【 Cause of malfunction 】
① The speed of the water pump is too high.
② The pump shaft of the water pump is bent, and the bearings are severely worn or damaged.
③ The packing of the water pump packing box is too tight.
④ The impeller of the water pump is stuck by debris or has severe friction with the pump casing.
⑤ The flow rate of the water pump is too high.
⑥ The two transmission shafts driven by couplings are not coaxial or the transmission belt is too tight.
⑦ The power of the power machine supporting the water pump is too low.
⑧ The head of the water pump is too high.
[Maintenance Method]
① The idea is to reduce the speed of the water pump (by replacing pulleys with different diameters) or switch to a lower speed water pump to match the speed of the power machine.
② After parking. Disassemble the water pump body and inspect the pump shaft and bearings. If the pump shaft is bent, it should be straightened, repaired or replaced.
a. The method of straightening the water pump shaft is to take out the water pump shaft for bench calibration and identify the bent part. If necessary, a dial gauge can be used on the platform or lathe for inspection, or the pump shaft can be mounted on a V-shaped iron. First, place the V-shaped iron firmly, then support the dial gauge with the stem pointing towards the axis, and slowly turn the pump shaft. With the shaft bent, every revolution, the dial gauge has a maximum reading and a minimum reading, and the difference between the two readings is the bending degree of the shaft. There are many methods to straighten the pump shaft, and the simplest and most practical one on site is the twisting method: when straightening the shaft, place it on a hardwood (or a square iron with copper foil), requiring the support to be softer than the twisting rod and have a larger contact surface with the twisting rod. With the concave surface facing downwards, use a hammer or a twisting rod to strike. When striking, start from the place with the highest curvature, and the range of impact is 1/3 of the circumference, which can be pre drawn on the axis. The number of hits on the center of the 1/3 arc should be higher, and the number of hits on both sides should be lower. At first, it straightens faster, but later it slows down. During the twisting process, it is also necessary to measure the changes in the bending of the shaft in a timely manner; If the bearing is worn or damaged, it should be repaired or replaced.
b. There are two methods for disassembling bearings: one is to disassemble at the length of the shaft; One is to disassemble inside the end cover.
Use a specialized puller to pull the bearing out of the shaft; If there is no puller, use a copper rod with a wedge-shaped end to support the inner ring of the bearing in an inclined direction. While tapping with a hammer, move the copper rod along the inner ring of the bearing to evenly distribute the force near the bearing until the bearing is knocked off; In addition, two thick iron plates can be used to clamp the bearing under the inner ring of the bearing, and supported by a cylinder or bracket that can accommodate the shaft. A thick wooden board or copper plate can be placed on the upper end of the shaft and tapped to remove the bearing. Because the fit between some end cap bearing holes and the outer ring of the bearing is tighter than the fit between the inner ring of the bearing and the shaft. Therefore, when disassembling the end cap, the bearing should be left in the bearing hole of the end cap. When disassembling the bearing, place the end cap stopper facing upwards steadily, and place a wooden board around the bearing hole of the end cap, but be careful not to press against the bearing. Then use a copper rod or other metal rod with a diameter slightly smaller than the outer edge of the bearing to press against the outer ring of the bearing, and use a hammer to knock out the bearing from above.
c. Remove the bearing from the shaft and clean it thoroughly in cleaning oil (kerosene, diesel, gasoline).
d. Firstly, inspect the ball bearings and inner and outer raceways for defects such as scratches, cracks, or rust spots. Then, fix the inner ring of the bearing and let it roll. If the bearing is normal, it should be in rotational balance, with an average speed, no noise, and a vertical rest; If the bearing is abnormal, it will manifest as noise, vibration, twisting, or sudden cessation of rolling. Or when pushing the bearing by hand, there may be collision sounds or excessive tactile clearance.
e. Repair methods for bearing failures: Based on the cause of the bearing failure and the degree of wear, exchange use and replacement repair methods are generally used. The exchange use method is to exchange the position of the load end (with severe bearing wear) with the non load bearing when the wear of the bearing does not exceed the agreed value and can still be inherited for use; The replacement repair method means that when the outer or inner ring of the bearing is cracked, the ball is broken, the bracket between the balls is broken, the bearing body is severely discolored and annealed, the raceway has deep scratches or rust pits, and the bearing wear exceeds the allowable value, a new part should be replaced.
③ After parking, use a wrench to adjust the cover screw of the water pump packing box, based on the pump shaft rolling freely and moderate water leakage (usually 60 drops per minute).
④ After parking, disassemble the water pump body and check the working condition of the impeller. If there are impurities entangled around the impeller, the impeller should be removed and the entangled objects should be cleaned up; If friction is caused by a small gap between the impeller and the pump casing, the gap between the impeller and the pump casing should be adjusted to a larger value.
⑤ Appropriate measures can be taken to reduce the outflow rate of the water pump to eliminate it. There are many methods to adjust the flow rate of a water pump, and the four most common ones are as follows:
One is the variable flow regulation method, which adjusts the flow rate by changing the opening degree of the gate valve on the outlet pipeline of the water pump. Its advantage is that it can ensure the balance between the water output of the pump and the water inflow of the well, avoiding the forced shutdown caused by excessive pumping, which exposes the water inlet of the pump. The disadvantage is that it can cause pump vibration and shorten the service life of the equipment. Therefore, it is generally not advisable to use this method to regulate flow.
The second method is variable speed regulation, which adjusts the flow rate by reducing (increasing) the speed of the water pump. The change in water pump speed can be achieved by replacing water pump pulleys with different diameters or changing the speed of the power machine. It should be noted that the decrease in water pump speed should not exceed 30% of the rated speed, and the increase should be controlled within 10% of the rated speed. In general, this method should be preferred.
The third method is variable diameter adjustment, which means turning the outer diameter of the impeller appropriately to reduce the flow rate and head of the water pump.
The fourth is the variable pressure regulation method, which is a method of reducing the number of impeller stages in multi-stage centrifugal pumps to reduce the flow and head of the water pump, improve the efficiency of the device, and achieve the goal of economic operation.
⑥ Check the transmission condition of the drive shaft and belt after parking. If a coupling is used for transmission, the installation positions of the power machine and water pump can be adjusted to align the two shafts on the same axis. If a belt drive is used, the tension of the belt should be adjusted reasonably.
a. Coupling installation method
Place the steel ruler on the two halves of the coupling, then roll the motor shaft by hand, rotate 180 °, and check if the height of the two halves of the coupling is consistent. If the height is inconsistent, it should be corrected by increasing or decreasing the thickness of the anti vibration material under the motor base until the height is consistent. Once the two machines are in coaxial position, the coupling and motor can be fixed separately, and the installation bolts and nuts can be tightened.
b. Correction method for non coaxial transmission shaft
⑦ According to the technical parameters indicated on the water pump nameplate, reconfigure the power machine to meet the power requirements of the water pump.
⑧ The following methods can be used to adjust the high head of the supporting water pump:
One is to appropriately reduce the speed of the water pump to reduce the head and eliminate the overload of the power machine. This method has a large adjustment range, but the deceleration should not exceed 30% of the rated speed. For water pumps that use belt transmission, it can be achieved by replacing pulleys with different diameters.
The second method is to turn the impeller of the water pump or replace it with a smaller one to reduce the head of the water pump, but this method has a limited range of adjustment.
The third is to replace the low head water pump that matches the power machine.
