Plastics production: Safe pressure measurement up to 330 �C

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 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 make 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 both 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 kind of transmitter using the turndown function. This means that the output signal is distributed only on the scaled range. Thus, the measured values could 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 subject to process temperatures between 100 �C and 330 �C. For this reason, WIKA has designed a measuring unit consisting of 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 adverse effects due to the high process temperatures. The complete design can be minimised in volume to reduce any temperature error effects during measurement to the very least and thus achieve the best possible accuracy.
Plastic is highly viscous at the pressure measurement points
At the measuring points of the IPT-20, the plastic is in a highly viscous form. The diaphragm seal, combined with the 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 additionally, you will find a synopsis of other products and solutions for the chemical industry and petrochemical industry sectors, in addition to a brochure to download. For Severe who have any questions, your contact will gladly help you.
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You can also find out more concerning the turndown function of WIKA process transmitters in the following video:

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