The main parts of fluorine plastic centrifugal pump

Centrifugal pump is composed of many parts, the following is taken fluoroplastic centrifugal pump as an example, to discuss the role of the main parts, materials and composition.

One. Impeller

Impeller is also known as the working wheel or runner, its role is to transfer the mechanical energy of the power machine to the medium being transported, so that it flows through the impeller to increase the kinetic energy. In the selection of impeller materials, in addition to the mechanical strength under centrifugal force, but also should consider the wear and corrosion resistance of the material. At present, the impeller is made of cast iron, cast steel and bronze. According to the structure, the impeller is divided into single suction and double suction two kinds. Single suction impeller it absorbs water on one side, and the front and rear cover plates of the impeller are asymmetric. Single suction impeller is used for single suction centrifugal pump. Double suction impeller it absorbs water on both sides, the impeller cover plate is symmetrical, double suction centrifugal pump with double suction impeller, the pump flow is larger, it can balance the axial force automatically.

According to the situation of its cover, the impeller is divided into closed, open and half open three forms. The impeller with two cover plates is called a closed impeller. Between the cover plate is equipped with 6~12 pieces of backward bending impeller, only blade and no cover plate impeller is called open impeller, semi open and open impeller blade is less, generally only 2~5 pieces, these two kinds of impeller efficiency is lower relative to the closed impeller, suitable for the discharge of pollution or containing a large number of solid particles of liquid

Two. The pump shaft

The function of the pump shaft is to support and drive the impeller to rotate, and transfer the energy of the power machine to the impeller. It is required that the shaft end of the pump is straight and has enough strength and stiffness, so as not to cause damage to the impeller and pump shell caused by the impeller swinging due to the bending of the shaft during the operation of the pump. The pump shaft is generally made of carbon steel or stainless steel. One end of the pump shaft is fixed with a flat key and a nut. When rotating, the impeller is tightened; In large and medium-sized pumps, the axial position of the impeller is located by the bushing and the nut of the bushing. The other end of the pump shaft is equipped with a coupling.

Three. Pump shell

The pump shell of the centrifugal pump is a volute that contains and delivers liquid. It is composed of a pump cover and a snail body. The pump cover is the suction chamber of the pump, whose function is to lead the water in the suction pipe to the impeller evenly with the minimum loss. According to the structure, the suction chamber can be divided into straight cone suction chamber, annular suction chamber and semi-spiral suction chamber. The cochlear body consists of a cochlear chamber and a diffusing cone tube. The main function of the flash chamber is to collect the water flow thrown by the impeller and to keep the water velocity in the chamber as a constant with the increasing of its cross section so as to reduce the head loss. After discharge from the cochlear chamber, the water flows into the pressure tube through the diffused cone. The purpose of the diffused cone is to reduce the velocity of water flow and convert part of the kinetic energy of water flow into pressure energy. The inlet and outlet pipe flanges of the pump shell are each provided with a borehole for installing a vacuum gauge and a pressure gauge to measure the pressure at the inlet and outlet of the pump. The top of the pump shell is provided with a water filling (or air extraction) hole, so that before the pump starts to fill water or to remove the air in the pump shell. The bottom of the pump shell is provided with a water hole to empty the water in the pump after stopping the pump to prevent freezing in winter. The bottom of the pump shell is provided with a bolt hole for fixing the foundation. In addition to the bolt hole to fix the pump, other screw holes in the operation of the pump temporarily not used, need to use the wire with tired lines blocked.

In the above parts, the impeller and the pump shaft are the rotating parts of the centrifugal pump, and the pump shell is the fixed parts. There are three junctions between the two: the shaft seal device between the pump shaft and the pump shell, the leakage reduction ring at the joint between the impeller and the pump shell, and the bearing at the rotational connection between the pump shaft and the pump seat.

Four. Shaft sealing device

When the pump shaft goes out of the pump shell, there must be a gap between the rotating pump shaft and the fixed pump shell. If no corresponding measures are taken, the high pressure water flowing from the impeller will flow out through this gap in large quantities; If the pressure at the gap is vacuum, air will enter the pump from there. Therefore, a shaft sealing device must be set up. Shaft seals come in many forms, and the most common type used for vane pumps is the packing seal. It is composed of bottom lining ring, packing, water sealing ring, packing gland and other parts, commonly used packing is immersed in oil, immersed in graphite asbestos rope. In recent years, a variety of high temperature resistance, wear resistance and corrosion resistance of the new type of filler, such as carbon fiber, stainless steel fiber and synthetic resin fiber woven packing. In order to improve the sealing effect, the packing is generally made of rectangular section. The compaction of the packing is regulated by the gland nut. If the pressure is too tight, the mechanical wear of the pump shaft and the packing increases, the mechanical loss also increases, and the water in the pipe can drip through the filling gap in serious cases. At present, some fluorine plastic centrifugal pump adopts rubber ring seal, mechanical seal and other type of shaft seal device.

Five. Leakage reduction ring

There is a gap between the outer edge of the inlet of the fluoroplastic centrifugal pump impeller and the inner edge of the pump cover. This clearance is the interface of high and low pressure water. If the clearance is too large, the high pressure water flowing from the impeller leaks back to the inlet side of the impeller through this clearance, reducing the water output of the pump and reducing the effective bar of the pump. But when the gap is too small, it will cause mechanical wear. Therefore, in order to extend the service life of the impeller and the pump cover, usually it is?inlaid with a metal ring in the gap of the pump cover, or in the pump cover and the impeller, The mouth ring is called the leakage reduction ring, the leakage reduction ring is used for wear, in the operation, the friction of this part is inevitable, when the friction gap is too large, just replace the leakage reduction ring without the impeller and pump cover scrapped.?Therefore, the leakage reduction ring, also known as wear ring, is a wearing part.??

Six. Bearing

The bearing is installed in the bearing seat to support the weight of the rotating part and bear the axial and radial load generated by the rotating part in the operation, and reduce the friction of the pump shaft rotation. Bearings are divided into two categories: rolling bearings and sliding bearings. Single stage single suction centrifugal pump usually uses single row centripetal ball bearing, it is composed of outer ring, inner ring, rolling body and cage. The inner ring is mounted on the journal and rotates with the shaft. There is a raceway on the outer ring, when the inner and outer rings rotate relative, the rolling body rolls along the raceway, the role of the cage is to evenly separate the rolling body. Bearings are lubricated with thin or dry oil.

Seven. Coupling

The coupling connects the pump to the shaft of the motor, causing them to rotate together and transmit torque. Coupling, also known as "backrest" wheel, which has two type: rigid and elastic. The rigid coupling is actually connected with two round flannels, which has no room to adjust the decentration of the pump shaft and the power shaft in connection and operation.?Therefore, the installation accuracy is high, mostly used for vertical units.?The cylinder pin coupling consists of half coupling, cylinder pin, retaining ring and elastic ring made of rubber or leather, which allows a small amount of deformation when running and can compensate for a small amount of deviation between the two axes.?The claw type elastic coupling is composed of two half claw type coupling and a star type elastic block made of rubber. It has the advantages of simple structure, convenient installation and small transmission torque. It is suitable for small horizontal unit.

Eight. Axial force balancing device

When fluorine plastic centrifugal pump in operation, because the area of the impeller before and after the cover plate is different, the impeller on both sides of the pressure is not equal, in the impeller has produced an axial force △P pointing to the inlet direction, in addition to the impeller toward the inlet direction of the axial force, but also cause vibration, wear and increase bearing load. Therefore, the axial force must be balanced somehow.?For the single stage single suction centrifugal pump, the balance hole is generally opened in the rear cover plate of the impeller near the hub, and the leakage reduction ring is installed on the rear cover plate.?After the high pressure comes through the leakage reduction ring, the pressure drops, and flows back to the impeller inlet through the balance hole, so that the pressure on the front and rear cover plates of the impeller is close, so that most of the axial force is eliminated, and a small part of the axial force that has not been eliminated is borne by the bearing.?The advantage of this method is simple structure, but the disadvantage is that the efficiency of the pump is reduced.?In addition, the rear cover plate of the impeller can also be used to add balance rib plate, so that the pressure on both sides of the impeller tends to balance.?For multistage pumps, the balance plate or balance drum is added behind the final impeller, or the method of symmetrical layout of the impeller is adopted to eliminate the axial force.??

For more technicial questions please feel free to contact Kelly~

Kelly - International Trade Pumps Engineer

Anhui Tenglong Pump And Valve Manufacturing Co., Ltd.(TEFLOW)

No. 30 fortune east road, Jingkai district Jing County, Xuancheng City, Anhui Province, China

Web:www.teflowpump.com,???????????????????????????????????????????????????teflow-pumps.en.made-in-china.com?

Tel:+86-15156345852

WeChat: 15156345852

Whatsapp :+86 15156345852

Skype: live:liuqin1991123456

Mail: [email protected]

TEFLOW designates the only international trade sector