Standard pressure gauges and thermometers generally cope 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 can be explained using the WIKA POLARgauge� for example. This product family has been designed designed for measurement at extremely low ambient temperatures right down to -70 �C. The instruments are mainly used in crude oil and gas processing; for example, in the local pressure and temperature monitoring of pumping stations and pipelines.
Minus 40 �C ? this value is frequently exceeded faster than one thinks. That 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 will be 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 useful for this protect the instrument from condensation formation within the case resulting from temperature fluctuations. They thus avoid the window from frosting, so that the measured value can be read safely.
However, nearly all silicone oils used for this purpose commence to solidify at temperatures below -40 �C. The movement then no longer works, or can even freeze. Application-aligned tabs on 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 enables 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 does not have any elastomers.
2. The elastomers
Elastomers are found in every mechanical pressure gauges or thermometers. They offer a secure sealing between your 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 suprisingly low ambient temperatures. They become brittle over time 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 been eliminated in every critical points. The seal between your 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.
Summary of the WIKA POLARgauge� series
Note
You can get further information on the POLARgauge� series on the WIKA website via the following links. Colossal 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 every application. Do you want to buy differential pressure gauge models? In our WIKA online-shop you will find some of our standard designs. In case you have any further questions, your contact will gladly help you.