Pressure measurement in the production of PBAT, a biodegradable plastic, faces a special 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 totally biodegradable. PBAT thus plays a part in greater sustainability. Among other things, it can be used to create 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 ? Colossal . The exact 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 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 regarding 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, Scam measuring instrument remains protected against adverse effects caused by the high process temperatures. The entire design can be minimised in volume to lessen any temperature error effects during measurement to a minimum 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. Because of this, it enables pressure measurement minus the risk of media entrapment.
Note
Technical information on the model IPT-20 process transmitter can be found on the WIKA website. There additionally, you will 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: