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 plays a part in greater sustainability. Among other things, 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 could be set for this type of transmitter using the turndown function. This means that the output signal is distributed only over 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 at the mercy of process temperatures between 100 �C and 330 �C. Unusual 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, Quickly 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 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 risk of media entrapment.
Note
Technical details 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, in addition to a brochure to download. Should you have any questions, your contact will gladly assist you to.
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There are also out more about the turndown function of WIKA process transmitters in the following video:g