Pressure and temperature measurement at extremely low ambient temperatures

Standard pressure gauges and thermometers generally cope with ambient temperatures right down to -40 �C. But what should be the features of a mechanical measuring instrument that works perfectly well in polar climates with even lower temperatures? This is often explained utilizing the WIKA POLARgauge� as an example. This product family has been designed designed for measurement at extremely low ambient temperatures down to -70 �C. The instruments are mainly used in crude oil and gas processing; for example, in the neighborhood pressure and temperature tabs on pumping stations and pipelines.
Minus 40 �C ? this value is often exceeded faster than one thinks. This is demonstrated with a turn to Russia. There, Painful with standard temperature values even indicate a lot more than -60 �C for a few regions. For mechanical instruments which is operated in such ambient conditions, two critical points must be observed:
For pressure measurement at extremely low ambient temperatures only available with filled case: The WIKA pressure gauge model PG23LT.
1. The case filling
A measurement at extremely low ambient temperatures requires filled-filled measuring instruments. The liquids useful for this protect the instrument from condensation formation within the case caused by temperature fluctuations. They thus prevent the window from frosting, so that the measured value can be read safely.
However, the majority of silicone oils used for this purpose begin to solidify at temperatures below -40 �C. The movement then no more works, or can even freeze. Application-aligned monitoring of the parameters (e.g. process pressure) can’t be ensured.
Therefore, for the POLARgauge� series a special low-temperature silicone oil has been specified. This oil remains in a state that allows correct measurement and measured value display, even at -70 �C.
The case of the POLARgauge� model PG23LT (r.) in comparison to a standard version (l.): It has no elastomers.
2. The elastomers
Elastomers are found in all mechanical pressure gauges or thermometers. They offer a secure sealing between your individual components. In detail, these are the flat gasket at the window, and with pressure gauges additionally the blow-out device on the rear of the case and the vent valve for pressure compensation.
However, the sealing materials found in standard designs cannot durably withstand suprisingly low ambient temperatures. They become brittle as time passes and lose their sealing properties. This results in the event filling escaping. This, in turn, leads to the formation of condensation and the frosting of the window.
Therefore, in the development of the POLARgauge� series, elastomers have already been eliminated in every critical points. The seal between the window and case is made of a special material. It really is adapted to extremely low ambient temperatures. The vent valve has a stainless steel cap.
Overview of the WIKA POLARgauge� series
Note
You can get more info on the POLARgauge� series on the WIKA website via the next links. The product family currently comprises four instrument types: The Bourdon tube pressure gauge model PG23LT, the differential pressure gauge models 733.51, 733.31 (filled versions of the models 732.51, 732.31), the bimetal thermometer model 55 and the gas-actuated thermometer model 73. Thus, a suitable variant is available for every application. Would you like to buy differential pressure gauge models? In our WIKA online-shop you will discover a few of our standard designs. In case you have any more questions, your contact will gladly assist you to.

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