Ametek Process Instruments - THERMOX

- Model Standard Bureau of Mines - Dew Point Tester



The Need: Natural gas pipeline operations are dramatically impacted by the presence or formation of liquids within the gas pipeline. The dew point of the natural gas must be periodically checked in order to ensure that troublesome liquid formation is not occuring in the pipeline. Operators and technicians need an accurate, rugged means of determining the dew point of the gas within the pipeline.

Chandler EngineeringTM met this industry need with the development of the this device: the Standard Dew Point Tester. This device works as follows:

The sample gas to be analyzed is slowly passed, at pipeline pressure, over a mirror. The mirror is slowly cooled through the use of a manually regulated refrigerant gas. A thermometer accurately reads the temperature of the mirror while an operator observes the mirror for the formation of dew. When dew is observed, the dew point temperature is read off the thermometer. The type of dew formed on the mirror can be determined by an experienced user. Use of this device is described by ASTM D1142.

This device is completely manual. The observor is not only the 'detector', they must also manually control the rate of mirror cooling and read the indicated temperature at the appropriate time. When used by a skilled operator, this device will produce extremely accurate dew point measurements.

The Standard Dew Point Tester, is available in a variety of dew point temperature and pressure ranges.

  • Meets ASTM D1142
  • Portable and rugged for repeatable results
  • No calibration needed
  • RTD traceable to NIST (Chanscope II)
  • Easy to maintain and use

Natural Gas

Designed for accuracy in the rugged environment typically found in the gas industry. A special model is available for offshore use.

Sour Gas

Corrosion-resistant materials are used for H2S atmospheres.

Industrial Gases

The tester is ideally suited for the measurement of the dew point of pressurized N2, O2, H2, Ar, air, and other bottled gases.

Heat Treating Furnaces

Chandler instruments are easy to use and produce reliable, accurate answers. They have been used for years in this application.

The Chandler Bureau of Mines Dew Point Tester is a primary instrument used to measure the dew point temperature of any gas. It is rugged, portable, and can provide very repeatable results. Because of its primary nature, the standard dew point tester requires no calibration. Consequently, it is frequently used to verify results of electronic instruments.

The Chandler Dew Point Tester is a chilled mirror device that operates by achieving the conditions required by the definition of dew point. When a gas is cooled out of contact with liquid water, the humidity or water content remains constant, but the percentage of saturation increases until it reaches 100% and moisture begins to condense. The temperature at this point is known as the dew point or frost point.

The Chandler “Bureau of Minestype” Dew Point Tester consists of a small high pressure chamber through which the gas sample flows. A polished mirror is at one end of the chamber and a viewing window at the other. The operator controls an expandable gas through a valve, cooling the polished mirror until the dew point is observed. The observed dew point temperature and pressure may be entered into the moisture content software supplied with the dew point tester to calculate the water content of the sample. Hydrocarbon dew points in natural gas can be obtained using the same method.

Chanscope II Dew Point Tester

±0.2°C (±0.4°F) at 40°C (104°F) to -90°C (-130°F)
(NIST Certification Included)

Dew Point Temperature Ranges: -29°C (-20.2°F) to ambient, with liquid Propane
-62°C (-79.6°F) to ambient, with liquid Carbon Dioxide
-129°C (-200.2°F) to ambient, with optional liquid Nitrogen chiller

Chiller Devices Available:

Regular (Propane)

Quick Chiller – Can be used for Dew Point measurements down to:
-30°C (-22°F) with Propane
-70°C (-94°F) with liquid Carbon Dioxide

Liquid Nitrogen Chiller – Dipstick type used for Dew Point measurements down to:
-129°C (-200.2°F) and below with
liquid Nitrogen
-75°C (-103°F) with Dry Ice/Acetone

NOTE: The Quick Chiller and the Liquid Nitrogen Chiller allow faster Dew Point determinations but care should be taken to allow components to reach thermal equilibrium reducing error caused by temperature overshoot.

Ambient Temperature Range:
-20°C (-4°F) to 40°C (104°F)

Operating Pressure: Up to 5000 psig (34.6 MPa)
Optional LCD readout pressure gauge available

Connections: Sample inlet and outlet: 1/8” NPT; Refrigerant, 1/8” tube

Power: Battery-powered (NiMH), 100-240VAC, 50/60 Hz, smart charger.

Ship Weight: 25 lb (11 kg)

Carrying Case: 14” x 18” x 7” (35.5cm x 45.7cm x 17.8cm), water-tight, form-fitted resin case

Model 13 Bureau of Mines Dew Point Tester

Accuracy: ± 0.5°F (± 0.25°C)

Dew Point Temperature Range: Dependant on which thermometer is chosen.

Operating Pressure: Up to 5000 psig (34.6 MPa)

Optional LCD readout pressure gauge available
Connections: Sample inlet and outlet: 1/8” NPT; Refrigerant, 1/8” tube

Ship Weight: 25 lb (11 kg)

Carrying Case: 14” x 18” x 7” (35.5cm x 45.7cm x 17.8cm)

Digital Readout

The Chanscope II version allows lighted, magnified viewing of the dew point with a digital temperature display superimposed on the viewing window in tenths of degree. The unit also has a button-hold feature to retain the measured value. The model uses accurate platinum RTD and LED readout to give the operator instantaneous feedback during a test.

Pressure Range

Models are available in ranges of 1,000, 3,000 or 5,000 psig (7.0, 20.8, and 34.6 MPa).

Regular Chiller

Uses liquid propane: -29°C (-20.2°F) or liquid carbon dioxide -62°C (-79.6°F) as a refrigerant. Its geometry optimizes thermal uniformity for superior control and accurate determination.

Quick Chiller

Uses the same expandable gases but directs them onto the back of the polished mirror. Fast reaction time is achieved, but there is an increased risk of overshooting the dew point until all components reach thermal equilibrium.

Liquid Nitrogen Chiller

Uses an immersion rod and Dewar flask containing N2 for temperatures down to -129°C (-200.2°F).


A wide range of thermometers are available in Centigrade or Fahrenheit, including certified RTD traceable to NIST. Thermometers are filled with a biodegradable liquid, eliminating the safety concerns of mercury.

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