What to maintain the diesel water pump
The basic structure of diesel water pump is composed of impeller, pump body, pump shaft, bearing, sealing ring and stuffing box.
The impeller is the core part of the high-lift self-priming pump. It has a high speed and a large output, and the blades on the wheel play a major role. The impeller must pass a static balance test before assembly. The inner and outer surfaces on the impeller are required to be smooth to reduce the frictional loss of the water flow.
The pump body is also called the pump casing, which is the main body of the water pump. It plays the role of supporting and fixing, and is connected with the bracket on which the bearing is installed.
The function of the pump shaft is to connect the motor with the coupling and transmit the torque of the motor to the impeller, so it is the main component for transmitting mechanical energy.
The bearing is a component that is sleeved on the pump shaft to support the pump shaft, and there are two types of rolling bearings and sliding bearings. Rolling bearings use tallow as a lubricant to refuel. Generally, the volume of 2/3 to 3/4 is too much, and it will generate heat. If it is too small, it will make noise and generate heat. Sliding bearings use transparent oil as lubricant, add oil to the oil level line. Too much oil will seep along the pump shaft and float, and too little bearing will overheat and burn out, causing an accident.
The sealing ring is also called the leakage reducing ring. If the gap between the impeller inlet and the pump casing is too large, the water in the high-pressure area of the pump will flow to the low-pressure area through this gap, which will affect the water output of the pump and reduce the efficiency! If the gap is too small, the friction between the impeller and the pump casing will cause wear and tear. In order to increase the backflow resistance, reduce internal leakage, and delay the service life of the impeller and the pump casing, a sealing ring is installed at the joint between the inner edge of the pump casing and the impeller external aid, and the sealing gap should be kept between 0.25 and 1.10mm.
The water pipeline must be highly sealed, and check whether the connection between the water pump and the water pipeline is loose.
To add bearing lubricating oil to the bearing body to observe that the oil level should be at the center line of the oil mark, and the lubricating oil should be replaced or supplemented in time. After the oil-immersed water pump works for 500 hours, it is necessary to replace the sealed oil. The oil in the pump motor cavity should be changed once a year.
Jog the pump motor to see if the pump motor turns correctly. When the pump runs normally, open the outlet pressure gauge. If the pressure is suitable, gradually open the gate valve, and check whether the pump motor has a load.
If the pump has any small fault remember not to let it work. If the packing of the water pump shaft is worn out, it should be added in time. If the diesel water pump is continued to be used, air will leak. The direct effect of this is that the energy consumption of the motor increases and the impeller is damaged.
If the pump vibrates strongly during use, be sure to stop and check the cause, otherwise it will also cause damage to the pump.
When the bottom valve of the water pump leaks, some people will fill the inlet pipe of the pump with dry soil and flush the bottom valve with water, which is not advisable. Because when the dry soil is put into the water inlet pipe, the dry soil will enter the pump when the pump starts to work, which will damage the pump impeller and bearing, which shortens the service life of the pump. When the bottom valve leaks, it must be repaired. If it is serious, it needs to be replaced with a new one.
After using the water pump, you must pay attention to maintenance. For example, when the water pump is used up, the water in the water pump should be cleaned up. It is best to remove the water pipe and rinse it with clean water.
The tape on the pump should also be removed, then rinsed with water and dried in the light. Do not put the tape in a dark and damp place. The tape of the water pump must not be stained with oil, let alone some sticky things on the tape.
Carefully check whether there are cracks on the impeller, and whether the impeller is fixed on the bearing for looseness. If there are cracks and looseness, it should be repaired in time. If there is mud on the pump impeller, it should be cleaned up.
During the long-term operation of the water pump, wear of the bearing chamber of the water pump bearing frame, wear of the bearing position, cracks and rupture of the pump body, cavitation of the water pump, and erosion wear often occur.
After the above problems occur, the solution is to repair welding or brush plating after machining, both of which have certain drawbacks. The thermal stress generated by the high temperature of repair welding cannot be completely eliminated, which is easy to cause material damage, resulting in bending or breaking of parts;
The brush plating is limited by the thickness of the coating, which is easy to peel off, and the above two methods use metal to repair the metal, which cannot change the “hard-to-hard” cooperation relationship, and will still cause re-wear under the combined effect of various forces.
Self-priming water pump is a kind of water conservancy machinery for pumping water. Excellent performance, deep suction, large flow, labor-saving and time-saving operation, is the best water pump machinery in the real society. The self-priming water pump starts the motor, the power is linked, the rotating assembly is driven by the impeller centrifuge, the bubbles surge upward, generating suction, the air in the water inlet pipe is discharged out of the pump body through the water outlet pipe, the air is drained, and the water passes through the water outlet pipe outflow.
Self-priming, as the name implies, is that when the suction pipe of the pump is filled with air, the negative pressure (vacuum) formed when the pump is working is used to raise the water pressure lower than the suction port under the action of atmospheric pressure, and then discharge from the drain end of the pump . Before this process, there is no need to add “water diversion (water for guiding)”. A pump with this capability is called a “self-priming pump”.
Some centrifugal or rotary vane pumps must add “water diversion” to form a closed environment in the pump cavity before absorbing water, and then the pump can run to form a negative pressure to achieve the purpose of absorbing water. For example, the manual water pump used in rural areas. Pumps without self-priming ability must add “water diversion” before each suction.
The height of self-priming is called the suction stroke. The unit is usually meters.
Also called the maximum self-priming height. That is, the maximum height that the pump can automatically suck up the water without adding water (the vertical distance between the pump inlet and the liquid surface to be pumped). Our pumps are all self-priming pumps, and the marked suction lifts refer to this situation. Some centrifugal pumps have no self-priming ability, and water must be added for the first use. Although some diaphragm pumps also have self-priming ability, the standard suction stroke is often different from the vertical height that can pump water when the inlet pipe is full of air. Please pay attention to this.
The height of the suction stroke is related to the power, flow, structure, etc. of the pump, but limited by the volume and power, the self-priming suction stroke of the general miniature water pump is not easy to make higher, because one atmospheric pressure can increase the water pressure at most At a height of 10.3 meters (because of the pressure generated by an atmospheric pressure ≈ 10.3 meters of water column), the maximum self-priming suction range is about 10.3 meters. However, in actual operation, due to the sealing performance, the suction lift generally does not exceed 6.5 meters.
Centrifugal water pump consists of pump casing, impeller, pump shaft, pump frame, etc.
Before starting, the pump should be filled with water. After starting, the rotating impeller drives the water in the pump to rotate at a high speed. After the water is thrown out, the pressure near the impeller is reduced, and a low pressure area is formed near the rotating shaft. The pressure here is much lower than the atmospheric pressure, and the water outside is under the action of atmospheric pressure, and the bottom valve is flushed and enters the pump from the water inlet pipe. The rushing water is thrown out again with the high-speed rotation of the impeller, and is pressed into the water outlet pipe. The impeller is continuously rotated at high speed by the power machine, and the water is continuously pumped from the low to the high.
The total head of the pump = suction head + pressure water head, where the suction head is determined by atmospheric pressure.
The pumping height of the centrifugal pump is called the lift. It uses the method of “sucking in” and “throwing out” to pump water.
The first-stage lift is called the “suction lift”, which relies on the rotation of the blades to form a low-pressure area, and presses the water into the low-pressure area by atmospheric pressure, and 1 standard atmospheric pressure can support a water column with a height of 10.336 meters, so the limit value of the suction lift is 10.336 meters;
The second-stage lift is called “pressed water lift”, and the water is thrown out by the rotation of the blades.
Therefore, the head of the centrifugal pump is the sum of the two-stage head, that is, its pumping height is far more than 10.336 meters.
What are the misunderstandings in the use of centrifugal pumps?
Some people use high-lift pumps for low-lift pumping. Many operators believe that the lower the pumping head, the smaller the motor load. Under the misunderstanding of this misunderstanding, when purchasing a water pump, the pump head is often selected to be very high. In fact, for centrifugal pumps, when the model of the pump is determined, the power consumption is proportional to the actual flow of the pump. The flow of the pump will decrease with the increase of the lift, so the higher the lift, the smaller the flow and the smaller the power consumption. Conversely, the lower the lift, the greater the flow and the greater the power consumption. Therefore, in order to prevent the motor from overloading, it is generally required that the actual pumping head of the pump should not be lower than 60% of the nominal head. Therefore, when the high head is used for pumping water with a low head, the motor is easily overloaded and heated, and the motor can be burned in severe cases. For emergency use, a gate valve for adjusting the water output must be installed on the water outlet pipe (or block the small water outlet with wood or other objects) to reduce the flow and prevent the motor from overloading. Pay attention to the temperature rise of the motor. If the motor is found to be overheated, the flow rate of the water outlet should be reduced or shut down in time. This is also prone to misunderstanding. Some operators think that blocking the water outlet and forcibly reducing the flow will increase the motor load. In fact, on the contrary, the regular high-power centrifugal pump drainage and irrigation units are equipped with gate valves on the outlet pipes. In order to reduce the motor load when the unit starts, the gate valve should be closed first, and then the gate valve should be gradually opened after the motor starts.
Some people will use large-diameter water pumps with small water pipes to pump water. Many operators think that this can increase the actual head. In fact, the actual head of the pump = total head ~ loss head. When the model of the pump is determined, the total head is fixed; the loss of head mainly comes from the resistance of the pipeline. The smaller the pipe diameter, the greater the resistance and the greater the loss of head. Therefore, after reducing the pipe diameter, the actual head of the pump can’t be increased. , but will reduce, resulting in a decrease in pump efficiency. Similarly, when the small-diameter pump uses a large water pipe to pump water, the actual lift of the pump will not be reduced, but the loss of lift will be reduced due to the reduction of the resistance of the pipeline, which will increase the actual lift. There are also operators who think that when a small-diameter pump uses a large water pipe to pump water, it will inevitably increase the motor load. They think that after the pipe diameter is increased, the water in the outlet pipe will put more pressure on the pump impeller, which will greatly increase the motor load. As everyone knows, the size of the liquid pressure is only related to the height of the lift, and has nothing to do with the cross-sectional area of the water pipe. As long as the lift is constant, the size of the impeller of the pump remains the same, no matter how big the pipe diameter is, the pressure acting on the impeller is constant. Only after the diameter of the pipe increases, the water flow resistance will decrease, and the flow rate will increase, and the power consumption will also increase appropriately. However, as long as it is within the rated lift range, no matter how the pipe diameter is increased, the pump can work normally, and it can also reduce the loss of the pipeline and improve the efficiency of the pump.