After a certain period of use, the fire pump should be disassembled and repaired (the period of medium repair is 6 months, and the period of overhaul is 12 months). The impeller and large mouth ring are vulnerable parts, which should be repaired and replaced regularly. The main damage form of the impeller and the large mouth ring is wear, which causes the change of the fit clearance. When the clearance exceeds a certain value, the efficiency of the pump will drop sharply, accompanied by large vibration and noise. At this time, it must be repaired. The time interval between such damage is generally proportional to the running time of the pump, and the planned preventive maintenance method can generally be adopted.
Generally speaking, the impeller located in the middle of the pump is the most prone to wear (the first stage impeller is made of alloy cast steel, and the other impellers are made of cast iron), and the large mouth ring wears heavily, and the outer diameter of the impeller inlet wears lightly. Cut the outer diameter of the impeller inlet on a lathe, or polish it smooth with emery cloth, and then replace the new ring according to the outer diameter of the repaired impeller inlet to meet the original matching requirements. In order to improve the maintenance efficiency, mark the matching mouth ring and impeller during the repair process to prevent confusion and increase the maintenance amount.
When the outer diameter of the impeller inlet is greatly worn, it can be repaired by surfacing welding, electroplating and spray welding repair methods. When surfacing welding, homogeneous electrodes should be used for surfacing welding. Appears and is then turned on a lathe or ground to size on a grinder. When the outer diameter of the impeller inlet is severely worn or broken, the repair value has been lost at this time, and a new one can be replaced.
During the maintenance of the fire pump, in addition to paying attention to the external wear, attention should also be paid to the internal blockage of the impeller. Because there will be many impurities in mine water, such as small pieces of wood, bark, and small coals. It is often stuck in the flow channel of the impeller, which affects the flow rate and efficiency of the pump. This situation mostly occurs in the first and second impellers and must be removed. Several gaps that need to be guaranteed during the repair process are: the gap between the large and small mouth rings is 0.4-0.5 mm, the matching gap between the outer diameter of the water wheel outlet and the inner diameter of the guide wing inlet is 0.8-1.2 mm, the outer diameter of the balance plate tail sleeve and the string water sleeve The gap of the inner meridian is 0.8-1.0 mm. Common methods for repairing pump shaft bending and straightening of clean water pumps
1. Align the shaft with a manual screw corrector. Put the shaft on the platform, supported by 2 V-shaped irons, let the convex side of the curved part face up, so that the screw can just withstand it, and then rotate the handle to make the head of the screw press the pump tightly. axis. The straightener can be moved in the direction of the shaft bend, and the correction repeated several times until it is completely straightened (with some amount of reverse bending).
2. Tapping and straightening with a twisting rod This method is to tap the curved concave surface of the shaft with a twisting rod, so that the surface of the shaft is extended and straightened. When straightening, put the concave surface of the shaft upwards, and use the apex of the curved convex surface as a support point to support it strictly, press down with clips at both ends, and then hit the twisting rod with a 1~2 kg hammer to make the shaft The concave material surface is extended by striking. First strike from the center of the lowest concave surface, gradually move to both sides, and proceed along the arc surface of 1/3 of the circumference, but the closer to the center, the greater the beating density. Be careful not to damage the surface of the shaft when hitting.
3. Heating and straightening the pump shaft at the convex surface with a large curvature, heating locally, the temperature is controlled below 600 ℃, and then leveling the fulcrums at both ends of the shaft, and placing supporting pads below to maintain the level of the line, and then Apply pressure to the curved (convex) part, and the temperature should rise slowly, not too fast. The heating area and pressure should be determined according to the specific situation. The support plate is lower than the required straightening position, generally 1~4mm, this value is related to the type of shaft material, heating temperature, pressure and force application speed, etc. After the pump shaft is straightened to meet the requirements, apply asbestos heat preservation to the heated part of the shaft for several hours and then cool it down. After straightening, annealing should be performed to allow the shaft to rotate slowly. Heating to about 350°C, keeping it warm for more than 1 hour, then wrapping the heating place with asbestos, rotating the shaft to cool to about 70°C, and then cooling naturally in the air.
Before the fire pump is running, it is necessary to pay attention to debugging, mainly to make the values of all aspects meet the relevant requirements, to ensure that it can be used normally, and there is no abnormality. During debugging, sometimes the pressure does not meet the specified requirements. At this time, we need to consider that the cause of this situation is probably due to the reverse rotation of the motor. If we find the cause, we should prescribe the right medicine. Turn, we need to see the three-phase wires, and it can be solved by exchanging any of their phase sequences.
If there is still a problem after changing the phase sequence, then the outlet pipe of the pump should be provided with some deflation facilities. After the pump has started to run, the outlet valve should be adjusted, and the outlet pressure should reach a certain value, which is normal. , if it is not achieved, it will affect the water output effect of the pump, or cause the pump to run beyond the pressure.
We should also conduct regular checks on the pump below. During the checks, the power supply and circuit of the fire protection system must be kept normal, and the electrical equipment should be normal. During the inspection, the weight of the fire pump should be even and there should be no abnormal sounds. Then check the refueling. The center of the oil window should be used as the standard, and the amount of refueling should be kept in balance with the center line. Sometimes there is definitely no way to be extremely accurate, so the position is slightly lower than the center line, which is also possible. Also, check the pump priming time. All these data need to be recorded.
After the fire pump is started, the floating ball should be running, and there should be no water in the exhaust pipe. If there is water during the inspection, the gasket must be replaced to ensure that the sealing body is tight and the exhaust It is also normal. The main things to be checked regularly are these, and the other is to see whether the various parts of the fire pump are firmly connected and whether they can run smoothly.