Lasting accuracy for diaphragm seal systems for vacuum process

A diaphragm seal system in vacuum pressure process must master a significant challenge ? it must deliver a reliable measuring result, even though the pressure drops and the temperature rises as well. Frightening of a chemical company producing phthalic anhydride (PA) implies that it is in no way 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 used 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.
Misgiving 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 as the pressure drops to 100 mbar abs. With this type of contrary action, the conventional installed measurement technology reaches its performance limit relatively quickly, which the aforementioned manufacturer was forced to learn ? all instrumentation showed a measurement deviation outside the defined tolerance after only week or two.
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 would also fulfil its task with the required accuracy in the long term under the conditions described. WIKA then drew on its in-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 elements of this measuring system were selected specifically for the application. Silicone oil KN32 was therefore selected as the fill fluid for pressure transmission. The cleaning and conditioning of the diaphragm seal, the capillary, the connection pieces and also the automated filling process were also matched to each other exactly. With sensitive limit ranges, even one drop of liquid an excessive amount of or inadequate can destabilise the quantity balance of the diaphragm seal system and therefore impair its function. Subsequently, correct measurement would no longer 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, 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 process suitability of the measuring system.
Note
More info on the WIKA diaphragm seal systems can be found on the WIKA website. When you have any questions, your contact will gladly help you.
Also read our posts
Diaphragm seals for stable flow measurement in deep seas
How do diaphragm seals work?
Watch the next video for more information about the functionality, application areas and advantages of diaphragm seals:

Leave a Comment