External gear pump and internal gear pump

External gear pumps have  two gears involved which may be of a simple spiral or twin type. These three types of gears are  shown in the pictures  The fluid moves between the gear teeth and is displaced by the teeth. The presence of low clearances between the gear teeth and also between the teeth and the chamber walls minimizes fluid return from high pressure to low pressure right.


External gear pump


Gears are simple and generally less expensive to manufacture than spirals and twigs. Although these types of gears have good features, they can be loud and inefficient. The fluid trapped between the teeth involved has no room for exit. As this fluid is pressurized by low-pressure chlorines, it can produce a very loud sound. Some builders use a discharge gap (safety) in this range to give it room for fluid escape. This reduces noise and increases efficiency, especially for viscous liquids, another advantage of simple gears, with minimal thrust.


External gear pump


Another way to provide a loophole for trapped fluid is to use a spiral gear. This shape of the spiral provides space for the liquid to exit. The snake gear pumps provide a space for fluid outflow. Spiral gear pumps are usually efficient and quiet and have only one drawback; they are driven by thrust to the bushing pump thrust.

Axial wear at a gear pump much faster than radial wear reduces its performance, so maintaining these clearances in the axial direction is very important. And they are very good and don't show much secretive power. The machining process on these types of gears is very difficult to perform, so they are sometimes used to make them from a spiral connected gear (which is in the opposite direction to each other). Be.


External gear pump


In most gear pumps, the first gear (which is coupled to the actuator) moves the other gear. Another type of design uses timing gears.Separate sets of gears are typically separated from the pumping fluid, causing the two main gears to stay engaged without the need for direct contact. The use of timing gears, which are common in many types of rotary two-rotor pumps, creates larger clearances between the pump gears and, as a result, the pump can be easily damaged without damaging the gears. Adapt yourself to some abrasives. The benefits of external gear pumps include relatively high speed performance and relatively high pressure output.

These gears are usually supported by bearings on both sides, so there is no suspension. These pumps have relatively low noise (especially if used for coils or twigs), largely fluctuating and cost-effective. He noted that except when used with timing gears, these pumps do not withstand solid and abrasive particles.


Iranian gear pump


The weakest element in most pumps (external or internal gear type) is the drive gear.

It may be believed that because the drive gear carries 100% of the load, its bearings should have the most wear and tear, but this belief is completely false.

The loads applied to the radial bearings are the result of the pressure changes caused by the pump and the forces applied by the drive gear to the drive gear. This results in more loading on the removable gears than on the drive gears. This problem is usually exacerbated by the dampening of the gears by the suction pump.

Therefore, when examining wear on a gear pump, its removable gear bearings must first be carefully considered. With the wear of the bearings, the cushion will not be supported and the tooth will start to wear to the pump body or the wear plate. This will increase the interference between the gears and slip and reduce pump performance, especially at high pressures. Considering the gear material, it should be borne in mind that most gear pumps pump suction fluids. In these types of pumps, gears are made of different types of metals, especially steel. To produce high pressures, the hardness varies from soft steel to hard steel.


Gear steel pump


Bronze and non-metallic materials such as plastic, carbon, Teflon and ceramic composites are also used for pumping non-lubricating fluids.Choosing the right material is usually done according to parameters such as chemical resistance, mechanical properties and cost. For example, although Teflon has very good chemical resistance, due to its physical properties there are problems such as excessive wear, low pressure performance, and fluid temperature limitation (due to high thermal expansion).

Due to the need for low clearances in gear pumps, there is no limit to virtual wear. Most gear pumps cause early breakdowns due to wear.However, some of them are made of wear-resistant materials and can perform well in some applications. These pumps use hardened shafts, gears, or ceramic bushings or highly wear-resistant plastic composites. A very slow start-up is another way to extend the life of the pump under all operating conditions that are purposefully used for wear applications.

Internal gear pump

Internal gear pumps, like external gear pumps, move and pressure the fluid by engaging and releasing the gear teeth. In the inner gear pumps, the rotor with the internal cut gear is engaged and propelled by a rotary gear with the outer cut gear. Pumps of this type usually have a crescent-shaped section that passes the fluid through the pump with minimal backflow.


How the inner gear pump works


The benefits of an internal gear pump include a low number of moving parts, a relatively low cost and only one leak. These pumps can usually work well in any direction, and their reverse rotation can reverse the direction of flow. Its disadvantages include the presence of a bearing in the pumping fluid (which should support suspended load) and the inability of the pumps to operate with abrasive solids.

Pumps lobe

In terms of functionality, these pumps are very similar to conventional types of lobe pumps.  In this type of pump, the rotors instead of the conventional lobes have arc-shaped pistons or rotor blades that move in circular cylinders mounted on the pump body. Like conventional lobe pumps, rotors are not in direct contact with each other and require timing gears.


How the pump lobe works

In this type of pump, the Lobf pump has a lower current flow than its conventional variants. This is due to the fact that circular lobes for conventional types of earring pumps are only in a single point on the outer surface of each lobe, in close contact with the body, while in double lobe pumps with peripheral pistons There is little clearance between the rotor and the body all along the arc. Lower flow rate means that these types of pumps are more energy efficient than conventional types of earrings. For liquids with a viscosity higher than SSU 2000, this advantage disappears.


Pump lobe

The advantages and disadvantages of these types of pumps are largely similar to those of conventional earring pumps, and the most common applications are food processing. Usually, the double-sided lobe pump with peripheral piston can not work well with conventional types of earring pumps with abrasive materials, and its arched rotor may also contact the body during high-pressure applications.

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