First, the common easy-to-failure problems and disposal of centrifugal pumps

1.1 The reason why the pump can not be started or the starting load is large and its disposal method is as follows:

(1) The prime mover or power supply is abnormal. The disposal method is to check the condition of the power supply and prime mover.

(2) Pump stuck. The disposal method is to check the coupling by hand, if necessary, to check for breakdowns, and to eliminate static and dynamic parts.

(3) The packing is too tight. The solution is to relax the packing.

(4) The discharge valve is not closed. The disposal method is to close the discharge valve and restart it.

(5) The equilibrium pipe is not smooth. The disposal method is to balance the balance.

1.2 The reason why the pump can not be started or the starting load is large and its disposal method is as follows:

(1) The lack of irrigation pump (or the pump gas is not discharged). The disposal method is to refill the pump.

(2) The pump is not steered correctly. The solution is to check the direction of rotation.

(3) The pump speed is too low. The disposal method is to check the speed and improve the speed.

(4) Infarction of the filter, the bottom valve is not working. The disposal method is to inspect the filter screen and remove impurities.

(5) The suction height is too high, or the suction tank presents a vacuum. The disposal method is to reduce the suction height; check the suction tank pressure.

1.3 The reason for the infix of the pump after draining the liquid and its disposal are as follows:

(1) Leakage in the suction line. The disposal method is to check the joints at the suction side and the sealing condition of the stuffing box.

(2) The suction side gas is not discharged when the pump is priming. The solution is to request a refill pump.

(3) The suction side is suddenly blocked by foreign matter. The disposal method is to stop the pump from handling foreign materials.

(4) Inhale large amounts of gas. The disposal method is to check whether the suction inlet is vortexed and whether the engulfing depth is too shallow.

1.4. The reason for the lack of flow and its disposal are as follows:

(1) Same as b, c. The disposal method is to take corresponding measures.

(2) Increased system static head. The disposal method is to check the liquid level and system pressure.

(3) Increased resistance loss. The disposal method is to check the pipeline and non-return valve and other obstacles.

(4) Excessive wear of the wear ring of the housing and the impeller. The disposal method is to change or repair the wear ring and impeller.

(5) Leakage of other parts. The disposal method is to check shaft seals and other parts.

(6) Pump impeller infarction, wear, corrosion. Disposal methods are cleaning, inspection, and interchangeability.

1.5. The reasons for the insufficient head and disposal methods are as follows:

(1) Same as (1), (2), (3), (4) of b, (1) of c, (6) of d. The disposal method is to take corresponding measures.

(2) Inverted impeller (double suction wheel). The disposal method is to check the impeller.

(3) Liquid density, viscosity and design conditions do not match. The solution is to check the physical properties of the liquid.

(4) The flow rate during operation is too large. The solution is to reduce traffic.

1.6. Reasons for the large power consumption in operation and its disposal methods are as follows:

(1) The impeller and wear ring, impeller and shell are ground. The disposal method is to check and repair.

(2) Same as item (4) of e. The solution is to reduce traffic.

(3) Increased liquid density. The solution is to check the liquid density.

(4) The packing is pressed too tightly or dryly. The disposal method is to relax the packing and check the water seal tube.

(5) bearing damage. The disposal method is to check the repair or change the bearings.

(6) The speed is too high. The disposal method is to check the driver and power supply.

(7) The pump shaft is bent. The solution is to correct the pump shaft.

(8) Axial force equilibrium installation failed. The solution is to check the balance hole and whether the return pipe can block.

(9) Coupling misalignment or axial clearance is too small. The disposal method is to check the alignment and adjust the axial clearance.

1.7. Causes and disposal methods of pump vibration or abnormal noise are as follows:

(1) Same as (4) in c, (5), (7), (9) in f. The disposal method is to take corresponding measures.

(2) The vibration frequency is 0~40% working speed. Too large bearing clearance, loose bearing shell, impurities in the oil, oil quality (viscosity, temperature) is bad, because the air or process liquid makes the oil blistering, smooth and bad, bearing damage. The disposal method is to take corresponding measures after the inspection, such as adjusting the bearing clearance, clearing the impurities in the oil, and changing the new oil.

(3) The vibration frequency is 60%~100% working speed. The bearing problem is the same as (2), or the seal gap is too large, the retainer is loose, and the seal wears. The disposal method is to check, adjust or change the seal.

(4) The vibration frequency is 2 times the operating speed. Misalignment, loose coupling, seal installation friction, shell deformation, bearing damage, bearing resonance, thrust bearing damage, shaft bending, poor fit. The disposal method is inspection, take corresponding measures, repair, adjustment or change.

(5) The vibration frequency is n times the working speed. Pressure pulsation, not center, shell deformation, seal friction, bearing or root resonance, pipe, machine resonance, disposal method is the same (4), strengthening the root or pipeline.

(6) The vibration frequency is very high. Shaft friction, seals, bearings, inaccuracies, bearing tremors, poor shrinkage, etc. The disposal method is the same as (4).

1.8. Causes of bearing heating and its disposal methods are as follows:

(1) The scratching of the bearing pad does not meet the request. The solution is to re-repair the bearing pad or change it.

(2) The bearing clearance is too small. The disposal method is to readjust the bearing clearance or scraping.

(3) The lack of smooth oil and poor oil quality. The disposal method is to increase the oil volume or change the smooth oil.

(4) Poor bearing assembly. The disposal method is to check the bearing assembly status according to the request and eliminate the request element.

(5) Cooling water circuit. The disposal method is inspection and repair.

(6) The bearing is worn or loose. The disposal method is to repair the bearing or scrap it. If you loose, tighten the bolts.

(7) The pump shaft is bent. The solution is to correct the pump shaft.

(8) The oil-stripping ring is deformed, and the oil-stripping ring cannot be rotated and it is not oiled. The disposal method is to update the oil throw ring.

(9) Coupling misalignment or axial clearance is too small. The disposal method is to check the alignment and adjust the axial clearance.

1.9. Causes of shaft seal heating and disposal methods are as follows:

(1) The packing is too tight or abrasive. The disposal method is to relax the packing and check the water seal tube.

(2) Displacement of the water seal ring and the water seal tube. The solution is to recheck the alignment.

(3) rinse, cool good. The disposal method is to check the flushing cooling circulation pipe.

(4) There is something wrong with the mechanical seal. The disposal method is to check the mechanical seal.

1.10. The reasons for the large rotor agitation and its disposal are as follows:

(1) improper operation, operating conditions away from the pump design conditions. Disposal methods: Strict operation, so that the pump has been operating near the design conditions.

(2) Balance is not smooth. The disposal method is to balance the balance.

(3) The balance plate and the balance plate material do not meet the request. The disposal method is to change the balance plate and balance tray of the material conformity request.

1.11. Causes of water attack and disposal methods are as follows:

(1) Due to a sudden power outage, the pressure of the system is shaken, and the negative pressure of the discharge system is present. The bubbles dissolved in the liquid escape to cause gas to exist in the pump or pipeline. The disposal method is to drain the gas.

(2) The high-pressure liquid column is suddenly poured back due to a sudden power failure, and the impact is on the check valve plate of the pump outlet. The disposal method is to stop the transformation of the piping and pipeline accessories of the unreasonable discharge system of the pump.

(3) The valve of the outlet pipe is closed too quickly. The solution is to gradually close the valve <br> <br> Second, the major parts of centrifugal pumps

2.1 Pump casing The pump casing is available in both axial and radial sections. Most single-stage pump casings are volute-type, and the multi-stage pump radial split casing is generally an annular casing or a circular casing. Ordinary volute-type pump casing spiral chamber is used to collect the liquid thrown from the impeller and lead to the diffuser to the pump outlet. The pump housing receives the full working pressure and thermal load of the liquid.

2.2 Impeller The impeller is the only part that performs the work. The pump passes through the impeller to perform work on the liquid. Impeller type has closed, open, semi-open three. The closed impeller consists of blades, front cover and rear cover. The semi-open impeller consists of a blade and a rear cover. As long as the open impeller blade, no front cover. The closed impeller has a higher efficiency and the open impeller has a lower efficiency.

2.3 Seal ring The function of the seal ring is to avoid leakage and leakage of the pump. The seal ring made of wear resistant material is fitted on the front and rear covers of the impeller and the pump casing. It can be replaced after wear.

2.4 Shaft and bearing The shaft is fixed at one end of the pump shaft and the coupling is mounted at one end. Depending on the size of the pump, bearings can be used with rolling and plain bearings.

2.5 Shaft Seal Shaft seals are usually mechanical seals and packing seals. Common to both the pump means are designed packing seal, mechanical seal means can <br> <br> three main parts of the detection and repair of centrifugal pump

3.1 impeller repair. Impeller friction with other parts, the resulting partial wear, can be used to repair welding. Impeller thickness reduction, cast iron impeller pores or slag inclusions, and cracks, is usually replaced with new spare parts or use "welding method repair welding method" to stop the repair. Filler impeller impeller at the inlet and outlet ends, the radial runout should not exceed 0.05mm. If there is not much (less than 0.1mm), the car goes to 0.06 to 0.1mm. If there is a lot of overshoot, the straightness of the pump shaft should be checked and the pump shaft should be straightened to eliminate the radial runout of the impeller. 3.2 sleeve repair. When the amount of wear is small, surfacing is used to stop the repair. If wear is severe and wear scars are deeper, new bushings should be replaced.

3.3 Pump shaft repair. After the direction of the bending and the bending of the pump shaft are measured, the straightening of the pump shaft can be stopped. When the depth of wear is not too large, repair by surfacing. After being surfacing, it is turned to its original size on a lathe. When the depth of wear is large, repairs can be stopped using the “add-on part method”. Axially worn or cracked pump shafts are generally not repaired and replaced with spare parts. The side of the keyway on the pump shaft, if the damage is subtle, can be repaired with a file. If the inclination is severe, the surfacing method should be used to stop the repair. In addition, the repair can be stopped by changing the position of the keyway.

3.4 pump repair. The size of the inner circle of the bore of the rolling bearing of the pump body is worn or presents defects such as steps and grooves. Make the bearing hole size large, and then insert the size of the rear bearing hole. The cast iron pump body exhibits slag inclusions or pores. When the pump body is cracked due to vibration, impact, or impact, repairs are made by repair welding or bonding. Fourth, the detection and maintenance of common wearing parts 4.1 Inspection and measurement of the sealing ring 4.11 Inspection of the wear condition of the sealing ring The wear of the sealing ring usually has two kinds of average wear and partial wear in the circumferential direction. Any kind of radial clearance wear will form the end of the seal ring.

4.12 Measurement of Radial Clearance between the Sealing Ring and the Outer Circle of the Impeller of the Impeller The caliper can be used to measure the radial clearance between the seal ring and the inlet end of the impeller. First measure the inner diameter of the seal ring, then measure the size of the outer diameter of the impeller inlet, and then calculate the radial gap between them to stop the control. If the limit clearance value is reached, a new seal ring should be replaced. Regarding the axial clearance between the seal ring and the impeller, the normal request is not high, and there is a gap between the two, and it is not necessary to attack the friction.

4.2. After the fit between the outer circle of the seal ring and the inner hole of the pump cover, there should not be any looseness. The size of the outer diameter of the seal ring is the size of the repair, and the fitting method can be applied. The interference value is about 0 to 0.02 mm. Finally, use a hammer to drive the seal ring into the hole in the center of the pump cover. The gap between the inner circle of the seal ring and the outer circle of the inlet end of the impeller forms a clearance fit. If the gap is too small, it can be larger or larger in the car, so that the two can maintain a certain radial clearance. If the gap is too large, you should change the new seal ring. The thickness of the seal ring is small and the strength is low. If there is a large wear or breakage, it is usually not repaired, and new spare parts should be replaced.

4.3 Packing seal installation and repair 4.31 Packing seal inspection and measurement The main components of the packing seal are stuffing box shell, packing, liquid seal ring, packing gland, bottom bushing and so on. Inspection and measurement of packing seals should focus on the following aspects:

4.32 Radial clearance between pump housing and bushing Firstly, the inner diameter of the center hole is measured with a vernier caliper, and the outer diameter of the bushing is measured and then calculated. The smaller the value of the radial gap a, the better, but it cannot exhibit friction. When the radial clearance is too large, the phenomenon of “eaten filler” appears. The radial clearance between the pump housing and the sleeve is 0.3~0.5mm.

4.33 radial clearance between the packing gland outer circle and the packing box inner circle? The stuffing box of the centrifugal pump plays a guiding role with regard to the advancement of the packing gland. Radial clearance is too large and packing glands are easily squashed and will incur friction and wear.

4.34 Radial clearance between the inner circle of the packing gland and the outer circumference of the sleeve? The radial clearance between the inner circle of the gland packing of the centrifugal pump and the outer circumference of the sleeve is too small. The inner circle of the packing gland and the outer circumference of the shaft sleeve This will cause friction and frictional heat, causing the filler to coke and fail, causing the gland and sleeve to wear. Under normal conditions, the radial clearance is 0.4~0.5mm.

4.4 Repair of Packing Seal Installation 4.41 Repair of packing gland The radial clearance between the packing gland outer circle and packing box inner circle is 0.1-0.2mm. If the radial clearance is too small, it can be turned or boring to the required size. If the radial clearance is too large, new packing glands should be replaced. The radial clearance between the inner circle of the packing gland and the outer circle of the sleeve is 0.4-0.5mm. If the clearance value is too small, the inner hole car with the packing glands on the lathe should be larger to ensure the proper clearance.

4.5 Mechanical seal installation and repair The mechanical seal of the centrifugal pump is based on a moving ring mounted on the pump shaft and a stationary ring fixed on the inner circle of the packing box. The end faces of the two rings tightly fit each other with the help of the elastic force of the spring and the pressure of the medium.

4.6 Inspection and measurement of mechanical seals 4.61 Inspection of moving and stationary ring surfaces The mating surfaces of the moving and stationary rings in mechanical seals are axially sealed. A 90° square can be used to measure the perpendicularity to the centerline. In addition, there are no non-smooth scratches, cracks, dents, etc. on each surface.

4.62 inspection of sleeves Shafts with different shades of appearance should be removed in time.

4.63 Inspection of springs mainly checks whether springs can break, corrode, or reduce spring force.

4.7 Mechanical seal installations and repairs 4.71 Repair of moving and stationary rings When friction surfaces are worn or cracked, new parts should be replaced. If lighter scratches are present and are not smooth, they should be ground and grinded and polished after rough grinding. After repairing the moving ring and the static ring, the contact surface roughness Ra is 0.2-0.4 μm, and the flatness of the contact surface is not more than 1 μm, and the vertical of the center line is not more than 0.4 mm. Inspection of the contact surface of the moving ring and the stationary ring after grinding: The contact surfaces of the moving ring and the stationary ring are attached together, and the two can only slide relative to each other, and cannot be opened. Grinding is acceptable.

4.72 The repair of the sleeve should be stopped on the grinding machine and should have a surface roughness Ra ≤ 1.6 μm. If the outer diameter of the sleeve is too small after polishing, the clearance between the sleeve and the spring seat, the moving ring and the stationary ring is too large, and a new sleeve should be replaced.

4.73 Replacement of springs Damage to springs is mostly due to corrosion or wear and loss of the original elasticity. For springs that lose their elasticity, new spare parts should be replaced. Mechanically sealed springs can be self-made. Both end surfaces of the wound spring should be flattened so that the force is averaged and the direction of rotation of the spring should be the same as that of the original spring.