Pressure measurement in the production of PBAT, a biodegradable plastic, faces a particular challenge: Temperatures as high as 330 �C prevail along the way. 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 really a copolymer from the polyester group. The plastic can replace polyethylene and is totally biodegradable. PBAT thus contributes to greater sustainability. Among other activities, 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 process steps in production include esterification and melt polymerisation. In both of these processes, WIKA?s customer, a petrochemical company, uses the IPT-20 transmitter for pressure monitoring.
Corresponding to the task, 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 utilizing the turndown function. Therefore the output signal is distributed only on the scaled range. Thus, the measured values can be more precisely determined.
Handles temperatures up to 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 at the mercy of process temperatures between 100 �C and 330 �C. Trapped is why, WIKA has designed a measuring unit comprising an IPT-20, a flush diaphragm seal and a 200 mm long connecting piece. Due to its length, the connecting element acts as a cooling element. Thus, the measuring instrument remains protected against undesireable effects caused by the high process temperatures. The complete design is also minimised in volume to reduce any temperature error effects during measurement to a minimum 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 the transmitter, is therefore implemented with a flush diaphragm. Due to this fact, 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, in addition to a brochure to download. Assuming you have any questions, your contact will gladly help you.
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You can also find out more about the turndown function of WIKA process transmitters in the following video: