Pressure measurement in the production of PBAT, a biodegradable plastic, faces a special 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 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 plays a part in greater sustainability. Among other activities, it can be used to make protective sheeting for agriculture and gardening, compost bags, shopping bags and medical disposables.
Full 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 exact measuring ranges can be set for this kind of transmitter utilizing 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 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. Because of this, 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, the measuring instrument remains protected against adverse effects caused by the high process temperatures. The entire design is also 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 an extremely viscous form. The diaphragm seal, combined with the transmitter, is therefore implemented with a flush diaphragm. Consequently, 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 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 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: