Gear Pumps Play an Important Role in Extrusion System for All Thermoplastics, （Except PVC）

A gear pump is a positive displacement pump consisting of a matched pair of gears.

The pump has two basic advantages:

1. It balances out irregularities in the linear (mass) flow.

2. It relieves some of the load on the extruder, allowing it to operate at lower pressures, thereby reducing the generation of frictional heat.

Before specifying a pump, three important pressures must be known or at least estimated: one is the pressure drop in the system behind the pump - the head resistance; the second is the suction pressure, which is regulated by the operator, and the third is the pressure at the tip of the screw, which is the sum of the controlled suction pressure, the resistance added by the screen, and contaminants captured by the screen.

Screens are typically used to protect the pump from hard contaminants that can clog tight clearances and lubrication passages, in addition to the usual functions of preventing contaminants from entering the product and controlling mixing in the final area of the screw (the tighter the screen, the higher the pressure, the better the mixing). The screens can be placed behind the pump, which will also take over the push-pressure work, but then they will lose their protective function, so they will remain in their normal position at the end of the screw.

Heiko specializes in the manufacture of all types of melt pumps and screen changers.