Rosemount 951C NOx Analyzer-Rev P Manuals & Guides

Rosemount Analytical

M

ODEL

NO

I

NSTRUCTION MANUAL

X ANALYZER

951C

748214-P

OTICE

N

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

Teflon® is a registered trademark of E.I. duPont de Nemours and Co., Inc.
Alconox is a registered trademark of Alconox, Inc.

SNOOP® is a registered trademark of NUPRO Co.

Manual Part Number 748214-P
December 2000
Printed in U.S.A.

Rosemount Analytical Inc.

4125 East La Palma Avenue

A

NAHEIM

, C

ALIFORNIA

92807-1802

C

P

REFACE

PURPOSE/SAFETY SUMMARY........................................................................P1

SPECIFICATIONS - LO RANGE........................................................................P4

SPECIFICATIONS - HI RANGE.........................................................................P5

CUSTOMER SERVICE, TECHNICAL ASSISTANCE AND FIELD SERVICE............P6

RETURNING PARTS TO THE FACTORY.........................................................P6

TRAINING ......................................................................................................P6

DOCUMENTATION............................................................................................P6

COMPLIANCES .................................................................................................P7

CONDENSED STARTUP AND CALIBRATION PROCEDURE..........................P9

ONTENTS

S

ECTION

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

1.2 APPLICATIONS ..........................................................................................2

S

ECTION

2.1 UNPACKING...............................................................................................3

2.2 LOCATION..................................................................................................3

2.3 VOLTAGE REQUIREMENTS......................................................................3

2.4 ELECTRICAL CONNECTIONS...................................................................4

2.5 GAS REQUIREMENTS...............................................................................7

2.6 SAMPLE REQUIREMENTS........................................................................8

1. I

2. I

2.4.1 Line Power Connections................................................................4

2.4.2 Potentiometric Recorder Connections...........................................6

2.4.3 Current Recorder Connections......................................................6

NTRODUCTION

NSTALLATION

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

i

ONTENTS

C

2.7 GAS CONNECTIONS................................................................................. 8

2.8 LEAK TEST................................................................................................. 9

S

ECTION 3. INITIAL STARTUP AND OPERATION

3.1 FRONT PANEL INDICATORS AND CONTROLS ...................................... 11

3.1.1 Display ..................................................................................... 11

3.1.2 Range Selection............................................................................ 11

3.1.3 Sample Pressure Gauge............................................................... 12

3.1.4 Ozone Pressure ............................................................................ 12

3.1.5 Zero and Span Potentiometers ..................................................... 12

3.1.6 Ozone Interlock............................................................................. 12

3.2 STARTUP PROCEDURE ........................................................................... 13

3.3 CALIBRATION............................................................................................ 16

3.3.1 Zero Calibration............................................................................. 16

3.3.2 Upscale Calibration....................................................................... 16

3.4 ROUTINE OPERATION.............................................................................. 16

3.5 CONVERTER TEMPERATURE ADJUSTMENT PROCEDURE................. 17

3.6 MEASUREMENT OF CONVERTER EFFICIENCY .................................... 19

3.7 RECOMMENDED CALIBRATION FREQUENCY....................................... 20

S

ECTION

4.1 NITRIC OXIDE DETERMINATION BY CHEMILUMINESCENCE

4.2 ANALYZER FLOW SYSTEM...................................................................... 21

4.3 SIGNAL PROCESSING ELECTRONICS SYSTEM.................................... 22

4.4 ANALYZER THERMAL SYSTEM............................................................... 23

4. T

4.2.1 Flow of Sample, Standard Gas or Zero Gas to Reaction

4.2.2 Ozone Generation......................................................................... 22

HEORY

METHOD...................................................................................... 21

Chamber....................................................................... 21

SECTION 5. ROUTINE SERVICING

5.1 SYSTEM CHECKS AND ADJUSTMENTS ................................................. 25

5.1.1 Display Fullscale Span Adjustment............................................... 25

5.1.2 Overall Sensitivity.......................................................................... 26

5.1.3 Ozone Output................................................................................ 26

5.1.4 Background Current...................................................................... 27

5.1.5 Excessive Photomultiplier Dark Current........................................ 27

5.2 SERVICING FLOW SYSTEM..................................................................... 28

5.2.1 Cleaning Sample Capillary............................................................ 28

ii

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

5.2.2 Ozone Restrictor Fitting.................................................................29

5.3 PHOTOMULTIPLIER TUBE/REACTION CHAMBER..................................30

5.3.1 Photomultiplier Tube/Reaction Chamber Removal........................30

5.3.2 Cleaning Reaction Chamber..........................................................30

5.3.3 Photomultiplier Tube and Housing.................................................32

5.3.4 Replacement of Photomultiplier Tube............................................32

5.4 OZONE GENERATION SYSTEM ...............................................................33

5.4.1 Lamp/Housing Removal.................................................................33

5.4.2 UV Lamp Replacement..................................................................34

5.4.3 Power Supply Removal..................................................................34

5.5 CONVERTER ASSEMBLY..........................................................................35

5.6 SERVICING ELECTRONIC CIRCUITRY ....................................................35

SECTION 6. REPLACEMENT PARTS

6.1 CIRCUIT BOARD REPLACEMENT POLICY ..............................................37

6.2 REPLACEMENT PARTS.............................................................................37

ONTENTS

C

ENERAL PRECAUTIONS FOR HANDLING

G

ARRANTY

W

IELD SERVICE AND REPAIR FACILITIES

F

TORING HIGH PRESSURE CYLINDERS

& S

FIGURES

2-1. Power Supply Board Voltage Select Switches ...........................................5

2-2. Temperature Control Board........................................................................5

2-3. Cable Gland ...............................................................................................6

2-4. Rear View of Model 951C...........................................................................7

3-1. Model 951C Controls, Indicators and Adjustments ....................................11

3-2. Signal Board...............................................................................................14

3-3. Power Supply Board...................................................................................15

4-1. Analyzer Signal Conditioning Circuit...........................................................23

4-2. Analyzer Thermal System..........................................................................24

6-1. Major Assemblies of the Model 951C.........................................................39

6-2. Photomultiplier Housing Assembly.............................................................40

6-3. Converter Assembly...................................................................................41

6-4. Case Heater Temperature Control Assembly.............................................42

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

iii

ONTENTS

C

TABLES

3- 1 . R e s ist a n c e o f C o n ver t e r Te mp e rat u r e S e n sor vs. T e m p e r a t u r e.............................18

D

RAWINGS (LOCATED IN REAR OF MANUAL

654063 Installation Drawing
654090 Flow Diagram, Low Range
654093 Flow Diagram, High Range

)

iv

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

P

REFACE

PURPOSE/SAFETY SUMMARY

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 Model
951C NOx Analyzer should be thoroughly familiar with and strictly follow the
instructions in this manual. Save these instructions.

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

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

WARNING is used to indicate the presence of a hazard which can cause severe
personal injury, death, or substantial property damage if the warning is ignored.

CAUTION is used to indicate the presence of a hazard which will or can cause
minor personal injury or property damage if the warning is ignored.

NOTE is used to indicate installation, operation or maintenance information which is

important but not hazard-related.

WARNING: 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 three-wire source of power.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

P1

REFACE

P

WARNING: 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: 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.

Keep all tube fittings tight to avoid leaks. See Section 2.6 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.

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

P2

This instrument requires periodic calibration with a known standard gas. See
Paragraphs 2.5 and 3.3. See also General Precautions for Handling and Storing
High Pressure Gas Cylinders, following Section Six.

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

REFACE

P

WARNING: TOXIC AND OXIDIZING GAS HAZARDS

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 clean-up kit, such as J. T. Baker product No. 4439­01, 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.

CAUTION: 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 (counter­clockwise) 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.

Failure to observe these precautions could result in personal injury and/or
damage to the product.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

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P

SPECIFICATIONS - LO RANGE

RANGES:

0 to 10, 0 to 25, 0 to 100, 0 to 250 ppm NOx

REPEATABILITY:

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

Z

ERO/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)

R

ESPONSE TIME

: (E

LECTRONIC

90% of fullscale in less than 1 minute

S

ENSITIVITY

:

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

D

ETECTOR OPERATING PRESSURE

atmospheric

T

OTAL SAMPLE FLOW RATE

:

1 Liter per minute at 20 psig

S

AMPLE PRESSURE

:

138 kPa (20 psig)

O

ZONE GENERATOR GAS

:

U.S.P. breathing-grade air

A

MBIENT TEMPERATURE RANGE

+ F

:

LOW

:

)

P4

4 to 40°C (40 to 104°F)

A

NALOG 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

P

OWER REQUIREMENTS

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

E

NCLOSURE

:

General purpose for installation in weather-protected areas

D

IMENSIONS

:

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

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

W

EIGHT

22.2 kg (49 lbs) approximate

:

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

SPECIFICATIONS - HI RANGE

RANGES:

0 to 100, 0 to 250, 0 to 1000, 0 to 2500 ppm NOx

REPEATABILITY:

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

REFACE

P

Z

ERO/SPAN DRIFT

:

less than ±1.0 ppm or ±1% of fullscale, whichever is greater, in 24 hours at
constant temperature

less than ±2.0 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)

R

ESPONSE TIME

S

ENSITIVITY

90% of fullscale in less than 1 minute

: (E

LECTRONIC

:

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

D

ETECTOR OPERATING PRESSURE

atmospheric

T

OTAL SAMPLE FLOW RATE

:

1 Liter per minute at 20 psig

S

AMPLE PRESSURE

:

138 kPa (20 psig)

O

ZONE GENERATOR GAS

:

U.S.P. breathing-grade air

A

MBIENT TEMPERATURE RANGE

4 to 40°C (40 to 104°F)

+ F

:

LOW

:

)

A

NALOG 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

P

OWER REQUIREMENTS

:

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

E

NCLOSURE

:

General purpose for installation in weather-protected areas

D

IMENSIONS

:

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

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

W

EIGHT

:

22.2 kg (49 lbs) approximate

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

P5

REFACE

P

CUSTOMER SERVICE, TECHNICAL ASSISTANCE AND FIELD SERVICE

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

Rosemount Analytical Inc.

Process Analytical Division

Customer Service Center

1-800-433-6076

RETURNING PARTS TO THE FACTORY

Before returning parts, contact the Customer Service Center and request a Returned
Materials Authorization (RMA) number. Please have the following information when
you call: Model Number, Serial Number, and Purchase Order Number or Sales Order

Number.

Prior authorization by the factory must be obtained before returned materials will be
accepted. Unauthorized returns will be returned to the sender, freight collect.

When returning any product or component that has been exposed to a toxic, corrosive
or other hazardous material or used in such a hazardous environment, the user must
attach an appropriate Material Safety Data Sheet (M.S.D.S.) or a written certification
that the material has been decontaminated, disinfected and/or detoxified.

Return to:

Rosemount Analytical Inc.

4125 East La Palma Avenue

Anaheim, California 92807-1802

USA

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
the Technical Services Department at:

Rosemount Analytical Inc.

Phone: [phone]

FAX: [phone]

D

OCUMENTATION

The following Model 951C NOx Analyzer instruction materials are available. Contact
Customer Service or the local representative to order.

748214 Instruction Manual (this document)

P6

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

COMPLIANCES

9

6

This product satisfies all obligations of all relevant standards of the EMC framework in
Australia and New Zealand.

N

REFACE

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748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

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NOTES

P8

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

C

ONDENSED 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 Section 3.

1. Set slider switch on the Signal Board (Figure 3-2) to 250 ppm (see Figure 3-2).

2. Apply power to the analyzer. The analyzer will now require approximately one to
two hours for temperature equilibrium before being ready for calibration.

3. Verify that the pressure regulator on the cylinder of zero gas (nitrogen or air) or
sample gas is set for supply pressure of 10 to 17 psig.

4. Verify that the pressure regulator on the cylinder of air (ozonator supply) is set for
supply pressure of 20 to 25 psig.

5. Establish correct pressure of sample gas:
a. Supply sample gas to rear-panel SAMPLE inlet at 10 to 17 psig (normally

15 psig).

b. Adjust SAMPLE Back Pressure Regulator so that SAMPLE Pressure

Gauge indicates the value appropriate to the desired operating range
(normal operating pressure is 3 to 5 psig). See Figure 3-1.

6. Establish correct pressure of zero gas:
a. Supply zero gas to rear panel SAMPLE inlet and set to 15 psig.
b. Note reading on SAMPLE Pressure Gauge. It should be the same as in

Step 5b. If not, adjust output pressure regulator on the zero gas cylinder as
required.

7. Establish correct pressure of upscale standard gas:

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

P9

ONDENSED STARTUP AND CALIBRATION PROCEDURE

C

a. Supply upscale standard gas to rear panel SAMPLE inlet.
b. Note reading on SAMPLE Pressure Gauge. It should be the same as in

Step 6b. If not, adjust output regulator on cylinder of upscale standard gas
as required.

Note
Supply pressure for sample, upscale standard gas and zero air must be the

same. If not, the readout will be in error.

8. Zero Calibration:
a. Set PPM RANGE Switch for range to be used for sample analysis. Set

SPAN Control at normal operating setting, if known, or at about mid-range if

normal setting is not known.
b. Supply zero gas to rear panel SAMPLE inlet.
c. Adjust ZERO Control for reading of zero on meter or recorder.

9. Upscale Calibration:
a. Set PPM RANGE Switch at setting appropriate to the particular span gas.
b. Supply upscale standard gas of accurately known NOx content to rear

panel SAMPLE inlet.

c. Adjust SPAN Control so that reading on meter or recorder is equal to the

know parts-per-million concentration of NOx in the span gas.

Note
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.

P10

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

I

NTRODUCTION

1

1.1 OVERVIEW

The Model 951C NOx Analyzer is designed to measure NOx using one of two sets of
ranges designated as Hi or Lo. The Hi Range set consists of spans with ranges of 0-100,
0-250, 0-1000, and 0-2500 ppm NOx. The Lo Range set consists of spans with ranges of
0-10, 0-25, 0-100, and 0-250 ppm NOx.

The NOx analyzer continuously analyzes a flowing gas sample for NOx [nitric oxide (NO)
plus nitrogen dioxide (NO2)]. The sum of the concentrations is continuously reported as
NOx.

The analyzer is based on the chemiluminescence method of NO detection. The sample is
continuously passed through a heated bed of vitreous carbon, in which NO2 is reduced to
NO. Any NO initially present in the sample passes through the converter unchanged, and
any NO2 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 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.

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

The display blanks when the analyzer is 10% or more over-range. Selecting a less sensitive
(higher) range restores the display function.

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

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

1

NTRODUCTION

I

1.2 APPLICATIONS

The Model 951C Analyzer has specific applications in the following areas:

• 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)

2

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

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 its contents are damaged. Retain the carton and
packing material until the instrument is operational.

2.2 LOCATION

See drawing 654063 for Outline and Mounting dimensions.
Install analyzer in a clean area, free from moisture and excessive vibration, at a stable

temperature within 4 to 40°C.
The analyzer should be mounted near the sample source to minimize sample-transport

time.
A temperature control system maintains the internal temperature of analyzer at 50°C

(122°F) to ensure proper operation over an ambient temperature range of 4°C to 40°C
(40°F to 110°F). Temperatures outside these limits necessitate use of special
temperature-controlling equipment or environmental protection. Also, the ambient
temperature should not change at a rate exceeding 10°C/hr.

The cylinders of air and span gas should be located in an area of constant ambient
temperature (±10°C).

2.3 VOLTAGE REQUIREMENTS

WARNING: 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 set up to operate on 115 VAC, 50/60 Hz
electric power. For operation on 230 VAC, 50/60 Hz, position voltage select switches S1,
S2, S3 (located on the Power Supply Board, Figure 2-1) and S3 (located on the
Temperature Control Board, Figure 2-2) must be in the 230 VAC position.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

3

NSTALLATION

I

Refer to Figure 2-4. Remove the 6.25 A fuse (P/N 902413) and replace with the 3.15 A fuse
(P/N 898587) provided in the shipping kit.

2.4 ELECTRICAL CONNECTIONS

The power and output (recorder and current) cable glands are supplied loose in the
shipping kit to allow cable installation to connectors or terminal strips.

Cable Gland Part No.

Power 899330

Remove rear cover to access terminals. Route each cable through the cable gland and
connect to the appropriate connector or terminal strip, tighten the gland.

Recorder 899329

2.4.1 L

INE POWER CONNECTIONS

Refer to Figures 2-3, 2-4 and drawing 654063. If this instrument is located on a bench or
table top or is installed in a protected rack, panel or cabinet, power may be connected via a
3-wire flexible power cord, minimum 18 AWG (max. O.D. 0.480", min. O./D. 0.270"),
through the hole labeled POWER, utilizing connector gland (P/N 899330) provided.

Route the power cable through the cable gland and connect the leads to TB1. Tighten the
cable gland adequately to prevent 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 (for bench top use) are available:

• Power Cord 634061

• North American power cord set (10 foot)

• Enclosure Support Kit 634958

• Enclosure support feet (4)

• Power Cord/Enclosure Support Kit 654008

• North American power cord set (10 foot)

• Enclosure support feet (4)

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

4

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NSTALLATION

5

I

IGURE

F

J5

J20

1

1

S2

230V

230V

115V

115V

115V

Set switch window for voltage required.

2-1. P

OWER SUPPLY BOARD VOLTAGE SELECT SWITCHES

1

115V

S1

J3

230V

115V

S2

230V

115V

S1

230V

115V115V 115V

115V

C10

S3

CS

655340 POWER SUPPLY BD

230V

S3

115V

115V

IGURE

F

SENSOR

AR1

J18

R10 R11 R7 R8

C2

CR1

C

B

Q2

C1

E

+

R18R19

R4

R3

K

A

R13

R2R1

Q1

G

CR2

R17R16 R12

TEMP CONTROL BD

Set switch window for voltage required.

2-2. T

EMPERATURE CONTROL BOARD

S3

3 2 1

U2

3

U1

J17

POWER
LINE
J5

2

1

S3

230

11

115

POWER
SUPPLY

J11

C4

R15

R6

C3

R9 R5

CR

1

E

B

J19

Q3

TEST

C

R14

1

1 2 1 2 3

T.I.F. HEATER

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

5

NSTALLATION

I

2.4.2 P

OTENTIOMETRIC RECORDER CONNECTIONS

Refer to Figures 2-3, 2-4 and drawing 654063. Potentiometric recorder connec-tions are
made on the rear panel. Route the potentiometric recorder cable through the cable gland in
the hole labeled RECORDER OUTPUT and connect to VOLT OUTPUT terminals.

Potentiometric recorder cable specifications are as follows:

• 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 C

URRENT RECORDER CONNECTIONS

Refer to Figures 2-3, 2-4 and drawing 654063. Current recorder connections are made on
the rear panel. Route the current recorder cable through the cable gland in the hole labeled
RECORDER OUTPUT and connect to CUR OUTPUT terminals

Current recorder interconnection cable specs are as follows:

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

• Load resistance: Less than 700 Ohms.

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

As supplied by the factory, the current output produces a zero of 4 mA. The current output
may be adjusted to produce a zero of 0 mA as follows:

1. Zero the instrument as in Section 3.4.

2. Adjust R23, the zero-adjust potentiometer on the Power Supply Board, to produce 0
mA current output.

INTERIOR EXTERIOR

Nut Gland Nut

Cable

Case Wall

IGURE

F

2-3. C

ABLE GLAND

6

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NSTALLATION

I

IGURE

F

20 PSI (138 kPa)

NOMINAL

2-4. R

SAMPLE

EXHAUSTAIR

IN

IN

10 PSI - 17 PSI

(70 kPa - 120 kPa)

EAR VIEW OF MODEL

951C (

RECORDER

OUTPUT

FUSE

CUR
OUTPUT

Current Output
Connections

COVER REMOVED

L1/HOT

L2/NEUT

GND

VOLT
OUTPUT

+ - G + -

)

POWER

Recorder
Connections

2.5 GAS REQUIREMENTS

The instrument requires two gases normally supplied from cylinders. They are:

Fuse

AC Power
Connections

IR

A

(U.S.P. B

REATHING GRADE

)

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

PAN GAS

S

This is a standard gas of accurately known composition, used to set an upscale calibration
point. The usual span gas is NO or NO2 in a background of nitrogen.

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, in the rear of this manual.

Note
For maximum calibration accuracy, the concentration of NO in the span gas

should be similar to that in the sample gas. Also, the span gas should be
supplied to the rear panel SAMPLE inlet at the same pressure as the sample
gas. To ensure constant pressure, a pressure regulator may be utilized
immediately upstream from the SAMPLE inlet.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

7

NSTALLATION

I

Each gas used should be supplied from a tank or cylinder equipped with a clean,
non-corrosive type, two-stage regulator. In addition, a shut-off valve is desirable. Install the
gas cylinders in an area of relatively constant ambient temperature.

2.6 SAMPLE REQUIREMENTS

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

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

2.7 GAS CONNECTIONS

WARNING: 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.

1. Remove plugs and caps from all inlet and outlet fittings. (See Figure 2-4.)

2. Connect EXHAUST outlet to external vent via tubing with O.D. of 1/4-inch (6.3 mm) or
larger. Use only stainless steel or Teflon tubing.

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

8

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NSTALLATION

I

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

5. Supply sample gas to rear panel SAMPLE inlet at appropriate pressure: 20 psig (138
kPa). The nominal input pressure is 20 psig (138 kPa).

2.8 LEAK TEST

The following test is designed for sample pressure up to 5 psig (35 kPa).

1. Supply air or inert gas such as nitrogen at 5 psig (35 kPa) to analyzer sample and air
input fittings.

2. Seal off analyzer exhaust fitting with a tube cap.

3. Use a suitable test liquid such as SNOOP (P/N 837801) to detect leaks. Cover all
fittings, seals, or possible leak sources.

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.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

9

NSTALLATION

I

NOTES

10

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

I

(S1)

)

(

)

NITIAL STARTUP AND OPERATION

3.1 FRONT PANEL INDICATORS AND CONTROLS

3

3.1.1 D

ISPLAY

The display is a 4-digit liquid crystal device which always displays NOx concentration in
parts-per-million. Se e Figure 3-1.

3.1.2 R

ANGE SELECTION

The Model 951C has eight customer selectable ranges, four LO ranges (10 ppm, 25 ppm,
100 ppm and 250 ppm) and four HI ranges (100 ppm, 250 ppm 1000 ppm and 2500 ppm).
The range is selected by positioning the RANGE Switch (S1) and the three jumpers on the
Signal Board to the des ired range controlling the recorder output. Refe r to Figure 3-2.

The display blanks for values 10% in excess of the range maximum. Moving the switch to
the left selects a higher fullscale value and restores the display.

POWER SUPPLY BOARD
(See Figure 3-3)

CASE HEATER TEMPERATURE CONTROL ASSEMBLY
(See Figure 6-4)
TEMPERATURE CONTROL BOARD (See Figure 2-2)

Voltage Select
(S3)

Voltage Select
(S3)

Voltage Select
(S1)

Voltage Select
(S2)

SAMPLE PRESSURE
GAUGE

SAMPLE PRESSURE
REGULATOR
(Adjustment Knob)

SIGNAL BOARD
(See Figure 3-2)

Display
(Signal Board DS1)

Adj. (R8)

Gain (R24)

Signal (R20

Cal (R18)

Range Select
Switch

Convertor
Heater
(R9)

Converter

Temp Check

(S4)

PMT
High Voltage

R30

TP2

Current Output
Zero (R23)

Current Output
Span (R20)

Zero Control
(Signal Board R100)

IGURE

F

748214-P Rosemount Analytical December 2000

3-1. M

ODEL

Span Control
(Signal Board R101)

951C C

Ozone Indicator Lamp
(Signal Board DS2)

ONTROLS

NDICATORS AND ADJUSTMENTS

, I

Model 951C NOx Analyzer

11

NITIAL STARTUP AND OPERATION

I

3.1.3 S

AMPLE PRESSURE GAUGE

The internal SAMPLE pressure (nominally 4 psig, 28 kPa) is adjusted by rotation of the
Sample Pressure Regulator. See Figure 3-1.

3.1.4 O

ZONE 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.

Note
If ozone lamp does not light, increase pressure slightly by adjusting pressure

regulator control on the air cylinder.

3.1.5 Z

ERO AND SPAN POTENTIOMETERS

See Figures 3-1 and 3-2. Screwdriver access holes through the front panel allow
adjustments of the ZERO and SPAN potentiometers (R100 and R101 on Signal Board.

3.1.6 O

ZONE INTERLOCK

The ozone-producing UV lamp will not ignite or stay lit unless adequate air pressure is
present at the AIR inlet (see Figure 2-4). Nominal set point pressure is 20 to 25 psig.

12

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NITIAL STARTUP AND OPERATION

I

3.2 STARTUP PROCEDURE

The following are detailed instructions on startup and calibration.

1. Supply electrical power to the analyzer. The analyzer will require approximately two
hours for temperature equilibration before calibration.

2. On Signal Board, Figure 3-2, set PPM RANGE Switch (S1) to 250 ppm.

3. Establish correct pressure for air by the following:

a. Adjust OZONE Pressure Regulator so that OZONE Pressure Gauge

indicates 20 to 25 psig (138 to 172 kPa).

b. To establish correct pressure of zero gas, supply zero gas to rear panel

SAMPLE inlet. Note 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. This should remain constant when the
analyzer input SAMPLE is switched from calibration gas standard to a zero gas
standard. This may be assur ed by setting the delivery from the SAMPLE and the
zero gas cylinder of span gas cylinder to the same value of delivery pressure,
nominally 20 psig (138 kPa). If not, adjust output pressure regulator on zero gas
cylinder as required.

4. Establish correct pressure of sample gas by the following:

a. Supply sample gas to rear panel SAMPLE inlet.
b. Adjust SAMPLE Backpressure Regulator so internal SAMPLE Pressure

Gauge indicates the value appropriate to the desired operating range.

Note
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 flowmeter (i.e., Brooks P/N 1350) at the EXHAUST outlet to measure flow.

5. Establish correct flow of upscale standard gas by the following:

a. Supply upscale standard gas to rear panel SAMPLE inlet.
b. Note reading on internal SAMPLE Pressure Gauge. It should be the same

as in Step 3b.

Note
Supply pressures for sample and upscale standard gases must be the same.

Otherwise, readout will be in error.

The analyzer is now ready for calibration.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

13

NITIAL STARTUP AND OPERATION

8

C14C15

3

38

C12C16AR6

00

654050 SIGNAL CONTROL BD

I

Lo Hi

E6

E7

Lo Hi

E1 E2

E4

E3

E1 E2

E4

E3

E5

E5

E6

E7

C

DS2

SIGNAL IN

E6
E7

R2

RP

1

K3

AR4

R

RP2

R39
R40
R23

J1

CR23

SPAN

10 100
25 250

TP6 TP 5 TP 4 TP3 TP 2 TP1

E1 E2

E3
DP SELECT

DS1

U7

+

C13

R35

R17

E

B

C9

R36

Q3

C

R101

CW
S
CCW

E4

RANGE

E5

CR1

R14 R12

C5

S1

10 100
25 250

RP1

1

U1

CR13

CR12

CR14

CR11

CR2

C8

U2

R22

(S1 pos)

1 (10) 10
2 (25) 25
3 (100) 100
4 (250) 250

S1

CR7

CR6

CR10

CR8

R19

CR9

C6

C10

R13

+

ADJ. GAIN SIG. CAL.

R41

R27

R25 R24 R20 R18

T1

CR16
CR15
C11

+

CR3

CR5

C7

CR19

CR4

R21

R1R2R3R4R5R6R7R8R9

R15

R30 AR1

R31

R16

U3

ZERO

R1

Range

CR17

CR20

CR21

CW
S
CCW

Lo

ppm

Fullscale

1 (10) 100
2 (25) 250
3 (100) 1000
4 (250) 2500

+

C17

C3

CR18

B

Q1

CR22

CE

AR2

R10

R11

C

R32 R33

VR1

R42

C2
C1

AR3

C4

J3

K1

B

K2

E

Q2

CS

Range

(S1 pos)

Hi

ppm

Fullscale

IGURE

F

3-2. S

R101 - SPAN Potentiometer R100 - ZERO Potentiometer

IGNAL BOARD

14

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NITIAL STARTUP AND OPERATION

U8

3

C26

Q

Q

Q10

Q

A

R16

Q2

Q1

R14

R18

R12

Q3

C9

CR6

R78

U23

C20

8

Q

Q5

C19

U22

9

U

Q

R69

Q

C

A

C25

59

J3

J18

J15

J9

C

S1

S2

S3

I

TP13

CR4

CONVERTOR

TP1

TP13

CR4

CONVERTOR

Q15

E

B

C

1

2

TP1

C8

CONV
TEMP

CHECK

C8

R77

CR2

R63

R27

R2

C17

TP2 TP5 TP6 TP7 TP8

CONV
TEMP

CHECK

S4

TP2 TP5 TP6 TP7 TP8

K

R2

G

S4

A

+

R4

B

C

E

R6

R13

C

B

E

R15

14

1

C

E

R71

B

B

21

R68

R64

+

R34

B

C

E

4

CURRENT

SPAN

R25
R21

R22
R24

R19

CR15

R20

R26

U7

VR1

VR2

VR3

TP14 TP15

VR6

1 2 3 4

C4

+

R23

R20

CURRENT

OUTPUT

SPAN

ZERO

TP3 TP4

C11

+

J11

1

CR7

+

C13

I

+

G
O

VR4

C14

CR8

+

C12

CR14

O
G

I

+

C15

C3

+

+

CR1

+

+

C2

+

+

VR5

I G O

CR18

C29

+

VR7

C1

G I O

+

CR2

+

C6

C5

K1

VR8

O G I

+

C27

+

CR19

+

R61

R56

R60

R

R57

J6

1

CR3

R1

12

E

2

C23

21

R48

B

R46

C

R44

C

R43
R41

8

O

VR9

I

1

C28

+

C

E

B

Q13

CR20

+

R58

J20

1

1

TP9 TP10 TP11 TP12

R54

C

E

+

R47

+

R49

E

R42

Q9

C

R40

B

G

E

R53

J5

1

CR13

24

B

C

J17

E

R4

U9

C22

R68

R82
R81
R80
R45

R51

J4

CR12

R55

1

1

S2

230V

230V

115V

115V

115V

655340 POWER SUPPLY BD

1

1

1

J12

1

U2

S1

230V

115V

115V

1

J8

1

1

R17
R18

C10

S3

115V

CS

R9

R30

CONV

PMT

HTR

HV

THERMO
COOLER

THERMO
COOLER

R39

C

Q7

E

CR10

R2

TP14 TP15

CR1

R2

J14

OUTPUT

ZERO

J13

B

R3

R3

CONV

RMT

HTR

C7

R7

RP1

U20

HV

R6

R11

J19

R72

J19

R38

CR24

R76

C

R75

R74

6

B

E

R37

AR2

R17

IGURE

F

3-3. P

OWER SUPPLY BOARD

230V

115V

115V

230V

115V

115V

230V

115V

115V

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

15

NITIAL STARTUP AND OPERATION

I

3.3 CALIBRATION

3.3.1 Z

1. On the Signal Board, Figure 3-2, set PPM RANGE Switch for the same range that will be

2. Supply zero gas to rear panel SAMPLE inlet.

3. After a stable reading is reached, adjust the zero by inserting a screwdriver in the ZERO

3.3.2 U

1. On the Signal Board, Figure 3-2, set PPM RANGE Switch to the position appropriate to

2. Supply upscale standard gas of accurately known NOx content to rear panel SAMPLE

3. Adjust SPAN Control so that reading on display or recorder is equal to the known

ERO CALIBRATION

used during sample analysis. Set SPAN Control at about mid-range.

slot on the front of the analyzer and turning until zero reading is obtained.

PSCALE CALIBRATION

the particular span gas.

inlet.

parts-per-million concentration of NOx in the span gas. If the correct reading is not
initially attainable by adjustment of the SPAN Control, make the electronic adjustment in
Step 4.

4. If necessary, increase sensitivity by raising photomultiplier voltage. This will interact with
zero. Repeat Zero Calibration and Upscale Calibration (through step 3).

3.4 ROUTINE OPERATION

After calibrating analyzer per Section 3.3, supply sample to SAMPLE inlet. Set PPM
RANGE Switch in appropriate position. The instrument will now continuously analyze the
sample stream.

The Model 951C is designed for continuous operation. Normally, it is never turned off
except for servicing or for a prolonged shutdown.

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

source.

16

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NITIAL STARTUP AND OPERATION

I

3.5 CONVERTER TEMPERATURE ADJUSTMENT PROCEDURE

Once the appropriate high voltage and electronic gain have been selected such that the
named calibration gas value is indicated by the Model 951C, the instrument is ready for
adjustment of the converter temperature.

The vitreous carbon converter used in this analyzer has a low surface area which 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.

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 reduces the nitric oxide
produced to nitrogen, which is not detected by the chemiluminescence reaction. The
remedy in this case is to adjust the converter temperature to a lower value to improve the
converter efficiency.

It is important that the converter temperature be periodically profiled to assure that it is
running at its 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 may be conveniently checked by momentarily
depressing switch S4 on the Power Supply Board while monitoring the resistance across
terminals TP1 and TP2. Table 3-1 allows for conversion of the observed resistance to the
operating temperature for the converter.

Follow this procedure to optimize the operating temperature of the converter:

1. Power instrument and allow it to stabilize at operating temperature (one to two hours).
Measure the operating temperature of the converter by the technique described above.
Note the value for future reference.

2. Admit a calibration gas of known (NO2) concentration into the analyzer and note the
concentration value determined when the full response has been achieved.

3. Refer to Figure 3-3. Turn the converter temperature adjust potentiometer R9, on the
Power Supply Board one turn counterclockwise from the setting established at the
factory, and allow fifteen minutes for operation at the new lower temperature setpoint.
Recheck the response and note the value for later use.

4. Increase the temperature of the converter by rotating the converter temperature adjust
potentiometer, R9, one quarter turn clockwise, wait fifteen minutes for thermal
equilibrium and then re-measure the NO2 calibration gas value. Note its value. 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.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

17

NITIAL STARTUP AND OPERATION

I

5. Decrease the temperature of converter operation by rotating the converter temperature
adjust potentiometer one eighth of a turn counterclockwise. This places the converter at
a temperature suitable for low ammonia interference and efficient NO2 conversion. Re­measure the indicated converter temperature and compare it to the initially recorded
value.

TEMPERATURE

(°C)

RESISTANCE

(Ohms)

0 400

25 438
100 552
200 704
250 780
300 856
350 932
400 1008
450 1084

ABLE

T

3-1. R

ESIST ANCE OF CONVERTER TEMPERA TURE SENSOR VS

EMPERA TURE

. T

Note
Converter temperature is not a direct measure of converter efficiency.

Temperature measurement is for reference purposes only.

18

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

NITIAL STARTUP AND OPERATION

I

3.6 MEASUREMENT OF 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).

The above procedure optimizes the operating temperature of the converter. It also serves
as an efficiency check if the concentration of NO2 in the calibration gas is documented
accurate relative to National Institute of Standards and Technology (NIST) Reference
Materials. If the concentration of the nitrogen dioxide calibration gas is not known
accurately, this procedure still serves to adequately provide the correct converter operating
temperature.

If the only available known standard is the nitric oxide calibration standard, the following
procedure may be performed. This procedure checks converter efficiency through the
utilization of gas-phase oxidation of nitric oxide into nitrogen dioxide over a range of
nitrogen dioxide concentrations. This technique is abstracted and adapted from 40 CFR, Pt.
60, App. A, Method 20, Paragraph 5.6.

1. Select the appropriate instrument range.

2. Admit a nitric oxide in nitrogen NIST traceable calibration gas of a value between 45%
and 55% of the instrument range selected to a clean, evacuated, leak tight Tedlar bag.
Dilute this gas approximately 1:1 with a 20.9% oxygen, purified air.

3. 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 which 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.

4. 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.

5. If the response at the end of the thirty minute period decreases more than 2.0 percent 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 with a new
converter.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

19

NITIAL STARTUP AND OPERATION

I

3.7 RECOMMENDED CALIBRATION FREQUENCY

After initial startup or startup following a shutdown, the analyzer requires about two hours
for stabilization before it is ready for calibration. Maximum permissible interval between
calibrations depends on the analytical accuracy required, and therefore cannot be specified.
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.

20

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

T

HEORY

4

4.1 NITRIC OXIDE 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 emission of photons (essentially red light).

The reactions involved are:

NO + O3 → NO2* + O
NO2* → NO2 + Red Light

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

(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.)

The intensity of the emitted red light is measured by a photomultiplier tube (PMT), which
produces a current of approximately 3 X 10-9 amperes per part-per-million of NO in the
reaction chamber.

4.2 ANALYZER FLOW SYSTEM

The analyzer flow system is shown in drawing 654090. Its 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.

4.2.1 F

LOW OF SAMPLE

, S

2

TANDA RD GAS OR ZERO GAS TO REACTION CHAMBER

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

The flow rate of the selected gas into the reaction chamber is controlled by a back pressure
regulator inside the analyzer. It provides an adjustable, controlled pressure on the upstream

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

21

HEORY

UV

T

side, where gas is supplied to the calibrated, flow-limiting sam ple capilla ry. The regu lator is
adjusted for appropriate reading on the internal SAMPLE Pressure Gauge. For operation at
NO and NO2 levels below 250 ppm, 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.

Excess sample is discharged with the effluent from the reaction chamber via the EXHAUST
outlet. Bypass flow is set by the restrictor at 1 L/min (nominal) to ensure proper functioning
of the SAMPLE Pressure Regulator and rapid system response. Excessive changes, on the
order of 5 psig (35 kPa), in the pressure of the sample or standard gas will affect the
bypass flow rate and can affect accuracy.

4.2.2 O

ZONE 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). W ithin the ozone generator, a
portion of the oxygen in the air is converted to ozone by exposure to an ultraviolet lamp.
The reaction is:

3O2 → 2O

3

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

4.3 SIGNAL PROCESSING ELECTRONICS SYSTEM

A block diagram of the signal-processing electronics is shown in Figure 4-1. Basic functions
of these electronics are acceptance of PMT output and conversion of it to potentiometric
and isolated current outputs, and providing a visual display of the concentration of the NOx
in the sample stream. All functions except the high-voltage source and the
voltage-to-current converter are contained on the Signal Control PC Board, 654050. The
two exceptions are located on the Power Supply Board, 654059.

The PMT drives a high input impedance amplifier which produces a voltage between 0 and
approximately 5 volts. The front panel Zero Control injects a small current into the PMT
amplifier to null any current from the PMT which is not related to the concentration of NOx
in the sample stream.

The PMT amplifier drives a programmable gain amplifier (PGA). The gain of the PGA is
controlled by the Range Switch.

The PGA drives the Span Amplifier. The gain of this amplifier is controlled by the front panel
Span Control. The output of the Span Amplifier is a voltage which is properly scaled to
represent the concentration of NOx in the sample stream.

The Span Amplifier drives the front panel Display and associated electronics, and the
isolated current output. It also provides the potentiometric output.

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4.4 ANALYZER THERMAL SYSTEM

The Analyzer Thermal System is shown in Figure 4-2. Its basic function is to provide a
stable thermal environment for the PMT.

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
means of a solid-state cooler which houses the PMT. The heat which 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 which
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 which support the Analyzer Thermal System and the NO2-to-NO Converter
are contained on the Power Supply Board.

IGURE

F

Photomultiplier

Tube

High Voltage

Supply

4-1. A

Signal/Control Board

PMT

Amplifier

Zero Cont rol

Programmable

Gain

Amplifier

Range Switch Span Control

Span

Amplifier

Power Supply Board

NALYZER SIGNAL CONDITIONING CIRCUIT

Display

Voltage-to-Current

Converter

Potentiometric
Output

Isolated
Current
Output

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

23

HEORY

p

T

IGURE

F

4-2. A

INLET VENT HOLES

SOLID-STATE COOLER

CASE HEATER

Fan Heater

FRONT PANEL

NALYZER THERMAL SYSTEM

To

View of Analyzer

PMT

Cooling Fins

Cooler Fan

EXHAUST FAN

24

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

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OUTINE SERVICING

5

WARNING: ELECTRICAL SHOCK HAZARD

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

WARNING: 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.

Note
The photomultiplier tube must not be exposed to ambient light. If the

photomultiplier tube is exposed to light while the power is on, either through a
loose fitting on the reaction chamber or any other leak, it will be destroyed. If
exposed to ambient light with the power off, the tube will be noisy for some
period of time. Unless appropriate precautions are observed, light can strike the
tube upon removal of fittings from the reaction chamber.

5.1 SYSTEM CHECKS AND ADJUSTMENTS

The following procedures may be used to determine the cause of unsatisfactory instrument
performance, or to make adjustments following replacement of components. If a recorder is
available, use it for convenience and maximum accuracy in the various tests.

5.1.1 D

If a recorder is used, and has been properly zeroed, it should agree with the display
reading. If not, obtain agreement by adjustment of R20 on the Signal/Control Board (see
Figures 3-1, 3-2). If agreement cannot be reached, check the recorder. If the recorder is
functioning properly, replace the amplifier board.

ISPLAY FULLSCALE SPAN ADJUSTMENT

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5.1.2 O

VERALL SENSITIVITY

Principal factors that determine overall sensitivity of the analyzer are the following: (a)
sample flow rate to the reaction chamber, (b) sensitivity of the photomultiplier tube (PMT),
and (c) PMT high voltage. If specified fullscale readings are unobtainable by adjustment of
the SPAN Control, sensitivity is subnormal. The cause of reduced sensitivity may be in
either the flow system (See Section 5.2) or the electronic circuitry (See Section 5.6).

If either the High Voltage Board or the Phototube/Reaction Chamber Assembly has been
replaced, a readjustment of the high voltage will probably be required to obtain the correct
overall sensitivity. Adjust R30 on the Power Supply Board (see Figures 3-1, 3-3) clockwise
to increase (negative) the photomultiplier high voltage and sensitivity, or counterclockwise
to decrease (negative) the voltage and sensitivity. The adjustment range is about -650 V to

-2100 V for the regulated DC voltage applied to the photomultiplier tube. Nominal setting is

-1100 volts. However, the voltage should be adjusted as required for overall system
sensitivity.

5.1.3 O

ZONE OUTPUT

To check for adequate output from the ozone lamp, a convenient technique is to calibrate
the analyzer on a high level NO standard such as 250 ppm NO at the nominal 4.0 psi
internal sample pressure setpoint, and note the reading. The sample pressure setpoint is
then sequentially set to pressures of 3.0, 2.0, and 1.0 psi after a stable span gas reading
has obtained at the higher pressure setpoint. The span gas value will change as the
pressure is changed. The difference in span gas value between two successive sample
pressure levels should be approximately the same for the 4.0 to 3.0, 3.0 to 2.0, and 2.0 to

1.0 pressure steps.
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 two
additional checks should be made. First, 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. Second,
substitute another lamp to see if the ozone output is increased.

If no other ozone lamp is available, the analyzer sample input pressure may 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 may occur.

WARNING: TOXIC GAS HAZARD

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

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5.1.4 B

ACKGROUND CURRENT

With zero air supplied to rear panel SAMPLE inlet, excessive background current is
evidenced by the inability to obtain zero display reading with adjustment of the ZERO
Control. If this cannot be accomplished, the cause must be found and corrected. The fault
may be in either the electronic circuitry or the sample flow system.

First, establish proper performance of the electronic circuitry. Turn on analyzer power.
Verify that ZERO Control and amplifier are functioning properly. Then, check for excessive
photomultiplier dark current and/or contamination of the reaction chamber or sample flow
system as follows:

5.1.5 E

XCESSIVE PHOTOMULTIPLIER DARK CURRENT

To check, shut off all flow to the ozone generator. Turn off ozone generator. Supply cylinder
air to rear panel SAMPLE inlet. Note response on display or recorder. If back-ground is still
excessive, possible causes are:

• leakage of ambient light to photomultiplier tube

• defective photomultiplier tube

• electrical leakage in socket assembly

ONTAMINATION OF REACTION CHAMBER OR SAMPLE FLOW SYSTEM

C

See Section 5.4.1.

.

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5.2 SERVICING FLOW SYSTEM

To facilitate servicing and testing, the Model 951C has front drawer access.
Drawing 654090 shows flow system details, including fittings, thread specifications and

connecting tubing.

5.2.1 C

LEANING SAMPLE CAPILLARY

If clogging of sample capillary is suspected, measure flow rate as described below.

1. T urn off instrument power and shut off all gases.

2. Refer to Figures 6-1 and 6-3. Cover and shade the fittings on the reaction chamber with
a dark cloth or other light-shielding material. Remove the fitting associated with the
sample capillary and place a cap over the open fitting to prevent entry of stray light.

Note:
If the opened fitting 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.

3. With instrument power off, supply suitable test gas (dry nitrogen or air) to rear-panel
SAMPLE inlet.

4. Connect a flowmeter to open end of sample capillary. Adjust internal SAMPLE Pressure
Regulator to normal operating setting of 4 psig (28 kPa). Verify that flowmeter indicates
appropriate flow of 60 to 80 cc/min.

5. If flow is correct, restore analyzer to normal operation.

6. If flow is low, the capillary requires cleaning or replacement (Proceed with the step 5
below).

7. Clean capillary with denatured alcohol, and purge with dry nitrogen or air for one minute.
Reconnect capillary.

8. W ith the photomultiplier still covered, slowly insert the free end of the capillary into the
corresponding fitting on the reaction chamber. Push the capillary in until it touches
bottom against the internal fitting. Then tighten fitting 1/4 turn past finger tight.

Note:
Do not overtighten capillary internal fitting, as overtightened fittings may restrict

the sample flow.

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5.2.2 O

ZONE RESTRICTOR FITTING

With instrument power off, supply suitable test gas (dry nitrogen or air) to rear panel AIR
inlet. Cover photomultiplier housing with a dark cloth. At the fittings on the reaction
chamber, disconnect the ozone tube and place a cap over the open fitting to prevent entry
of ambient light. Connect a flowmeter to open end of ozone tube. Adjust the OZONE
Pressure Regulator so that the OZONE Pressure Gauge indicates normal operating
pressure of 20 to 25 psig (138 to 172 kPa). Verify that test flowmeter indicates an
appropriate flow of 500 to 600 cc/min for 20 psig.

Subnormal flow indicates clogging in the flow path that supplies air to the ozone generator.
This path contains a Restrictor (P/N 655519), consisting of a metal fitting with internal fritted
(metal membrane) restrictor to reduce pressure. The fitting is upstream from the inlet port of
the ozone generator. If the internal restrictor becomes plugged, the assembly (P/N 655519)
must be replaced as it cannot normally be cleaned satisfactorily.

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5.3 PHOTOMULTIPLIER TUBE/REACTION CHAMBER

This assembly consists of the photomultiplier tube and socket, the thermoelectric cooler,
and the reaction chamber. Refer to Figure 6-1 for location and details of mounting. Refer to
Figure 6-3 for information on the assembly.

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

5.3.1 P

HOTOMULTIPLIER TUBE/REACTION CHAMBER REMOVAL

To remove the photomultiplier tube/reaction chamber assembly from the analyzer, do the
follow:

1. Disconnect power from the analyzer.

2. Release pressure from SAMPLE and AIR supplies.

3. Unplug the electrical cable from the Power Supply PC Board.

4. Disconnect the high-voltage cable and the signal cable from the left side of the
assembly. Note the two mounting screws just below the connectors.

5. Uncouple the sample and ozone capillaries and the exhaust line from the right side of
the assembly. Note the two mounting screws just below the fittings.

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

7. Lift the assembly from the analyzer.

8. Replace the assembly by reversing the order of steps 1 through 7.

5.3.2 C

LEANING REACTION CHAMBER

Note:
Photomultiplier tube will be permanently damaged if exposed to ambient light

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

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

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1. Cover and shade the Reaction Chamber/Photomultiplier Assembly with a dark cloth or
other light-shielding material.

Note:
Always wear surgical rubber gloves when handling the reaction chamber to

prevent contamination from handling.

2. Note the orientation of the fittings. Slowly rotate and withdraw the reaction chamber from
the housing. Ensure that no light strikes the photomultiplier tube.

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

4. Clean the reaction chamber by the appropriate one of the following two methods,
standard or alternate. The standard method is applicable in most cases. The alternate
method is applicable when the instrument has shown high residual fluorescence. That
condition 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.

TANDA RD CLEANING PROCEDURE

S

Using a stiff plastic bristle brush, such as a toothbrush, scrub the Teflon surface and gas
ports of the reaction chamber with clean distilled water and Alconox* detergent (P/N

634929). Alconox detergent is included in the shipping kit provided with the Model 951C

NOx Analyzer, and is available from Sargent-Welch Scientific Company under its catalog
number S-195650-A.

Using Alconox and clean, soft facial tissue (NOT industrial wipes), carefully clean the quartz
window. Vigorously flush reaction chamber and quartz window with clean distilled water.
Blow out all possible water from internal passages of reaction chamber. Dry reaction
chamber and quartz window in a warm oven at 125°F to 150°F (52°C to 66°C) for 30 to 45
minutes or purge-dry the parts with dry cylinder air or nitrogen to eliminate all moisture.

WARNING: ACID HAZARD

Hydrochloric acid (HC1) is a strong acid. It 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 hood or
well ventilated place. Wear goggles, rubber gloves and protective clothing.

LTERNATE CLEANING PROCEDURE

A

OR HIGH RESIDUAL FLUORESCENCE

- F

Holding the reaction chamber by the tube fittings, and using appropriate caution, immerse
the white Teflon part of the chamber in 50% concentrated Reagent Grade hydrochloric acid.

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OUTINE SERVICING

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After five minutes, rinse thoroughly with de-ionized water, then air dry as in the standard
cleaning method above.

Place parts in position and press on end-cap so that mating threads engage properly,
without cross threading. Turn mating parts in one continuous motion until the parts mesh.
Do not over-torque.

With reaction chamber now assembled, replace and reconnect it in reversed removal
sequence. Orient as noted in step 2.

5.3.3 P

HOTOMULTIPLIER 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 excluded 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 may result in an abnormally high noise level during instrument
readout on zero air or upscale standard gas.

The Photomultiplier Tube/Reaction Chamber Assembly incorporates several features for
exclusion of 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.

5.3.4 R

EPLACEMENT OF PHOTOMULTIPLIER TUBE

The photomultiplier tube assembly must be removed from the housing in order to replace
the tube. To remove, 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 a new tube into the socket.

5. Orient the metal shield and black plastic insulator as noted in step 2.

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

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5.4 OZONE GENERATION SYSTEM

This system consists of the ultraviolet lamp, lamp housing, and power supply. Refer to
Figure 6-1 for location and details of mounting.

WARNING: TOXIC CHEMICAL 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 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 L

AMP/HOUSING REMOVAL

To remove the lamp and housing, do the follow:

1. Disconnect power from the instrument.

2. Release pressure from SAMPLE and AIR supplies.

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

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

5. Disconnect the power cable from the Power Supply.

6. Uncouple the two Velcro straps which secure the housing to power supply.

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

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OUTINE SERVICING

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7. Lift the housing from the analyzer.

5.4.2 UV L

AMP REPLACEMENT

To replace the lamp, do the following:

1. Unscrew and remove end cap.

2. Unscrew aluminum outer lamp housing tube from lamp base, using care not to hit or
touch lamp assembly.

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

3. Replace O-ring in lamp base with new O-ring supplied in kit.

4. Insert replacement lamp assembly using care not to hit or touch lamp housing.

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

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

5.4.3 P

OWER SUPPLY REMOVAL

To remove the Power Supply, do the following:
Refer to Figure 6-1.

1. Remove the lamp and housing as in Section 5.4.2.

2. Disconnect the power lead from the Power Supply Board.

3. Remove the two screws which 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.

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5.5 CONVERTER ASSEMBLY

To check the heater blanket, verify the continuity of the heater coil.
To check the temperature sensor, refer to Section 3.4 and measure its resistance when

instrument power is off (should be about 440 ohms) and when instrument power is on
(should range from 800 to 1,000 ohms). See Table 3-1.

To remove the glass converter tube (see Figure 6-4):

1. Carefully disconnect the blue silicon connectors from the ends of the inlet and outlet
tubes.

2. 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 (P/N 615989) 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 contact 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 Sections 3.4 and 3.5.

5.6 SERVICING ELECTRONIC CIRCUITRY

For troubleshooting the electronic system, refer to Section 4 and the appropriate pictorial
diagrams at the back of the manual. The electronic system utilizes printed circuit boards
with solid-state components. After a malfunction is traced to a particular board, the
recommended procedure is to return it to the factory for repair.

748214-P Rosemount Analytical December 2000

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OUTINE SERVICING

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NOTES

36

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

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EPLACEMENT PARTS

6

The following parts are recommended for routine maintenance and troubleshooting of the
Model 951C NOx Analyzer. If the troubleshooting procedures do not resolve the problem,
contact your local Rosemount Analytical service office. A list of Rosemount Analytical
Service Centers is located in the back of this manual. Figures 6-1 through 6-5 show
locations of components and assemblies.

WARNING: PARTS INTEGRITY

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

6.1 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 isolation and replacement of the individual component. The cost
of test and replacement will exceed the cost of a rebuilt assembly from the factory.

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

6.2 REPLACEMENT PARTS

OMMON PARTS

C

Refer to Figure 6-1.

655519 Air Restrictor Fitting
657091 Capacitor Assembly
655166 Capillary, Bypass
655589 Capillary, Sample Hi
623719 Capillary, Sample Lo
654068 Temperature Control Assembly
654070 Converter Assembly

748214-P Rosemount Analytical December 2000

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EPLACEMENT PARTS

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655303 Exhaust Fan
654052 Fan Assembly
898587 Fuse 3.15 A
902413 Fuse 6.25 A
654390 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
654085 Pressure Switch
623936 Sample Flow Restrictor
644055 Sample Pressure Gauge
815187 Sample Regulator *
622917 Sensor, Temperature
654050 Signal Board
654878 Transformer/Inductor Assembly

HOTOMULTIPLIER ASSEMBLY

P

Refer to Figure 6-2.

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

ONVERTER ASSEMBLY

C

654070

Refer to Figure 6-3.

632784 Connector, Blue Silicone
657127 Heater
632782 Temperature Sensor
632795 Tube

654062

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December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

EMPERATURE CONTROL ASSEMBLY

T

Refer to Figure 6-4.

622733 Fan
622732 Heater
655335 Temperature Control Board
900492 Thermal Fuse

Photomultiplier Assembly
654062 (See Figure 6-2)

Power Supply Assembly
655332

Case Heater Temperature
Control Assembly 654068
(See Figure 6-4)

654068

I/O Assembly
654390

R

Transformer/Inductor Assembly
654878

Sample Flow Restrictor
623936

EPLACEMENT PARTS

Exhaust Fan
655303

Fan Assembly
654052

Pressure Switch
654085

Sample Regulator
815187

IGURE

F

748214-P Rosemount Analytical December 2000

6-1. M

AJOR ASSEMBLIES OF THE MODEL

Sample Pressure Gauge
644055

Sensor

622917
Air Restrictor
655519 (on Ozone Generator inlet)

Ozone Generator Power Supply
655129

951C

Converter Assembly
654070 (See Figure 6-3)

Ozone Generator 658156
UV Lamp Replacement Kit 658156

Model 951C NOx Analyzer

39

EPLACEMENT PARTS

R

Socket Assembly
654086

Magnetic Shield
636318

Thermocooler Housing
654943

Photomultiplier Tube
655168

Insulating Washer 649541

Thermal Shield 639722

O-Ring 008423

O-Rings 001522

PVC Tube

Magnetic Shield

Reaction Chamber 654381

Photomultiplier Tube

Photomultiplier Tube and Magnetic
Shield (PN 630916) to be Flush

Note: Silicone lubricant to be applied to o-rings.

IGURE

F

6-2. P

HOTOMULTIPLIER HOUSING ASSEMBLY

40

Magnetic Shield
630916

PVC Tube

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer

Connectors, Glass
Tube
632784

Temperature Sensor
632782

EPLACEMENT PARTS

R

IGURE

F

6-3. C

Converter Tube - Packed
632795

Heater
657127

ONVERTER ASSEMBLY

748214-P Rosemount Analytical December 2000

Model 951C NOx Analyzer

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EPLACEMENT PARTS

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Temperature Control Board
655335

Thermal Fuse
900492

IGURE

F

6-4. C

Heater Cable
Orientation

Fan
622733

Heater
633732

ASE HEATER TEMPERATURE CONTROL ASSEMBLY

42

December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer