[Daily Question 20090409] Discussion on the material and filling liquid of the membrane box of the transmitter with membrane box
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In different media, pressures and temperatures, let’s talk about the materials and filling fluids of the transmitters with membrane boxes that you have seen so far. How did you choose these?
Let me start with some ideas. 1. Double flange for acid water tank, 0.5MPa, 50℃ capillary length 10M, material: 316L ； Filling fluid: Silicone oil ； 2. Maleic anhydride pressure measurement, 0.58MPa, 56℃ capillary length 3M, material: 316L ； Filling fluid: Ethylene glycol
The material of the membrane box should be determined according to the nature of the medium. Stainless steel is usually used. The filling liquid should consider both the medium and the ambient temperature. Different isolation fluids should be selected according to the ambient temperature. This can be found in the selection sample.
General silicone oil, low temperature ethylene glycol.
I encountered something special. Methylamine solution: 10MPa, 140°C. Diaphragm material: duplex steel, silicone oil. It works great.
What we are using now is a double flange transmitter, the diaphragm material is JIS SUS316L, the isolation liquid filled in the middle is silicone oil, and the liquid contact temperature is -10---250 degrees. It's very good to use. Once installed, it generally doesn't require any maintenance:victory:
Generally, silicone oil (DC200) is used for oil filling, and the temperature is -40deg. C to 200deg. C can be used ； Under high temperature or vacuum conditions, DC704 and DC705 can be used ； In low temperature conditions, you can use SYLTHERM XLT, the temperature can reach - 70deg.C About ；
Generally, silicone oils of different viscosities are selected according to the temperature, and can be used in temperatures ranging from -45 to 340°C. For example, when using oxygen, it needs to be filled with inert oil, usually fluorine oil, ~60~150℃. In addition, the food industry also requires filling with cooking oil. Foreign silicone oil can reach 400 degrees, but it is not available in China. Special ingredients should be added.