Standard pressure gauges and thermometers generally cope 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 can be explained utilizing the WIKA POLARgauge� as an example. This product family has been designed specifically for measurement at extremely low ambient temperatures right down to -70 �C. Security are mainly used in crude oil and natural gas processing; for instance, in the neighborhood pressure and temperature monitoring of 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 some regions. For mechanical instruments which will be operated in 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 caused by temperature fluctuations. They thus avoid the window from frosting, so that the measured value can be read safely.
However, nearly all silicone oils useful for this purpose commence to solidify at temperatures below -40 �C. The movement then no more works, or can even 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.) compared to a standard version (l.): It has no 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, they are the flat gasket at the window, and with pressure gauges additionally the blow-out device on the trunk 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 over time and lose their sealing properties. This results in the event filling escaping. Pioneering , 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.
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 almost any application. Would you like to buy differential pressure gauge models? Inside our WIKA online-shop you will find some of our standard designs. Assuming you have any further questions, your contact will gladly help you.