Material Analysis
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HDPE pipe ovality (insufficient sizing)
Problem Phenomenon
The pipe is elliptical and difficult for socket connection, and the vacuum pressure test of the vacuum sizing tank is low.
Cause Analysis
Insufficient vacuum pressure prevents the softened pipe blank from closely attaching to the sizing sleeve; uneven spray water pattern makes one side cool and shrink faster; excessive roller spacing causes the incompletely cooled pipe to sag and deform.
Solution
①Confirm the vacuum pump provides stable and sufficient negative pressure; ②clean all spray nozzles to ensure uniform water curtain; ③densify roller support to prevent sagging; ④align the production line centerline.
Key Takeaway
Ovality is the result of the combined action of sizing, cooling, and support; systematic investigation from the four aspects of vacuum, water curtain, rollers, and centerline gives the best effect.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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