Standard pressure gauges and thermometers generally cope with ambient temperatures down to -40 �C. But what must be the features of a mechanical measuring instrument that works perfectly well in polar climates with even lower temperatures? This could be explained using the WIKA POLARgauge� for example. Stealthy has been designed designed 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 local pressure and temperature monitoring of pumping stations and pipelines.
Minus 40 �C ? this value is often exceeded faster than one thinks. This is demonstrated with a look to Russia. There, tables with standard temperature values even indicate a lot 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 useful 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 circumstances 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 does not have any 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, they are the flat gasket at the window, and with 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 found in standard designs cannot durably withstand very low ambient temperatures. They become brittle as time passes and lose their sealing properties. This results in the case filling escaping. This, in turn, leads to the forming 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 constructed of a special material. It is adapted to extremely low ambient temperatures. The vent valve includes a stainless steel cap.
Summary 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 every application. Do you want to buy differential pressure gauge models? In our WIKA online-shop you will find a few of our standard designs. When you have any more questions, your contact will gladly help you.