Pelletizer Die Head Maintenance and Replacement


The pelletizer die head is a valuable, high-precision component of the pelletizing line that requires a great deal of maintenance in addition to careful handling. In order to prevent downtime due to die head failure, proper operation and protective measures must be taken to ensure that the pelletizer die head is always available. Carelessness or mishandling during maintenance, cleaning or adjustment is the main cause of die head damage, so rigorous training must be given to all personnel who come into contact with the die head. The operator must thoroughly understand the function of the die head, know the effect of temperature changes, adjustment of the die hole or adjustment bar on the quality of the product, and also be aware of the sources of failure. The operator must also understand the importance of maintaining good contact between the heater and the die head and be able to determine if there is a fault in the line and where it is.

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  When the pelletizer extrusion has pulsations, it is not possible to constantly adjust the block of the gap die head (generally the device is not designed for this purpose). He must also be able to determine if the inlet pressure has exceeded its limits based on the measurement of the inlet pressure. Also, note that the mouth die or the flow block must not be adjusted quickly, but should vary moderately within the adjacent area, otherwise, the bolt and the flow block may be damaged. (Note: Only scrapers made of soft materials (copper, brass, soft aluminum) can be used to remove the melt inside the mouth die so as not to scratch the die, and the pelletizer die head mouth die gap width should also be measured with soft materials such as brass gauges. (Even the slightest scratch can lead to streaks on the extrudate and reduce product quality).

When the pelletizer die head needs to be changed frequently, which is often the case especially in film and sheet extrusion, it must be left to a dedicated person, preferably someone who has experience in disassembling, inspecting and installing a new pelletizer die head before use. The disassembly, cleaning, repair and maintenance of the pelletizer die head should be carried out in a designated place, which should be far from the production site, clean and well padded with corrugated plates, with a small crane when used, and the chain of the pulley set often damages the die head when lifted manually. To avoid this danger, consider using twine, which can greatly reduce the time to replace the die head.

Heater inspection is also necessary. The pre-heater should be equipped with a certain number of heating wires and control system. Individual control of each pelletizer die heater is not necessarily required at this point, but this depends on the size of the die. If the die head needs to be thoroughly cleaned, the main bolts of the die head must be loosened, but do not have to be taken off, the pelletizer die head is still connected to the pelletizer, only the ones related to the runners need to be loosened.


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