Common Technical Issues in PPR Pipe Production and Suggested Troubleshooting

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with over 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”.

In the extrusion production of PPR pipes, process stability and equipment performance directly affect final product quality. To help manufacturers efficiently diagnose faults and improve yield rates, we have summarized the following 13 common issues and their potential causes for field reference.

Uneven inner wall surface

Possible causes: excessively high screw temperature or excessive screw speed, leading to unstable melt flow.

Black streaks on the pipe surface

Possible causes: excessive die head temperature, or clogged/uncleaned filter screens, resulting in material degradation or contaminant accumulation.

Bubbles on the inner wall

Possible causes: moisture in the raw material, which vaporizes at high temperatures. Proper pre-drying is recommended.

Sudden drop in extrusion output

Possible causes: high temperature in the screw feeding section causing bridging; water ingress into the cooling system; or low melt pressure at the die head, reducing extrusion thrust.

Rough inner wall surface

Possible causes: low mandrel temperature, low barrel temperature, or high screw temperature—all of which can impair melt homogenization or fluidity.

Dull pipe surface

Possible causes: die temperature being either too low or too high, both of which can negatively affect surface gloss. Precise temperature control based on material properties is required.

Wrinkles on the pipe surface

Possible causes: uneven temperature distribution around the die head; excessively high cooling water temperature; or low traction speed, resulting in insufficient stretching.

Cracks on the inner wall

Possible causes: impurities in the raw material; low mandrel or barrel temperature, leading to poor melt fusion; or excessive traction speed, causing high internal stresses.

Scorch marks on the pipe surface

Possible causes: excessively high barrel or die head temperature; uncleaned die head or filter screens; impurities in the pellets; insufficient heat stabilizer or poor thermal stability of the material; or malfunctioning temperature controllers. Timely calibration is essential.

Excessive longitudinal or transverse shrinkage

High transverse shrinkage is often related to an oversized radial gap between the sizing sleeve and the die inner diameter; high longitudinal shrinkage is usually due to excessive traction speed.

Uneven wall thickness

Possible causes: misalignment between the die and mandrel; non-uniform temperature distribution at the die head; unstable traction unit operation; or fluctuating compressed air pressure.

Brittle products

Possible causes: insufficient plasticization in the barrel; excessive screw speed; low die head temperature; or high resin viscosity, which reduces impact toughness.

Pipe bending

Possible causes: uneven wall thickness; inconsistent temperature around the die head; misalignment among the cooling tank, traction unit, and cutting center; or non-concentric holes at both ends of the cooling tank, leading to asymmetric cooling.

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.