In the overhaul of all 3GQGB screw asphalt pumps in power plants, due to their large number of stages, high pressure and high speed, the technical content of the 3GQGB screw asphalt pump is high. In the maintenance of the 3GQGB screw asphalt pump, the quality of the inspection is completely determined by the correct measurement and adjustment of the clearance to ensure the measurement and adjustment of the inspection gap of the 3GQGB screw asphalt pump.
Maintenance gap adjustment of 3GQGB screw asphalt pump
In the overhaul of all 3GQGB screw asphalt pumps in power plants, due to their large number of stages, high pressure and high speed, the technical content of the 3GQGB screw asphalt pump is high. In the maintenance of the 3GQGB screw asphalt pump, the quality of the inspection is ensured by the correct measurement and adjustment of the gap under the condition that the static and dynamic parts are free from defects. In the numerous gaps and maintenance data of the screw asphalt pump, each gap and maintenance data are not independent, but are related to each other and mutually constrained. The value of each gap is determined by the manufacturing and operational requirements of the 3GQGB screw asphalt pump.
At present, the high-pressure, large-lift is used in the 3GQGB screw asphalt pump. The double-shell pump is stable in operation, easy to overhaul, and widely used. The following is a brief description of the effect, measurement and adjustment of the gaps of the 3GQGB screw asphalt pump in combination with the double housing.
1. Disintegration of 3GQGB screw asphalt pump
a) Compare with the data at the time of the previous overhaul, and analyze the reasons for the change of the data;
Compare with the data at the time of reloading to avoid reloading errors.
1.1 The clearance force of the bearing bush and the gap of the pad
The gap at the top of the bearing bush is generally 0.15% to 0.2% of the shaft diameter, and the gap of the tile is half of the top clearance. The tile cover tension is generally from 0.00mm to 0.03mm. The clearance is intended to ensure lubrication and cooling of the bearing bush and to avoid the effects of shaft vibration on the bearing bush. If there is any discrepancy with the standard during the disintegration process, it should be analyzed, and a targeted treatment plan should be developed and processed.
1.2.3 GQGB screw asphalt pump working volume
The working volume of 3GQGB screw asphalt pump is 0.8mm~1.2mm. The value of the work quantity is mainly to ensure that the mechanical seal does not cause mechanical collision and extrusion under the start and stop conditions and accident conditions of the 3GQGB screw asphalt pump. It is also an important measure to prevent static and static friction during the operation of 3GQGB screw asphalt pump.
1.3 The gap between the high and low pressure side end caps and the inlet and outlet ends
Measuring the gap between the high and low pressure side end caps and the inlet and outlet ends of the 3GQGB screw asphalt pump is to check whether the fastening bolts are loose or not, and at the same time, to leave the bolts for the 3GQGB screw asphalt pump.
1.4.3 Measurement of semi-twisting amount of GQGB screw asphalt pump
The half-twist of the 3GQGB screw asphalt pump is measured without removing the balance disc. The half-turn of the 3GQGB screw asphalt pump should be half of the total volume of the asphalt pump. Generally, the value is about 4 mm. Checking the amount of half-turn and comparing the raw data can find out the reason why the balance disc wear and the efficiency of the 3GQGB screw asphalt pump are reduced.
1.5.3 Review of the total amount of GQGB screw asphalt pump
After the balance plate is removed, the total volume of the 3GQGB screw asphalt pump can be measured. The total volume is the value inherent in the manufacture and installation of the 3GQGB screw asphalt pump. Generally, the total volume of the 3GQGB screw asphalt pump is 8mm~10mm. If the total amount of 3GQGB screw asphalt pump changes, it means that the fastening bolts in the middle section are loose or the axial part of the static and dynamic parts is worn.
1.6.3 GQGB screw asphalt pump at all levels
The 3GQGB screw asphalt pump should disintegrate the middle section and the impeller after the core pack is taken out. In the process of disintegration, the enthalpy measurement should be carried out step by step. In the process of measuring the enthalpy of each level, the axial direction of the middle section of each stage should also be dealt with. The gap is measured. The amount of enthalpy in the middle section should be near the total enthalpy value, generally not more than 0.50mm. If the numerical deviation is large or the original data is large or small, the cause should be carefully analyzed and eliminated. The measurement of the gap at the middle of each stage is to check the error of the final assembly.
1.7 Measurement of each data in the disintegration process, the purpose is to analyze the data according to the data, find out the cause of the failure of the 3GQGB screw asphalt pump, and formulate the plan for this maintenance and the targeted treatment measures. At the same time, reference is made during the reloading process to check the error of the reloading process.
2. Measurement and adjustment of gap in the maintenance of static parts of GQGB screw asphalt pump
2.1 Measurement and adjustment of the radial clearance of each middle stop
The adjacent two pump segments are stacked, and then the pump section is reciprocated. The difference in the dial gauge reading is the gap. Then, according to the above method, the average of the 90° orientation is measured again. The gap value is generally 0.04 mm to 0.08 mm, and when it is larger than 0.1 mm, repair is required. The simple repair method can evenly weld 6-8 places around the interrupted convex stop with a large gap, each length is 25mm~40mm, and then the port is turned to the required size. The gap data of each middle section is very important in the maintenance of 3GQGB screw asphalt pump. If the gap is too large, the relative sway of the rotor is increased, resulting in the offset of the flow gap of the 3GQGB screw asphalt pump, and the gap between the two sides is reduced. During operation, it is possible that the static friction will cause the 3GQGB screw asphalt pump to lock up. If the gap is too small, it may happen that the middle section is not installed properly. The total amount of 3GQGB screw asphalt pump is artificially reduced, and the efficiency of the 3GQGB screw asphalt pump is reduced, which causes static and static friction and damages the equipment. Botou Taibang Pump & Valve Manufacturing Co., Ltd.
2.2 Radial clearance measurement and adjustment of vane and pump casing
The guide vanes of the 3GQGB screw asphalt pump are generally made of stainless steel "target=_blank> stainless steel. When the guide vane is damaged seriously, the new vane should be replaced. The new vane should be smoothed before use. Improve the efficiency. The radial clearance between the guide vane and the pump casing is generally 0.04mm~0.06mm. The positioning pin of the fixed vane and the pump casing are interference fit, and the tightening force is 0.02mm~0.04mm, which is matched with the guide vane. The guide vanes should be pressed in the pump casing to prevent the guide vane and the pump casing baffle from being worn flat. For this purpose, the rear side of the vane can be drilled in the circumferential direction and as close as possible to the outer edge to drill 3 to 4 holes, plus copper nails. The two planes are pressed by the interference of the copper nails, as shown in Fig. 2a. Before installing the copper nails, the axial gap between the vanes and the pump casing is measured by the sealing surface of the pump section. Place 3~4 lead wires under the guide vanes, put the guide vanes on the other pump section, gently tap the soft metal with a sledgehammer, and take out the lead wire to measure the thickness. The difference between the average thickness of the lead wires in the two places. Is the gap value. The height of the copper nail should be 0.5mm more than the measured gap value. After pressing the pump housing, guide vanes will have a certain preload.
2.3.3 Measurement and adjustment of GQGB screw asphalt pump seal ring and vane sleeve clearance
The seal ring and the vane bushing are respectively mounted on the pump casing and the vane. Their materials are mostly made of brass and their hardness is much lower than that of the impeller. When rubbing against the impeller, the first to damage is the seal ring and the vane bushing. If it is found that the wear amount exceeds the specified value or there is a crack, it must be replaced. The radial (diameter) clearance of the seal ring and the impeller varies with the diameter of the seal ring, generally 1.5 ‰ to 3 内径 of the inner diameter of the seal ring; The maximum allowable clearance after wear shall not exceed 4 ‰ 8 ‰ of the inner diameter of the seal ring (the seal diameter is small, take a large ratio; the diameter is large, take a small ratio). The sealing ring is matched with the pump casing. If there is a fastening screw, the clearance can be used. The value is 0.03mm~0.05mm. If there is no fastening screw, the clamping should have a certain tightening force, and the tightening force is 0~0.03mm. The gap between the vane bushing and the impeller should be slightly smaller than the gap between the seal ring and the impeller (1/10 smaller). The guide vane and the vane bushing are interference fit (interference of about 0.015 mm to 0.02 mm) and need to be fastened with a set screw.
3. Measurement and adjustment of gap in overhaul of rotor parts of 3GQGB screw asphalt pump
3.1.3GQGB screw asphalt pump shaft bending
The high-pressure structure is precise, the gap between the moving and static parts is small, the rotation speed of the rotor is high, and the load on the shaft is heavy, so the requirements on the shaft are strict. The bending of the shaft is generally not allowed to exceed 0.02 mm, and the straight shaft should be operated when it exceeds 0.04 mm. Excessive bending of the pump shaft will increase the sway of the 3GQGB screw asphalt pump rotor. The increase of the rotor sway of the 3GQGB screw asphalt pump will increase the gap between the seal ring and the vane bushing to prevent static and dynamic wear, and increasing the clearance will reduce the efficiency. And the gap is increased to a certain amount, and eddy current is also formed, causing vibration.
3.2. Impeller and pump shaft assembly clearance
Multi-stage 3GQGB screw asphalt pump impeller and pump shaft assembly is generally clearance fit, the gap value is between 0.00mm ~ 0.04mm. This is determined by the machining tolerance of the 3GQGB screw asphalt pump shaft and impeller. Too small or excessive clearance increases the difficulty of assembly, affects the thermal expansion of the rotor components, and increases the mass of the 3GQGB screw asphalt pump rotor. Excessive clearance increases rotor sway, resulting in unstable rotor dynamic balance. The matching part of the inner hole of the impeller and the shaft will increase the matching clearance due to long-term use and multiple disassembly and assembly. At this time, the matched shaft section or the inner hole of the impeller can be repaired by spraying.
3.3 adjustment of pump shaft key and keyway clearance
The impeller and the pump shaft are rotated by a key. The key and pump shaft keyway should be an interference fit with a tightening force between 0.00mm and 0.03mm. The key and impeller keyway should be clearance fit, and the value is also between 0.00mm and 0.03mm.
3.4 rotor small
a) Purpose of the small package
Rotor small package, also known as pre-installation or trial installation, is the key to determining the quality of the assembly. The purpose is to measure and eliminate the tight sway of the rotor to avoid internal friction, reduce vibration and improve the shaft sealing condition; adjust the axial distance between the impellers to ensure the alignment of the outlet center of each impeller; determine the adjustment sleeve size.
b) Determination of the axial expansion gap of the rotor set
Because the rotor assembly is different from the pump shaft material, the pump shaft is outside the pump body. Therefore, in the hot state, the pump shaft and the rotor assembly are not expanded. Generally, the rotor package has a larger expansion than the pump shaft, so a thermal expansion gap is left to the rotor assembly during assembly of the rotor. The value of the expansion gap of the rotor is determined by the length of the rotor and the oil temperature. Generally, the rotor with about 10 impellers has an expansion gap of about 1 mm. If the expansion gap is too large, the rotor set should not be fastened. If the expansion gap is too small, the rotor may be bent under hot conditions, causing static and static friction and damage to the equipment.
c) Inspection before small installation
Check the dimensions of the components on the rotor to eliminate significant overshoot. The sway of the kit on the shaft should generally not exceed 0.02mm. For all sets of components on the shaft, such as impellers, balance discs, bushings, etc., the verticality of the end-to-axis centerline should be checked on a special tool. The false shaft and the set member maintain a clearance of 0.00mm to 0.04mm, and the set member is rotated by hand. After one rotation, the runout value of the dial indicator should be below 0.015 mm, and the perpendicularity of the other end face is checked in the same manner. It is also possible to measure the assembly on a flat plate without using a false shaft. Such a measurement method cannot obtain a vertical error between the end surface and the center line of the shaft, and the parallel error of the upper and lower end faces is obtained.
d) Measurement of rotor sway of 3GQGB screw asphalt pump
After doing the above preparations, clean the kits and install them on the shaft in the order from the low pressure side to the high pressure side. Tighten the sleeve locks and leave the expansion gap (for the hot sleeve rotor, only the first and last ends) Two-pole impeller, not installed in the middle of the stage). Then, the shaking of each part is measured separately.
After the rotor sloshing degree meets the requirements, the relative position of each component should be marked. The impeller should be well typed and removed in turn, waiting for the final assembly.
4, 3GQGB screw asphalt pump core package assembly and assembly clearance adjustment
4.1. Measurement of total rotor volume
In the core package assembly process, the total enthalpy measurement of each stage of the impeller should be carried out to ensure the axial clearance of the 3GQGB screw asphalt pump. The deviation between the maximum and minimum enthalpy during the assembly process should not exceed 0.50 mm, otherwise the cause should be checked and eliminated. The total volume is related to the centerline of the impeller outlet centerline and the guide vane inlet centerline, which directly affects the efficiency of the 3GQGB screw asphalt pump and the operating cycle of the 3GQGB screw asphalt pump. The 3GQGB screw asphalt pump core package is assembled and penetrated into the outer casing. After the 3GQGB screw asphalt pump inlet and outlet ends are installed and the tightening bolts are all tightened, the total enthalpy measurement is also performed. At this time, the bearing and the shaft seal are not installed. There is no balance disc, but a special sleeve is used instead of the balance disc on the shaft, and the sleeve nut is placed, a dial gauge is installed on the shaft end, and then the rotor is turned, and the dial gauge reading of the rotor at the front and rear end positions is poor. That is the total volume of the 3GQGB screw asphalt pump. The measured enthalpy value is compared with the grading volume, and if there is any discrepancy, the cause is analyzed and eliminated.
4.2. Adjustment of the axial position of the rotor (half the amount)
After the measurement and adjustment of the total rotor volume is completed, the balance plate and adjustment are set and the lock nut is fastened to the small position. The dial indicator is placed on the frame, and the rotor is turned back and forth. The difference in the dial gauge reading is the rotor half-turn. . The rotor half volume should be half of the total volume. If the half volume does not match the total volume, the adjustment sleeve should be adjusted to match.
4.3. Adjustment of work volume
Large-scale 3GQGB screw asphalt pumps are equipped with working capacity adjustment devices, some for 3GQGB screw asphalt pump thrust tile adjustment, some for 3GQGB screw asphalt pump thrust bearings for adjustment, measurement method and rotor measurement total half-turn In the same way, the working volume can be adjusted by adding or subtracting the working surface or the non-working surface of the thrust bearing (or thrust tile). Generally, the working volume of the 3GQGB screw asphalt pump is 0.8mm~1.2mm. When the pump is started and stopped and the balance plate has not established a pressure difference, the axial thrust of the impeller is received by the working block of the thrust bearing. Once the balance disc establishes the differential pressure, the axial thrust of the impeller is completely balanced by the balance disc, and the thrust disc is out of contact with the working disc. To achieve such a requirement, push the rotor toward the inlet side so that the thrust plate abuts against the working block. At this time, the balance plate and the balance seat should have a gap of 0.01 mm. If the gap is too large or there is no gap, adjust the gasket on the back of the working tile, or adjust the position of the balance plate on the shaft. The oil film thickness of the thrust bearing during operation is about 0.02mm~0.03mm. To make the thrust bearing not work during normal operation of the pump, the clearance between the balance disc and the balance seat should be greater than 0.03mm~0.045mm. In order to be in working tile and non-working tile do not work. If the thrust bearing is still in operation, the axial clearance of the balance disc and the balance seat should be readjusted.
The axial clearance between the thrust disc and the non-working tile is much smaller than the back clearance of the rotor impeller (ie, the amount of semi-turn). When the 3GQGB screw asphalt pump generates the boring shaft due to cavitation or unstable working conditions, the thrust disc and the non-working tile The block acts first, so that the rotor does not rub against the pump casing.
4.4.3 Adjustment of radial clearance of GQGB screw asphalt pump
After the pump body is installed, the end caps and tile brackets at both ends can be installed to adjust the concentricity of the rotor and the stator (upward shaft).
The concentricity requirement for the rotor and the stator is that the half lift is equal to half or a little smaller of the total lift (considering the rotor static deflection), the sides of the gap are equal and the four corners are uniform.
Measurement of the lifting shaft: Before the bearing bush is installed, one dial indicator is installed on each end of the bearing frame, and the center line of the measuring rod of the table is perpendicular to the center line of the shaft and contacts the journal. Use the crowbar to lift the shaft smoothly at both ends of the shaft at the same time. The difference in the dial gauge reading in the up and down position is the total lift of the rotor.
Pick up the rotor and place it in the lower tile. At this time, the reading of the dial gauge should be half the amount of rotor lift, and it should be half of the total lift, otherwise it needs to be adjusted. If there are adjustment bolts under the bearing frame during adjustment, you only need to loosen and tighten the bolts. If there is no adjustment bolt, the thickness of the gasket under the bearing bush can be adjusted.
For the concentricity of the rotor and the stator, it is generally determined by the uniformity of the gap between the sides of the bearing bush. After placing the lower tile, measure the gap between the four bushings of the bearing bush with a feeler gauge. The adjustment should be uniform and the one-side clearance of the tile should be half of the gap at the top of the bearing pad.
4.5. Adjustment of bearing bush and mechanical seal clearance
The adjustment of the bearing clearance force is adjusted with reference to the requirements stated in the disintegration process. The principle of gap adjustment of mechanical seal is: the compression of the static seal of the mechanical seal is half of the total compression. The adjustment method is to push the 3GQGB screw asphalt pump rotor to the low pressure side of the 3GQGB screw asphalt pump, and adjust the mechanical seal ring and pump. The tightness of the shaft seal ensures the pre-tightening force of the high and low pressure side mechanical seals.
5. Adjustment of other gaps
5.1. Coupling Center
The adjustment of the center of the 3GQGB screw asphalt pump coupling is an important gap adjustment in the overhaul. The direct adjustment of the center is the direct increase of the vibration of the 3GQGB screw asphalt pump. The coupling center generally requires the deviation of the outer garden to be less than 0.05mm, and the deviation of the two pairs of wheel openings is less than 0.04. In the overhaul of all 3GQGB screw asphalt pumps in the power plant, the technology for overhaul is given because of its high number of stages, high pressure and high speed. Higher content. In the maintenance of the 3GQGB screw asphalt pump, the quality of the inspection is ensured by the correct measurement and adjustment of the gap under the condition that the static and dynamic parts are free from defects. In the numerous gaps and maintenance data of the 3GQGB screw asphalt pump, each gap and maintenance data are not independent, but are related to each other and mutually constrained. The value of each gap is determined by the manufacturing and operational requirements of the 3GQGB screw asphalt pump.
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