What are the differences of internal gear pump and external gear pump?

Usually, we divide gear pumps to internal gear pump and external gear pump. Do you know what are the differences of these two types of gear pump? Now, let me tell you about the gear pump differences.

Internal gear pump is a new kind of positive displacement gear pump. Internal gear pumps use gears with external rotor to generate flow and mesh with gears with internal rotor. When the gear comes out of the mesh on the inlet side, the liquid is sucked into the pump. The liquid is discharged through the engagement of gears. Some include a crescent-shaped baffle for separating the inlet and outlet volumes between the two gears.

External gear pumps use two sets of same gears with external teeth to create flow. The rotation of the gears is such that the liquid comes into the inlet port and flows into and around the outer of the two rotating gears. As the liquid comes around the periphery it is discharged to the outlet port. External gear pumps also have safety valve to protection the pipeline.

1. Gear Pumps In Application

Internal gear pump is much better to transfer high viscosity oil, such as molasses, bitumen, glue, resin, latex, or some other liquids with lubricating around 30CST to 60000cst;

External gear pump is better to transfer liquids like oil with 5CST to 1500CST, such as diesel oil, lube oil, lubricating oil, engine oil, crude oil, ISO oil etc.

Both internal gear pump and external gear pump have cast iron, SS304 and SS316 material, it is according to liquids and gear pumps working temperature.

2. Different Gear Pumps Structure

Internal gear pump are mainly composed of internal rotor, outside rotor, shaft, pump casing, front cover, seal, bearing etc. Internal gear pump have mechanical seal type and packing seal type, it is according to the liquids. Internal gear pump only have two bearings and internal gear pump with small outlet size and low flow capacity.

External gear pump are mainly composed of 4 pcs of gears, shaft, pump body, pump cover, bearing sleeves and seals. All of external gear pump’s parts can be lubricated by delivered medium when gear pumps working. External gear pump have four sliding bushing to support shaft and external gear pump with big outlet size with high flow capacity.

3. Advantage of Internal Gear Pump

1) Steady delivery without pulsation, little vibration and noise when internal gear pump working;

2) Outstanding self-priming ability, it can suck the liquid up very quickly;

3) Internal gear pump in little wear and long using life, so it with high efficiency;

4) Internal gear pump can change the capacity though change the pump speed, high viscosity with lower speed, if viscosity it not too thick, the internal gear pump can with speed around 400-500rpm;

4. Advantage of External Gear Pump 

1) Little vibration and noise with long using life of external gear pump;

2) External gear pump cost is cheaper than internal gear pump

3) External gear pumps have widely using scope, such as petroleum, ship building, food factory, refinery and paper making etc. it can transfer the liquids with small solids.

4) External gear pump is easy installing and repair, so customer can operational it very easy.

5) External gear pump also can drive by diesel engine if the capacity is big.

That is the differences of external gear pump and internal gear pump, if you have any questions about it, please feel contact me. I will be always here to help you.