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Teach you how to overhaul the centrifugal pump-these details must not be ignored
浏览次数: Time: 2019-09-26 12: 49Views :
Today, we will explain that the centrifugal pump needs to be operated in accordance with the requirements and procedures in the three stages of disassembly, maintenance and reassembly when disassembling and overhauling. When disassembling: 1. Before removing the thrust bearing, use a dial indicator to measure the balance plate clearance and make a record.
Today, we will explain that the centrifugal pump needs to be operated in accordance with the requirements and procedures in the three stages of disassembly, maintenance and reassembly when disassembling and overhauling.
When disintegrating:
1. Before removing the thrust bearing, use a dial indicator to measure the balance plate clearance and make a record;
2. When disassembling the multi-stage pump, the parts must be marked according to the original assembly order, so as to avoid confusion and incorrect installation during reassembly;
3. Small pieces (such as keys) that are not convenient for marking can be put together with the impeller or guide vane (middle section) of the same level;
4. When disassembling, you can intuitively feel if there are abnormal parts, such as loose fit.
During maintenance:
1. Check whether the surface of each part is normal, and the mating surfaces must be free from scratches, rust, etc.
2. Measure whether the tolerance of key coordination parts is qualified;
3. Whether the gaps of the measuring wheel sealing ring, casing sealing ring, guide vane sealing ring, interstage bushing, etc. are within the tolerance range, and the excessive wear needs to be replaced;
4. Check whether the bearing is intact;
5. All seals and gaskets should be replaced with new ones.
When loading:
1. Install the rotor first and re-run the dynamic balance test;
2. Reinstall the parts in the reverse order of disassembling the pump. When reinstalling, pay attention to measure the gap value at each seal ring again to ensure that it is correct;
3. Measure the total rotor string before installing the balance plate;
4. After installing the balance plate, measure the rotor half-string amount;
5. Compared with the total string quantity and half string quantity required on the general assembly drawing of the manufacturer, it should basically meet the drawing requirements. Under normal circumstances, the amount of half string is about half of the total string amount;
6. Tighten the main bolts evenly, paying attention to the angle;
7. Suction a dial indicator on the shaft, and rotate the shaft to meter the balance plate. The tolerance is according to the requirements of the drawing, and generally should not exceed 0.06;
8. When installing thrust bearings, pay attention to adjusting the clearance of the balance disk. Use the adjustment ring in front of the bearing to adjust the clearance of the balance disk to the requirements of the drawing.
9. Each component of the centrifugal pump has a corresponding standard for maintenance, and it must be carried out in strict accordance with the standard during the maintenance.
Pump shaft:
1. Clean and inspect the pump shaft. The pump shaft should be free from cracks, severe wear and other defects. If there is any wear, crack, erosion, etc., it should be recorded in detail and its cause analyzed.
2. Check the straightness of the pump shaft of the centrifugal oil pump, and its value should not be greater than 0.05mm over the entire length. The surface of the journal must be free of defects such as pits and grooves. The maximum allowable value of the surface roughness is 0.8 μm. The journal circularity and cylindricality errors should be less than 0.02 mm.
3. The parallelism error between the centerline of the centrifugal pump keyway and the centerline of the shaft should be less than 0.03mm / 100.
impeller:
1. Clean and inspect the impeller surface at all levels. The impeller surface should be free of cracks, wear and other defects. The surface of the impeller flow channel should be smooth and free from scaling and burrs.
2. Check the seal rings of the suction and discharge ports of the impellers at all levels. There should be no looseness, the surface of the seal rings should be smooth, no burrs, and the maximum allowable value of surface roughness Ra should be 0.8 μm. Taking the impeller inner hole as a reference, check that the radial runout of the impeller is not more than 0.05 mm. End runout is not more than 0.04 mm.
3. The impeller and the shaft adopt interference fit, generally H7 / h6. The interference between the key and the keyway is 0.09 ~ 0.12 mm. After assembly, the clearance at the top of the key of the centrifugal pump is 0.04 ~ 0.07mm.
4. The impeller must be statically balanced.
Pump head, pump casing and guide vane:
1. Clean and inspect the impellers at all levels. There should be no defects such as wear, cracks, erosion, etc.
2. The anti-rotation pin of the centrifugal pump guide impeller should not be bent, broken or loose. The surface of the sealing ring of the pump head and the pump casing should be free of pits, scars, grooves, and the maximum allowable value of the surface roughness Ra is 0.8 μm. The ring should not loosen.
3. Taking the centrifugal pump head and the centrifugal pump casing end as the reference, measure the inner diameter of the seal ring to run round, its value is not greater than 0.50 mm, and the end face round run shall not be greater than 0.04 mm.
4. Measure the gap between the centrifugal pump head, the pump casing seal ring and the assembly seal ring. The value should be between 0.50 and 0.60 mm.
Bearing:
1.Sliding bearings
(1) The interference between the bearing and the bearing gland is 0.02 to 0.04mm. The lower bearing bush is in uniform contact with the bearing seat, and the contact area should be greater than 60%.
(2) When the bearing is replaced, the contact angle between the journal and the lower bearing is 60 to 900 seals. The contact area should be uniform, and the contact points should be not less than 2 to 3 points per square centimeter.
(3) The bearing alloy layer and bearing lining should be firmly combined, and the surface of the alloy layer must not have defects such as pores, slag inclusions, and peeling.
(4) The gap at the top of the bearing should meet the requirements in the table below.
(5) The data on the horizontal plane of the bearing side clearance is half of the top clearance.
2.Rolling bearings
(1) The cooperation between the rolling bearing and the shaft under axial and radial loads is H7 / js6.
(2) The cooperation between the rolling bearing and the shaft that only bear radial load is H7 / k6.
(3) The outer ring of the rolling bearing and the inner wall of the bearing housing are Js7 / h6.
(4) For pumps that use rolling bearings for axial thrust, the axial clearance of the outer ring of the rolling bearings should be 0.02 to 0.06 mm.
(5) When the rolling bearing is disassembled and assembled, the temperature for hot-packing shall not exceed 100 ℃, and direct heating with flame is strictly prohibited.
(6) The surfaces of rolling elements, oil and slideways of rolling bearings should be free of corrosion, pits and spots, and should be smooth and free of noise.
Coupling
1. The coupling between the coupling and the shaft is H7 / js6.
2. The axial clearance at both ends of the coupling is generally 2-6mm.
3. To install the toothed coupling, ensure that the outer teeth are in the middle position of the inner tooth width.
4. When the elastic ring pin coupling is installed, the elastic ring and the pin should have an interference fit and have a certain tight force. The diameter clearance between the elastic pin and the coupling hole is 0.40 to 0.60 mm.
5. The plane clearance of the coupling: 2.2 ~ 4.2mm for cold oil pump, 1.55 ~ 2.05mm for hot oil pump than the front string.
6. The rubber ring for the coupling is smaller than the perforation diameter by 0.15 ~ 0.35mm.
7. Use special tools when removing the coupling to keep it smooth and clean to avoid injury.
Rotor
1.Circular runout of the rotor
(1) The tolerance of the round runout of the single-stage centrifugal pump rotor should meet the requirements of the table.
(2) The round runout of the multi-stage centrifugal pump rotor should meet the requirements of the table.
2. For multi-stage pumps, the rotor should be checked for dynamic balance if necessary, and its requirements should meet the technical requirements.
3. The fit between the shaft sleeve and the shaft is H7 / h6, and the surface roughness is ▽ 1.6.
4. The balance and the shaft are H7 / js6.
5. Impeller
(1) The cooperation between the impeller and the shaft is H7 / js6.
(2) The impeller should be statically balanced. For impellers with an operating speed of 3000 r / min, the allowable remaining unbalanced weight on the outer diameter must not exceed the requirements of the table.
(3) The impeller is to find the balance by the method of removing weight. In the appropriate part, the thickness is not more than 1/3 of the wall thickness.
(4) For the hot oil pump, when the impeller and the shaft are assembled, a gap of 0.10 to 0.40 is left at the top of the key, and the axial clearance between the impeller and the front and rear partitions is not less than 1 to 2 mm.
seal
1.Mechanical seal
(1) The diameter gap between the gland and the shaft sleeve is 0.75 ~ 1.00mm, and the thickness of the gasket between the gland and the seal cavity is 1 ~ 2mm.
(2) The roughness of the contact part between the sealing gland and the static ring seal is ▽ 3.2.
(3) The shaft or shaft sleeve where the mechanical seal is installed, the surface must be free of defects such as rust spots and cracks, and the roughness is ▽ 1.6.
(4) The root of the anti-rotation groove at the end of the static ring and the top of the anti-rotation pin should maintain an axial gap of 1 to 2 mm.
(5) The work after compression of the spring should meet the design requirements, and its deviation is ± 2mm.
(6) The rotation direction of the mechanical seal and coil spring should be opposite to the rotation direction of the pump shaft.
(7) The gland bolts should be tightened evenly to prevent the gland end face from deviating.
2, packing seal
(1) The diameter clearance between the oil seal ring and the shaft sleeve is generally 1.00 ~ 1.50mm.
(2) The diameter gap between the oil seal ring and the stuffing box is 0.15 ~ 0.20mm.
(3) The diameter gap between the packing gland and the shaft sleeve is 0.75 ~ 1.00mm.
(4) The diameter gap between the filler gland and the filling box is 0.10 ~ 0.30mm.
(5) The diameter clearance of the existing bushing of the stuffing bottom sleeve is 0.70 ~ 1.00mm.
(6) The diameter gap between the pressure reducing ring and the sleeve is 0.50 to 1.20mm.
(7) The outer diameter of the stuffing ring should be smaller than the stuffing box hole diameter by 0.30 ~ 0.50mm, the inner diameter is larger than the shaft diameter by 0.10 ~ 0.20mm.
(8) At the time of installation, the cuts of two adjacent landfills should be staggered by at least 90 °.
Spindle
1. The cylindricalness of the neck is 1/4000 of the shaft diameter, the maximum value does not exceed 0.025, and the surface should be free of scratches and roughness of ▽ 1.6.
2. Based on the two journals, find the radial circle runout tolerance of the coupling and the middle of the shaft is 0.04mm.
3. The key and the keyway should cooperate closely, and no gasket is allowed. The interference between the key and the keyway should meet the requirements of the table.
Packing gland
1. The end face of the packing gland must be vertical.
2. The gap between the packing gland and the shaft sleeve diameter is 0.75 ~ 1.0mm.
3. The gap between the outer diameter of the stuffing gland and the stuffing box is 0.1 ~ 0.15mm.
4. The mechanical seal gland rubber pad should be 1.50 ~ 2.50mm higher than the contact surface.
Seal ring
1. The gap between the oil seal ring and the shaft sleeve is 1.00 ~ 1.50mm.
2. The outer diameter of the oil seal ring is perpendicular to the end face.
3. The outer diameter gap between the stuffing box and the oil seal ring is 0.15 ~ 0.2mm.
Shafts and sleeves
1. Allowable bending of the shaft diameter is not more than 0.013mm, for the middle part of the low speed pump shaft is not more than 0.07mm, and for the middle part of the high speed pump shaft is not more than 0.04mm.
2. The shaft surface is smooth without cracks and wear.
3. The surface of the shaft sleeve keeps Ra = 1.6um.
4. H7 / h6 is adopted for shaft and shaft sleeve.
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