Cleaning of Vent Hole Procedures

For Purging Vented Barrels (Injection And Extrusion)

Vented barrels are typically used for applications in which volatile gasses need to be released. They are also used when hygroscopic (moisture-absorbing) materials are processed and moisture in the form of vapor must be released from the barrel. In this case, it is a less-expensive alternative to using dryers. It is also common to have vented barrels when a two-stage (barrier/mixing) screw is used.

Pressure increases within the barrel and is greatest at the point before the vent – this area represents a concentrated energy region (high pressure = high shear). Consequently, you are likely to find greater degraded contamination in this area. Pressure then drops sharply in the vent area and starts to build again after the vent.

For proper cleaning of the vent hole, ASACLEAN requires agitation and pressure within the barrel to perform at its best. Higher pressure allows ASACLEAN to better address the surfaces of the barrel and screw. Since there is little-to-no pressure in the vent area, it is likely that ASACLEAN may not sufficiently remove all deposits.

Cleaning Of The Vent Hole Recommended Procedures:

These recommendations should be made if following our standard purging instructions has not proven successful.

  1. Use a vent plug or cap to close the vent; often, machine manufacturers supply plugs or the customer may make their own. Follow standard purging instructions. It is important to keep an eye on pressure gauges while purging to avoid machine damage or injury.
  2. If a vent plug is not available or a customer is reluctant to plug the vent, add ASACLEAN pellets directly through the vent while also feeding through the hopper. Note that these vents may sometimes be very small or difficult to access and it may be necessary to feed the ASACLEAN pellet by pellet. Follow standard purging instructions.
  3. Vent-up method: For injection molding, block the nozzle and perform metering (turn the screw) while applying back pressure. ASACLEAN is forced to come out of the vent. Continue until ASACLEAN coming from the vent looks fairly clean. Proceed using standard purging instructions. This method is not to be used for the extrusion process.

For further insight into our recommended purging procedures, visit the Purging Process Resource Center. This page offers you training videos, guidelines, technical documentation and more to help answer your purging compound questions.

Ready to learn even more about ASACLEAN purging compound products and services? Click here to schedule your free, 10-minute consultation with a Purging Process Expert at ASACLEAN.

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