Cause of Pitting on PE Pipe

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.

I. Material Oxidation and Degradation

The raw materials within the extruder die and barrel may oxidize and degrade due to prolonged heating. This can cause relatively large pits or hollows (pitting) on the surface of the produced PE pipe. This phenomenon is particularly pronounced when using substandard formulations or incorporating recycled material. To address this, precise control of processing temperatures and reduction of material residence time in the barrel are essential. Implementing rapid cooling or regular cleaning of the die and barrel can also significantly improve the situation.

II. Excessive Moisture Content in Raw Material

When the moisture content in the raw material is too high, bubbles can easily form on the pipe surface during extrusion. Upon solidification (sizing), these bubbles collapse, leaving pits on the surface. Therefore, thorough drying of the raw material is necessary to effectively reduce its moisture content.

III. Uneven Cooling Water in Sizing Sleeve

Uneven distribution of cooling water within the sizing sleeve can also cause pitting on the pipe surface. As the pipe diameter increases, the required cooling water volume also rises. Insufficient water volume or uneven distribution makes it difficult to form a complete and uniform water film on the pipe surface. Consequently, it is necessary to appropriately adjust the flow rate of the sizing sleeve inlet pipes and the distribution of the water channel apertures based on the pipe diameter. This ensures the cooling water forms an even film, effectively resolving the pitting issue.

If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.