Working principle and maintenance of gear oil pumps

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This post was last edited by Black gold on 2011-3-25 00:53. A gear pump operates by the mutual rotation of two gears, and it has low requirements regarding the medium used. The normal pressure is below 6 MPa, with a high flow rate. A gear oil pump contains a pair of rotating gears within its pump body – one driving and one driven. Through the intermeshing of these two gears, the entire working chamber inside the pump is divided into two separate sections. A is the intake chamber, and B is the discharge chamber. When the gear oil pump is in operation, the driving gear causes the driven gear to rotate; as the gears move from engagement to disengagement, a local vacuum is created on the suction side (A), and liquid is drawn in. The liquid that has been drawn in fills the tooth grooves of the gears and is carried to the discharge side (B); when the gears engage, the liquid is forced out, forming high-pressure liquid that is then discharged from the pump through its outlet. Schematic diagram of the gear oil pump structure. Features of the gear oil pump: 1. Compact structure, easy to use and maintain. 2. It has good self-priming capability, so there is no need to fill it with liquid before each start-up of the pump. 3. The lubrication of the gear oil pump is achieved automatically by the liquid being transported, so no additional lubricant is required during normal operation. Gear oil pumps are widely used in industries such as petroleum, chemicals, shipping, power generation, grain and oil processing, food processing, healthcare, building materials, metallurgy, and defense research. Gear oil pumps are suitable for transporting lubricating oils that contain no solid particles or fibers, are non-corrosive, have a temperature not exceeding 150°C, and have a viscosity of 5–1500 cst, as well as other liquids with properties similar to those of lubricating oils. It is suitable for use in situations where solidification occurs at room temperature, as well as in outdoor installations in cold regions where insulation is required during the manufacturing process. Regarding maintenance: 1. Repair of wear on the drive shaft and bushings – When the drive shaft and bushings of a gear pump become worn, the clearance between them increases, which inevitably affects the amount of oil pumped. In such cases, the normal clearance fit can be restored by repairing the drive shaft or bushing. If the drive shaft is only slightly worn, it is sufficient to press out the old bushing and replace it with a bushing of standard size; the clearance can then be brought back within the allowable range. If the drive shaft and bushing are severely worn and the clearance between them exceeds the acceptable limits, not only must the bushing be replaced, but the diameter of the drive shaft should also be increased using chromium plating or vibration surfacing, after which it must be ground to the standard size to restore the proper fit with the bushing. 2. Repair of the lubricating oil pump housing – Repair of housing cracks: Housing cracks can be repaired by welding with Cast 508 nickel-copper welding rods. The welds must be tight and free of pores, and the flatness error at the joint with the pump cover shall not exceed 0.05 millimeters. 3. Repair of wear in the bore of the driving shaft bushing and the bore of the driven shaft: When the bore of the driving shaft bushing is worn, the wear marks can be removed by reaming, after which a bushing of an increased size can be used. Wear in the holes of the driven shaft is also eliminated by honing to remove the signs of wear; thereafter, the driven shaft 4 is fabricated according to the actual dimensions of the hole after honing. As for the repair of the interior cavity of the pump casing, when this cavity becomes worn, it is generally repaired by inserting a lining into it – that is, the cavity is enlarged first and then a cast iron or steel liner is inserted. After fitting the sleeve, line the inner cavity. 5. Repair of the valve seat: Pressure limit valves come in two types – ball valves and plug valves. After the spherical valve seat is worn out, a steel ball can be placed on the seat, and then the steel ball can be gently tapped with a metal rod until the ball valve fits tightly against the seat. If the valve seat is severely worn, the wear marks can be removed by reaming first, and then it can be made tight using the above method. After the plunger-type valve seat is worn, a small amount of valve sand can be inserted for grinding until a tight fit is achieved. 5. Repair of the pump cover 　Repair of the working surface: If the wear on the working surface of the pump cover is minor, the wear marks can be removed by manual grinding. This is done by placing a small amount of emery dust on a flat surface or thick glass plate, then placing the pump cover on top of it and grinding it until the wear marks are gone and the working surface is smooth. When the wear depth of the working surface of the pump cover exceeds 0.1 millimeters, it should be repaired by turning first and then grinding.