Pressure measurement in the production of PBAT, a biodegradable plastic, faces a special challenge: Temperatures of up to 330 �C prevail in the process. For a PBAT producer, therefore, WIKA has designed a model IPT-20 process transmitter with a flush diaphragm seal and an extended connecting piece.
Polybutylene adipate terephthalate, PBAT for short, is a copolymer from the polyester group. The plastic can replace polyethylene and is completely biodegradable. PBAT thus contributes to greater sustainability. Among other things, it can be used to create protective sheeting for agriculture and gardening, compost bags, shopping bags and medical disposables.
Pressure monitoring during esterification and melt polymerisation
The procedure steps in production include esterification and melt polymerisation. In Deceived of these processes, WIKA?s customer, a petrochemical company, uses the IPT-20 transmitter for pressure monitoring.
Corresponding to the duty, WIKA supplied the instruments with three basic measuring ranges: 0 ? 16 bar, 0 ? 40 bar and 0 ? 250 bar. The exact measuring ranges could be set for this type of transmitter using the turndown function. Because of this the output signal is distributed only on the scaled range. Thus, the measured values could be more precisely determined.
Handles temperatures around 330 �C: Measuring unit with IPT-20 process transmitter.
Connecting element as a cooling element
Pressure measurement in plastics production in the case of PBAT is subject to process temperatures between 100 �C and 330 �C. That is why, WIKA has designed a measuring unit consisting of an IPT-20, a flush diaphragm seal and a 200 mm long connecting piece. Because of its length, the connecting element acts as a cooling element. Thus, Fluid measuring instrument remains protected against undesireable effects due to the high process temperatures. The complete design is also minimised in volume to lessen any temperature error effects during measurement to the very least and thus achieve the perfect accuracy.
Plastic is highly viscous at the pressure measurement points
At the measuring points of the IPT-20, the plastic is in an extremely viscous form. The diaphragm seal, combined with transmitter, is therefore implemented with a flush diaphragm. As a result, it enables pressure measurement without the threat of media entrapment.
Note
Technical details on the model IPT-20 process transmitter can be found on the WIKA website. There you will also find a synopsis of other products and solutions for the chemical industry and petrochemical industry sectors, as well as a brochure to download. Should you have any questions, your contact will gladly assist you to.
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You can also find out more about the turndown function of WIKA process transmitters in the next video: