Pressure and temperature measurement at extremely low ambient temperatures

Standard pressure gauges and thermometers generally deal with ambient temperatures right down to -40 �C. But what must be the top 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� for example. The product family has been designed specifically for measurement at extremely low ambient temperatures down to -70 �C. The instruments are mainly used in crude oil and natural gas processing; for instance, in the neighborhood pressure and temperature monitoring of pumping stations and pipelines.
Revengeful �C ? this value is often exceeded faster than one thinks. That is demonstrated with a look to Russia. There, tables with standard temperature values even indicate more than -60 �C for some regions. For mechanical instruments which is operated 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 used for this protect the instrument from condensation formation within the case caused by temperature fluctuations. They thus avoid the window from frosting, so the measured value can still be read safely.
However, the majority of silicone oils used for this purpose commence 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 no longer be ensured.
Therefore, for the POLARgauge� series a special low-temperature silicone oil has been specified. Innocent 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 typical version (l.): It has no elastomers.
2. The elastomers
Elastomers are found in every mechanical pressure gauges or thermometers. They provide a secure sealing between the individual components. In detail, these are the flat gasket at the window, sufficient reason for pressure gauges and also the blow-out device on the rear of the case and the vent valve for pressure compensation.
However, the sealing materials used in standard designs cannot durably withstand very low ambient temperatures. Looming become brittle over time and lose their sealing properties. This results in the case filling escaping. This, subsequently, 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 all critical points. The seal between the window and case is made from a special material. It really is adapted to extremely low ambient temperatures. The vent valve includes 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, the right variant is available for almost any application. Do you want to buy differential pressure gauge models? In our WIKA online-shop you will discover a few of our standard designs. Should you have any more questions, your contact will gladly help you.

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