GE Sensing XMTC Data sheet

GE
Oil & Gas
XMTC
Panametrics Thermal Conductivity Binary Gas Transmitter
Applications
A thermal conductivity gas transmitter for use in the following industries and applications:
Metals Industry
in N2 atmosphere in metal heat-treating
2
furnaces
Electric Power Industry
in cooling systems for generators
2
Petroleum Industry
in hydrocarbon streams
2
Chemical Industry
• H
in ammonia synthesis gas
2
• H
in methanol synthesis gas
2
• H
in chlorine plants
2
Methane Industry
in methane
• CO
2
Landfi ll/Biogas Industry
in biogas
• CO
2
• CH
in biogas
4
Gas Production Industry
Purity monitoring of argon, hydrogen, nitrogen and helium
Food Industry
CO
in fermentation processes
2
Features
• Ultra-stable glass-coated thermistors
• Single or dual gas push-button calibration
• PC interface package for digital output
• Type IP66/4X construction
• ATEX, IECEx, FM and CSA certifi ed for Zone I and Division 1 hazardous areas
The microprocessor-based XMTC is a compact, rugged, online thermal conductivity transmitter that measures the concentration of binary gas mixtures containing hydrogen, carbon dioxide, methane or helium. The analyzer also combines computer enhanced signal measurement with fast-response software, real-time error detection and digital communication via an RS232 or RS485 interface.
Theory of Operation
Two ultrastable, precision glass-coated thermistors are usedone in contact with the sample gas and the other in contact with the reference gas (such as air in a sealed chamber). The thermistors are mounted so that they are in close proximity to the stainless steel (or Hastelloy entire transmitter is temperature-controlled, and the thermistors are heated to an elevated temperature in a constant-current Wheatstone bridge. The thermistors lose heat to the walls of the sample chamber at a rate that is proportional to the thermal conductivity of the gas surrounding them. Thus, each thermistor will reach a different equilibrium temperature. The temperature difference between the two thermistors is detected in the Wheatstone bridge, and the resulting bridge voltage is amplifi ed and converted to a linear 4 to 20 mA output proportional to the concentration of one of the constituents of the binary or pseudo binary gas mixture.
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) walls of the sample chamber. The
Sample System
A sample system is mandatory for use with the XMTC. The design of the sample system will depend on the conditions of the sample gas and the requirements of the application. In general, a sample system must deliver a clean, representative sample to the XMTC at a temperature, pressure and fl ow rate that are within acceptable limits. Standard XMTC sample conditions are: a temperature of less than 122°F (50°C) for a cell operating temperature of 131°F (55°C) with a fl ow rate of 0.5 SCFH (250 cc/min) at atmospheric pressure. A higher temperature option is available.
GE offers sample systems for a wide variety of applications. For assistance in designing your own sample system, please consult the factory.
Relative Thermal Conductivities of Common Gases
Air/N
2
CH
CO
2
SO
2
Ar
Cl
2
C2 - C
6
Note: Graph is relative thermal conductivity at 212°F (100°C)
Ne
4
He
H
2
Minimal Calibration and Service
The XMTC is the most stable thermal conductivity analyzer on the market today. The rugged XMTC measuring cell resists contamination and remains insensitive to fl ow variations. Since the design uses no moving parts, the transmitter can easily withstand the shock, vibration and harsh environment found in many industrial applications. If the transmitter requires maintenance, its modular construction permits fast and easy servicing. Users can fi eld-calibrate it quickly and replace the plug-in measuring cell with a precalibrated spare in minutes.
Gas Formula Chemical Gas Formula Chemical
Acetylene 0.90 C2H
Air 1.00 N
Argon 0.67 Ar n-Hexane 0.66 C6H
n-Butane 0.74 C4H
Carbon Dioxide 0.70 CO
Chlorine 0.34 Cl
Ethylene Alcohol 0.64 C
Ethylene 0.98 C
Ethylene Oxide 0.62 C2H4O Sulfur Dioxide 0.38 SO
Freon-11 0.37 CCI3F Water Vapor 0.77 H2O
Helium 5.53 He
2
n-Heptane 0.58 C7H
2/O2
Hydrogen 6.80 H
10
Methane 1.45 CH
2
Methyl Chloride 0.53 CH3Cl
2
Neon 1.84 Ne
2H5OH4
n-Pentane 0.70 C5H
2H4
16
14
2
4
12
2
Choosing the Reference Gas
The simple two-port version can be selected for measurement of zero-based gas mixtures using the sealed reference gas (air). There is a four-port version for improved performance using a specifi c fl owing reference gas.
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