Preparation Before Purging
- Turn off resin, colorant and additive feeds.
- Empty the extruder.
- Clean hopper and feed throat.
- Remove screen pack
Note: It is a good practice to change the screen pack periodically. It may be convenient to combine this with purging.
- Seal vents on extruder.
- Maintain temperatures and begin run at low screw speed.
- Load Purgex into the hopper.
Note: Amount of Purgex needed is equivalent to 10 minutes of residence time.
(throughput per hour ÷ 60 minutes × 10 minutes)
(Example: 300 lbs. per hour ÷ 60 minutes × 10 minutes = 50 lbs.)
Purging The Extruder
- Begin feeding Purgex.
- Increase screw speed until safe pressure limits have been reached.
- Purge through entire downstream system including die, if possible (die gap must be at least .030 inches).
- Use maximum safe screw speed (within safe pressure limits) for one minute then vary the screw speed from maximum to low to medium, completing the purge at maximum.
- Follow the Purgex feed with the next resin, and observe material for acceptability.
- Repeat steps 1-4 if contamination remains.
- When acceptable resin appears, prepare extruder for production.
- Begin production.
Comments & Recommendations:
- When sealing the vent it is advisable to monitor the upstream pressure.
- Vent plugs are available from extruder manufacturers and other suppliers.
- After long runs and/or heavily contaminated barrels and screws, it may be helpful to increase the extruder temperatures by 50°F (10°C).
Questions? Call our Technical Support team at (800)-803-6242.