What kind of oil is inside a shockproof pressure gauge?
3 Answers
Shockproof pressure gauges contain damping fluid, typically silicone oil or glycerin. Here is an introduction to the relevant content: 1. Function of shockproof pressure gauges: Shockproof pressure gauges are instruments filled with damping fluid inside the casing, which can resist vibrations in the working environment and reduce the impact of medium pressure pulsation. 2. Function of damping fluid: Damping fluid relies on the viscous resistance of the liquid medium to attenuate the kinetic energy of moving machinery, shortening the swinging or movement time of machinery. Below is extended information on precautions for using ordinary pressure gauges: 1. Usage range: It is advisable to use 1/3 to 2/3 of the full range for working pressure, with the maximum usage not exceeding 3/4 of the full scale. 2. Inspection cycle: The inspection cycle generally should not exceed six months. For situations where the medium pressure fluctuates significantly, higher accuracy is required, or stricter safety factors are needed, the inspection cycle can be appropriately shortened based on specific conditions. 3. Working environment: The working environment should be free of corrosive gases.
The liquid filled in shockproof pressure gauges isn't ordinary oil. I only learned during my last repair of workshop pressure gauges that glycerin or silicone oil is commonly used. This oil film both cushions needle vibration and isolates humid air to prevent corrosion. Glycerin is cost-effective and works between -5°C to 50°C, but it freezes solid at -10°C in factories. Silicone oil is more expensive but has wider temperature resistance, remaining liquid even at -40°C. The fluorinated oil used in refinery pipeline pressure gauges is even more impressive, offering top-tier chemical corrosion resistance - though it costs nearly half a new gauge. Remember never to substitute with engine oil, as high temperatures will carbonize and clog the capillary tube.
I've been thinking about filling the pressure gauge with oil for a long time, mainly choosing oil based on the working environment. In ordinary workshops, glycerin is the most convenient option—it has moderate viscosity and rust prevention, but strong oxidizers must be avoided. Food factories must use food-grade silicone oil; otherwise, contaminating the production line could cause serious issues. For marine use, the oil must be salt spray-resistant, requiring special synthetic ester oils. Once, I forgot to change the oil, and the glycerin solidified in cold weather, jamming the gauge needle—almost leading to a misjudgment of boiler pressure. This oil needs to be replaced every three years; otherwise, performance degrades, and the needle will shake like it's having a seizure.
