If the application is suspect of possible presence of liquids for example:
• Compressed air with possible oil and/or water,
• Gas Insulated Switchgear or Transformer, SF
6
or N
2
blanket with suspected oil carryover,
• Natural Gas with possible Triethylene Glycol carryover,
Consult with Phymetrix for specialized sampling systems.
5.3
Tubing and Fittings
Make sure all tubing is constructed of materials suitable for low dewpoint measurement, i.e.
stainless steel or Teflon, do not use rubber or plastic tubing (refer to section 4.1 for more details).
Check for leaks after connecting.
Flow meters can be a source of moisture ingress especially if they have a plastic flow tube;
ensure flow meters are connected at the analyzer exhaust, not at inlet. However metering valves
should be at the inlet in order to maintain constant atmospheric pressure in the sampling chamber.
5.4
Sample Pressure
Pressure variations will effect the measurement. Higher pressure is more likely to produce
condensation and thus erroneous readings or even damage the sensor. If the sample pressure
needs to be reduced use a suitable pressure dropping device such as a stainless steel needle valve
or pressure regulator with a stainless steel diaphragm or a flow control orifice. Make sure Joule-
Thomson effects do not cool the gas below hydrocarbon and water dewpoints.
Exhaust
Main Pipe
Flow
Metering Valve
or
Pressure Regulator
Sample Cell
Sample pickup
away from walls
PLMa
Install this
side UP
6