9th ISFFM Arlington, Virginia, April 14 to 17, 2015

Temperature Effects on the Performance of Tunable Diode Laser

Moisture Analyzers

John Geerligs: NOVA Chemicals Corporation

Jeff Crowe: NOVA Chemicals Corporation
Robert McBrien: NOVA Chemicals Corporation
2928 16th Street NE, Calgary, AB, CA T2E 7K7
Corresponding Author: jeff.crowe@novachem.com

Abstract
Measuring water content in natural gas is critical to operating a pipeline system. High water
content can lead to the formation of gas hydrates and increased corrosion of the pipeline.
Measuring water vapor down to the ppm range in natural gas is a difficult technical challenge.
The objective of this work was to test the AMETEK 5100 HD and SpectraSensors SS2000e gas
analyzer for measuring water content in natural gas. Each device employs Tunable Diode Laser
Absorption Spectroscopy (TDLAS) to detect water in natural gas. Water was added to a steady
gas flow to test the analyzer accuracy and response time. The response to a 20% ethylene
glycol (balance water) and a 20% methanol (balance water) solution (by weight) was also
evaluated. Baseline accuracy was established with a Scott moisture standard distributed by Air
Liquide. Each analyzer was subjected to changes in sample gas temperature and analyzer
environment temperature.
This paper presents a detailed description of the test procedures and a discussion of the results.
This work was performed under the auspices of the NOVA Metering Consortium (METCON).
The Consortium was formed to test and evaluate the performance of new metering
technologies, providing industry with the necessary information to make informed decisions
concerning the suitability of new technologies to various applications.

1 Introduction
Detecting low concentrations (ppm) of water in natural gas is a difficult technical challenge [ 1].
Water is a small polar molecule that has a propensity to adhere to most surfaces. Adsorption
and desorption from surfaces feeding the gas analyzer can cause a significant delay in
measured water content. Only high quality stainless steel (e.g., 316L) should be used for the
sample lines and components upstream of the gas analyzer.
The amount of water that adsorbs on surfaces of a sample system is a function of temperature.
Higher temperatures result in lower quantities of water adsorbing to surfaces. It is
recommended that sample lines upstream of the gas analyzer be insulated and heated. It is
even more important to maintain a stable sample system temperature, from the process
connection to the analyzer sample cell or analyzer enclosure.
Natural gas contains many components which may condense on sensor surfaces, but most
spectroscopic analytical technologies are not designed to operate in the presence of liquids.
Temperature control can help ensure the sample is kept in the gas phase. Analytical
technologies designed to monitor the water concentration in natural gas also require pressure
reduction and control. The sample pressure should be reduced as close as possible to the
source of sample extraction using a heated vaporizing regulator.
The objective of this work was to test the AMETEK 5100 HD and SpectraSensors SS2000e gas
analyzers for measuring water content in natural gas. Each analyzer was subjected to changes
in sample gas temperature and analyzer environment temperature.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

2 Experimental Methods

2.1 Tunable Diode Laser Analyzers

The SpectraSensors SS2000e and AMETEK 5100 HD water analyzers were tested for this
work. Each analyzer employs Tunable Diode Laser (TDL) Absorption Spectroscopy to detect
water in natural gas. TDLAS is described in detail in the Operator’s Manuals [ 2, 3]. Each
analyzer’s specifications are listed in Table 1 and Table 2. All sample line material and heating
requirements outlined in the introduction were met by each analyzer.

Table 1: SpectraSensors SS2000e specifications [2]

Measurement range 0–422 ppmv
Typical repeatability ±4 ppmv or ±2% of reading
Measurement response time 0.25–2 sec (flow rate dependent)
Measurement principle Tunable diode laser absorption spectroscopy
Environmental/gas temperature
-20–50 °C (-4–122 °F)
range
Sample cell pressure range 700–1400 mbara (10–20 psia)
Maximum cell pressure 70 kPag (10 psig)
Sample flow rate 0.5–1 L/min (1–2 SCFH)
Bureau of Mines Chilled Mirror, Portable TDL or
Recommended verification
Binary Gas with Methane Background

Table 2: AMETEK 5100 HD specifications [3]

Measurement range 0–300 ppmv
Accuracy ±6 ppm (2% of full scale)
Measurement response time <2 sec (flow rate dependent)
Measurement principle Tunable diode laser absorption spectroscopy
Environmental/gas temperature range -20–50 °C (-4–122 °F)
Sample cell pressure range 70–170 kPaa (10–25 psia)
Sample flow rate 1–10 L/min (2–20 SCFH)
Verification Built in sealed reference cell

The SS2000e and 5100 HD analyzers were enclosed in a Class 1, Division 2 installation at the
Didsbury Gas Dynamic Test Facility. A photograph of each installation is shown in Fig. 1 and
Fig. 2.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

Fig. 1. SpectraSensors SS2000e, Class 1, Division 2 installation with heated enclosure open

Fig. 2. AMETEK 5100 HD, Class 1, Division 2 installation with heated enclosure open
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

2.1.1 SpectraSensors SS2000e

Fig. 3 shows the flow schematic of the sample control system provided with the SpectraSensors
SS2000e.

Fig. 3. SpectraSensors SS2000e sample control system P&ID

The sample gas first goes to an isolation valve before passing through a particulate and liquid
filter (Genie membrane filter). It then goes to a pressure regulator and gauge, followed by the
sample cell flow control and indicator. The membrane filter bypass goes to a pressure gauge
followed by a flow control and indicator and then combines with sample gas return and out to an
exhaust vent (Sample/Bypass Return). A validation gas inlet (Val Gas) is provided which first
goes to an isolation valve, then to the sample supply pressure regulator and gauge, bypassing
the inlet filters. The enclosure is thermostatically controlled to 40°C (104°F) with a 100 watt
heater. Internal heating is provided to protect the vertical oriented sample cell from
environmental temperature fluctuations.

2.1.2 AMETEK 5100 HD

Fig. 4 shows the flow schematic of the sample control system provided with the AMETEK 5100
HD.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

Fig. 4. AMETEK 5100 HD sample control system P&ID

The sample enters the enclosure at the upper right and goes to an isolation valve with a long
stem, accessible for control from the outside of the enclosure. The sample then passes through
a liquid filter (i.e., a Genie membrane filter). The liquid filter bypass flow goes to a drain vent at
the right side of the enclosure and is controlled by a valve with long stem, accessible outside of
the enclosure. The filtered gas sample flows through the sample cell and a flow control valve. It
is vented from the right side of the enclosure through sample out. The sample flow control valve
has a long stem accessible for control outside of the enclosure. The enclosure is an insulated,
unsealed, stainless steel container with a thermostatically controlled heater set to 55°C (131°F).
This heater protects the horizontally oriented sample cell from environmental temperature
fluctuations. Flow meters for the sample and filter bypass were not provided within the
enclosure.

2.1.3 Performance Verification

Performance of an analytical device needs to be verified by testing with samples that are
traceable to recognized standards (e.g., NIST). One way this can be accomplished is by use of
a bottled calibration gas. A certified working class calibration Scott moisture standard was
available from Air Liquide America Specialty Gases LLC. The Scott moisture standard
specifications are listed in Table 3.

Table 3: Scott moisture standard specification

Certificate of accuracy Certified working class calibration standard
Manufacturer Air Liquide America Specialty Gases LLC
Cylinder size 30AL
Pressure 1300 psig
Concentration Water 35.9 ppmv (±5%) / methane balance
Traceability NIST
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

The AMETEK 5100 HD uses a built-in, sealed, reference cell for quick analyzer verification. The
cell contains water in a buffer gas that does not absorb in the spectral range of interest. The
analyzer response is compared to the reference cell continuously during operation.
For this project the performance of the TDL analyzers were also compared against a Chandler
dew point instrument (chilled mirror).

2.2 Test Facility

Analyzer performance tests were conducted at the TransCanada Pipelines Limited (TCPL) Gas
Dynamic Test Facility near Didsbury, Alberta, Canada. Details of the TCPL Gas Dynamic Test
Facility have been presented in past publications. Testing has shown the facility to be in
excellent agreement (within ±0.23%) with other facilities worldwide [ 4, 5, 6]. A diagram of the
facility setup is shown in Fig. 5. A summary of the facility test capabilities are listed in Table 4.

Fig. 5. TCPL Didsbury Gas Dynamic Test Facility schematic

Table 4. TCPL Didsbury Gas Dynamic Test Facility specification

Natural gas flow range 60 – 1,700 ACMH (2,000 – 60,000 ACFH)
Temperature range 5 ºC – 18 ºC (41 ºF – 64 ºF)
Pipeline pressure 5000 to 6000 kPa (725 to 870 psia)
Calibration capabilities ANSI 600 meters sized NPS2 to NPS8
Maximum Reynolds No. 12,000,000
Flow calibration ± 0.23% mass flow
Repeatability ± 0.1% mass flow
Traceability NIST
ACMH = actual cubic meters per hour, referenced to standard conditions
ACFH = actual cubic feet per hour, referenced to standard conditions
Standard conditions: Pressure = 101.325 kPaa (14.7 psia); Temperature = 15ºC (60˚F)

2.3 Experimental Setup

Liquid (water, 80:20 water/glycol, and 80:20 water/methanol, by weight) was injected at the
upstream end of the Downstream Pad. This is approximately 160 pipe diameter (D) upstream of
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

the gas analyzers located in the Meter Building. The piping between the Upstream Pad and
Metering Building was NPS4 Sch. 40.
The sample gas pressure reduction and control system setup in the Meter Building for both the
SpectraSensors SS2000e and AMETEK 5100 HD met the all requirements presented in the
introduction and the analyzer specifications listed in Table 2 and Table 1. The sample supply
(Fig. 6) was obtained from the NPS4 natural gas pipeline via a center-of-pipe quill probe that
enters through the top of the pipe. The gas temperature was measured at this location (TI in Fig.
7) with a thermowell, RTD, and electronic transmitter. The gas sample goes to an isolation
valve, then to a pressure transmitter (PI). The pipeline sample supply was also connected to a
Chandler dew point instrument as well as a three-way valve that controls the inlet to the heated
vaporizing pressure regulator. All connecting tubing was 1/8 inch stainless steel. The Scott
moisture standard was also connected to the three way valve so that the sample gas can be
switched between pipeline gas and moisture standard gas. The pressure regulator outlet was
set to 20 psig (140 kPag) and connected to the sample inlet of the TDL analyzers via 1/8 inch
stainless steel tubing. This line was also connected to a pressure relief valve set to 30 psig (207
kPag) to protect the analyzers.

Chandler
Dew
Point

Sample Gas
Probe temperature

Vaporizing Flow
Regulator control

PRV

Fig. 6. TDL analyzer Gas sampling system photograph showing NPS4 pipe (center of photo)
sample gas source, temperature and pressure instrumentation, vaporizing pressure regulator,
Chandler dew point instrument (at top right of blue metal frame), and Scott moisture standard
(large bottle in right of photo) in the Meter Building location.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

Fig. 7. TDL analyzer gas sampling system schematic

2.4 Test Procedures

The testing procedure is summarized as follows:
1. Set up natural gas flow in NPS4 pipe (3.5 kg/s, 9 m/s) and wait for gas temperature to
stabilize.

2. Measure gas composition using gas chromatograph.

3. Start test and log gas mass flow rate, gas pressure, gas temperature and TDL analyzer
water concentration.

4. Record test conditions and elapsed time for reconciliation with data log.

3 Results
Table 5 lists all the tests conducted and the test conditions.
 9th ISFFM Arlington, Virginia, April 14 to 17, 2015

Table 5: Test conditions

Gas pressure Gas temperature
Test Description
kPa-a (psia) °C (°F)

1 Initial accuracy using Scott moisture standard. 5435 (788.5) 11 (52)

2 Enclosure temperature change. 5435 (788.5) 11 (52)

3 Enclosure temperature recovery. 5435 (788.5) 11 (52)

80:20 water/glycol injection into pipeline at 100

4 5375 (790) 9.8 (50)
mL/min.

5 80:20 water/glycol injection into pipeline at 80 mL/min. 5390 (782) 11.2 (52)

6 Water injection into pipeline at 19 mL/min. 5818 (844) 11.6 (53)

Water injection into pipeline at 19 mL/min. Gas

7 4680 (679) 5.6 (42)
temperature change from 11.6 °C to 5.6 °C.

8 Continued water injection into pipeline at 19 mL/min. 4670 (677) 5.8 (42)

9 Water injection recovery back to pipeline gas. 4650 (674) 5.9 (42)

80:20 Water/Methanol injection into pipeline gas at 19

10 5812 (843) 11.8 (53)
mL/min.

3.1 Presentation of Measurements

TDL analyzer water concentrations are presented in the figures as 1-minute averages versus
elapsed test time in minutes.

3.2 Scott Moisture Standard Verification

The Scott moisture standard was verified using an AMETEK 3050 water concentration analyzer.
The result, shown in Table 6, was 35.6 ppmv, which is in good agreement with the moisture
standard specification uncertainty range of 34 to 37 ppmv.
The Scott moisture standard water dew point was also measured at high pressure using the
Chandler dew point instrument. The dew point was -7°C to -8°C (19°F to 17°F) at a pressure of
1300 psig (8960 kPag). Using the Alpha Dewpoint Equivalents Calculator the water
concentration was found to be 34 to 37 ppmv [ 7].

Table 6: Moisture standard verification measurements

Moisture std. Chandler chilled Chandler AMETEK 3050
pressure mirror equivalent 5-min avg.
kPag (psig) °C (°F) (ppmv) (ppmv)
8960 (1300) -7 to -8 (19 to 17) 34 to 37 35.6
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

3.3 TDL Accuracy Verification

For Test 1, the pipeline gas was 5435 kPa-a (788.5 psia) and 11°C (52°F). The pipeline gas
water dew point was -25°C (-13°F) when measured with the Chandler dew point instrument.
This is equivalent to 11 ppmv water concentration using the gas pressure and composition [ 8].
The gas composition (listed in Table 7) was measured with a Daniel GC and was stable for all
tests.

Table 7: Pipeline gas composition

Component mol %
Nitrogen 0.4902
Carbon Dioxide 0.8804
Methane 91.3300
Ethane 5.8072
Propane 1.1293
n-Butane 0.1503
iso-Butane 0.1265
n-Pentane 0.0241
iso-Pentane 0.0349
hexane 0.0272

The result of cycling the analyzer between pipeline gas and the Scott moisture standard is
shown in Fig. 8. Each value shown on the chart represents a 1-minute-averaged result. Both
analyzers read slightly low with both the Scott moisture standard and pipeline gas.

60
55
SpectraSensors 2000E
50 Scott Moisture spec
45 pipeline gas ppmv from Chandler DP conversion
40 Ametek 5100
ppmv Water

35
30
25
20
15
10
5
0
0 5 10 15 20 25 30

Elapsed time (min)

Fig. 8. Test 1: Initial accuracy response cycling between Scott moisture standard (35.9 ±5%
ppmv) and pipeline gas (11 ppmv). 0 min – Pipeline gas; 4 min – Moisture standard; 13 min
Pipeline gas; 23 min – Moisture standard
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

3.4 Environment Temperature Response

Test 2 in Fig. 9 shows the result of exposing the analyzer sample cell to a rapid change in
environmental temperature while connected to the Scott moisture standard. At 33 minutes the
Meter Building temperature was reduced from 25°C (77°F) to 5°C (41°F). The SS2000e showed
a 1 ppmv drop in water concentration to 33 ppmv while the 5100 HD showed a 2 ppmv drop in
water concentration followed by a recovery to 30 ppmv. At 42 minutes the analyzers enclosure
doors were opened exposing the sample cell to a temperature change from about 40°C (100°F)
to 18°C (68°F). This resulted in a further drop in the SS22000e response to 29 ppmv by 48
minutes. The 5100 HD water concentration dropped to 26 ppmv but recovered back to 30 ppmv.
At 52 minutes the enclosure doors were closed, the building doors were closed, and building
heat was turned back on.

60
55
SpectraSensors 2000E
50
Scott Moisture spec
45 Ametek 5100
40
ppmv Water

35
30
25
20
15
10
5
0
35.0 37.5 40.0 42.5 45.0 47.5 50.0 52.5 55.0 57.5

Elapsed time (min)

Fig. 9. Test 2: Response to sample cell environmental temperature change. 33 min – Meter
Building doors opened and heat turned off; 42 min - Enclosure doors opened cooling sample
cell from 40°C (104°F) to 18°C (64°F); 52 min - Enclosure doors closed and Meter Building heat
turned on

Test 3 in Fig. 10 shows the continued recovery of the sample cell after the enclosure doors were
closed. At 82 minutes the sample gas was switched to pipeline gas. The SS2000e and 5100 HD
reach their baseline value seen in previous tests by approximately 97 minutes.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

60
55
Ametek 5100
50
Scott Moisture spec
45 SpectraSensors 2000E
40
ppmv Water 35
30
25
20
15
10
5
0
60 65 70 75 80 85 90 95

Elapsed time (min)

Fig. 10. Test 3: Continued temperature recovery from Fig. 9. 82 min - Pipeline gas

3.5 Water/Glycol Increased Dew Point

In Test 4, the pipeline gas was 5375 kPa-a (790 psia) and 9.8°C (50°F). The pipeline gas dew
point was -25°C (-13°F) when measured with the Chandler water dew point instrument. This is
equivalent to 11 ppmv after conversion [7] using the gas pressure and composition. Fig. 11
shows the result of an increase in moisture content from injecting 80% water and 20% ethylene
glycol, by weight, at 100 mL/min (3.38 oz./min) into the pipeline gas. At 3 minutes the
water/glycol injection begins. Both the SS2000e and 5100 HD show a similar transient
response. At 34 minutes the sample gas was switched to the Scott moisture standard. At 38
minutes the sample gas was switched to pipeline gas. At 42 minutes the water/glycol injection
was turned off. Both the SS2000e and 5100 HD slowly recovered back to pipeline gas
background level. The slow recovery is due to water clearing out of the pipeline and not the
response time of the analyzers.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

120
SpectraSensors 2000E
110
Scott Moisture spec
100 Chandler
90 Contract Limit
80 Ametek 5100
ppmv Water 70
60
50
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 11. Test 4: Injection of 80:20 water/glycol into the pipeline gas at 100 mL/min (3.38
oz./min). 0 min – Pipeline gas; 3 min - Water/glycol injection started; 34 min - Moisture standard;
38 min - Pipeline gas; 42 min - Water/glycol injection stopped

Test 5 in Fig. 12 shows the result of a repeat increase of moisture content with an injection of
80% water and 20% ethylene glycol, by weight, at a lower rate of 80 mL/min (2.7 oz. /min).
Pipeline gas temperature was 11.2 °C (52 °F). At 4 minutes the sample was switched to pipeline
gas and the water/glycol injection started. At 25 minutes the sample gas was switched to Scott
moisture standard resulting in the same response as in Test 4. At 29 minutes the sample gas
was switched to pipeline gas. At 34 minutes the water/glycol injection was turned off. Again,
both the SS2000e and 5100 HD slowly recovered back to pipeline gas background level.

120 SpectraSensors 2000E

110 Scott Moisture spec
100 Chandler
90 Contract Limit
80 Ametek 5100
ppmv Water

70
60
50
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 12. Test 5: Injection of 80:20 water/glycol into the pipeline gas at 80 mL/min (2.7 oz. /min).
0 min – Moisture standard; 4 min – Pipeline gas with water/glycol injection started; 25 min –
Moisture standard; 29 min - Pipeline gas; 34 min - Water/glycol injection stopped
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

3.6 Water Increased Dew point

Test 6 in Fig. 13 shows the result of an increase in moisture content with an injection of water at
a rate of 19 mL/min (0.64 oz. /min). Pipeline gas temperature was 11.6 °C (53 °F). At 0 minutes
the sample gas was connected to pipeline gas which was still recovering to background level
after the previous test. After recovery the SS2000e was reading 11 ppmv and the 5100 HD was
reading 7 ppmv. Between 7 and 23 minutes the sample gas is alternated between the Scott
moisture standard and pipeline gas. At 23 minutes the sample gas was switched to pipeline gas
resulting in a return to background levels. At 32 minutes water injection began.

100
90 SpectraSensors 2000E
80 Scott Moisture spec
pipeline gas ppmv before water injection
70 Ametek 5100
ppmv Water

60 Chandler
50
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 13. Test 6: Injection of water into the pipeline at 19 mL/min (0.64 oz. /min). 0 min - Pipeline
gas; 7 min - Moisture standard; 12 min - Pipeline gas; 18 min - Moisture standard; 23 min -
Pipeline gas; 31 min – Water injection started

3.7 Gas temperature Change

Test 7 in Fig. 14 shows the result of changing the pipeline gas temperature while connected to
pipeline gas with an injection of water at 19 mL/min (0.64 oz. /min). At 0 minutes the sample gas
was connected to pipeline gas which was still increasing in water concentration from the
previous test. At 19 minutes the pipeline gas was cooled from 11.6 °C (53 °F) to 5.6 °C (42 °F)
by diverting the pipeline gas through the Didsbury Nozzle Bank (Fig. 5). After 25 minutes there
was a negative slope in the water concentration, down to new equilibrium level due to less
evaporation of water in the cooler gas. At 31 minutes the sample gas was switched to the
moisture standard which resulted in a reading of 34 ppmv for the SS2000e and 30 ppmv for the
5100 HD. At 35 minutes the sample gas was switched to pipeline gas which resulted in an
immediate return to the previous pipeline water concentration value. At 53 minutes the
vaporizing pressure regulator electric heating was turned off which resulted in no significant
change.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

100
90
80
70

ppmv Water
60
50
40 SpectraSensors 2000E
30 Scott Moisture spec
20 Chandler
Contract Limit
10 Ametek 5100
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 14. Test 7: Continued injection of water into the pipeline gas at 19 mL/min (0.64 oz. /min).
19 min - Gas temperature changed from 11.6 °C (53 °F) to 5.6 °C (42 °F); 31 min - Moisture
standard; 35 min - Pipeline gas with water injection; 53 min - Heated vaporizing pressure
regulator turned off

Test 8 in Fig. 15 shows the result of continuing water evaporation with cooler pipeline gas while
maintaining an injection of water at 19 mL/min (0.64 oz. /min). At 0 minutes the sample gas was
connected to the pipeline, continuing from the previous test. At 10 minutes the vaporizing
pressure regulator electric heating was turned back on, resulting in no significant change. At 25
minutes the water injection was stopped, resulting in a slow drop towards background level as
the pipeline dried out.

100
90
80
70
ppmv Water

60
50
40
30 SpectraSensors 2000E
20 Ametek 5100
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 15. Test 8: Continued injection of water into the pipeline gas at 19 mL/min (0.64 oz. /min).
10 min - Heated vaporizing pressure regulator turned on; 25 min – Water injection stopped
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

Test 9 in Fig. 16 shows the result of continuing recovery from water injection with cooler pipeline
gas. At 34 minutes sample gas was switched to the moisture standard which resulted in a
reading of 34 ppmv for the SS2000e and 30 ppmv for the 5100 HD.

100
90 SpectraSensors 2000E
80 Scott Moisture spec
70 Ametek 5100
ppmv Water

60
50
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 16. Test 9: Continued recovery of pipeline gas after water injection was stopped. 0 min -
Pipeline gas recovery from water injection 30 minutes after end of previous test, 34 min -
Moisture standard

3.8 Water/Methanol increased Dew Point

Test 10 in Fig. 17 shows the results of an increased moisture content in the pipeline gas by
injecting a mixture of 80% water and 20% methanol, by weight, at the rate of 19 mL/min (0.64
oz./min). Pipeline gas temperature was 11.8°C (53°F). At 0 minutes the sample gas was
connected to the moisture standard. At 2 minutes the sample was switched to pipeline gas
resulting in an immediate drop to 24 ppmv for the SS2000e and 20 ppmv for the 5100 HD. This
value was higher than background level due to the previous water injection test. At 10 minutes
the water/methanol injection began at 19 mL/min (0.64 oz./min). The SS2000e and 5100 HD
reached equilibrium at 70 ppmv and 60 ppmv, respectively. At 37 minutes the sample gas was
switched to the Scott moisture standard which resulted in a reading of 34 ppmv for the SS2000e
and 30 ppmv for the 5100 HD. At 42 minutes the sample was switched back to pipeline gas. At
46 minutes the water/methanol injection was stopped, resulting in a slow decline towards
pipeline background water concentration level.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

100
90 SpectraSensors 2000E
80 Scott Moisture spec
70 Ametek 5100

ppmv Water
60
50
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60

Elapsed time (min)

Fig. 17. Test 10: Injection of 80:20 Water/methanol into the pipeline at 19 mL/min. 0 min -
Moisture standard; 2 min – Pipeline gas (recovering from water injection); 10 min –
Water/methanol injection started; 37 min - Moisture standard; 42 min - Pipeline gas; 46 min -
Water/methanol injection stopped

4 Discussion and Conclusion

The SpectraSensors SS2000e water analyzer has a stated accuracy of ±4 ppmv or 2% of
reading (whichever is greater). The SS2000e has been shown to meet this stated accuracy. The
SS2000e consistently measured the correct moisture content of the Scott moisture standard,
within the specified moisture standard uncertainty. The Scott moisture standard was verified to
be within its uncertainty specification by an independent test using an AMETEK 3050 water
concentration analyzer and a Chandler dew point instrument.
The AMETEK 5100 HD water analyzer had a stated accuracy of 2% of full scale (±6 ppmv at
300 ppmv). The 5100 HD has been shown to meet this stated accuracy. The average
concentration measurement when connected to the Scott moisture standard sample gas was 30
ppmv, 4 ppmv below the minimum range specification (34 to 37ppmV) of the Scott moisture
standard. The AMETEK 5100 HD water concentration reading for background pipeline gas was
5 to 10 ppmv below the equivalent water concentration obtained with a Chandler dew point
measurement.
A significant decrease in analyzer measure water content (5 ppmv) was seen when both sample
cells were exposed to ambient conditions (open enclosure). The SpectraSensors analyzer
showed a decrease in measured water content while the AMETEK showed a decrease in
measure water content followed by a slight recovery.
When the analyzers were exposed to a decrease in gas temperature (11.6°C [53°F] to 5.6°C
[42°F]) with the vaporizing pressure regulator turned off, there was no significant change in
measured water concentration, most likely because the heated enclosures control the sample
gas temperature.
The SpectraSensors SS2000e and AMETEK 5100 HD Analyzer gave repeatable and consistent
results when the sample cell temperature was controlled by the heated enclosure.
9th ISFFM Arlington, Virginia, April 14 to 17, 2015

5 Acknowledgements
Thanks are expressed to Tod Martens from Benchmark Instrumentation & Analytical Services
Inc. and Jesse Zapien from SpectraSensors for arranging to provide the SpectraSensors
SS2000e water analyzer for testing.
Thanks are given to Maynard Witzaney and Franco Imbrogno from G.A.S. Analytical Systems
Ltd. and Stuart Simmonds from AMETEK PI for arranging to provide the AMETEK 5100 HD for
testing.
The authors also wish to thank the industry METCON members and their companies at the time
of this work for their interest in this testing and support of metering research in general: Blaine
Sawchuk, Canada Pipeline Accessories Co. Ltd; Abisai Gonzalez, Southern California Gas
Company; Gurinder Parmar, Spectra Energy; Katherine Molberg, FortisBC Energy Inc.; and
Darren Pineau, TransCanada Pipelines Limited.

[1] Potter, D.R., ”Analytical Devices for the Measurement of Water Vapor in the Natural Gas
Process and Transmission Industry”, GAS2011.
[2] SpectraSensors, “Operator’s Manual H2O and/or CO2 in Natural Gas”, 4900002068 rev. F 8-
23-11, http://www.spectrasensors.com/ss2000e/.
[3] AMETEK Process Instruments, “Model 5100/5100 HD Tunable Diode Laser Spectrometer”,
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