What is a Gear Pump?

A gear pump is a rotary pump that relies on the change and movement of the working volume formed between the pump cylinder and the meshing gear to transport or boost the liquid. The two closed spaces are composed of two gears, the pump body and the front and rear covers. When the gears rotate, the volume of the space on the disengagement side of the gear changes from small to large, a vacuum is formed, and the liquid is sucked in. Small, squeeze the liquid into the pipeline. The suction chamber and the discharge chamber are separated by the meshing line of the two gears. The pressure at the outlet of a gear pump depends entirely on the amount of resistance at the pump outlet.

Advantages: simple and compact structure, small size, light weight, good processability, cheap price, strong self-priming force, insensitivity to oil pollution, large speed range, resistance to impact loads, convenient maintenance and reliable work.

Disadvantages: unbalanced radial force, large flow artery flow, high noise, low efficiency, poor interchangeability of parts, difficult to repair after wear, cannot be done

1. Viable circuit for improving gear oil pump performance

   Gear oil pumps are generally limited to constant-flow hydraulic sources because of their structural limitations.

   Installed directly on the pump

   1. Compact structure, small size and light weight

   by

   JB / T 7041-2006

   What should I avoid while using a gear pump?

   Gear pump is suitable for various industries and has a wide range of media. This gear pump has some advantages such as firm structure, easy installation, easy disassembly, simple maintenance, uniform and continuous flow, slight wear, long service life, etc.
   1. During the process of using the gear pump, it is necessary to add grease frequently. Grease is relatively easy to volatilize, so you must pay attention to replacement, and then keep the bearings clean.

   2. The electric oil pump should be placed in a relatively dry, non-corrosive and relatively clean environment when used or finished.

   3. The gear pump should be inspected and repaired frequently during the use. It should be checked to check the power cable inside the electric oil drum; whether the internal wiring, plug, switch can still be used normally; whether the bearing parts are damaged Places, etc.

   4. Every part on the gear pump should be kept well. During the process of disassembling the gear pump, every part should be kept well and kept clean.

   1. Maintenance of gear pump shaft after wear

   The wear of the shaft in the gear pump is mainly due to the friction and wear between the two ends of the shaft and the supporting needle, which makes the shaft diameter smaller. If it is slightly worn, the diameter of the shaft can be enlarged by hard chromium plating to repair the shaft. If the shaft is severely worn, it should be remanufactured with 45 steel or 40cr steel. After the rough shaft and rough turning, the bearing parts should be heat treated with a hardness of hrc60-65, and then ground to make the surface roughness ra of the mating parts of the bearing Greater than 0.32m; the allowable difference between the roundness and cylindricity of the shaft is 0.005mm; the h7 / h6 and the surface roughness ra should not be greater than 0.63m with the gear matching part.

   2. Gear pump pump body after maintenance

   The surface wear of the pump body is mainly the arc-shaped working surface of the oil suction section. If there is slight wear, you can use oilstone to grind and remove burrs. The pump body is formed from cast iron casting blanks, and should be replaced with new ones when severe wear occurs. If both ends of the internal gear of the pump are repaired by grinding, the width of the pump body must also be changed, which is the same as the size of the gear at both ends of the gear.

   3. Maintenance after the gear pump end caps are worn

   The end cover of the gear pump is made of cast iron. After the wear phenomenon occurs, it can be ground and flattened slightly. If the wear is more serious, it should be ground and flattened on a surface grinder. The plane contact between the ground end cap and the pump body should be no less than 85%. The tolerance of flatness, the tolerance of the perpendicularity of the end face to the center line of the hole, the tolerance of the parallelism of the two end faces, and the center of the two axis The tolerances of the parallelism of the lines are all 0.01mm. 5m Surface roughness ra after grinding should not be greater than 1. 5m.

   4.Maintenance and replacement of needle roller bearings for gear pumps

   After the parts in the pump are repaired, the bearing needle should be replaced. The requirements for needle rollers are: the dimensional error of all needle diameters should not exceed 0.003mm, the length tolerance is 0.1mm, and the clearance between the shaft and the shaft should be about 0.01mm; The needles should be arranged parallel to each other.

   The reliability test includes two methods: laboratory and on-site, and one method can be selected according to specific conditions.

   1. Complete sample test --- The test is carried out until the test pump reaches the end of its maintenance life.

   2. Incomplete sample test:

   (1) Timing censoring test ---- The test is stopped when the test is performed before the test time T * specified before the test.

   When the sample size is large, especially the laboratory test can choose the timing censoring test scheme.

   (2) Fixed-term censoring test-a test that stops when the number of failures r specified before the test is performed

   When the user limits the number of pump failures, a fixed-term censoring test scheme can be selected.

   1. Before disassembling, you should make full preparations, and be familiar with the equipment structure, technological process, and operating status; take care when disassembling to avoid damaging the equipment parts.
      Second, review the data For the clearance of each part of the gear pump, a comprehensive inspection should be done, and some clearance standards are shown in Table 1-1.
      Third, check the detailed inspection of the removed parts, color inspection of the gear, cracks are not allowed; the conical degree of the journal is qualified, there should be no scratches on the surface, the maximum allowable value of roughness Ra is 1.6m; end cap , Bracket, pump body must not have obvious defects.
      4. Repair or replacement The parts exceeding the standard shall be replaced, and the parts to be repaired shall meet the standards after repair.
      V. Assemble and adjust the axial clearance of the end face of the gear, the end cover, and the bracket, which is adjusted by changing the thickness of the gasket between the end cover, the bracket and the pump body; when tightening the end cover bolts, use symmetrical force evenly. Rotate the rotor while tightening it. When the rotor is unable to move, loosen the bolts and tighten it tightly; when filling or installing oil seals, you still need to turn the rotor while tightening the cover, so as not to get too tight.
      6. The hydraulic pressure test of the test run is 1.5 times the working pressure, and it is not leaked for 5 minutes. During the test run, there is no leakage, the operating sound is normal, there is no abnormal vibration, and the outlet pressure meets the requirements to be qualified.

   Repair common sense

   Gear pump repair knowledge has increased with the use of time, gear pumps will show lack of pump oil, or even oil and other problems, the main reason is that the relevant parts are too worn. The main wear parts of gear pumps are mainly automatic shafts and bushings, passive gear intermediate holes and shaft pins, pump housing inner cavity and gears, gear end faces and pump covers. After the smooth oil pump wears down and its primary skill target fails to meet the requirements, it should be disassembled and differentiated, the wear site and level should be investigated, and a response method should be adopted to repair it.
   First, the repair of the wear of the automatic shaft and the bushing After the automatic shaft and the bushing of the gear pump are worn, the common gap between them will increase, which will definitely affect the oil quantity of the pump. The normal common clearance can be restored by repairing the automatic shaft or bushing. If the wear of the automatic shaft is slight, you only need to press out the old bushing and replace it with a bushing of the specified size, and the common gap can be restored to the agreed limit. If the wear of the automatic shaft and the sleeve is severe and the common clearance is severe and exceeds the standard, it is not only necessary to change the sleeve, and the automatic shaft also uses chrome plating or vibration surfacing to increase its diameter, and then grind to the standard size to restore the sleeve. Common requirements.
   2. Repair of smooth oil pump casing Repair of casing crack: The casing crack can be repaired by casting 508 nickel copper electrode. Welds must be tight and pores, and the flatness error of the connection surface with the pump cover is not greater than 0.05 mm. Repair of the wear of the automatic shaft bushing hole and the driven shaft hole: After the automatic shaft bushing hole is worn, the worn out can be eliminated by reaming, and then the bushing can be used to increase the response size. The wear of the driven shaft hole is also eliminated by reaming, and then the repair of the inner cavity of the driven shaft pump casing is prepared according to the actual size of the hole after the reaming: After the inner cavity of the pump casing is worn, it is generally repaired by the inner cavity insert method. Stand-alone dust collectors line the inner cavity with a cast iron or steel bushing. After inserting the sleeve, the inner cavity is sized to the required size, and the bushing protruding from the end face is ground off so that it is flush with the connection surface of the pump casing. Repair of valve seat: There are two types of pressure limiting valves: ball valve and plunger valve. After the ball valve seat is worn, a steel ball can be placed on the valve seat, and then the steel ball is quietly struck with a metal rod until the ball valve and the valve seat are in close contact. If the valve seat is severely worn, it can be reamed first to remove the wear marks, and then used to make it close. After the plunger valve seat is worn, you can put a little valve sand and grind it until it is tight.
   Third, the repair of the pump cover task plane repair: If the pump cover task plane wear is small, you can use manual grinding method to eliminate wear and tear, that is, put a little valve sand on the platform or thick glass plate, and then put the pump cover on it for grinding Until the wear and tear disappears and the mission is flat. When the wear depth of the pump cover task plane exceeds 0.1 mm, it should be repaired by turning and grinding first. Repair of automatic shaft bushing holes in the dust collector bag cage: The repair of the wear of the automatic shaft bushing holes on the pump cover is the same as that of the automatic shaft bushing holes in the casing. Fourth, the gear overturning gear pump gear wear is mainly in the tooth thick parts, while the wear of the gear end face and the tooth tip are relatively light. The gear is worn on one side at the tooth thickness, so the gear can be turned 180 degrees to use. When the end face of the gear is worn, the end face can be ground flat, and the smooth surface of the oil pump casing can also be ground to ensure that the gap between the end face of the gear and the pump cover is within the limits of the specification.

   With the growth of the population and the development of the economy, the issue of energy has become increasingly important. Especially in China, energy conservation has become increasingly important. In order to strengthen the concept of ensuring energy conservation of enterprises, China may start to use more severe price levers for production electricity. Therefore, energy saving has become an important direction for the development of current gear pumps.

   As a major variety of pumps, gear pumps have undergone many important developments. The early gear pumps were all hydraulic. Due to the needs of environmental protection and energy saving, as well as the mature application of servo motors and the significant drop in price, in recent years, more and more electric precision gear pumps have been added. In order to analyze this development trend I list the comparative features among them:

   The all-electric gear pump has a series of advantages, especially in terms of environmental protection and energy saving. According to reports, as of the end of December 2014, the more advanced all-electric gear pump can save 70% of electricity. In addition, due to the use of servo motor injection The control accuracy is high, the speed is relatively stable, and it can be adjusted in multiple stages. However, all-electric gear pumps are not as good as full-hydraulic gear pumps in terms of service life, and full-hydraulic gear pumps must use servo valves with closed-loop control to ensure accuracy. Servo valves are expensive and increase costs.

   The full hydraulic gear pump has many unique advantages in forming precision and complex shapes. It has developed from the traditional single-cylinder liquid-filled and multi-cylinder liquid-filled to the current two-plate direct-pressure type, of which two-plate direct-pressure This type is the most representative, but its control technology is difficult, the machining accuracy is high, and the hydraulic technology is difficult to master.

   Electric-hydraulic gear pump is a new type of gear pump that integrates hydraulic and electric drive. It combines the high-performance of a full hydraulic gear pump with the advantages of an all-electric energy-saving. Has become the development direction of gear pump technology.

   According to the requirements of the gear pump equipment process, the power consumption of the gear pump oil pump motor accounts for 50% -65% of the power consumption of the entire equipment, so it has great energy saving potential.

   Causes of Gear Pump Rotation

   Causes of Gear Pump Rotation

   The axial or radial clearance is too small. Adjust it again.

   There is dirt in the pump. Disintegrate to clear foreign bodies.

   Incorrect assembly. The machining reference plane of the two pin holes of the gear pump is not the assembly reference plane. If the pin is driven in first, and then the screw is tightened, the pump will not move. The correct method is to tighten the screw while turning the gear pump, and finally drill the pin hole and drive the pin.

   Poor coaxiality between pump and engine coupling. The coaxiality should be guaranteed within 0.1mm.

   The parts inside the pump are not demagnetized. All parts must be demagnetized before assembly.

   Needle sleeve quality is unqualified or the needle is broken. Repair or replace.

   The working oil outlet is blocked. Remove foreign objects.

   When we use gear pumps, we cannot avoid the wear of the gear pump, so many problems will occur, so we must learn the most common maintenance technology for gear pumps. With the problem to be able to make an accurate judgment on it, let me talk about the most common maintenance techniques for everyone:
   1. Maintenance of working plane: If the working surface of the pump cover is relatively small, you can grind it yourself to eliminate the wear marks, that is, put a little valve sand on the platform or thick glass plate, and then place the pump cover on it for grinding until The wear marks are worn away and the work surface is flat. If the wear depth of the working surface of the pump cover exceeds 0.1 mm, it must be repaired by turning and grinding first.
   2. Maintenance of the drive shaft bushing hole: The repair of the wear of the drive shaft bushing hole on the pump cover is the same as the repair method of the wear of the drive shaft bushing of the casing.
   Repair of the inner cavity of the pump casing: After the inner cavity of the pump casing is worn, it is repaired by the inner cavity inserting method, that is, after the inner cavity is enlarged, it is set with a cast iron or steel bushing. After inserting the sleeve, the inner cavity is sized to the required size, and the bushing protruding from the end face is ground away to be flush with the joint surface of the pump casing.
   3. Valve seat maintenance: There are two types of pressure limiting valves: ball valves and plunger valves. After the ball valve seat is worn, a steel ball can be placed on the valve seat, and then the steel ball is lightly tapped with a metal rod until the ball valve and the valve seat are tight. If the valve seat is severely worn, it must be reamed to remove the wear marks, and then it must be made close. After the plunger valve seat is worn, you can put a little valve sand to grind it until it is tight.
   The above is the maintenance of the most basic parts of gear pumps. In the process of application, we may encounter different problems in other aspects. We have to seriously discuss these different problems to find out where the problems are s reason.