lo.

The Model 951C’s range is not user-selectable—it is configured at the factory based
on the purchase order. Any desired changes to the analyzer’s range must be
handled at the factory.

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The Hi range set consists of spans with the following ranges:

• 0-100 ppm NO

• 0-250 ppm NO

• 0-1000 ppm NO

• 0-2500 ppm NO

X

X

X

X

The Mid range set consists of spans with the following ranges:

• 0-20 ppm NO

• 0-50 ppm NO

• 0-200 ppm NO

• 0-500 ppm NO

X

X

X

X

The Lo range set consists of spans with the following ranges:

• 0-10 ppm NO

• 0-25 ppm NO

• 0-100 ppm NO

X

X

X

• 0-250 ppm NO

X

The span range is selected by setting the PPM RANGE Switch and
the five configuration jumpers on the signal board to the desired range
sensitivity for the recorder output.

3.1.3 Blinking backlight

The backlight blinks when the analyzer’s sensitivity is 10% or more
over the range setting.

To restore function, set the PPM RANGE Switch to a less sensitive
(higher) range by moving it one step to the right.

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3.1.4 Sample pressure gauge

The internal sample pressure (nominally 4 psig or 28 kPa) is adjusted
by rotation of the sample pressure regulator.

Using the MID ranges (20, 50, 200, and 500 ppm NOx), set the sample pressure
regulator to 4.0 psig (28 kPa).

3.1.5 Ozone pressure

The ozone pressure is determined by the pressure regulator of the air
supply cylinder. A nominal pressure of 20 to 25 psig (138 to 172 kPa)
is recommended. Proper operation is indicated when the front panel
ozone indicator lamp is lit.

If ozone lamp does not light, increase pressure slightly by adjusting pressure
regulator control on the air cylinder.

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Figure 3-1. Model 951C Controls, Indicators and Adjustments

3.1.6 Zero and span potentiometers

You can adjust the Zero, Range1 and Range2 potentiometers on the
signal board by way of screwdriver access holes on the front panel .

3.1.7 Ozone interlock

The ozone-producing UV lamp will not ignite or stay lit unless
adequate air pressure is present at the air inlet. Nominal setpoint
pressure is 20 to 25 psig (138 to 172 kPa).

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Figure 3-2. Signal board

Figure 3-3. Signal board test points

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3.2 Starting the analyzer

To start up the Model 951C, do the following:

1. Supply electrical power to the analyzer. The will take the
analyzer approximately two hours to reach temperature
equilibrium, which is necessary to calibrate the analyzer.

2. Make the following adjustments to the signal board:

(a.) Using a small flat screwdriver, set the PPM RANGE

Switch to the range that will be used for sample
analysis.

Figure 3-4. PPM Range Select Switch

3 - 6

Range

(S1 Pos)

11020 100

22550 250

3 100 200 1000

4 250 500 2500

Other Remote Remote Remote

ppm Fullscale

Lo Range Mid Range Hi Range

(b.) Set the configuration jumper settings to your desired

position based on the information provided in Figure 3-

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Figure 3-5. Configuration Jumper Settings

(c.) Set the Range2 selection jumpers to Range 4, 2500ppm

as shown in Figure 3-6.

Figure 3-6. Range 2 Selection Jumpers

PPM Range

Range Position

Lo Mid Hi

JP1 10 20 100

JP2 25 50 250

JP3 100 200 1000

JP4 250 500 2500

3. Adjust the ozone pressure regulator so that the ozone pressure
gauge rests at 20 to 25 psig (138 to 172 kPa).

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4. Do the following to establish the correct zero gas pressure:

(a.) Supply zero gas to rear panel sample inlet.
(b.) Note the reading on internal sample pressure gauge. It

should be the same as the nominal 4 psig (28 kPa)
sample pressure indicated on the internal sample
pressure gauge.

(c.) The internal sample pressure should remain constant

when the analyzer input sample is switched from a
calibration gas standard to a zero gas standard. This
can be assured by setting the delivery pressure from the
sample gas and the zero gas cylinder equal to the
delivery pressure of the span gas cylinder, which is 20
psig (138 kPa). If this cannot be accomplished, adjust
the output pressure regulator on the zero gas cylinder
as required.

5. Do the following to establish the correct sample gas pressure:

(a.) Supply sample gas to the rear panel sample inlet.
(b.) Adjust the sample back pressure regulator so that the

internal sample pressure gauge indicates the value
appropriate to the desired operating range.

The inability to obtain a flow of one liter per minute at the exhaust outlet usually
indicates insufficient sample supply pressure at the sample inlet. Use a 2400 cc flow
meter (i.e., Brooks PN# 1350) at the exhaust outlet to measure flow.

6. Do the following to establish the correct flow of upscale
standard gas:

(a.) Supply upscale standard gas to the rear panel sample

inlet.

(b.) Adjust the sample back pressure regulator so that the

internal sample pressure gauge indicates the value
appropriate to the desired operating range.

Supply pressures for sample and upscale standard gases must be the same.
Otherwise, readout will be inaccurate.

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The analyzer is now ready for calibration.

Figure 3-7. Power Supply Board

3.3 Setting up remote range switching

The Model 951C can be configured to switch ranges, via a control
system such as a PLC or DCS, when a pre-defined NOx

measurement setpoint is reached.

You will need the following to configure the Model 951C for remote
range switching:

• A control system—typically a PLC or DCS.

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• A single pole double throw (SPDT) switch that is controlled by
the control system.

To configure the Model 951C for remote range switching, do the
following:

1. Review the following table, which lists the range spans for each
type of Model 951C analyzer, to find the setpoint range that
should trigger the remote range switching feature.

Remote Range
Connector (J2)

Range 1 10 20 100

Range 2 25 50 250

Range 3 100 200 1000

Range 4 250 500 2500

Lo Mid Hi

2. Connect the SPDT to the appropriate range node—typically
Range 3 or Range 4—on the terminal strip (J2) located on the
back end of the analyzer.

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Figure 3-8. Model 951C rear panel showing J2

3. Install a jumper on the corresponding Range2 Selection
jumper on the Signal board. For example, if you connect the
SPDT to Range 3 at J2, then you would install a jumper at JP3
of Range2 Selection.

Figure 3-9. Range2 Selection jumpers

4. Set up your control system so that the SPDT switches when
the Model 951C’s analog output reaches or exceeds the
desired switch point that you selected in Step 1.

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3.4 Calibrating the analyzer

There are two kinds of calibration: zero calibration and upscale
calibration.

3.4.1 Zero calibrating

An effective zero calibration requires that the analyzer be exposed to
clean air.

To perform a zero calibration, do the following:

1. On the signal board, set PPM RANGE Switch to the same
range that will be used during the sample analysis.

2. Set the front panel RANGE1 potentiometer to mid-range—that
is, do not set it all the way to the left, nor all the way to the right.

3. Supply zero gas to the rear panel sample inlet and wait
approximately two minutes.

4. Set the sample pressure to 4.0 psig (27.6 kPa).

5. After a stable reading is reached, turning the ZERO
potentiometer on the front panel of the analyzer until a zero
reading is obtained.

3.4.2 Upscale calibrating

1. On the signal board, set the Upscale Calibration PPM RANGE
Switch to the position appropriate to the particular span gas.

2. Supply upscale standard gas to the rear panel sample inlet.

3. Set the sample pressure to 4.0 psig (27.6 kPa).

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4. Using a screwdriver, turn the front panel RANGE1
potentiometer so that the reading on the display or recorder is
equal to the known concentration of NOX in the span gas. If the

correct reading is unattainable using this method, go to Step 5.

5. Adjust the R30 potentiometer on the power supply board
clockwise to raise the photomultiplier voltage and increase the
sensitivity of the analyzer. Repeat the zero calibration and
upscale calibration procedures.

6. If necessary, do the following:

(a.) Increase the upscale readings on the LCD display by

adjusting the R43 potentiometer until the display shows
the correct span gas readings.

(b.) Adjust the R25 potentiometer so that the reading on the

display and the recorder is equal to the known
concentration of NOX in the span gas.

3.5 Optimizing the converter temperature

The converter temperature can be adjusted once the appropriate high
voltage and electronic gain have been selected and the value
displayed by the Model 951C matches the calibration gas value.

The vitreous carbon converter used in this analyzer has a low surface
area that gradually increases during high temperature operation of the
converter material.

Initially, the temperature of the peak of the converter efficiency starts
at a relatively high value because significant heat must be supplied to
make the converter active enough to reduce the input nitrogen dioxide
to nitric oxide at the required 95% level. During the operation of the
analyzer, the temperature of the peak will fall as the surface area of
the converter is increased and less external energy is required to
cause adequate conversion.

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In extreme cases, where converter re-profiling has not been
conducted, the converter is so active that it not only reduces nitrogen
dioxide to nitric oxide, but it also reduces the nitric oxide to nitrogen,
which is not detected by the chemiluminescence reaction. The
remedy in this case is to lower the converter temperature, thereby
improving the converter efficiency.

It is important that you periodically monitor the converter temperature
to assure that it is running at peak efficiency. An interval of one week
is recommended. The nominal range of operational temperatures for
the converter is 275° C to 400° C (527° F to 750° F). The operating
temperature of the converter can be checked on the power supply
board by momentarily pressing the CONV TEMP CHECK (S4) switch
while monitoring the resistance across the TP1 and TP2 terminals.

Table 3-1 allows for conversion of the observed resistance to the

operating temperature for the converter.

Table 3-1. Resistance of converter temperature sensor vs. temperature

TEMPERATURE (°C) RESISTANCE (Ohms)

0400

25 438

100 552

200 704

250 780

300 856

350 932

400 1008

450 1084

Do the following to optimize the operating temperature of the
converter:

1. Turn on the analyzer and allow it to stabilize at operating
temperature. This should take approximately two hours.

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2. Measure the operating temperature of the converter by
accessing the power supply board and momentarily pressing
the CONV TEMP CHECK (S4) switch while monitoring the
resistance across the TP1 and TP2 terminals. Note the value
for future reference.

3. Supply a calibration gas of known NO2 concentration to the
analyzer and note the concentration value determined when

the full response has been achieved.

4. Access the power supply board and turn the converter
temperature adjust potentiometer (R9 CONV HTR) one full turn
counterclockwise from the factory-established setting.

5. Allow the analyzer to operate for 15 minutes at the new, lower
temperature. Recheck the response and note the value for
later use.

6. Increase the temperature of the converter by rotating the
converter temperature adjust potentiometer one quarter turn
clockwise; wait fifteen minutes for thermal equilibrium and then
re-measure the NO2 calibration gas value. Note its value.

7. Repeat this procedure of one quarter turn adjustments of the
potentiometer, waiting for thermal stability and determination of
the calibration gas value until either a 95% value is obtained or
the final one quarter turn adjustment gives an efficiency
increase of less than one percent.

8. Decrease the temperature of converter operation by rotating
the converter temperature adjust potentiometer (R9 CONV
HTR) one eighth of a turn counterclockwise. This places the
converter at a temperature suitable for low ammonia
interference and efficient NO2 conversion. Re-measure the

indicated converter temperature and compare it to the initially
recorded value from Step 2.

Converter temperature is not a direct measure of converter efficiency. Temperature
measurements are for reference purposes only.

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3.6 Measuring converter efficiency

It is the responsibility of the user to measure efficiency of the NO2 to
NO converter during initial startup, and thereafter at intervals

appropriate to the application--normally once a month.

Optimizing the operating temperature of the converter also serves as
an efficiency check if the concentration of NO2 in the calibration gas

matches the value that is documented in the National Institute of
Standards and Technology (NIST) Reference Materials. If the
concentration of the nitrogen dioxide in the calibration gas is not
known accurately, the optimization procedure still serves to provide
the correct converter operating temperature.

If the only available known standard is the nitric oxide calibration
standard, perform the following procedure to measure converter
efficiency:

This technique is adapted from 40 CFR Part 60 - Standards of Performance for New
Stationary Sources, Appendix A, Method 20, Paragraph 5.6.

1. Select the appropriate analysis range.

2. Add gas from the mid-level NO in N2 calibration gas cylinder to
a clean, evacuated, leak-tight Tedlar bag.

According to the 40 CFR Part 60, “mid-level” is defined as a gas concentration that
is equivalent to 45 to 55 percent of the analysis range.

3. Dilute the gas approximately 1:1 with 20.9% O2 purified air.

4. Immediately attach the bag outlet to the input of the pump
supplying pressurized gas to the analyzer. It is important to use
a sample delivery pump that does not consume nitrogen
dioxide as it delivers sample to the analyzer. Losses of nitrogen
dioxide in the pump will be reported as converter inefficiency.

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5. Operate the analyzer and continue to sample the diluted nitric
oxide sample for a period of at least thirty minutes. If the
nitrogen dioxide-to-nitric oxide conversion is at the 100% level,
the instrument response will be stable at the highest value
noted.

6. If the response at the end of the thirty minute period decreases
more than 2% of the highest peak value observed, the system
is not acceptable and corrections must be made before
repeating the check. If it is determined that observed
subnormal conversion efficiencies are real, and not due to
errors introduced by nitrogen dioxide consumption in the
sample pump or other parts of the sample handling system,
verify that the converter is peaked at the optimum temperature
before replacing the converter.

3.7 Recommended calibration frequency

After initial startup or startup following a shut-down, the analyzer
requires about two hours for stabilization before it is ready for
calibration. The maximum permissible interval between calibrations
depends on the analytical accuracy required, and therefore cannot be
specified here. It is recommended that initially the instrument be
calibrated at least once every 8 hours. This practice should continue
until experience indicates that some other interval is more
appropriate.

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3 - 18

Section 4: Theory

NOTICE

4.1 Nitric oxide concentration is determination by chemiluminescence method

The chemiluminescence method for detection of nitric oxide (NO) is
based on its reaction with ozone (O3) to produce nitrogen dioxide

(NO2) and oxygen (O2). Some of the NO2 molecules thus produced
are initially in an electronically excited state (NO2*). These revert
immediately to the ground state, with the emission of photons

(essentially red light).

The reactions involved are:

NO + O3  NO2* + O

NO2*  NO2 + Red light

Any NO2 initially present in the sample is reduced to NO by a heated bed of vitreous
carbon through which the sample is passed before being routed to the reaction

chamber.

As NO and O3 mix in the reaction chamber, the intensity of the emitted
red light is proportional to the concentration of NO.

The intensity of the emitted red light is measured by a photomultiplier
tube (PMT) that produces a current of approximately 3x10 -9 amperes

per part per million of NO in the reaction chamber.

2

4.2 Analyzer flow system

The analyzer flow system’s basic function is to deliver regulated flows
of sample, calibration gas, or zero gas and ozonized air to the
reaction chamber. The discharge from the reaction chamber flows
from the analyzer via the exhaust outlet.

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Figure 4-1. Flow diagram, Lo and Mid range

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Figure 4-2. Flow diagram, Hi range

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4.2.1 Flow of sample, standard gas or zero gas to reaction chamber

Suitably pressurized sample, standard gas or zero gas is supplied to
the analyzer through the rear panel sample inlet.

A back pressure regulator inside the analyzer controls the flow rate of
the selected gas into the reaction chamber. It provides an adjustable,
controlled pressure on the upstream side, where gas is supplied to the
calibrated, flow-limiting sample capillary. The back pressure regulator
is adjusted for appropriate reading on the internal sample pressure
gauge. For operation at NO and NO2 levels below 250 ppm, the

correct setting on the sample pressure gauge is 4 psig (28 kPa). This
results in a flow of approximately 60 to 80 cc/min to the reaction
chamber.

The reaction chamber discharges excess sample with the effluent via
the exhaust outlet. The restrictor sets bypass flow at 1 L/min (nominal)
to ensure the proper functioning of the sample pressure regulator and
rapid system response. Excessive changes of sample or standard gas
pressure, on the order of 5 psig (35 kPa) or more, will affect the
bypass flow rate and can affect accuracy.

4.2.2 Ozone generation

Suitably pressurized air from an external cylinder is supplied to the
rear panel air inlet. The proper pressure setting is 20 to 25 psig (138
to 172 kPa). Within the ozone generator, a portion of the oxygen in the
air is converted to ozone by exposure to an ultraviolet lamp. The
reaction is:

UV

3O2  2O

From the generator, the ozonized air flows into the reaction chamber
for use in the chemiluminescence reaction.

3

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4.3 Signal conditioning and display

The signal conditioning and display board provides the following
functions:

• Signal conditioning circuit

• An analog to digital converter

• Display device

• Range control circuits

• Post signal amplifier and output amplifier circuit

• Display/backlight blink control

• Range conditions

• Remote control circuits

Figure 4-3. Analyzer block diagram

All of the above functions are on a single board located at the front of
the analyzer. Certain control requirements, such as range calibration
and zero offset adjustment, are available as screw-driver adjustments
on the front panel. A digital LCD is mounted on the front side of the
board for data display purposes as are control potentiometers.

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NOTICE

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4.3.1 Circuit functions

4.3.1.1 Signal conditioning amplifiers

Boards assembly 6A00326G01/02 is a high input impedance
electrometer amplifier board.

Current output from the detector unit is converted to voltage by the
electrometer amplifier and then further amplified by post amplifier.

The electrometer amplifier gain can be reduced by a factor of 10 by
shorting JP1 and by shorting pins 1 and 2 on P1 with the included
jumpers; this is used for higher range selection.

4.3.1.2 Gain amplifier

The precision amplifier allows for two selectable gains, one for 10,
100, and 1000 spans, and the other for 25, 250, and 2500 spans.

Intermediate gain ranges as required by the Model 951C Lo range,
Mid range or Hi range can be obtained by interpolating between the
requisite ranges using boolean logic and analog switches.

4.3.1.3 Range 1 and Range 2 selection

The signal output can be adjusted from the front panel for calibration
purposes. A second range can be chosen by placing a jumper on
JP1, JP2, JP3, or JP4. Selecting the programmed range activates the
K2 relay, which allows that range to be calibrated.

If no jumper is present only Range 1 can be calibrated.

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DECEMBER 2013 748214-X

4.3.1.4 Post amplifiers

The conditioned signal and the range calibration potentiometers
(R101 and R102) are provided to the post amplifier. This amplifier has
switch controlled feed back resistors that permit gain selections of any
range, as determined by the range switch and associated logic. An
adjustment potentiometer (R25) allows a small correction for inter
range calibration purposes.

The output of the post amplifier is provided to the analog-to-digital
converter (ADC) for digitization and display purposes. Potentiometer
R43 allows you to adjust the signal to the ADC to match the display
signal with the recorder signal, if required.

Potentiometer R25 allows you to match the recorder output to the
display. The recorder output amplifier signal can be trimmed to
precisely match the recorder calibration. Note that this adjustment
does not affect or change the analyzer’s display.

4.3.1.5 Analog-to-digital converter

The LCD is a special integrated circuit where the ADC and LCD
drivers are combined. The signal data is digitized and provided in the
correct format to the LCD.

4.3.1.6 Display, backlight and over range blink circuits

The blink or over range display function is initiated when the voltage
output goes 10% over the span range.

4.3.1.7 Remote control circuits

The Model 951C has a fully isolated remote control interface. Optical
isolators and a remote 24V power supply ensure that no direct return
path exists between the user’s system and the 951C when in remote
control mode.

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Relay K1 switches between the internal range switch control (SW1)
and the external remote range control. When SW1 is set to 5 it
activates K1 and creates a fully isolated system.

Optical isolators connect via a ribbon cable to the remote connector
panel at the rear of the Model 951C. A ten terminal barrier strip
provides connection for remote range selection.

To select one of the four ranges, connect any input terminal (1 through

4) to RTN terminals 5 or 6.

For remote operation, connect a 24V power supply to terminals 5, 6,
7, or 8. Negative or low side is connected to 5 or 6. Positive or high
side is connected to 7 or 8. For protection purposes the high side is
fused.

The local range switch (SW1) must be in position 5 to disconnect local control and
restart remote control mode.

For local operation, set the local range switch (SW1), which is located
on the top of the signal board, to a value between 1 and 4. An external
24V supply is not required.

4.4 Analyzer thermal system

The basic function of the analyzer thermal system is to provide a
stable thermal environment for the photomultiplier tube (PMT).

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Model 951C Instruction Manual

DECEMBER 2013 748214-X

Figure 4-4. The analyzer thermal system

The temperature of the PMT must be held within a half degree band at
approximately 18° C if it is to produce a useful signal for low
concentrations of NOx. This is accomplished by using a solid state

cooler to house the PMT. The heat that is radiated from the cooler is
carried away by the cooler fan.

The solid state cooler must work against a relatively constant load in
order to maintain the temperature of the PMT. This load is produced
by a case heater and exhaust fan that control the temperature inside
the case within a one degree band—approximately 50° C for ambient
temperatures from 4° C to 40° C.

The electronics that support the analyzer thermal system and the NO

2

to NO converter are located on the power supply board.

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748214-X DECEMBER 2013

4 - 10

Section 5: Routine servicing

WARNING

WARNING

NOTICE

ELECTRICAL SHOCK HAZARD
Servicing requires access to live parts which can cause death or serious injury.
Refer servicing to qualified personnel.

INTERNAL ULTRAVIOLET LIGHT HAZARD
Ultraviolet light from the ozone generator can cause permanent eye damage. Do not
look directly at the ozone generator’s ultraviolet source. Use ultraviolet filtering
glasses when interacting with the ozone generator.

Do not expose the photomultiplier tube to ambient light. If ambient light touches the
PMT while the power is on, either through a loose fitting on the reaction chamber or
any other leak, the PMT will be destroyed. If exposed to ambient light while the
power is off, the PMT will be noisy for a period of time afterwards. Unless
appropriate precautions are observed, light can strike the tube when removing
fittings from the reaction chamber.

5.1 System checks and adjustments

The following procedures can be used to determine the cause of
unsatisfactory performance, or to make adjustments following the
replacement of components. If a recorder is available, use it for
convenience and maximum accuracy in the various tests, otherwise
use a digital multimeter to measure voltage output.

5.1.1 Adjusting the display fullscale span

If a recorder is used, and has been properly zeroed, it should agree
with the display reading. If not, do the following to adjust the display
reading:

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Instruction Manual Model 951C

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1. Adjust the R25 potentiometer on the signal board.

2. If agreement between the display and the recorder cannot be

reached, check the recorder.

3. If the recorder is functioning properly, replace the signal board.

5.1.2 Factors affecting the overall sensitivity of the analyzer

The following principal factors determine the overall sensitivity of the
analyzer:

• Sample flow rate to the reaction chamber

• Sensitivity of the photomultiplier tube (PMT)

• PMT high voltage

Sensitivity is subnormal if specified fullscale readings are
unobtainable by adjustment of the span control. The cause of reduced
sensitivity may be in either the flow system or the electronic circuitry.

If either the high voltage board or the phototube/reaction chamber
assembly has been replaced, readjust the high voltage to obtain the
correct overall sensitivity by turning the R30 potentiometer on the
power supply board clockwise to increase the photomultiplier high
voltage and sensitivity, or counterclockwise to decrease the voltage
and sensitivity. The adjustment range is about 650 V to 2100 V for the
regulated DC voltage applied to the photomultiplier tube. The nominal
setting is 1100 volts; however, the voltage should be adjusted as
required for overall system sensitivity.

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5.1.3 Monitoring ozone output

TOXIC GAS HAZARD
Use extreme caution in troubleshooting the ozone generator. Ozone is toxic.

To check for adequate output from the ozone lamp, do the following:

1. Calibrate the analyzer on a high-level nitrogen oxide standard
such as 250 ppm nitrogen oxide at the nominal 4.0 psi internal
sample pressure setpoint, and note the reading.

2. Note the readings obtained after setting the sample pressure
setpoints to 3.0, 2.0, and 1.0 psi. The span gas value will
change as the pressure is changed. The difference in span gas
value between any two successive sample pressure levels
should be approximately the same--that is, the difference
between the 4.0 and 3.0 psi readings should approximately
match the difference between the 3.0 and 2.0 psi readings.

If the size of the span gas value difference increases as the
sample pressure is lowered, the analyzer output is limited by
the amount of ozone production from the lamp and the
following two additional checks should be made:

(a.) Verify that the sample flow (not including bypass) does

not exceed the nominal 60 to 80 cc/min, at 4.0 psi
internal sample pressure.

(b.) Substitute another lamp to see if the ozone output is

increased. If no other ozone lamp is available, the
analyzer sample input pressure can be reduced to the
pressure where the ozone limitation is not present. If the
lamp output is low and the sample pressure is reduced
to restore operation to the condition where ozone
limitation is not occurring, some degradation in analyzer
response time characteristics can occur.

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5.1.4 Finding the cause of excessive background current

Excessive background current prevents the proper functioning of the
zero control. The source of excessive background current can be
found in either the electronic circuitry or the sample flow system.

To find the cause of excessive background current, do the following:

1. Make sure the electronic circuitry is functioning properly.

2. Turn on the analyzer.

3. Verify that the zero control and the amplifier are functioning
properly.

4. To check for excessive photomultiplier dark current, do the
following:

(a.) Shut off all flow to the ozone generator and then turn off

the ozone generator itself.

(b.) Supply cylinder air to the rear panel sample inlet and

note response on display or recorder. If background
current is still excessive, the possible causes are:

• Leakage of ambient light to photomultiplier tube

• Defective photomultiplier tube

• Electrical leakage in socket assembly

5. To check for reaction chamber or sample flow system
contamination, see “Servicing the photomultiplier tube and the

reaction chamber” on page 5-9.

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DECEMBER 2013 748214-X

5.2 Servicing the flow system

To facilitate servicing and testing, the Model 951C has front drawer
access.

5.2.1 Cleaning the sample capillary

If you suspect that the sample capillary is clogged, do the following to
measure the flow rate:

1. Turn the analyzer off and shut off all gases.

2. Cover the reaction chamber with a dark cloth or other light
shielding material.

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Figure 5-1. Photomultiplier housing assembly

5 - 6

3. Remove the sample capillary fitting and make sure the
chamber is covered by the cloth to prevent the entry of stray
light through the hole left by the removal of the capillary fitting.

If the opening in the reaction chamber is inadvertently exposed to ambient light, the
instrument will temporarily give a highly noisy background reading. If so, this
condition may be corrected by leaving the instrument on, with high voltage on, for
several hours. If high voltage is on during exposure, the photomultiplier tube will be
destroyed.

Model 951C Instruction Manual

NOTICE

DECEMBER 2013 748214-X

4. Supply dry nitrogen or air to the sample inlet on the rear panel.

5. Connect a flowmeter to the open end of the sample capillary.

6. Set the internal sample pressure regulator to 4 psig (28 kPa).

7. Check the flowmeter and do one of the following:

• If the flow is between 60 to 80 cc/min, then the sample
capillary is not clogged; proceed to step 8.

• If the flow is below 60 cc/min, the capillary requires cleaning
or replacement. To clean the sample capillary, wash it with
denatured alcohol, and then purge it by blowing dry
nitrogen or air through it for one minute. Proceed to step 8.

8. With the photomultiplier still covered, slowly insert the free end
of the capillary into its fitting on the reaction chamber. Push the
capillary until it touches bottom against the internal fitting.
Tighten the fitting 1/4 turn past finger tight.

Do not over-tighten capillary internal fitting, as over-tightened fittings may restrict
the sample flow.

5.2.2 Confirming a faulty ozone restrictor fitting

If you suspect that the ozone restrictor fitting is faulty, do the following
to measure the flow rate:

1. Turn the analyzer off.

2. Supply dry nitrogen or air to the rear panel air inlet.

3. Cover the photomultiplier housing with a dark cloth.

4. Disconnect the ozone generator tube from the reaction
chamber and make sure the chamber is covered by the cloth to
prevent the entry of ambient light.

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Figure 5-2. Major assemblies of the Model 951C

5 - 8

5. Connect a flow meter to the open end of the ozone generator
tube.

6. Adjust the ozone pressure regulator so that the ozone pressure
gauge indicates a normal operating pressure of 20 to 25 psig
(138 to 172 kPa). The flow meter should indicate an
appropriate flow of 500 to 600 cc/min for 20 psig.

Model 951C Instruction Manual

DECEMBER 2013 748214-X

If the flow is less than 500 cc/mm, that indicates clogging in the
flow path that supplies air to the ozone generator. This path
contains an air restrictor assembly (PN# 655519) that consists
of a metal fitting with an internal restrictor to reduce pressure.
The assembly is upstream from the inlet port of the ozone
generator. If the air restrictor gets clogged, the assembly must
be replaced as it cannot be cleaned satisfactorily in the field.

5.3 Servicing the photomultiplier tube and the reaction chamber

The photomultiplier assembly consists of the photomultiplier tube and
socket, the thermoelectric cooler, and the reaction chamber.

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Figure 5-3. Photomultiplier housing assembly

5 - 10

The assembly must be removed from the analyzer in order to clean
the reaction chamber or to replace the photomultiplier tube.

Model 951C Instruction Manual

NOTICE

DECEMBER 2013 748214-X

5.3.1 Removing or replacing the photomultiplier assembly

To remove the photomultiplier assembly, do the following:

1. Turn the analyzer off and shut off all gases.

2. Unplug the electrical cable from the power supply PC board.

3. Disconnect the high voltage cable and the signal cable from

the left side of the assembly. Unscrew the two mounting screws
that are located just below the connectors.

4. Uncouple the sample and ozone capillaries and the exhaust

line from the right side of the assembly. Unscrew the two
mounting screws that are located just below the fittings.

5. Loosen the mounting screws described in steps 4 and 5 above.

6. Lift the assembly from the analyzer.

To replace the assembly, reverse the removal procedure.

5.3.2 Cleaning the reaction chamber

The photomultiplier tube will be permanently damaged if exposed to ambient light
while powered with high voltage. The photomultiplier tube will develop temporary
electronic noise if exposed to ambient light with high voltage off. A temporary noisy
condition can be corrected by leaving instrument on, with high voltage on, for
several hours. The required recovery time depends on the intensity and duration of
the previous light exposure. The noise level on the most sensitive range usually
drops to normal within 24 hours.

If the sample gas is properly filtered, the reaction chamber should not
require frequent cleaning. In the event of carryover or contamination,
however, the chamber should be disassembled and the quartz
window and the optical filter should be cleaned according to the
following procedure:

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Instruction Manual Model 951C

CAUTION

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1. Cover and shade the reaction chamber and photomultiplier
assembly with a dark cloth or other light-shielding material.

Always wear surgical rubber gloves when handling the reaction chamber to prevent
contamination from handling.

2. Note the orientation of the capillary fittings. Slowly rotate and
withdraw the reaction chamber from the thermocooler housing.
En-sure that no light strikes the photomultiplier tube.

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DECEMBER 2013 748214-X

Figure 5-4. Photomultiplier housing assembly

3. Unscrew the plastic end cap to free the quartz window and the
red plastic optical filter. Note the sequence in which these are
assembled.

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NOTICE

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4. Use one of the following methods to clean the reaction
chamber, as appropriate:

• The standard method is applicable in most cases.

• The alternate method is applicable when the instrument has

shown high residual fluorescence, which is indicated by
high residual currents on a zero gas and high differentials
between zero gas readings obtained with the ozone lamp
on and off.

5.3.2.1 Standard Cleaning Procedure

Do the following to clean the reaction chamber and its components:

1. Use clean, distilled water, Alconox® detergent (PN# 634929),
and a stiff plastic bristle brush, such as a toothbrush, to scrub
the Teflon surface and gas ports of the reaction chamber.

Alconox detergent is included in the shipping kit, and is available for purchase from
numerous vendors.

2. Use Alconox and a clean, soft facial tissue—not an industrial
wipe—to carefully clean the quartz window.

3. Vigorously flush the reaction chamber and the quartz window
with clean, distilled water.

4. Blow out all water from the internal passages of the reaction
chamber.

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Model 951C Instruction Manual

WARNING

DECEMBER 2013 748214-X

5. Dry the reaction chamber and the quartz window in an oven set
to 125° F (52° C) for 30 to 45 minutes or blow dry the parts with
cylinder air or nitrogen to eliminate all moisture.

ACID HAZARD
Hydrochloric acid is irritating to the skin, mucous membranes, eyes and respiratory
tract. Direct contact causes severe chemical burns.

Avoid contact with eyes and skin and avoid breathing fumes. Use in a hooded or
well-ventilated place. Wear goggles, rubber gloves and protective clothing.

5.3.2.2 Alternate cleaning procedure for high residual fluorescence

Do the following to clean the reaction chamber and its components:

1. Hold the reaction chamber by its tube fittings and carefully
immerse the white Teflon part of the chamber in 50%
concentrated reagent grade hydrochloric acid for five minutes.

2. Thoroughly rinse the acid-washed region with deionized water,
then air dry with cylinder air or nitrogen to eliminate all
moisture.

5.3.3 Reconstructing the photomultiplier assembly

To replace the photomultiplier assembly, do the following:

1. Place the reaction chamber parts in their original positions and
press on the end cap so that the mating threads engage
properly, without cross threading.

2. Turn the mating parts in one continuous motion until the parts
mesh. Do not over torque.

3. With reaction chamber now assembled, reconnect it to the
thermocooler housing.

To return the photomultiplier assembly to its place in the analyzer, see

“Removing or replacing the photomultiplier assembly” on page 5-11.

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5.3.4 Photomultiplier tube and housing

The photomultiplier tube operates at high DC voltages (nominal
setting is 1100 volts) and generates small currents that are highly
amplified by the signal conditioning circuitry. It is therefore important
that ambient humidity and condensed water vapor be kept from the
interior of the photomultiplier housing. Ambient humidity can result in
electrical leakage, observed as abnormally high dark current. Water
vapor or condensed moisture in contact with the photomultiplier tube
can result in an abnormally high noise level during instrument readout
on zero air or upscale standard gas.

The photomultiplier tube and reaction chamber assembly incorporates
several features to protect against humidity and moisture. The
photomultiplier socket assembly is potted with high impedance
silicone rubber compound and is sealed from external influences with
epoxy and rubber gasket material. The socket assembly and the
reaction chamber are sealed with O-rings into opposite ends of the
tubular photomultiplier housing. The socket end of the housing may
be sealed with either one or two O-rings, depending on the length of
the phototube.

5.3.5 Replacing the photomultiplier tube

To replace the photomultiplier tube, do the following:

1. Note the orientation of the connectors.

2. Slowly rotate and withdraw the socket assembly from the
housing. Note the orientation and placement of the metal shield
and the black plastic insulating cover.

3. Carefully unplug the photomultiplier tube from the socket.

4. Plug the new tube into the socket.

5. Orient the metal shield and black plastic insulator as noted in

Step 2.

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WARNING

DECEMBER 2013 748214-X

6. Carefully rotate and insert the tube, shield and cover into the
housing. Orient as noted in Step 1.

5.4 Ozone generator assembly

The ozone generation assembly consists of the ultraviolet lamp, lamp
housing, and power supply.

TOXIC CHEMICAL HAZARD
The ozone generator lamp contains mercury. Lamp breakage can result in mercury
exposure. Mercury is highly toxic if absorbed through the skin or ingested, or if
vapors are inhaled. Handle lamp assembly with extreme care.

If lamp is broken, avoid skin contact and inhalation in the area of the lamp or the
mercury spill. Immediately clean up and dispose of the mercury spill and lamp
residue as follows:

Wearing rubber gloves and goggles, collect all droplets of mercury by means of a
suction pump and aspirator bottle with long capillary tube. Alternatively, a
commercially available mercury spill clean-up kit, such as J. T. Baker product No.
4439-01, is recommended.

Carefully sweep any remaining mercury and lamp debris into a dust pan. Carefully
transfer all mercury, lamp residue and debris into a plastic bottle which can be tightly
capped. Label and return to hazardous material reclamation center.

Do not place in trash, incinerate or flush down sewer. Cover any fine droplets of
mercury in non-accessible crevices with calcium polysulfide and sulfur dust.

5.4.1 Removing the ultraviolet lamp and lamp housing

To remove the lamp and housing, do the following:

1. Turn the analyzer off and shut off all gases.

2. Disconnect the air supply tubing from the front of the housing.

3. Disconnect the ozone tube leading to the reaction chamber.

4. Disconnect the power cable from the power supply.

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NOTICE

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5. Uncouple the two velcro straps that secure the housing to the
power supply.

6. Lift the housing from the analyzer.

5.4.2 Replacing the ultraviolet lamp

To replace the lamp, do the following:

1. Unscrew and remove the end cap.

2. Unscrew the aluminum outer lamp housing tube from the lamp
base, being careful not to hit or touch the lamp assembly.

Do not touch the lamp. Fingerprints may cause a decrease in lamp output.

3. Replace the O-ring in the lamp base with one of the new O­rings that is supplied in the kit.

4. Insert the replacement lamp assembly being careful not to hit
or touch lamp housing.

5. Insert a new O-ring into the new end cap. Screw the end cap
onto the end of the lamp housing.

6. Replace the lamp and housing by reversing the steps in this
section.

5.4.3 Removing the power supply

To remove the power supply, do the following:

1. Remove the ultraviolet lamp and lamp housing. See

“Removing the ultraviolet lamp and lamp housing” on page 5­17 for help.

2. Disconnect the power lead from the power supply board.

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Model 951C Instruction Manual

DECEMBER 2013 748214-X

3. Remove the two screws that secure the power supply to the
bottom plate of the analyzer.

4. Lift the power supply from the analyzer.

5. Replace the power supply by reversing the order of the steps in
this section.

5.5 Converter assembly

To check the heater blanket, verify the continuity of the heater coil.

To check the temperature sensor, refer to “Optimizing the converter

temperature” on page 3-13 and measure the converter’s resistance

when the power is off—it should be about 440 ohms—and when the
power is on—should range from 800 to 1,000 ohms.

Table 5-1. Resistance of converter temperature sensor vs. temperature

TEMPERATURE (°C) RESISTANCE (Ohms)

0400

25 438

100 552

200 704

250 780

300 856

350 932

400 1008

450 1084

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5.5.1 Removing the glass converter tube

To remove the glass converter tube, do the following:

1. Turn off the analyzer.

2. Carefully disconnect the blue silicon connectors from the ends
of the inlet and outlet tubes. The inlet tube is partially filled with
glass wool and has a larger inside diameter than the outlet
tube. Further, the outlet tube and the sample capillary connect
to the same stainless steel tee.

3. Release the assembly and disconnect the heater and sensor
connectors from the temperature control board.

4. Remove the lacing from the heater blanket, and remove the
converter tube. Note the position of the temperature sensor
and its leads as the aluminum foil is unwrapped.

5. Replace the defective part and reassemble. The temperature
sensor should touch the converter tube with the top of the
sensor at the midpoint of the converter. Route sensor leads
axially to the outer end.

6. Condition the converter as described in “Optimizing the

converter temperature” on page 3-13 and “Measuring
converter efficiency” on page 3-16.

5.6 Servicing the electronic circuitry

To troubleshoot the electronic system, refer to Section 4. The
electronic system utilizes printed circuit boards with solid state
components. After a malfunction is traced to a particular board, return
it to the factory for repair.

5 - 20

Section 6: Replacement parts

WARNING

PARTS INTEGRITY
Tampering with or unauthorized substitution of components may adversely affect
safety of this product. Use only factory-approved components for repair.

6.1 Matrix

Each analyzer is configured per the customer sales order. Below is
the 951C sales matrix which lists the various configurations avail-able.

To identify the configuration of an analyzer, locate the analyzer name­rating plate. The sales matrix identifier number appears on the
analyzer name-rating plate.

Model Description

951C Process Chemiluminescence NO

Level 1 Ranges

01 Low Ranges: 0-10, 0-25, 0-100, 0-250 ppm NO

02 High Ranges: 0-100, 0-250, 0-1000, 0-2500 ppm NO

04 Mid Ranges: 0-20, 0-50, 0-200, 0-500 ppm NO

Level 2 Output

01 Selectable: 0-5 VDC, 0/4-20 mA

Level 3 Case

01 Standard

Level 4 Spare

00 None

Analyzer (19" Rack Mount) (951C)

x

x

x

x

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Level 5 Sample Restrictor

01 Standard sample inlet, restrictor included

02 User controlled sample flow (no sample restrictor included)

6.2 Circuit board replacement policy

In most situations involving a malfunction of a circuit board, it is more
practical to replace the board than to attempt to isolate and replace an
individual component. The testing and replacement costs will
probably exceed the cost of a rebuilt assembly from the factory.

The following lists do not include individual electronic components. If
circumstances necessitate replacement of an individual component
that can be identified by inspection or from the schematic diagrams,
obtain the replacement component from a local source of supply.

6.3 Replacement parts

The following parts are recommended for routine maintenance and
troubleshooting of the Model 951C. If the trouble-shooting procedures
do not resolve the problem, contact your local Rosemount Analytical
service office. A list of Rosemount Analytical Service Centers is
located in Section 7.

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6.3.1 Common parts

Figure 6-1. Major Assemblies of the Model 951C

655519 Air Restrictor Fitting

657091 Capacitor Assembly

655166 Capillary, Bypass

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Instruction Manual Model 951C

748214-X DECEMBER 2013

655589 Capillary, Sample Hi

623719 Capillary, Sample Lo

654068 Temperature Control Assembly

654070 Converter Assembly

655303 Exhaust Fan

654052 Fan Assembly

898587 Fuse 3.15 A

902413 Fuse 6.25 A

662168 I/O Assembly

652173 Ozone Generator

658156 Ozone Generator UV Lamp Replacement Kit

655129 Ozone Generator Power Supply

654062 Photomultiplier Assembly

655332 Power Supply Assembly

662273 Pressure Switch

623936 Sample Flow Restrictor

644055 Sample Pressure Gauge

815187 Sample Regulator

622917 Sensor, Temperature

6A00337G01/02/03 Signal/Control Board

654878 Transformer/Inductor Assembly

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Model 951C Instruction Manual

DECEMBER 2013 748214-X

6.3.2 Photomultiplier assembly

Figure 6-2. Photomultiplier Housing Assembly

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654943 Housing

649541 Insulating Washer

636318 Magnetic Shield

630916 Magnetic Shield

001522 O Ring

008423 O Ring, Photomultiplier

655168 Photomultiplier Tube

654381 Reaction Chamber

654086 Socket Assembly

639722 Thermal Shield

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DECEMBER 2013 748214-X

6.3.3 Converter assembly 654070

Figure 6-3. Converter Assembly

632784 Connector, Blue Silicone

657127 Heater

632782 Temperature Sensor

632795 Tube

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Instruction Manual Model 951C

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6.3.4 Temperature control assembly 654068

Figure 6-4. Case Heater Temperature Control Assembly

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DECEMBER 2013 748214-X

622733 Fan

622732 Heater

655335 Temperature Control Board

900492 Thermal Fuse

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Instruction Manual Model 951C

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748214-X DECEMBER 2013

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Return of material

If factory repair of defective equipment is required, proceed as
follows:

1. Secure a return authorization from a Rosemount Analytical Inc.
Sales Office or Representative before returning the equipment.
Equipment must be returned with complete identification in
accordance with Rosemount instructions or it will not be
accepted.

Rosemount CSC (Customer Service Center) will provide the
shipping address for your instrument.

In no event will Rosemount be responsible for equipment
returned without proper authorization and identification.

2. Carefully pack the defective unit in a sturdy box with sufficient
shock absorbing material to ensure no additional damage
occurs during shipping.

3. In a cover letter, describe completely:

• The symptoms that determined the equipment is faulty.

• The environment in which the equipment was operating

(housing, weather, vibration, dust, etc.).

• Site from where the equipment was removed.

• Whether warranty or non-warranty service is expected.

• Complete shipping instructions for the return of the

equipment.

4. Enclose a cover letter and purchase order and ship the
defective equipment according to instructions provided in the
Rosemount Return Authorization, prepaid, to the address
provided by Rosemount CSC.

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Rosemount Analytical Inc.
Process Analytic Division
Customer Service Center
1-800-433-6076

If warranty service is expected, the defective unit will be carefully
inspected and tested at the factory. If the failure was due to the
conditions listed in the standard Rosemount warranty, the defective
unit will be repaired or replaced at Rosemount's option, and an
operating unit will be returned to the customer in accordance with the
shipping instructions furnished in the cover letter.

For equipment no longer under warranty, the equipment will be
repaired at the factory and returned as directed by the purchase order
and shipping instructions.

Customer service

For order administration, replacement Parts, application assistance,
onsite or factory repair, service or maintenance contract information,
contact:

Rosemount Analytical Inc.
Process Analytic Division
Customer Service Center
1-800-433-6076

Training

A comprehensive Factory Training Program of operator and service
classes is available. For a copy of the current operator and service
training schedule contact:

Rosemount Analytical Inc.
Process Analytic Division
Customer Service Center
1-800-433-6076

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©2013 Rosemount Analytical, Inc. All rights reserved.

The contents of this publication are presented for informational purposes
only, and while every effort has been made to ensure their accuracy, they
are not to be construed as warranties or guarantees, express or implied,
regarding the products or services described herein or their use or
applicability. All sales are governed by our terms and conditions, which are
available on request. We reserve the right to modify or improve the designs
or specifications of our products at any time without notice.

Rosemount Analytical Inc., a division of Emerson Process Management,
reserves the right to make changes to any of its products or services at any
time without prior notification in order to improve that product or service
and to supply the best product or service possible.

All rights reserved. The Emerson logo is a trademark and service mark of
Emerson Electric Co. All other marks are the property of their respective
owners.

www.emersonprocess.com