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 utilizing 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 utilized in crude oil and gas processing; for instance, in the local pressure and temperature tabs on pumping stations and pipelines.
Minus 40 �C ? this value is frequently 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 a few 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 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 particular low-temperature silicone oil has been specified. This oil remains in circumstances that allows correct measurement and measured value display, even at -70 �C.
Non-controlling of the POLARgauge� model PG23LT (r.) in comparison to a standard version (l.): It has no elastomers.
2. The elastomers
Elastomers are found in all mechanical pressure gauges or thermometers. They provide 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 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 already been eliminated in every critical points. The seal between your window and case is made from a special material. It really 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 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 almost any application. Do you want to buy differential pressure gauge models? Inside our WIKA online-shop you will find some of our standard designs. In case you have any more questions, your contact will gladly help you.g