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| Author | Topic: Temperature Sensors |
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L.Moreira Member Posts: 1 |
posted December 05, 2002 08:30 AM
   
I deal with temperature measurement and calibration in Brazil. A customer of mine needs to know if the thermometer used during the measurement of flow rate of plastomers extrusion is a total immersion or partial immersion one. Uffortunatelly I know nothing about plastics processes and hope you might help us. My customer has ordered the ASTM standard referenced but it will take a few days to arrive. He needs the information asap. I thank in advance for your attention. IP: Logged |
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Peter P Senior Member Posts: 61 |
posted December 05, 2002 09:10 AM
If you mean "Melt Flow Rates of Termoplastics by Extrusion Plastometer" according to ASTM D1238, then the thermometer is mercury in glass, located in a pocket in the apparatus. It is advised that the pocket contains a small amount of oil to improve thermal contact. See ------------------ [This message has been edited by Peter P (edited December 07, 2002).] IP: Logged |
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zabielski Senior Member Posts: 386 |
posted December 06, 2002 08:41 AM
In general, the actual temperature of plastics flow while inside a barrrel is captured by a tip of the thermocouple that is slightly immersed in the flow path after the screw and breaker plate - more likely in an adapter assembly - just before exiting into a die assembly. However, there are turn screw types that alllows you to move that T/C into the center and across to the other side and back again. The T?C tip is rely placed in the center of the melt constantly, as the pressure and velocity tends to permanently bend them. The screw in - screw-out types are popular for R&D work, as well as production work, but are used more in the R&D field. IP: Logged |
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Bob Cunningham Senior Member Posts: 115 |
posted December 07, 2002 06:09 PM
I think most of the "fixed depth" type thermocouples are submersed in the flow, 3/8" (9.5mm). Variable depth thermocouples are seldom used - they are most popular for R&D machines where a temperature profile needs to be established. All melt thermocouples will be influenced by the temperature of the barrel wall - metal conducts heat better than plastic. -Bob Cunningham IP: Logged |
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