GEAR PUMPS

2020/07/21 11:07:38

Gear pumps are a type of rotary positive displacement pump, meaning they pump a constant amount of fluid for each revolution.
Gear pumps transfer fluid by gears coming in and out of mesh to create a non-pulsating pumping action. Gear pumps are able to pump at high pressures and excel at pumping high viscosity liquids efficiently.
Gear pump according to the material can be stainless steel 304 316 316L, carbon steel, cast iron, cast steel
Gear pumps can be into interna gear pump and external gear pump according to the structure, internal gear pump is also known as NYP high viscosity rotor pump in china, similar to the VIKING PUMP in the USA，Internal gear pump designs only use spur gears, This pump has been widely used mainly in three kinds of media:

*Fluids that are pure and have a certain degree of viscosity, such as lube oil and crude oil.
*High-viscosity materials that contain no particles, like rubber, asphalt, paint, adhesives, dyes, lubricants, polyols, food and medicine.
*High-temperature and high-viscosity polymers, like PA, PB, PC, PE, PS, HIPS, ABS, PP, PET and PVA.

External Gear Pump there are many models in China, such as Kcb Gear pump, YCB Gear pump, 2cy Gear pump, etc
These Pump is a higher flow, Low pressure external gear pump. Designed for the transfer of lubricating fluids with varying viscosities up to 1500cSt, designed for handling larger volumes of fuels and lubricating oil, Diesel, kerosene and so on

What are the main features and advantages of gear pumps?
The gear pump is compact and simple, with a limited number of moving parts. They cannot match the pressure generated by reciprocating pumps or the flow rate of centrifugal pumps, but they provide higher pressure and throughput than vane pumps or lobe pumps. Gear pumps are particularly suitable for pumping oil and other high viscosity fluids.

In both designs, the external gear pump can withstand higher pressures (up to 3000 psi) and flow due to stronger shaft support and smaller tolerances. Internal gear pumps have better suction capacity and are suitable for high-viscosity fluids, although their useful working range is from 1cP to 1,000,000cP or more. Since output is proportional to speed, gear pumps are often used for metering and mixing operations. Gear pumps can be designed to handle corrosive liquids. Although they are usually made of cast iron or stainless steel, new alloys and composite materials enable the pump to handle corrosive liquids such as sulfuric acid, sodium hypochlorite, iron chloride and sodium hydroxide.

External gear pumps can also be used in hydraulic power applications, usually in vehicles, cranes and mobile factory equipment. Using oil pumped from other locations in the system (usually by tandem pumps in the engine) to drive the gear pump in reverse, will produce a hydraulic motor. This is particularly useful for providing power in areas where electrical equipment is heavy, expensive or inconvenient. For example, tractors rely on engine-driven external gear pumps to power their services.

What are the limitations of gear pumps?
The gear pump is self-priming and can be dry-lifted, although it will improve its oil absorption characteristics if the gear gets wet. The gears need to be lubricated with pumped liquid and should not be idling for a long time. For example, some gear pump designs can run in either direction, so the same pump can be used to load and unload the container.

The tight tolerance between the gear and the housing means that these types of pumps are prone to wear, especially when used with abrasive liquids or feeds that contain entrained solids. However, certain designs of gear pumps, especially internal variants, allow the handling of solids. The external gear pump has four bearings in the pumped medium and has strict tolerances, so it is not suitable for handling abrasive fluids. Internal gear pumps are more robust, with only one bearing (sometimes two) running in the fluid. The gear pump should always install a filter on the suction side to prevent it from attaching to large, possibly damaging solids.

Generally, if you want the pump to be able to handle abrasive solids, it is recommended to choose a pump with a larger capacity so that it can run at a lower speed to reduce wear. However, it should be remembered that the volumetric efficiency of gear pumps will decrease at lower speeds and flows. The operating speed of the gear pump should not exceed the recommended speed.

For high temperature applications, it is important to ensure that the operating temperature range is compatible with the pump specifications. The thermal expansion of the housing and gears reduces the clearance in the pump, which also leads to increased wear and, in extreme cases, to pump failure.

Despite the best precautions, gear pumps usually wear gears, housings and bearings over time. As the gap increases, the efficiency will gradually decrease and the flow direction slip will increase: the pumped fluid leaks from the discharge port back to the suction side. The flow slip is proportional to the cube of the gap between the gear teeth and the sleeve. Therefore, in practice, the effect of wear is small until it reaches a critical point, from which the performance will rapidly decrease.

The gear pump continues to pump to the back pressure, and if it is blocked downstream, it will continue to pressurize the system until the pump, pipeline or other equipment fails. Although for this reason, most gear pumps are equipped with safety valves, it is always recommended to install safety valves elsewhere in the system to protect downstream equipment.

For shear-sensitive liquids (such as food, paint and soap), internal gear pumps running at low speeds are usually preferred. The higher speed and lower clearance of the external gear design make them unsuitable for these applications. When hygiene is important, internal gear pumps are also preferred because of their mechanical simplicity and the fact that they are easy to disassemble, clean and reassemble.

What is the main applications of the gear pump?
Gear pumps are usually used to pump high-viscosity fluids such as oil, paint, resin or food. They are the first choice for any application that requires precise metering or high voltage output. The output of gear pumps is not greatly affected by pressure, so they tend to use gear pumps in any irregular supply.

The following table lists some typical applications of external and internal gear pumps:

Type of gear pump	External	Internal
Various fuel oils and lube oils	√	√
Chemical additive and polymer metering	√
Chemical mixing and blending	√
Industrial, agricultural and mobile hydraulic applications	√
Acids and caustic (stainless steel or composite construction)	√
Resins and polymers		√
Alcohols and solvents	√	√
Asphalt, bitumen, and tar		√
Polyurethane foam (Isocyanate and polyol)		√
Food products: corn syrup, peanut butter, cacao butter, chocolate, sugar, fillers, vegetable fats, vegetable oils, animal feed		√
Paint, inks, and pigments		√
Soaps and surfactants		√
Glycol		√

Summary
The gear pump moves fluid by repeatedly enclosing a fixed volume in interlocking gears or gears, and mechanically transmits it to deliver a smooth, pulse-free flow proportional to the speed of the gear. There are two basic types: external and internal. The external gear pump consists of two identical interlocking gears and is supported by an independent shaft. The internal gear pump has two interlocking gears of different sizes, one interlocking gear rotates inside the other.

Gear pumps are usually used to pump high-viscosity fluids such as oil, paint, resin or food. They are also the first choice in applications requiring precise dosing or high-voltage output. External gear pumps can withstand higher pressures (up to 2.5Mpa), while internal gear pumps have better suction and are more suitable for high viscosity and shear-sensitive fluids.

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GEAR PUMPS