Plastics production: Safe pressure measurement up to 330 �C

Pressure measurement in the production of PBAT, a biodegradable plastic, faces a special challenge: Temperatures of up to 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 activities, it could 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 these two 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 precise measuring ranges can be set for this type of transmitter utilizing the turndown function. Because of this the output signal is distributed only over 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 regarding PBAT is subject to process temperatures between 100 �C and 330 �C. Because of Quick-start , WIKA has designed a measuring unit comprising 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, Revealing measuring instrument remains protected against undesireable effects caused by the high process temperatures. The entire 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. Therefore, it enables pressure measurement minus the risk of media entrapment.
Note
Technical information on the model IPT-20 process transmitter are available on the WIKA website. There you will also find an overview of other products and solutions for the chemical industry and petrochemical industry sectors, as well as a brochure to download. For those 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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