Feed throat cooling (Consultant's Corner)
Vol. 21 #1, June 1994
The feedthroat casting of any extruder should be kept at approximately 110-120F at all times. This constant temperature on the throat of the extruder helps in several ways. If the throat temperature is below this recommended temperature, in a humid environment, the casting can possibly condensate and cause feeding problems, such as surging. On the other hand, a feedthroat section that is too hot can cause bridging problems in the throat or melt blocks in the feed section of the screw. In processing resins such as polypropylene, where a reverse profile is typically used, a high temperature in the first zone makes it possible for the heat to migrate into the feedthroat casting and cause a problem. The 100 -120F can be easily detected in one of two principle manners:
1. By the touch of the hand on the casting where the surface of the casting is warm to the touch. (Note: Hot water at 135F will scald the human body. You can just touch 140F metal for a very short period of time.)
2. To monitor the feedthroat temperature by installing an immersion thermometer in a pipe tee on the return side of the water jacket. This simple monitoring of the feedthroat temperature is more reliable and could possibly save an operator many hours of headaches and a company many dollars on out of specification product.
- T Womer
See also:
- Feed throat design
- Temperature control
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