Common sense of disassembly and assembly of piston compressor
1. Precautions for maintenance
1. The maintenance procedures must be strictly implemented throughout the entire maintenance process, and various safety measures must be implemented.
2. Before disassembling, close all the outer pipe valves associated with the compressor, open the vent valve, and discharge the gas in the cylinder to normal pressure. When the working medium is a toxic, harmful, flammable, or explosive gas, blind plates and water seals must be installed at the inlet and outlet valves; gas replacement should be carried out after pressure relief, and it can be disassembled after passing the analysis.
3. When disassembling the suction and exhaust valve covers and cylinder heads, two nuts should be left symmetrically. Use a screwdriver or wrench to check the starting point of the gland to check that the cylinder has been unloaded to normal pressure before removing all the nuts.
4. When dealing with temporary failures, the parts on the cylinder should not be removed until the temperature of the cylinder drops below 120°C. Otherwise, the high temperature vaporization of the lubricating oil may cause the cylinder to catch fire and explode.
5. Strictly implement the hot-fire system, apply for a "hot-fire certificate" and implement safety and fire prevention measures before the hot-fire.
6. Before overhauling, the power supply should be cut off, the warning should be listed, and it should be watched by special personnel. It is forbidden to switch on.
7. Overhaul and cranking of large compressor units should monitor each other to avoid personal or equipment accidents.
2. General disassembly procedures and basic requirements
1. When disassembling, the compressor should be disassembled from the outside to the inside and from top to bottom according to the different structure of the compressor. It is strictly forbidden to dismantle or knock indiscriminately to avoid damage or deformation of the mechanical parts.
2, try to use special tools to disassemble, so that the parts are not damaged. If the connecting rod small head tile is removed, it should be pressed out with a press or pulled out with a special tool. Do not strike it with a hand hammer. When removing the air valve assembly, use a special tool. The valve seat parts are clamped and deformed; for the connecting bolts of the cylinder, piston, and piston rod, special dead-end wrenches must be used, and pipe wrenches are not allowed to be directly stuck on the nut or piston rod for disassembly.
3. Lifting equipment should be used to disassemble the parts of large compressors, and should be fastened, hung firmly, placed and cushioned.
4. The disassembled parts should be cleaned according to the requirements of clean and civilized maintenance, and they should be placed neatly in order and covered tightly; important parts should be placed on special racks, and precision parts should be specially kept. Relevant matching parts should be marked for the assembly position, and some should be worn or wrapped together to avoid messy or wrong assembly, which will affect the quality of assembly.
3. General requirements for compressor assembly
Compressor assembly, generally install related components first, and then overall assembly. The assembly of the compressor to be overhauled is different from that of the newly manufactured compressor. In order to give full play to the role of the original parts, the gap between the parts and the matching is not as strict as the requirements for new parts. In some cases, it is allowed Slightly larger or smaller than the specified, or even exceed the specified limit of use. In order to more effectively eliminate the errors during machining and the accumulated errors during assembly, manual operations such as frustration, scraping and grinding must be done carefully, which is conducive to the geometric accuracy and matching requirements of the assembly. For example, the matching of the bearing bush and the journal must be scraped and ground to achieve good contact; to eliminate defects such as burrs, scratches and marks on the parts, and improve assembly quality and accuracy. In addition, the following points should be noted:
1. Each new replacement part must be inspected and tested before installation, and only when it meets the requirements can be assembled.
2. The components should be assembled according to the drawings and procedures. The assembly procedure is the reverse process of disassembly. The assembly work must be carried out carefully in accordance with the technical requirements, and do not forget to install or incorrectly install; the same type of parts should be assembled according to the mark; strictly prevent foreign objects from falling into the cylinder, body, and intake and exhaust pipes.
3. For the smooth surface of the moving parts, a proper amount of lubricating oil should be added during assembly. For example, when the crosshead pin and bushing, piston, piston ring, and piston rod are installed in the cylinder, a proper amount of lubricating oil must be dripped.
4. After each assembly is assembled, it should be tested and qualified. For example, the coaxiality of the piston rod and piston should be measured after the assembly is completed; some parts of the assembly should be tested before they can be assembled. For example, the piston ring should be tested for light leakage and open clearance in the cylinder before passing the piston上Assembly.
5. When tightening the bolts of each component, in addition to the appropriate size of the wrench opening and the nut, appropriate force must be used. Different torques should be selected according to the diameter of the bolt. If the force is too large, the prestress of the bolt will increase and it is easy Fatigue fracture; if the force is too small, the tightening force is not enough and it is easy to loosen, and cause vibration or air leakage. When tightening multiple bolts of the same group, they should be symmetrically and evenly, and the gaps of the tight parts should be checked at any time, and they should be evenly tightened. If the gap is found to be skewed, it should be disassembled and inspected, and the abnormality should be eliminated before re-tightening. It is not allowed to adjust by the different tightening force of the bolts.
6. The assembled parts must be clean, and no foreign matter is allowed to enter the bearings, cylinders, gaps, fillers and inlet and outlet pipes.
Fourth, the installation requirements of the fuselage
1. Before the fuselage or crankcase is in place, it should be coated with chalk on the outside and kerosene on the inside for a leak detection test. After 8 hours, no leakage is considered qualified, and then cleaned up; when cleaning the middle body, the lubricating oil circuit must be cleaned. The smooth flow of the oil circuit.
2. Regardless of whether the fuselage uses shim or not, the grid structure at the bottom of the fuselage must be filled with cement mortar during installation and must not be suspended in the air.
3. When the fuselage is in place, the axis of the main shaft and the middle body slideway should coincide with the centerline of the base, the allowable deviation is 5mm, and the allowable deviation of elevation is ±5mm.
4. The row and axial levelness of the horizontal compressor body and the middle body shall be measured at the middle body slideway and the bearing seat hole respectively, and the values at both ends shall prevail, and the middle value shall be used as a reference; both The level deviation shall not be greater than 0.05mm/m. The inclination of the horizontality of the row direction, within the allowable deviation range, the M-shaped body should be high toward the motor end; the overall structure of the H-shaped compressor main shaft system (such as H22) should be high toward the inner bearing housing holes of the two fuselages; the motor adopts Double independent bearings should be high to the outer bearing housing holes of the two fuselages.
5. For dual-row two-frame compressors, the coaxiality deviation of the main bearing hole axis shall not be greater than 0.03mm, and the axial levelness of the fuselage shall remain unchanged.
6. The alignment and leveling of the vertical compressor body should be measured on the joint surface of the body and the middle body, the body and the cylinder, and the middle body and the cylinder; for the multi-stage cylinder and the body is cast as a whole The unit can be measured on the joint surface of the cylinder and the cylinder. The longitudinal and lateral horizontality deviation of the fuselage shall not be greater than 0.05mm/m.
7. When aligning and leveling the body of the L-type compressor, the horizontality of the horizontal column of the fuselage can be measured on the fuselage slide, and the deviation of the horizontality shall not be greater than 0.05mm/m; the tendency of the horizontality should be high To the cylinder head end. The axial levelness of the horizontal row fuselage can be measured at the bearing hole of the fuselage or the two bearing hole frame ruler, and the levelness deviation shall not exceed 0.05mm/m; the levelness tendency should be higher to the motor end. The horizontality of the vertical column of the fuselage can be measured on the connecting stop surface of the fuselage and the cylinder (using a block gauge and a flat ruler) or on the fuselage slide, and the level deviation shall not be greater than 0.05
8. For the alignment and leveling of the body of the double L-type compressor, in addition to complying with the regulations of the L-type compressor, the motor should be aligned and leveled first. The high and low pressure compressors should be installed on both sides of the motor based on the motor. body. The axial levelness of the fuselage should be higher toward the outer bearing housing holes of the two fuselages.
9. The parallelism deviation of the axis of each row of the multi-row compressor shall not be greater than 0.10 mm/m.
10. When the anchor bolts are tightened, the level of the fuselage and the tightness of the beams and the fuselage should not change; the length of the bolts exposed to the nuts should be greater than 1.5 bolts.
5. Assembly of crankshaft and main bearing
1. Before assembling, apply compressed air to blow the oil holes of the crankshaft and the main bearing, and clean the crankshaft and the main bearing, so that the oil path is unblocked and the surface is clean.
2. The tightening device of the crankshaft and balance iron must be tightened.
3. The inner and outer surfaces of the main bearing bush should be smooth, and the mating surface should be smooth, and there should be no defects such as cracks, pores, scratches, bruises, crushes, inclusions, etc.
4. After the bearing seat hole bolts are tightened, the fit between the back of the bearing housing and the inner hole of the bearing housing should not be less than 85% of the backing area when the outer diameter of the bearing housing D≤200 mm; when D>200mm, it should not be less than the lining 70% of the back area; if there is a non-fitting surface, it should be distributed, and the maximum concentration area should not be greater than 10% of the backing area or the 0.02mm feeler gauge is qualified.
5. The non-working surface of the tile back should have a coating, the coating should be uniform, and there should be no coating tumors. The alloy inner surface of the bearing bush is not suitable for scraping. If it is in poor contact with the journal, only a small amount of scraping can be used. The scraping allowance is generally 0.04~0.08mm.
6. The babbitt alloy layer of the repaired bearing (lower half bearing) should have an arc length of more than 2/3 in contact with the crankshaft journal, and the contact point should be 2~5 points/cm². When repairing scraping, the crankshaft and crankcase should be at the same level; a feeler gauge should also be used to detect the four-corner clearance between the bearing bush and the journal, and the clearance value should not exceed 0.04mm. The centerline of the main bushing and the centerline of the crankshaft should be coaxial.
7. The radial clearance between the crankshaft (main shaft) bearing bush and the main journal should meet the requirements in Table 1-1. The method of adding and subtracting gaskets at the tile mouth is commonly used to obtain the required gap for each tile; the measurement of the gap usually adopts the lead pressure method and the feeler plug measurement, and the size of the feeler plug measurement is about 0.02 smaller than the actual gap.
mm. The side clearance of the tile mouth is 1/2 of the top clearance, and the unevenness shall not exceed 0.02 mm.
Table 1-1 Radial clearance between spindle bearing bush and journal (unit: mm)
Note: 1. D in the table is the diameter of the main shaft or crank pin journal, mm;
2, the larger the journal diameter is.
8. After placing the semicircular copper ring on both sides of the spindle with axial positioning, the axial positioning gap on both sides should be equal, and the gap should be selected between 0.20~0.50mm.
9. After the main bearing bush is repaired and scraped, check the coaxiality between the crankshaft centerline and the base centerline in the horizontal and vertical directions. A level gauge is commonly used to measure the horizontal deviation between the centerline of the crankshaft and the centerline of the fuselage. The difference between the level of the crankshaft journal and the level of the bearing hole of the base should be less than 0.02mm/m; in the horizontal direction, a gauge can be used to measure the crank and the machine. The distance between the end faces of the bearing hole of the seat, the distance between the left and right sides should not exceed 0.01mm/m.
10. The tightening torque of the bearing seat bolts and the elongation after tightening should meet the specified requirements.
11. After the crankshaft is installed, place the crank pin at the four positions of 0°, 90°, 180°, and 270°, and measure the distance between adjacent crank arms with an inner micrometer. The deviation shall not exceed 10 4 piston stroke value. Check the parallelism of the crank neck to the main journal at four positions perpendicular to each other, and the deviation shall not exceed 0.15mm/m.
12. After the bearing shell assembly is qualified, the crankshaft should be checked for each crankshaft, and the crankshaft should not exceed 0.02 mm/100 mm.
13. After the above is completed, lift the crankshaft to take out the main bushes, clean the crankshaft, main bushes, fuselage bushings and cover and other parts; place each main shaft lower bush and crankshaft according to the marks, and install the gaskets on both sides of the bushing; Put a proper amount of lubricating oil on the neck; place the upper half-watt of each main shaft according to the number, adjust the gasket of the socket, and cover each head according to the number; tighten the main shaft bolts, cross evenly and tighten to the specified tightening force; plug and measure the roof of the tile Clearance, confirm that the tile gap meets the requirements, and finally install the anti-loosening back cap or other anti-loosing devices.
After the crankshaft and the main bearing are assembled, turn the crankshaft to check whether the assembly is correct by hand; if there is a sense of friction, it should be disassembled and checked, and the abnormality should be eliminated and then reinstalled.
Six, the installation of the cylinder
1, check before installation
Check carefully before installation. Water pressure test (including cylinder and water jacket) should be done if it is not specified; clean and check the connecting surface of the cylinder block and the middle body, the contact surface of the cylinder valve cavity and the valve seat, etc., there should be no For defects such as mechanical damage, the cylinder mirror surface must not have cracks, looseness, pores and other defects; use an internal micrometer to detect the cylindricity of the working surface of the cylinder at all levels, and the deviation shall not be lower than the national standard 8 tolerance value.
2. Installation requirements for the cylinder of the horizontal compressor
(1) When connecting the cylinder and the middle body, the connecting bolts should be tightened symmetrically and evenly. The cylinder support must be in good contact with the cylinder support surface, and the force should be uniform.
(2) When using the wire drawing method to align the coaxiality between the cylinder axis and the axis of the central slideway, the following requirements should be met:
The coaxiality deviation between the cylinder axis and the axis of the middle body slideway should meet the requirements in Table 1-2. If it exceeds the regulations, the cylinder should be moved horizontally or radially, or the connection stop should be scratched for adjustment, and no offset pad or external force should be used for adjustment. . The contact area of the treated spigot surface should reach more than 60%. Adjust the cylinder level, the deviation should not be greater than 0.05
mm/m, and the inclination direction should be consistent with the middle body (high to the cylinder head end), but it must meet the requirements in Table 1-2. Check the coaxiality deviation between the axis of the packing seat and the axis of the cylinder, and it should also meet the above regulations.
Table 1-2 Coaxiality deviation between the cylinder axis and the axis of the central crosshead slide
3. Installation of vertical compressor cylinder
(1) When connecting the cylinder and the body, the cylinder and the cylinder or the cylinder and the middle body, the bolts should be tightened symmetrically and evenly. The supporting surface should be in good contact and the force should be even.
(2) The level of cylinder can be measured on the contact surface of the cylinder head and the upper stop of the cylinder; when the diameter of the cylinder working surface is greater than 150mm, it can also be measured on the mirror surface of the cylinder liner. The level deviation shall not be greater than 0.05mm/m.
(3) When the level meter cannot be placed on the contact surface of the cylinder stop, a block gauge and a flat ruler can be added, and the levelness can be measured on the flat ruler.
(4) The coaxiality of the cylinder and the body, the cylinder and the cylinder or the cylinder and the middle body, and the contact area of the contact stop surface should be more than 60%.
(5) When using a laser collimator to align the coaxiality between the axis of each cylinder and the axis of the middle body slide, the center of the photoelectric receiving target placed in the cylinder mirror should be coincident with the cylinder axis. The deviation between the center line of the photoelectric receiving target and the axis of the laser beam shall not be lower than the 9-level tolerance value specified by the national standard.
Seven, the assembly of the connecting rod assembly
1, before assembly
The crosshead and connecting rod bearing bushes should be inspected. The alloy layer of the crosshead and the alloy layer of the connecting rod large-end bushing should be smooth and round, and there should be no cracks, pores, shrinkage, scratches, bruises, crushing, inclusions, etc. Defects: The alloy layer and the tile back should be firmly bonded; the oil path of the connecting rod body and the crosshead should be cleaned and unblocked.
2, the connecting rod small head tile and small head hole are interference fit
When the tile is inserted into the hole, its inner hole will shrink, and the shrinkage size is generally approximately equal to the size of the interference. Therefore, the size of the outer circle of the connecting rod small-end tile should be enlarged accordingly. The assembly interference of the small head tile is related to the material and diameter of the tile. For example, the interference of the copper tile is generally 0.4/1000~0.5/1000 of the diameter, and its exact size should be in accordance with the requirements of the drawing. According to the size of the small head tile and the different assembly conditions, generally those with an outer diameter of less than 100mm are assembled by pressing-in method; those with an outer diameter greater than 100mm can be assembled by freezing if conditions permit, which is convenient and has good assembly quality.
3. Scraping and grinding of large head tiles
Scrape the back of the large-head tile so that the bonding surface should have a contact area of more than 70%-85%; when scraping the large-head tile of the connecting rod, the scraping must be even. The wall thickness of the tile should be checked frequently during the scraping to make it coaxial The thickness on the section is equal, and the tile is perpendicular to the centerline of the connecting rod. The matching gap between the big head tile and the curved neck, the thick-walled tile is usually adjusted by the tile gasket; the thin-walled tile