First, self-priming centrifugal pump structure and working principle 1.1 self-priming centrifugal pump structure Self-priming centrifugal pump structure can basically be divided according to the shaft position horizontal self-priming centrifugal pump and vertical self-priming Centrifugal pump two categories, at the same time according to the pressure chamber type, inhalation can be divided into the volute and guide vane. Self-priming centrifugal pump composition is relatively simple, mainly consists of four parts: the prime mover, impeller, pump housing and shaft seal device. The prime mover is a self-priming centrifugal pump power plant, generally through the coupling drive or other drive way to connect it with the pump body to provide kinetic energy; impeller generally 6-12 after the curved leaves, its main role is to The mechanical energy of the prime mover is transmitted to the fluid being delivered. The pump housing, also known as the volute, is a transformable device that collects the liquid thrown by the impeller. The shaft seal is a seal between the pump shaft and the pump housing. Its role is to prevent high pressure liquid from leaking out of the pump housing along the perimeter of the shaft or outside air entering the pump housing. 1.2 self-priming centrifugal pump works to the common pump, for example, before the start of the pump housing should be filled with liquid, start the impeller driven by the motor high-speed rotation, when the impeller rotation, the impeller inlet water pressure drops below Atmospheric pressure, and along the radial direction of the impeller water pressure continues to rise, much higher than the atmospheric pressure, thus, in the intake pipe to form a certain suction. Atmospheric pressure in the outside world, the low water pushed open the inlet valve, along the inlet pipe into the pump casing, thrown into the outlet pipe by the impeller. Second, self-priming centrifugal pumps and troubleshooting suggestions Self-priming centrifugal pump failure due to a variety of reasons, the common equipment failure, installation failure , Operating faults and selection errors. Such as: the pump can not start normally, the pump is not water or lack of flow, pump vibration and noise, bearing fever, pump power, cavitation etc [4]. To determine the self-priming centrifugal pump failure, it should be combined with the basic indicators of equipment status and rich experience in the maintenance diagnosis, the following describes some common faults. 2.1 Startup Failure 2.1.1 Motor does not start properly If the motor is used as a prime mover, first manually turn the motor cooling fan to see if the rotation is flexible: If it is flexible, the starting capacitor may be invalid or the capacity is reduced. When the same value Start the capacitor; If you can not move, indicating the rotor is stuck, when the rust after cleaning grease, or remove foreign matter card rotor. 2.1.2 pump reverse rotation Encounter such cases occur in the first use, this time should be immediately shut down, such as the motor, should be replaced any two-phase three-phase power supply, pump rotation direction can change, if the diesel engine For power, you should consider the belt connection. 2.1.3 self-priming centrifugal pump does not turn after rotation as normal rotation but no water, may be due to 1) the suction port blocked by debris, should be removed after the installation of filtration devices; 2) suction pipe or instrument leakage may be caused by 3) When the water absorption is too high, it should be reduced 4) The cavitation occurs in the impeller; 5) The water injected into the pump is not enough; 6) The air in the pump , Emptying method is to close the pump outlet regulating valve, open the loop valve; 7) water resistance is too large, should check the length of the water pipe or cleaning the outlet pipe; 8) pump speed is not enough, should increase the pump speed. 2.2 Operation Failure 2.2.1 The reasons for lack of flow or stoppage are as follows: 1) impeller or inlet and outlet pipes are blocked and the impeller or pipe should be cleaned; 2) the sealing ring and impeller should be worn seriously and the damaged seal ring or impeller should be replaced; 3) the pump shaft speed is lower than the specified value, the pump speed should be adjusted to the specified value; 4) the bottom valve opening degree is not enough or the check valve is blocked, should open the bottom valve or parking check valve; , So that the pump inhaled air; 6) suction pipe leaks; 7) packing leaks; 8) seal ring wear, the new seal ring should be replaced or impeller round, with thick seal ring; 9) Serious wear and tear; 10) excessive sand in the water, should increase the filtering facilities or to avoid boot. 2.2.2 Abnormal sound or excessive vibration Pump in normal operation, the entire unit should be smooth, the sound should be normal. If the unit has a noise or abnormal vibration, it is often a precursor to pump failure, should be immediately shut down to check and eliminate hidden dangers. The causes of vibration of pump unit is very complex, mainly from the cause of vibration caused by mechanical, hydraulic, electrical and so on, from the vibration mechanism to see the main increase in vibration, stiffness, and resonance. The reason may be: Mechanical: 1) impeller balance is not calibrated, when the moment of correction; 2) shaft and motor shaft is not the heart, when corrected; 3) the foundation is not strong, arm support is not strong, 4) The pump or motor rotor is unbalanced. Hydraulic aspects: 1) Suction is too large, the impeller inlet cavitation; flow through the impeller in the low pressure zone bubbles, collapse to the high pressure bubble, resulting in impact caused by vibration, this time should reduce the pump installation height; 2) Pump running at non-design point, the flow is too large or too small, will cause the pump pressure changes or pressure pulsation; 3) Pump suction foreign body, clogged or damaged impeller, should be shut down clean. 4) Into the pool shape is irrational, the dragon is when several pumps run in parallel, the inlet pipe layout improper, there is a vortex pump suction conditions worse. Resonance caused by vibration, mainly the rotor's natural frequency and pump speed generated when, should be for the reasons for the above failure to make a judgment to take the appropriate solution. 2.2.3 bearing overheating operation, if the bearing hot, should check the reasons for the following aspects and for processing: 1) lack of oil, or poor oil circulation; 2) poor quality lubricating oil, impurities, bearing corrosion, wear and rotation Flexible; 3) bearing wear and tear; 4) pump and motor are not the same; 5) bearing inner ring with the pump shaft journal fit too loose or too tight; 6) belt belt drive too tight; 7) Large, one by one impeller balance hole to clear [3,5,6]. 2.2.4 Excessive pump power consumption If there is abnormal ammeter reading during the operation of the pump, if the motor is overheating, it may be that the pump is over-powered and may cause the following reasons: 1) Some rotating parts in the pump are rubbing, such as impeller and seal ring, Impeller and housing; 2) pump speed is too high; 3) the proportion or viscosity of the delivered liquid exceeds the design value; 4) the packing is too tight or the stuffing box is not filled with water; 5) the bearing is worn or damaged; Or axis offset; 7) pump operation deviates from the design point to operate at high flow rates. The third self-priming centrifugal pump routine maintenance 3.1 self-priming centrifugal pump use matters needing attention 3.1.1 pre-boot preparation To ensure the safe operation of the pump, boot before doing the necessary checks: first slow-coupling by hand Or pulleys, observe the pump steering is correct, the rotation is flexible, smooth, the pump with or without debris, the bearings are running properly, the belt tension is appropriate; Check all the screws are solid; Check the unit there is no interference with running debris; Check Submerged depth of suction pipe is sufficient; have to close the valve to reduce the starting load, and pay attention to start the valve should be promptly opened. 3.1.2 Check in operation After the boot, should check whether the various instruments work properly, stable, the current should not exceed the rated value. Gauge pointer should be in the design range; check the water pump is normal, check the various parts of the unit is leaking; check packing compaction, usually at the filler should be a small amount of leakage (no more than 10 to 20 drops per minute), machinery Seal leakage should not be greater than 10 ml / h (about 3 drops per minute); rolling bearing temperature should not be higher than 75 ℃; sliding bearing temperature should not be higher than 70 ℃. And pay attention to the presence or absence of abnormal sound, abnormal vibration, reduce the amount of water; timely adjustment of the submerged depth of the water inlet; regular removal of trash floating debris; through the belt drive, but also pay attention to whether the belt slipping. 3.1.3 Shutdown and shutdown precautions Shutdown valve should be shut down before shutdown to prevent water backflow, damage to the parts; each shutdown, should promptly wipe the pump body and pipeline grease, keep the appearance of the unit Clean, and timely detection of hidden dangers; winter shutdown, the water should immediately drain the net, to prevent cracking the pump body and internal parts; after the end of the season, to carry out the necessary maintenance [7]. 3.2 self-priming centrifugal pump periodic inspection Self-priming centrifugal pump cycle inspection can be divided into the following three general: 1) routine inspection,
