|
PROBLEM
|
POSSIBLE CAUSES
|
SOLUTIONS
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| EXCESSIVE EXTRUDER
DRIVE POWER REQUIREMENT |
Extruder drive problem (uneven phase current). Excessive dosing.
Improper temperature gradient.
Improper stabiliser & lubricant.
|
Check drive performance.
Reduce feeder speed.
Check thermocouple.
Calibrate temperature controller.
Check quality & quantity of stabiliser & lubricant.
|
| OOZING FROM
VENT PORT |
Low die temperature.
Improper lubricant. Excessive screw barrel wear.
Improper screw flank clearance. |
Increase die head
temperature.
Check quality of lubricant.
Replace screw barrel.
Check axial clearance. |
| DISCOLOURED
MATERIAL |
Improper screw
cooling.
Improper barrel & die temp.
Hard chrome plating peeled off.
Improper additive. |
Checking distilled
water circulation in screw.
Check thermocouple.
Rechrome plate die surface.
Check compound formulation. |
| PIPE OD FINISH
ROUGH |
Low die temperature
Low external lubricant.
Improper barrel degassing system.
Moisture in compound. |
Increase die temperature.
Increase external lubricant in compound.
Check degassive system. |
| SCRATCH MARK
ON PIPE OD |
Damage on die
surface.
Damage in callibration sleeve. |
Remove damage
mark & rechrome plate die.
Increase & polish entry radius. |
| WAVINESS ON
PIPE OD |
Improper pipe
cooling in initial portion.
Air leakage from floating plug.
Excessive air pressure. |
Increase number
of spray nozzles in initial portion.
Reduce air pressure. |
| DULL APPEARANCE ON PIPE
OD |
Die temperature low.
Die length long. |
Increase die temperature.
Reduce die length. |
| PIPE ID FINISH ROUGH |
Improper gelling of material.
Moisture in compound.
High temperature of screw lead to sticking of melt.
Melt fracture. |
Increase barrel rear zone
temperature.
Check degassing system.
Check distilled water quantity in screw.
Increase die temperature or die heat retention capacity. |
| RING MARKS ON PIPE ID |
Stick-slip action of floating
plug.
Variation in haul of speed. |
Increase cooling efficiency.
Increase length of calibration sleeve.
Reduce dimension of floating plug.
Set belts for positive grip.
Check drive system. |
| SPIDER LINES MARK ON PIPE
ID |
Improper die head pressure.
|
Increase die land length.
Increase mandrel temperature.
Increase die head volume. |
| IMPROPER WALL THICKNESS
DISTRIBUTION |
Non uniform annular die gap.
Non uniform die head / die temperature.
Hard chrome plating peeled off.
Die leakage. |
Adjust annular gap in die.
Check uniformity of heaters.
Polish & rechrome plate die / mandrel.
Stop die leakage. |
| PIPE FAILS IN IMPACT |
Pipe too brittle. |
Water temperature in cooling
bath should not be below 15°C.
Check compound formulation & reduce filler quantity. |
| PIPE FAILS IN REVERSION |
Excessive material swelling. |
Reduce die land length.
Reduce die annular gap.
Modify compound formulation(Increase internal lubricant, reduce external
lubricant).
Reduce pipe drawdown. |
| PIPE FAILS IN PRESSURE TEST |
Porosity. |
Increase extruder torque by
increasing feeder speed.
Check degassing system.
Modify compound formulation. |
| POOR STRENGTH/ SPLITTY PIPE
|
Pipe degraded. |
Reduce filler quantity.
Use coated CaCO3.
Thermal stresses due to sudden cooling by chilled water (use chilled
water more than 15°C in spray bath).
Check temperature controller.
Reduce percentage of recycled material.
Reduce drawdown ratio. |
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Courtesy: Mr. P.M. Jariwala, Kolsite Industries
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