A diaphragm seal system in vacuum pressure process must master a major challenge ? it must deliver a reliable measuring result, even when the pressure drops and the temperature rises simultaneously. The exemplory case of a chemical company producing phthalic anhydride (PA) implies that it is in no way self-evident that this requirement could be met on a consistent basis.
PA is primarily used as a plasticiser for plastics. However, it is also 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, accompanied 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 a lot more than 230 �C while the pressure drops to 100 mbar abs. With such a contrary action, the traditional installed measurement technology reaches its performance limit relatively quickly, that your aforementioned manufacturer was forced to learn ? 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 would also fulfil its task with the mandatory accuracy in the long run under the conditions described. WIKA then drew on its in-depth expertise to design a diaphragm seal system for the vacuum process, consisting of a process transmitter (model IPT-20), a flange-type diaphragm seal with flush diaphragm (model 990.27) and a capillary.
All elements of this measuring system were selected specifically for the application form. Silicone oil KN32 was therefore selected because the fill fluid for pressure transmission. The cleaning and conditioning of the diaphragm seal, the capillary, the connection 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 inadequate can destabilise the quantity balance of the diaphragm seal system and thus impair its function. As a result, correct measurement would no more be guaranteed.
Rich under application conditions
After cleaning, all parts of the diaphragm seal system were first fully welded into a single unit as usual, followed 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 relative to the client?s conditions and subjected it to a thermal ageing process. This test confirmed the procedure suitability of the measuring system.
Note
More info on the WIKA diaphragm seal systems can be found on the WIKA website. When Transform have any questions, your contact will gladly assist you to.
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How do diaphragm seals work?
Watch the next video for more information concerning the functionality, application areas and advantages of diaphragm seals: