Construction and Maintenance of Main Parts of Agricultural Pumps

Drainage and irrigation machinery is the main machinery used in agricultural mechanization and farmland water conservancy mechanization, and agricultural water pump is an important part of irrigation and drainage machinery. It plays an important role in drought resistance and drought relief in agricultural production and guaranteeing harvest increase. Agricultural water pumps all over the country have exposed some problems at the same time that they have played a decisive role, which has affected the work of drought relief and drainage. The maintenance of agricultural irrigation and drainage machinery, and the necessary maintenance and repair of agricultural water pumps, make these machines in the best working condition, and has extremely important significance for ensuring the bumper harvest of agriculture. The following is a brief explanation of the construction and maintenance of the main components of the agricultural water pump:

First, the pump shaft

1. Function and structure: The function of the pump shaft is to transmit power and drive the impeller of the water pump. The pump shaft is generally supported by bearings. One end is equipped with a coupling or a pulley, and the impeller is fixed at the other end or in the middle. Axial pump shaft is relatively slender, and the contact surface of the rubber bearing and packing is plated with chromium or fitted with a stainless steel sleeve to increase wear resistance and corrosion resistance. Some shafts of centrifugal pumps and mixed-flow pumps are equipped with bushings on the contact section with the packing to protect the shaft from direct contact with the packing. After wear, only the shaft bushes need to be replaced to extend the service life of the shaft.

2. Inspection and maintenance: After the pump runs for a period of time, the pump shaft is prone to bending and wear. Except for accidental bending of the shaft due to long operation time, disassembly and transportation, etc., the main reason is that the quality of the shaft itself has a problem, such as The strength or rigidity is not enough, the heat treatment does not meet the requirements, the impeller assembly is unbalanced, the power shaft and the pump shaft are not the same, the belt is pulled too tightly, the bearing installation is skewed, lubrication is poor, etc., and the pump shaft is worn or bent early. After this phenomenon occurs, it should be promptly overhauled to ensure the normal operation of the pump, otherwise it will cause the imbalance of the rotor and the wear of the dynamic and static parts.

After initially confirming that the pump shaft has been bent, use a dial indicator on the platform or lathe to check the condition of the shaft, or place the pump shaft on the V-shaped iron. The V-shaped iron should be placed firmly and then the dial indicator must be replaced. At the top, the shaft is pointing to the axis, and then the pump shaft is slowly pulled. When the shaft is bent, the dial gauge has a maximum reading and a minimum reading for each revolution. The difference between the two readings indicates the degree of bending of the shaft. There are many ways to straighten the shaft, but for the water pump, the most straightforward method on the site is to hit the straight shaft method. In the case of a straight shaft, place the shaft on hardwood (or square iron with copper skin), with the concave side down, and beat it with a hammer or crowbar. When hitting, start from the place where the bending is largest, and the range of hitting is 1/3 of the circumference, which can be drawn on the shaft in advance. The number of hits in the center of the 1/3 arc is more, and the less the number of hits on both sides, the faster the initial stretch and the slower later. In the process of beating, it is also necessary to measure the changes of shaft bending in time, and do not overdo it. The support when straightened is softer than the crowbar, and the contact surface is larger.

For shafts that are used for a long time and wear too much, new shafts should be replaced. After shaft sleeves are worn out, new shaft sleeves can be replaced. In addition, it can be sprayed or repaired at the shaft wear and then machined to the required dimensional accuracy.

Second, the impeller

1. Function and Structure: The function of the pump impeller is to transfer the mechanical energy of the power machine to the water and increase the energy of the water. The impeller consists of a blade and a hub, and the blade and the hub are cast as one body, and the blade is also made into an adjustable assembly on the hub. Impeller has closed, semi-closed, open type points. Centrifugal pump impeller blade thickness is generally 3-6 mm, and the number of blades is 6-10. Too few blades will generate turbulence in the impeller channel. Too many blades will increase the friction loss of the fluid. In order to reduce the volume leakage loss, the impeller inlet is often provided with a sealing ring.

2. Maintenance: The general causes of wear or damage to the impeller are: Impeller imbalance or improper installation; Due to the bending of the pump shaft, the pump shaft is not concentric with the power machine shaft, the bearing or packing wears too much, etc.; the mud sand erosion wears into the groove. The debris is sucked into the impeller, destroying the impeller, causing cavitation, creating cellular voids. If the impeller wears too much or has been damaged, the new impeller should generally be replaced. The partial damage can be repaired by welding, and the impeller can also be repaired with epoxy resin mortar. That is, a layer of epoxy resin mortar is applied to the entire worn blade, and a better control effect can be obtained. The repaired impeller should generally be subjected to a static balance test.

Three, pressure water room

1. Function and structure: Pump water pressure chamber is composed of volute and guide vane. The function of the pressure chamber is to eliminate the rotational movement of water and convert it into pressure energy to send the water to the outlet pipe or the next impeller. Centrifugal pump and mixed flow pump common pressure chamber is spiral, known as the scroll. Vortex is generally used single-stage single-suction, single-stage double-suction, multi-stage open-type pumps.

2, maintenance: due to hot and cold, excessive pressure or improper installation, handling collisions and other reasons, may cause the volute or vane body cracks. Check generally use a small hammer to gently tap the pump shell, if the sound is broken and dumb, indicating that there is a crack, to determine the location and length, can be poured on the pump shell kerosene, then wipe dry, and then coated with a layer of white powder, along the crack The white powder appeared spotted due to the kerosene emission, and cracks were clearly visible. For cracks that are not long and the sealing requirements are not strict, a small hole can be drilled at both ends of the crack to make the crack no longer expand, as a temporary solution. Cracks and sealing requirements should be cold and hot welding.

In addition, during the operation of the pump, close attention should be paid to the parts and devices such as the mouth ring, bearing, elbow, shaft seal, etc. The failure should be promptly checked and repaired to ensure the normal operation of the pump.

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