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A diaphragm seal system in a vacuum process must master a significant challenge ? it must deliver a reliable measuring result, even though the pressure drops and the temperature rises at the same time. The example of a chemical company producing phthalic anhydride (PA) implies that it is in no way self-evident that requirement can be met on a consistent basis.
PA is primarily used as a plasticiser for plastics. However, additionally it is found in the production of synthetic resins and dyes. The plant operator obtains this compound via the catalytic oxidation of o-xylene in the gas phase, followed by vacuum pressure distillation process.
Critical phase for pressure measurement
In this process, the critical phase for pressure measurement occurs in the distillation column. There, the procedure temperature can rise to more than 230 �C while the pressure drops to 100 mbar abs. With digital pressure gauge of contrary action, the conventional installed measurement technology reaches its performance limit relatively quickly, which the aforementioned manufacturer was forced to find out ? all instrumentation showed a measurement deviation beyond your defined tolerance after only fourteen days.
Diaphragm seal system adapted in every elements to the vacuum process
The diaphragm seal system is tailored exactly to the conditions of the vacuum process and tested under application conditions.
Consequently, the business approached WIKA with the obtain a measuring solution that could also fulfil its task with the required accuracy in the long term under the conditions described. WIKA then drew on pressure gauge octa -depth expertise to create a diaphragm seal system for the vacuum process, comprising a process transmitter (model IPT-20), a flange-type diaphragm seal with flush diaphragm (model 990.27) and a capillary.
All components of this measuring system were selected designed for the application. Silicone oil KN32 was therefore selected as the fill fluid for pressure transmission. ไดอะแฟรม and conditioning of the diaphragm seal, the capillary, the bond pieces as well as the automated filling process were also matched to each other exactly. With sensitive limit ranges, even one drop of liquid too much or too little can destabilise the volume balance of the diaphragm seal system and thus impair its function. As a result, correct measurement would no more be guaranteed.
Test under application conditions
After cleaning, all parts of the diaphragm seal system were first fully welded into a single unit as usual, accompanied by the filling and adjustment of the machine. Before delivery, however, there was another crucial step ? in its laboratory, WIKA simulated vacuum pressure process for the diaphragm seal system in accordance with the customer?s conditions and subjected it to a thermal ageing process. This test confirmed the process suitability of the measuring system.
Note
Further information on the WIKA diaphragm seal systems can be found on the WIKA website. For those who have any questions, your contact will gladly help you.
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How do diaphragm seals work?
Watch the following video for more information concerning the functionality, application areas and advantages of diaphragm seals: