Pressure monitoring at high temperature is a demanding measuring requirement. This requires a specially designed diaphragm seal. With model 990.45, WIKA offers such an instrument in its portfolio and was therefore awarded the contract by the operator of an oil refinery. The operator was looking for a pressure measurement solution for the construction of a new visbreaking plant.
Visbreaking (“viscosity breaking”) is a thermal cracking process. It reduces the viscosity of residual oil and thus increases the yield of more valuable middle destillates. The corresponding plants in the refineries heat the heavy residues from crude oil processing to around 450 °C under pressure. Achieving the desired degree of conversion depends on precise control of both the operating temperature as well as the pressure.
Pressure monitoring at high temperature requires a measuring system with capillary
The model 990.45 diaphragm seal from WIKA is suitable for connecting pressure gauges and process transmitters to high-temperature processes.
The process requires continuous pressure monitoring at high temperature. Conventional measuring instruments are not suitable for use at temperatures up to 450 °C. The connection to the process must therefore be made using a special diaphragm seal such as model 990.45 from WIKA. Its internal diaphragm and other wetted parts are manufactured from high-quality stainless steel.
Due to the high temperatures, the diaphragm seal and measuring instrument are usually connected via a flexible capillary. This extension of the distance between process connection and measuring instrument is necessary to ensure readability. The system fill fluid for pressure transmission is a suitable high-temperature silicone oil.
The diaphragm seal not only protects the attached measuring instrument from thermal effects, but also from any process-related deposits and contamination. This is why the customer opted for a version with integrated flushing bore. It saves time when cleaning the diaphragm seal diaphragm when a measuring system is mounted.
Diaphragm seal system with integrated pressure gauge and “Ex h” suitability
For the instrumentation of the 28 measuring locations for pressure monitoring at high temperature, the refinery operator decided upon the WIKA pressure gauge model 233.50 with nominal size 160. It has a liquid-filled case, making it resistant to vibrations as well as dynamic pressure loads. When assembled with the model 990.45 diaphragm seal, the operator has a measuring system with an accuracy class of 1.0. In addition, it meets the requirements of ignition protection type “Ex h” in the equipment categories 2G and 2D.
Note
You will find further information about model 990.45 high-temperature diaphragm seal and model 233.50 pressure gauge on the WIKA website (also available in the WIKA online shop). With the diaphragm seal, both pressure gauge and process transmitters can be connected to a process. On the website you will also find an overview of other measurement solutions for the oil and gas industry. If you have any questions, your contact will gladly help you.
Also read our posts
Lasting accuracy for diaphragm seal systems for vacuum process
Diaphragm seal system with diaphragm monitoring – also digital
Diaphragm seals for stable flow measurement in deep seas
Flushing rings in diaphragm seal systems have several advantages