Process Engineering Division – Instrumentation and Automation Technology Exchange Forum – Daily Question – Question No. 2020-01-07
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This post was last edited by It will be better tomorrow on 2020-1-7 08:16 in the Process Engineering Section – Instrumentation and Automation Technology Discussion Forum – Daily Question – Question No. 2020-01-07. What are the main properties of the filling liquid inside a transmitter diaphragm box? What are the differences between silicone fluorocarbon oils? Answer: It has a low coefficient of thermal expansion; it does not solidify at low temperatures, and it does not volatilize or vaporize at high temperatures. Its viscosity does not change significantly with temperature, which ensures stable performance of the instrument. Low-temperature silicone oils can reach a minimum temperature of -40°C, while high-temperature silicone oils can reach a maximum temperature of 315°C. Fluorine oil is an inert liquid with low chemical reactivity; it is therefore used in transmitters for oxygen or chlorine measurement, operates within a temperature range of -45 to 250°C, has low viscosity, and is expensive.
Performance: It can transmit pressure, has a low coefficient of thermal expansion, does not condense at low temperatures, and does not evaporate or vaporize at high temperatures; its viscosity does not change significantly with temperature variations. Difference: Fluorine oils have inert chemical properties and are commonly used in environments for oxygen and chlorine testing; they are more expensive than silicone oils.
The interior of the diaphragm box needs to be filled with a filling fluid in order to transmit pressure. There are low-temperature silicone oils and high-temperature silicone oils; low-temperature silicone oils can withstand temperatures down to -40°C, while high-temperature silicone oils can handle temperatures up to 315°C. Fluorine oil is an inert liquid with low chemical reactivity; it is therefore used in transmitters for oxygen or chlorine measurement. Its operating temperature range is from -45 to 250°C, it has a low viscosity, and its price is higher than that of silicone oil.
Coefficient of expansion, thermal stability, freezing point
Silicone oil can be used in most applications, but when the medium to be measured is chlorine or contains chlorine, it is necessary to be careful: fluorine oil must be used instead, as chlorine is highly corrosive and highly permeable, and it reacts with silicone oil to cause explosions
The interior of the diaphragm box needs to be filled with a filling fluid in order to transmit pressure. The requirements for this filling fluid are: a low coefficient of thermal expansion, no freezing at low temperatures, and no volatilization or vaporization at high temperatures.
Performance: It can transmit pressure, has a low coefficient of thermal expansion, does not condense at low temperatures, and does not evaporate or vaporize at high temperatures; its viscosity does not change significantly with temperature variations. Difference: Fluorine oils have inert chemical properties and are commonly used in environments for oxygen and chlorine testing; they are more expensive than silicone oils.
Corrosion-resistant, incompatible with process media
It is usually silicone oil and fluorine oil. It is characterized by a low thermal temperature coefficient, does not freeze at low temperatures, and does not volatilize or vaporize at high temperatures. Viscosity does not change significantly with temperature. High-temperature silicone oils can reach up to 315°C, while low-temperature silicone oils can go as low as -40°C. Fluorinated oils fall within the range of -40°C to 315°C.
Properties of the filling liquid: it does not freeze at low temperatures, nor does it vaporize at high temperatures; it has a low expansion coefficient, and it does not undergo any chemical reaction with the medium being tested； Silicone oil and fluorinated oil differ significantly mainly in terms of the medium being tested and temperature