Basic concept of gear pump

In terms of terminology, the gear pump is also called a positive displacement device, which is like a piston in a cylinder. When a tooth enters the fluid space of another tooth, the liquid is mechanically squeezed out. Because liquids are incompressible, liquids and teeth cannot occupy the same space at the same time, so the liquid is eliminated. Due to the constant meshing of the teeth, this phenomenon continues to occur continuously, thus providing a continuous elimination amount in the outlet of the pump, and the discharge volume is the same for each rotation of the pump. With the continuous rotation of the drive shaft, the pump continuously exhausts the fluid. The flow of the pump is directly related to the pump speed.

 

In fact, the pump is very small amount of fluid loss, which makes the operation efficiency of the pump can't reached 100%, because the fluid is used for lubrication bearing and gear on both sides, and the pump body is impossible without clearance fit, so cannot make fluid 100% from an outlet, so a small amount of fluid loss is inevitable. However, the pump can still run well, and for most extrusions, it can still reach 93% ~ 98% efficiency.

 

The pump will not be affected much by the viscosity or density of the fluid in the process. If there is a damper, such as a filter on the outlet side or a limiter, the pump pushes the fluid through them. If the change in damper work, i.e. if the mesh become dirty, blocked, or limiter back pressure increased, the pump will continue to maintain a constant flow, until reach the device in the weakest parts of the mechanical limit (usually equipped with a torque limiter).

 

For a pump rotation speed, in fact, there is a limit, this mainly depends on the process fluid, if transfer is oil, pump can be rotating at high speed, but when the fluid is a kind of high viscosity polymer melt, the restrictions could be greatly reduced.

 

Promote viscous fluid into the suction side of the two tooth space is very important, if not fill the space, the pump will not be able to discharge accurate flow, so the PV value (pressure) x velocity is also a limiting factor, and it is a process variable. As a result of these restrictions, the gear pump manufacturer will provide a range of products, i.e., different specifications and displacement (the amount discharged each week). These pumps will be combined with specific application processes to optimize system capabilities and prices.

 

The gear and shaft of the PEP-II pump are integrated with the shaft, and the long working life can be obtained by using the solid hardening process. The "D" type bearing combines the forced lubrication mechanism to make the polymer pass through the bearing surface and return to the inlet side of the pump to ensure the effective lubrication of the rotating shaft. This feature reduces the possibility of polymer retention and degradation. Precision machining of pump body can make "D" type bearing and gear shaft accurate match, ensure the gear shaft not eccentric, prevent gear wear. The seal structure of Parkool and teflon seal together constitute water - cooled seal. The seal does not actually touch the surface of the shaft, which is sealed by cooling the polymer to a semi-molten state. It can also be sealed with Rheoseal, which has a reverse spiral groove on the inner surface of the seal, allowing the polymer to be pushed back to the inlet. In order to facilitate installation, the manufacturer designed a ring bolt mounting surface to fit the flange mounting of other equipment, making it easier to manufacture the cylinder flange.

 

The PEP-II gear pump has a heating element matching the pump's specifications, which can be selected by the user, which can guarantee fast heating and heat control. Unlike the way the pump is heated, the damage to these components is limited to one board and is independent of the entire pump.

The above: Hazard of reverse flow of hydraulic oil