Pressure gauges in general can handle ambient temperatures as low as −40°F (−40°C). However, once you get closer to the Arctic Circle, temperatures exceeding −40°F become the norm. Even in these extreme conditions, you will find many operations – especially in oil and gas – where pressure gauges are used, for example, in the local monitoring of pumping stations and pipelines. With an understanding of the limitations of a conventional pressure gauge in such conditions and the affects extremely low temperatures can have, WIKA developed Model PG23LT, a new liquid-filled pressure gauge specifically designed for ambient temperatures down to −94°F (−70°C).
A pressure gauge subjected to extremely low ambient temperatures requires a liquid-filled case, as the liquid filling prevents moisture from forming inside the case. Moisture inside the case can cause moving parts to freeze over, thus preventing the pointer from moving. Moisture can also form behind the window, causing it to fog up, or in extreme conditions, to frost over. Either form of moisture will prevent the user from reading the instrument. Another benefit of the liquid case filling is that it lubricates the gauge internals, which extends the gauge’s life when it is exposed to vibrations, and reduces or eliminates pointer flutter.
Chilly Problems with Standard Liquid-Filled Pressure Gauge
However, most silicon oil-filled pressure gauges do not work effectively beyond−40°F (−40°C). Below that temperature, the fill liquid becomes too viscous, resulting in slower response times and inaccurate pressure readings. In extreme cold, the case fill begins to solidify and the gauge might stop working altogether.
WIKA’s engineered solution Model PG23LT comes with a special low-temperature silicone case fill to ensure accurate readings even at extremely low temperatures.
Another critical component to a hermetically sealed and liquid-filled pressure gauge are elastomers. O-rings and gaskets prevent 1) moisture from entering the case and 2) the case fill from leaking out. Flat gaskets are used to seal the window, the blow-out back at the rear of the case, and the vent valve on top of the case for pressure compensation.
Standard sealing materials, however, will not withstand very low ambient temperatures. Over time they become brittle and will lose their sealing properties. When developing the PG23LT, WIKA tried to eliminate elastomers at critical points. The window seal and O-ring to seal the blow-out back are made from a special material that can withstand extremely low temperatures. The fill plug, normally made from rubber, has been replaced with a stainless steel hex screw or compensating valve, depending on the pressure range.
Model PG23LT: Cool Running in Extremely Low Temperatures
The PG23LT comes in ranges from 0…10 psi (0.6 bar) up to 0…15,000 psi (1,000 bar). The standard enclosure rating is IP65 per EN/IEC 60529 for pressure ranges up to 230 psi (16 bar) and IP66/IP67 (NEMA 4/4X) for ranges 300 psi (20 bar) and up.
For safety critical applications, the gauge is available in safety design “S3” per EN 837-1 with a blow-out back and a solid baffle wall separating the gauge internals from the window. The PG23LT is supplied with a Certificate of Compliance (2.2 test report) to confirm its suitability for ambient temperatures down to −94°F (−70°C). If needed, the PG23LT can be supplied with industry approvals such as ATEX. EAC and Metrology approvals for export into CIS (Commonwealth of Independent States) countries are also available. Overall, WIKA’s PG23LT is the best solution for all applications in extreme low ambient conditions.
Choosing the right liquid-filled pressure gauge to fit the particular conditions of your application will ensure that your process works properly.
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