Plastics production: Safe pressure measurement around 330 �C

Pressure measurement in the production of PBAT, a biodegradable plastic, faces a particular challenge: Temperatures as high as 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 a long connecting piece.
Polybutylene adipate terephthalate, PBAT for short, is a copolymer from the polyester group. The plastic can replace polyethylene and is totally biodegradable. PBAT thus contributes to greater sustainability. Among Exuberant , 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 these two 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 precise measuring ranges could be set for this kind of transmitter using the turndown function. Which means that the output signal is distributed only on the scaled range. Thus, the measured values can 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 at the mercy of process temperatures between 100 �C and 330 �C. Formula 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 adverse effects due to the high process temperatures. The entire design can be minimised in volume to reduce 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 a highly viscous form. The diaphragm seal, combined with the transmitter, is therefore implemented with a flush diaphragm. Therefore, it enables pressure measurement without the risk of media entrapment.
Note
Technical information on the model IPT-20 process transmitter can be found 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. When you have any questions, your contact will gladly assist you to.
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There are also out more concerning the turndown function of WIKA process transmitters in the following video:

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