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
P3
REFACE
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: 1-714-986-7600
FAX: 1-714-577-8006
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
P
748214-P Rosemount Analytical December 2000
Model 951C NOx Analyzer
P7
REFACE
P
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.
CableGland Part No.
Power899330
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.
Recorder899329
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
115V115V115V
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 21 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.
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.
22
December 2000 Rosemount Analytical 748214-PModel 951C NOx Analyzer
OUTINE SERVICING
R
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 SwitchSpan 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
R
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
748214-P Rosemount Analytical December 2000
Model 951C NOx Analyzer
25
OUTINE SERVICING
R
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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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.
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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.
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NOTES
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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.
655519Air Restrictor Fitting
657091Capacitor Assembly
655166Capillary, Bypass
655589Capillary, Sample Hi
623719Capillary, Sample Lo
654068Temperature Control Assembly
654070Converter Assembly
748214-P Rosemount Analytical December 2000
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655303Exhaust Fan
654052Fan Assembly
898587Fuse 3.15 A
902413Fuse 6.25 A
654390I/O Assembly
652173Ozone Generator
658156Ozone Generator UV Lamp Replacement Kit
655129Ozone Generator Power Supply
654062Photomultiplier Assembly
655332Power Supply Assembly
654085Pressure Switch
623936Sample Flow Restrictor
644055Sample Pressure Gauge
815187Sample Regulator *
622917Sensor, Temperature
654050Signal Board
654878Transformer/Inductor Assembly