Measuring at overpressure ____________________________________________________________
Vaisala _________________________________________________________________________ 44
CHAPTER 9
MEASURING AT OVERPRESSURE
The probes HMP362, HMP364 and HMP368 are designed for
humidity measurement at overpressure. The maximum measurement
pressures depend on the probe as follows:
HMP362
: 0...167 bar (16,7 MPa), for natural gas, sample cell
HMP302SC available
HMP364
: 0...100 bar (10 MPa), for pressurized rooms and processes,
probe is provided with a nut, fitting screw and sealing
washer
HMP368
: 0...40 bar (4 MPa), for pressurized pipelines, ball valve set
available
The accuracy of the dewpoint measurement is affected by pressure in
the measurement chamber. The actual pressure in the sampling cell
shall be set to the transmitter by using the serial line command
PRES
(
Setting the ambient pressure for calculations
), page 42 or by using
the keypad commands, page 33.
CAUTION
In pressurized processed it is essential to tighten the
supporting nuts and screws very carefully to prevent
loosening of the probe by the action of pressure.
Pressure regulator recommended
When sampling pressurized processes exceeding the maximum
measurement pressure of the probe, the pressure in the measurement
chamber must be regulated to acceptable level or below. It is
recommended to use pressure regulator before the measurement
chamber to prevent remarkable pressure variations.
