Standard pressure gauges and thermometers generally cope with ambient temperatures right down to -40 �C. But what should be the top features of a mechanical measuring instrument that works perfectly well in polar climates with even lower temperatures? This is often explained using the WIKA POLARgauge� for example. The product family has been designed specifically for measurement at extremely low ambient temperatures right down to -70 �C. The instruments are mainly used in crude oil and gas processing; for instance, 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, tables with standard temperature values even indicate more than -60 �C for some regions. For mechanical instruments which is operated in such ambient conditions, two critical points should 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, in order that the measured value can be read safely.
However, nearly all silicone oils used for this purpose begin to solidify at temperatures below -40 �C. The movement then no longer works, or may also freeze. Application-aligned tabs on 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. This oil remains in a state that enables 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 does not have any elastomers.
2. The elastomers
Elastomers are found in every mechanical pressure gauges or thermometers. They offer a secure sealing between the individual components. At length, 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 very low ambient temperatures. They become brittle over time and lose their sealing properties. This results in the event 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 of 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 following links. The merchandise 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 almost any application. Would you like to buy differential pressure gauge models? In Gift -shop you will discover some of our standard designs. If you have any further questions, your contact will gladly assist you to.