What should I pay attention to when using the precision gear pump?

①The oil suction height of precision gear pump should not be greater than 500mm.

②precision gear pump should be directly connected to motor through flexible coupling, generally do not connect rigidly or connect to power source through gear vice and belt mechanism to avoid unilateral force, resulting in pump shaft bending, unilateral wear and pump shaft oil seal failure.

③The limit speed of precision gear pump should be limited, not too high or too low. If it is too high, the oil will not be able to fill the entire gap between the teeth, which will cause cavitation and produce vibration and noise; if it is too low, it will not be able to form the necessary vacuum in the suction chamber of the pump, which will cause poor oil suction.

④When choosing, the precision gear pump is mostly a single direction pump, divided into left and right pumps. When buying, you need to pay attention to it, otherwise it can't be oiled or the oil quantity is not enough when using it in reverse, and it often makes the pump shaft oil seal overturned and broken.

⑤ General precision gear pump use YA-N46 (GB 2512-1981) ordinary hydraulic oil, working oil temperature control in 0 ~ 80 ℃, filtering precision 25μm or so.

After using precision gear pump for a long time, the relative sliding surface of gears will be worn and scratched. The wear of the end face will lead to the increase of axial clearance and internal leakage; the wear of the tooth top circle will lead to the increase of radial clearance; the wear of the tooth shape will cause the increase of noise and pressure swing. When the wear and strain is not serious, it can be slightly grinded (to research) polished and used again, if the wear and strain is serious, it needs to be repaired or replaced according to the situation.

2. How to repair gears and gear shafts?
   
The wear part of precision gear pump pump shaft (gear shaft) is mainly at the journal in contact with needle bearing or sleeve. If the wear is slight, it can be repaired by polishing. If the wear is serious, it is necessary to use chrome plating process or re-process a new shaft, when re-processing, the coaxiality of the two journals is 0.02~0.03mm. The coaxiality of the gears mounted on the shaft or connected to the shaft is 0.01mm.

①Tooth shape repair

Use fine sand cloth or oil stone to remove the strain bump or burr that has been ground into multi-pronged parts, and then install the gear together with the shaft on the pump cover bearing hole to research, and use the method of coating the red Dan to calibrate the grinding effect. Properly swap the orientation of the meshing surface, after cleaning can continue to use. But the naked eye can observe the serious wear parts, should be re-made gear, be replaced.

②End face repair

Slight wear, the two gears can be placed on 0# abrasive cloth sanding, and then placed on the metallographic sandpaper polishing. When the wear and tear is serious, the two gears can be put on the flat grinding at the same time to grind away a little, and then grinding or polishing with metallographic sandpaper. At this time, the pump body should also be ground to the same size to ensure the original assembly gap (0.02 ~ 0.03mm). The difference between the thickness of the two gears should be within 0.005mm, and the verticality of the gear end face and hole or the runout of the gear axis should be controlled within 0.005mm.

③Top circle of teeth

Due to the existence of radial unbalance force, the external pre-cision gear pump will generally wear after a period of time. The radial clearance will increase after the tooth top circle is worn. For low pressure gear pumps, the internal leakage will not increase much. However, for medium and high pressure gear pumps, it will have an impact on the volumetric efficiency, and the plating of the outer circle (brushing the top circle of the tooth) or the replacement of the gear should be considered.

④The gear accuracy of low and medium pressure precision gear pump is 7～8 grade, and the gear accuracy of medium and high pressure precision gear pump is slightly higher than 0.5～1 grade, the tolerance of coaxiality between gear bore and tooth top circle (for gear shaft, it is tooth top circle and outer circle of journal) is <0.02mm, the non-parallelism of both end surfaces is <0.007mm, and the surface roughness is.

⑤Gear shaft

For gears and shafts connected together with the gear shaft, if the surface flaking or burn discoloration, should be replaced with a new gear shaft; if the surface is grayish white, only with increased clearance, can properly adjust the position of the meshing teeth, replace the new bearing; if the surface of the gear outer circle due to sweeping the bore hair, the top of the teeth are caked with iron chips, can use oil stone sand strip to grind off the caked material, and sand grinding pump bore bonding surface, the radial clearance is not over poor can continue to use, if the radial clearance is too large, the pump bore can be plated with copper alloy according to the situation, reduce the radial clearance.

3. How to repair the pump body, front and rear cover, sleeve and side plate?

The wear of the pump body is mainly on the inner cavity surface (the surface in contact with the top circle of the teeth - G6 surface), and mostly occurs on the suction side. If the pump body is symmetrical, it can be installed by turning the pump body 180°. If it is a non-symmetrical type, it is necessary to use the plating bronze alloy process or brush plating method to repair the wear parts of the inner cavity hole of the pump body.

The front and rear cover and sleeve repair parts are mainly the end face in contact with the gear. When the wear is not serious, the end face can be repaired by grinding on the flat plate. When the wear strain is serious, it can be put on the surface grinder to grind away the grooves first, and then grind slightly, but it should be noted that the relevant size of the unloading groove should be deepened and widened appropriately.

After the side plate is worn out, both sides of the plate can be put on the grinding plate or glass plate and ground flat with 1200# diamond sand, the surface roughness should be lower than Ra0.8, and the thickness difference should not exceed 0.005mm in the whole circle range.

 
4.How to assemble the precision gear pump?

After repairing the precision gear pump, the following matters should be noted when assembling.

①Clear the burrs on each part. The sharp edges of the gears are blunted with natural oil stones, but not rounded, and the parts are demagnetized after flat grinding. All parts are carefully cleaned by kerosene before they are put into the assembly.

②Assembly to measure and ensure the axial clearance: precision gear pump axial clearance δ = pump body thickness L0 - gear width L1, generally to ensure that δ in 0.02 ~ 0.03mm, while measuring the relevant dimensions and accuracy of other parts.

③precision gear pump assembly, some gear pumps have positioning pin holes. For the precision gear pump without positioning holes, when assembling, tighten each screw in diagonal order while rotating the pump shaft. If there is no light weight, then tighten several mounting screws thoroughly. For gear pumps with positioning holes (such as CB-B type), the pin holes are mainly used in the machining process of the parts, so there is no positioning reference to speak of when assembling, and then finally with the drilling and reaming of two pin holes, hitting the positioning pins.

④ For easy to install the reverse parts to pay attention to, do not install the wrong direction. In particular, to confirm whether it is a positive or negative pump.