Standard pressure gauges and thermometers generally deal 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� for example. This product family has been designed specifically for measurement at extremely low ambient temperatures right down to -70 �C. The instruments are mainly utilized in crude oil and gas processing; for example, in the neighborhood pressure and temperature monitoring of pumping stations and pipelines.
Minus 40 �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 a lot more than -60 �C for a few 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 resulting from temperature fluctuations. They thus prevent the window from frosting, so 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 longer 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 enables correct measurement and measured value display, even at -70 �C.
The case of the POLARgauge� model PG23LT (r.) compared 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 the individual components. At length, these are the flat gasket at the window, sufficient reason for pressure gauges and also the blow-out device on the trunk 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 as time passes and lose their sealing properties. This results in the event 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 been eliminated in all critical points. The seal between the window and case is constructed of a special material. Heart 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 further information 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 every application. Do you want to buy differential pressure gauge models? Inside our WIKA online-shop you will find a few of our standard designs. In case you have any more questions, your contact will gladly assist you to.