How to Properly Start an Extrusion Line Without Blowing a Rupture Plug

Extrusion machines manufacture plastic parts or coat items in layers of plastic.

Rupture plugs prevent machine damage if the pressure within an extruder is too high. Extruder machinery melts plastic at high temperatures, and pushes the melted plastic through narrow tubes or molds. If the plastic builds up, pressure will cause the rupture plug to break. All extruder operators must monitor the rupture plug to watch for leaking plastic. If you notice any material oozing out, shut down the machine to replace the rupture disc and pinpoint what's causing the pressure to build up.

Things You'll Need

• Safety glasses
• Air hose
• Plastic pellets

Instructions

1. Make sure the hopper is empty and cleaned out with an air hose. Put on safety glasses before performing this to keep plastic pieces out of your eyes. Check that the lines are cleared of melted plastic from previous jobs. When everything is clean, go to the heat controls. Turn up the heats to the temperature listed on the work order.

2. Fill the hopper with the plastic pellets needed for the job. Go to the control panel. Turn on the extruder motor and hit the clutch. The melted plastic will start going into the barrel, and is pushed through the barrel by a screw. As it leaves the barrel, it goes through a mold or tooling that provides the correct shape to the object being manufactured.

3. Monitor the progression of the extruded object. Check for uneven coating or lumps, which indicate plastic that has not melted correctly. Make sure you watch the rupture plug to see if plastic leaks out. If this happens, the pressure within barrel is too high indicating a problem. If you see plastic leaking out, turn off the machine.

4. Have maintenance inspect the extruder machine. In many companies, maintenance must find the problem causing the blockage and replace the rupture plug. Maintenance workers have specialized training that helps them pinpoint the problem area, and they know the correct size for the new rupture plug.

Tips & Warnings

• Wear gloves when handling rupture discs and other components on extruder machines. Temperatures are often well past 350 degrees F, and can cause serious burns if you touch a hot metal part.

• Make sure no one is standing in front of the machine when it starts up. Air in the cylinder can expel hot plastic from the barrel causing burns to anyone in the way. The control panel is usually on the side of the machine to prevent these injuries.

References

• Streamline Extrusion: Extrusion Line Safety
• Streamline Extrusion: The Plastic Extrusion Process for Tube, Hose, Pipe and Rod