Troubleshooting guide for HDPE/PP Pipes Applications
HDPE/PP Pipes Troubleshooting
Problem
Probable Cause
Suggested Remedy
Temperature Setting
Temperature setting are crucial parameter for proper plastic processing ,hence one should check temperature controller, thermocouple and solid state relay(SSR)
- when you cold start the machine ,wait for 2hours.
Rough surface inside or outside
- Presence of moisture
- Low melt pressure
- Uneven water cascading
- Uneven water cascading
- Foreign matter caught in the sleeve or sizing plate
- Too high linear extrusion speed
- Dirty metal surface
- Sticking or seizing on mandrel or sleeve surfaces
- Mismatched sleeve
- Rippled strip of roughness is caused by difference in wall thickness at that point
- Insufficient Mixing
- Dry material (resin and master batch)
- Low melt temperature
- Store resin and master batch in a cool, dry place
- Increase melt temperature
- Water cascading all around the pipe
- Remove foreign materials
- Increase the die land
- Clean the metal surface
- Smaller internal entrance angles into the die land section,Decrease screw temperature
- Proper alignment of the sleeve
- Give best outside surface to sizing sleeves -Decrease screw speed-Improve screw design
- Improve screw design
Wall thickness variation
- Improper centering
- Improper alignment of downstream equipments
- Presence of hot or cold spots in the die
- Too low output limitation, Uneven flow
- Loose mandrel
- Flooding of die
- Slipping of haul-off
- Wet pipe
- Low haul-off clamping force, Haul-off clamp lower or higher than the pipe extrusion height
- Spiral flow motion imparted to the melt by screws in certain types of extruders, Excessive die pressure and chanelling of flow along path of least resistance
- Adjust die bolts
- Ensure alignment of downstream equipment
- Avoid hot or cold spots by reducing the effect of cooling winds
- Current limitation should be 8:3-8:5 clamp
- Tighten mandrel
- Tighten properly all the die bolts
- Increase the clamping pressure of haul-off
- Make sure that the pipe is dry at the haul-off
- Adjust the height of haul-off
- Use breaker plate with bigger holes and without screen packs
Excessive reversion
- High die swell
- High linear speed
- Increase die temperature
- Use mandrel of higher diameter
- Use die ring of smaller diameter
- Reduce linear speed
Poor strength
- Weak spider line/pity pipe
- Too much draw down and too low temperatures
- Thermal degradation of resin
- Use of too much scrap in the feed
- Inadequate plasticisation, Low processing temperatures
- Higher quantities of lubricants and fillers
- Poor mixing
- Low motor torque
- High speed of extrusion
- Low speed of extrusion
- Low residence time in die head
- Thermal stress due to sudden cooling by chilled water
- Heaters or temperature controllers not functioning
- Moisture in resin/compound
- Raise melt temperature
- Avoid excessive draw down
- Add antioxidant master batch
- Reduce the amount of scrap
- Increase processing temperature
- Reduce the quantity of lubricants and fillers
- Increase back pressure
- Improve die design by increasing land length, Reduce screw temperature, Increase melt pressure
- Adjust extrusion speed
- Adjust extrusion speed
- Adjust extrusion speed, Increase die land
- Provide sufficient air gap, Reduce the temperature of cooling water, Use more number of cooling troughs
- Correct heaters and temperature controllers
- Dry the resin land master batch before extrusions, Keep resin and materbatches in a cool, dry place
Pipe breaking
- Insufficient feeding
- Jerks from the traction unit
- Low extruder temperatures
- Increase feeding
- Increase extruder temperature
- Avoid jerks from the traction unit
Weight variation from pipe to pipe
- Fluctuation in output voltage from DC motors
- High temperature in the die
- Make the output from the DC motor constant
- Reduce die temperatures
Burnt lines on pipes
- Improper hard chrome plating on die parts
- Contaminated die parts
- Stagnation of material on die parts
- Insufficient heat stabilisers
- Check for proper hard chrome plating on die parts
- Clean the die/polish the die parts
- Avoid pockets of stagnation
- Increase amount of antioxidants
Burning into the extruder
- Faulty thermocouples or temperature controllers
- Lower percentage of processing aids
- Excessive friction due to screw to screw rubbing
- Check thermocouples or temperature controllers
- Increase lubrication
- Check screw float
Ring formation inside the pipe
- Jerks from traction unit
- Frictional heat on extruder
- Higher temperature
- Higher lubrication percentage
- Avoid jerks from traction unit
- Reduce frictional unit, Reduce feeding quantity
- Reduce overall tempreture
- Reduce lubrication percentage
Lack of gloss
- Presence of moisture
- Low melt temperature
- Dirty metal surface
- Sticking or seizing on mandrel or sleeve surfaces
- Very high linear extrusion speed
- Uneven water cascading
- Misaligned sleeve
- Foreign matter caught in the sleeve or sizing plate
- Rippled strip of roughness is caused by difference in wall thickness at that point, Insufficient mixing
- Dry material before extrusion,Keep resin/master batch away from moisture
- Increase melt temperature, Increase melt pressure
- Clean the metal surface
- Smaller internal entrance angles into the die land section, Decrease screw temperature
- Reduce speed
- Water cascading all around the pipe
- Proper alignment of the sleeve
- Remove foreign materials
- Give best outside surface to sizing sleeves, Decrease screw speed, Improve screw design
Decoloured material
- Decomposition of resin/master batch
- Reduce temperatures, Reduce shear rate, Improve breathing of extruder and die interiors
Spitty pipe
- Low melt temperature Too cold extrusion
- Too high extrusion
- Excessive draw-down, Unbalanced orientation in extrusion direction
- Raise melt temperature
- Improve die design by increasing land length
- Avoid excessive draw-down
Circumferential ridges
- Vibration of haul-off
- Uneven haul-off speed, Irregular pull due to haul-off operating at the low end of its range
- Adjust mandrel temperatures
- Adjust haul-off speed
Circumferential waviness
- Material surging
- Non-uniform water cascade
- Leaking of water through the sizer
- Better mixing, Increase melt temperature, Reduce screw temperature, Reduce speed
- More uniform cooling by increasing the flow of water around the pipe
- Close the leakage
