Problem Possible causes Possible solution
  Die (extrudate) lines. Damage to the exit edges of the tip or die. Refinish tip or die exit edges to sharp and uniform about the diameters.
 Die drool or build-up on the tip or die faces. Adjust temperature of the die exit accordingly
  Extruder surging Too fast extruder throughput relative to OEM Extruder specifications Check OEM guaranteed extruder throughput and run extruder within specifications
 Improper extruder temperature settings Adjust temperature setting according to OEM recommendations
 Poor resin- extruder design match versus extruder OEM specifications for throughput Discuss with resin supplier and implement actions to ensure extruder runs within OEM specifications
 Extruder not set as per OEM design specifications Check with OEM and ensure compliance with design specifications
  Gels and other contaminations in pipe Resin contains foreign particles/ contaminated with gels etc Check with resin supplier for presence of gels etc
 Check regrind for contaminants
 Degraded resin coming off the die during extrusion Follow proper shut-down procedures for extruder to avoid long exposure of resin to excessive temperatures
  Localised thick spots in pipe wall Improper die setting Adjust the die setting
 Hot and cold spots in die profile temp Check for uniformity in die heating
 Uneven pipe drag downstream of the extruder Check for spots in cooling baths which could cause pipe drag
 Haul-off slipage Check and adjust haul-off
 Uneven melt delivery from die -extruder surging Check remedies for extruder surging
 Vacuum calibrator and die not levelled well Adjust the position of the vacuum bath relative to the die
  Pipe out of round Sizing device (calibrator) in adequate or out of shape Check the calibrator for concentricity.
 Ensure it is 3 - 5% larger than the final pipe diameter
 Pipe is too warm when it reaches the haul off unit Ensure sufficient downstream cooling length before pipe gets to the haul off unit
 Decrease throughput
 Wrong vacuum setting in vacuum tanks Ensure proper vacuum setting in vacuum tanks
  Pipe tear Haul-off too fast Check and adjust the speed of haul off
 Pipe too hot at the entrance to calibrator Check for water flows on calibrator and adjust to avoid hot spots
 Ensure adequate calibrator size
 Pipe dragging in cooling tanks Check and eliminate drag spots
  Pipe sag Melt temperature too high Adjust extruder temperature setting and throughput to lower melt temperature
 Die gap not adjusted to accommodate sag Adjust die gap - wider at the top and narrower at the bottom of the die
 Resin's inherent resistance to sag is not adequate for the pipe wall thickness Use low-sag resin
 No enough cooling capability in line Ensure adequate water temperature in cooling baths and enough cooling length
  Rough surface inside or outside Moisture in resin Ensure minimum of 1.5 hrs drying of resin at 70 - 90 °C
 Not adequate water flows setting to the calibrator Adjust water flows to calibrator
 Melt temperature too low Increase die/ and or extruder temperatures
  Thermal degradation of pipe-failed OIT Too high melt temperature Adjust extruder/ and or die temperatures accordingly
 Excessive extruder screw speed Lower extruder throughput
 Die too small for required throughput Ensure adequate die size
 Die pin too hot Check operation of pin cooling otherwise decrease throughput
 Extruder surging Check remedies for extruder surging
  Uneven pipe cut The saw blade is flexing Get thicker/ larger blades
 The saw blade is lose Check and fix
 Saw arm is entering pipe too quickly and with insufficient revolutions Adjust as required
 There is wear/slack in slip rings of the saw planetary components Check and fix
 Uneven speed of haul-off or cutting carriage Check uniformity of the speed of haul-off and cutting carriage
 Saw is not capable of cutting the pipe Check with OEM for saw specifications
 The saw arm is lose or bushes worn and is ‘floating Check and fix
  Uneven wall thickness Uneven melt delivery from the die -extruder surging Check remedies for extruder surging
 Uneven take-off speed Check haul-off unit
 Improper alignment of die and haul-off units Check for alignment
 Die and pin not centered evenly Even die gap
 Excessive sag of a polymer Check remedies for pipe sag
  Voids in pipe Moisture in resin Ensure minimum of 1.5 hrs drying of resin at 70 - 90 °C
 Trapped air Adjust extruder temperature setting and back pressure accordingly

The information contained in these guidelines is provided in good faith and may assist with problem solving and troubleshooting.

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