A diaphragm seal system in vacuum pressure process must master a major challenge ? it must deliver a trusted measuring result, even when the pressure drops and the temperature rises simultaneously. The exemplory case of a chemical company producing phthalic anhydride (PA) shows that it is by no means self-evident that this 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, 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 ? เกวัดแรงดันน้ำ showed a measurement deviation beyond your defined tolerance after only a fortnight.
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 company approached WIKA with the request for a measuring solution that could also fulfil its task with the mandatory accuracy in the long run beneath the conditions described. WIKA then drew on its in-depth expertise to design 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 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 one another 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 therefore impair its function. Due to this fact, correct measurement would no more be guaranteed.
Test under application conditions
After cleaning, all parts of the diaphragm seal system were first fully welded right into a single unit as usual, accompanied by the filling and adjustment of the system. Before delivery, however, there is another crucial step ? in its laboratory, WIKA simulated a vacuum process for the diaphragm seal system relative to 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. In case you have any questions, your contact will gladly assist you to.
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Just how do diaphragm seals work?
Watch the next video to learn more concerning the functionality, application areas and advantages of diaphragm seals: