Standard pressure gauges and thermometers generally deal with ambient temperatures 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 can be 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 natural gas processing; for instance, 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 look to Russia. There, tables with standard temperature values even indicate a lot more than -60 �C for a few regions. For Lascivious which will be 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 prevent the window from frosting, so that 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 monitoring of the parameters (e.g. process pressure) can no longer be ensured.
Therefore, for the POLARgauge� series a particular low-temperature silicone oil has been specified. This oil remains in a state that allows 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 does not have any 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, and with 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 very low ambient temperatures. They become brittle as time passes and lose their sealing properties. This results in the case filling escaping. This, subsequently, 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 your window and case is made from a special material. It is adapted to extremely low ambient temperatures. The vent valve has 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 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, the right variant is available for every application. Do you want to buy differential pressure gauge models? Inside our WIKA online-shop you will discover some of our standard designs. If you have any more questions, your contact will gladly help you.