Figure 5 Typical Phase Envelope For Northern Europe Natural Gas - Michell Instruments Condumax II User Manual

INSTALLATION
Pressure reduction and sample fl ow control is required to achieve the desired analysis
pressures and the stated sample fl ow requirements of the analyzer – see Section 2.7.
Care should be taken to counteract though directly applied heating the Joule-Thomson
cooling effect of sample expansion to reduced pressure. Established business practice
at custody transfer is to measure water dew point at full line whilst HC dew point is
determined at intermediate pressure, commonly 27 barg (400 psig), the cricondentherm
condition at which HC dew point temperature will be highest on the retrograde phase
envelope – see fi gure below:
Figure 5
As with the sample impulse tubing, the sample conditioning system (SCS) must be
maintained at a temperature above the highest expected water and HC dew point at
the prevailing process sample pressure and the analysis pressure for HC dew point,
either by housing the SCS together with the analyzer within a heated and thermostatic
controlled, insulated enclosure, or by positioning in a suitable indoor environment. The
enclosure for outdoor installed systems must be located within 100% shade from direct
sun, if necessary by the addition of an effective sun canopy with walls on three sides.
As with all precision analytical equipment, it is desirable to maintain a moderate operating
temperature. In the specifi c case of a HC dew-point analyzer, care should be taken not to
elevate the analyzer operating temperature higher than is necessary to maintain sample
integrity. Given the principle of cooled-mirror dew-point measurement, the measurement
range of HC dew point is limited by a cooling depression range capability. In the case
of the Condumax II, the lower range capability is >=50°C from the prevailing analyzer
operating temperature. When the analyzer system is installed outside in hotter climate
installation locations, or where the application requires measurement near or below the
measurement cooling depression limit, it may be necessary to provide auxiliary cooling
within the system enclosure. Such cooling can be achieved using a compressed air
driven vortex tube controlled by an adjustable thermostat.
14
H2O Dew Point
8
7
6
5
Water and
4
HC liquids
HC liquids
present in
3
preset in
gas
2
gas
1
0
-40 -30 -20
Temperature °C
Typical Phase Envelope for Northern Europe Natural Gas
Condumax II User's Manual
HC Dew Point
Wholly gaseous
Cricondentherm
-10 0 +10
97081 Issue 28.1, July 2018