Compressor overhaul and correct installation matters, super complete and detailed
Content covered by compressor overhaul
Compressors generally need to be overhauled after 12,000-26,000 hours of operation. In addition to all the work required for intermediate maintenance, the machine is usually disassembled, some parts are replaced, and sometimes the cylinder is bored (or replaced), and the piston is replaced. , Repair the fuselage and base, reconfigure the bearing and change the crankshaft (or chrome plating, spray plating and then grinding), etc. Many parts may be replaced during overhaul. It is to use the method of reinstallation and assembly to restore the normal working ability of the compressor.
Carry out a comprehensive inspection of the compressor or unit, including the circuit and the connections of each part, so that the compressor or unit reaches a sound level.
1. The compressor disintegrates;
2. Check the gap of each bearing bush (clearance and contact surface) to determine which parts should be replaced;
3. Crankshaft, connecting rod, crosshead piston rod flaw detection
4. Check the condition of the slide and refurbish;
5. Grease the motor;
6. Check the elastomer to determine whether to replace it;
7. Check the oil scraper ring and confirm repair or replacement;
8. Check the cylinder mirror and confirm repair or replacement;
8. Replace the packing and oil scraper ring, check the backlash of the seal ring and oil scraper ring, assemble the packing (coated with special anti-wear repair grease); and check whether the seal ring and oil scraper ring are flexible;
9. Replace the piston ring, check the backlash and radial height of the piston ring, support ring; check the clearance between the cylinder and the piston in advance;
10. Clean the crankcase;
11. Clean the crankshaft and check whether the dimensions of each journal of the crankshaft are qualified
12. Check the bearings to be installed
13. Prepare spacers, heating equipment and bearing clamping and lifting tools
14. Heating bearing
15. Assemble the bearing to the crankshaft journal, check whether it is in place and whether the bearing is flexible or not
16. Pre-assemble the bearing seat as required (note the axial position)
17. Install the balance iron, check whether it is in place, and lock the balance iron bolts;
18. Hoist the crankshaft as required, pay attention to heating and pre-install another bearing seat to the predetermined position;
19. Check the axial position of the crankshaft (adjust with bearing cover or positioning bearing);
20. Assemble the connecting rod and the crosshead, and check the clearance of the crosshead pin;
twenty one. Lift connecting rods, crossheads, and check the clearance of slides;
twenty two. Hoist the cylinder;
twenty three. Lift the piston with a threaded sheath, and place a baffle at the stuffing box and oil scraper ring to prevent the piston rod from hitting the packing and oil scraper ring;
twenty four. Check the internal and external clearance of the piston and the cylinder, and adjust to the requirements, tighten the connecting thread of the piston rod and the crosshead, and pay attention to loosening;
25. Install the cylinder head;
26. Gas valve
27. Install buffers and other pipelines;
28. Cranking inspection;
29. Check whether there are omissions, and deal with item by item acceptance;
30. Clean up the site and prepare for test drive.
2. The specific aspects of the repair of various types of compressors. The repair of piston compressors
2.1.1 Repair of crankcase slide or fuselage
The crankcase slide or the fuselage of the piston compressor is the installation basis of the moving parts and the cylinder, the force is complicated and the load is concentrated, and its dimensional accuracy and shape position deviation directly affect the trajectory of the moving parts. The vibration of the compressor is also transmitted to the foundation through the crankcase slide or the fuselage.
2.1.1.1 Cracks in the crankcase slideway or the fuselage cannot be repaired.
2.1.1.2 Slippery slide
When the compressor slide is in use, due to improper installation, uncleanness, or the presence of hard particles in the lubricating oil, sometimes the slide is roughened. This phenomenon should be repaired in time, otherwise it will enlarge the problem of roughing. Cause; burn the slide; phenomenon. Different repair methods can be used according to the degree of napping.
1) Slight longitudinal groove strain: as few as 1 and as many as 3 to 5, scratching horizontally with your nails can be clearly felt, and there will be longitudinal strains on the cross head. If this phenomenon is not repaired in time, it may develop into a large area of roughness. The repair method is: first crank, stop the crosshead at the dead center position, and fix the crankshaft so that it cannot rotate. Then use cambered whetstone dipped in engine oil to push and polish it longitudinally, and then polish it with water sandpaper. Do not allow grinding debris to fall between the skateboard and the slide. Then crank the crosshead to stop at another dead point to fix the crankshaft, and polish another section of the slide in the same way. And check the cross-head slide to see if there is any fuzziness. If the skateboard is also rough, remove the cross-head pin, exit the connecting rod, turn the cross-head from the maintenance window of the fuselage, so that half of the cross-head slide is exposed, and polish the slide with oilstone and sandpaper. Grind the other half of the slide from the other side window.
2) For longitudinal band strains whose width does not exceed 1/10 of the width of the slide plate, and the maximum is not more than 1/5, it can also be repaired according to the repair method of longitudinal groove strain.
3) When the slideway is completely roughened, the middle body or body should be replaced, or a large slideway should be bored on a boring machine. Two points should be paid attention to:
(1) When boring the slideway, ensure that the processed center line coincides with the original centerline;
(2) After boring the slideway, measure the inner diameter of the slideway and equip the crosshead according to the clearance requirements. The dovetail groove of the original crosshead skateboard surface car can also be poured into Babbitt alloy. The car is a size that matches the size of the slide. Attention should be paid to the outer circular surface of the crosshead slide plate to ensure that the centerline of the crosshead after processing coincides with the original centerline. If it is a crosshead with a replaceable slide structure, the slide can be replaced.
4) When the slideway wear is too large, the slideway clearance is too large (more than double the factory clearance), and the slideway surface is in good condition, a crosshead or a skateboard can be equipped.
After the crosshead is equipped, the size and uniformity of the slideway gap should be checked during installation, and can only be put into use after trial operation. The calculated value of the clearance between the crosshead and the slideway is 8/10000 of the inner diameter of the slideway, and the high-speed compressor is 12/10000.
5) Adding SL lubricating oil anti-wear repair agent to circulating lubricating oil will prevent the phenomenon of fuzzing, even if it occurs, fuzzing of slides will be automatically repaired.
2.1.2 Crankshaft repair
During the use of the crankshaft, sometimes the journal (main journal and crank diameter) wear or the keyway wear is too large.
(1) Axle journal wear
The long-term friction between the journal of the crankshaft and the bearing bush will cause uniform wear of the journal while the surface of the journal opposite to the oil groove of the bearing bush is not worn, and wear appears on both sides. Before changing the bearing bush, the surface of the journal should be polished with emery cloth, and the deviation of the journal cylindricity should not exceed half of the journal tolerance.
Nowadays, thin-walled bearings are mostly used in piston compressors. The gap between the main bearing bearing and the connecting rod head bearing is generally (8-13) d/10000, and the measured gap is even smaller than 0.02 mm. In use, it is feasible to calculate the clearance within 2.0/1000 of the journal size. If it exceeds 2.5/1000, replace the thicker bearing or repair the journal.
The most reliable method of repairing the journal is the thermal spray welding process, which is not easy to fall off after repair. The metal powder for thermal spray welding with the sprayed surface close to the crankshaft base material and slightly higher hardness (20-30HB) should be used.
The hardness of the journals repaired by the iron plating process is very low, and some have to be plated again every year, which is not worth the loss.
The crankshaft should be inspected for flaws before spraying. A crankshaft with cracks should not be repaired and cannot be used continuously.
(2) Shaft neck napping
Due to the deterioration of the lubricating oil, the blockage of the oil circuit and the shedding of wear-resistant alloy of the bearing bush, the surface of the journal will be severely worn. There are two ways to repair:
1) Grind the journal with a crankshaft grinder or lathe to make the geometric accuracy and roughness meet the requirements. The journal will be smaller than the original journal and bearing bushes must be prepared.
2) Thermal spray welding process repair.
After the crankshaft is repaired, the gap between the bearings may be inconsistent, and the bearing with a large gap will not be sufficiently lubricated. The following measures can be taken to solve:
1) Increase lubricating oil pressure: the lubricating oil pressure can be increased to 0.6 MPa. If the flow of the oil pump is insufficient, consider replacing the oil pump and cleaning the oil filter in time to avoid excessive pressure drop of the power filter. Some medium and small compressors lubricating oil pressure gauges are installed between the oil pump and the oil filter. They are not equipped with filtered oil pressure gauges or differential pressure gauges. When the filter is clogged, the value of the lubricating oil pressure gauge is not the oil supply pressure of the moving parts. , Appears; false oil pressure;. It is difficult to ensure that when the lubricated piston compressor runs for more than 10,000 hours, the pressure of the lubricating oil should not be reduced, but should be higher than the original pressure value. Generally, the lubricating oil pressure of the piston compressor should be 0.2～0.4 MPa at the highest temperature and the highest pressure. API618 stipulates that it should not be less than 0.1 MPa.
2) When the surface condition of a main journal of a symmetrically balanced compressor is poor or the clearance is too large, the diameter of the oil supply branch pipe (the oil pipe from the oil supply main pipe to the bearing seat) can be enlarged to enhance the oil supply capacity of the bearing.
3) Wear of keyway
The reason for the wear of the keyway of the rotor shaft is that the belt wheel (flywheel, coupling, or drive gear, etc.) is too loose with the journal, or the connection between the tapered bushing and the tapered shaft extension is loose, so that the keyway bears improper impulse impact Load. When this happens, the shaft journal and the shaft journal extending inward should be inspected first to find out whether there are cracks. Only when there is no crack, can the keyway or the key be repaired.
When repairing the crankshaft keyway, pay attention to repairing the hub keyway. You can check the width of the keyway of the inner hole and the keyway of the journal first, repair the wider keyway first, and repair one side of the keyway with a file or a scraper. When repairing, check the parallelism between the repaired surface and the unrepaired side with an internal micrometer. After the side surface is repaired, use the side surface as a reference to repair the other side surface, paying attention to the symmetry of the two keyway sides to the journal axis. Match the key according to the repaired keyway width, the width of the key and the width of another keyway, calculate the size of the one side of the keyway that should be repaired, repair the side of the keyway one by one according to the above method, and continuously check the width with the key.
Check the contact area of the original tapered shaft extension and the mating inner tapered surface. If the contact area is less than 70%, the tapered surface should be scratched.
The clearance between the cylindrical shaft extension and the inner hole of the mating part should be checked, the repair size should be determined, and the matching clearance should be controlled to zero. The inner cylindrical surface or shaft extension can be plated by brush plating. It can also be equipped with transmission parts or flywheels matched with journals.
2.1.3 Crosshead repair
The crosshead of the compressor will be broken, the slide plate is rough or excessively worn during use, the pin hole is worn, and the flange of the connecting piston rod is worn. The repair method is as follows:
(1) Repair of pin hole wear
(2) 1) Repair of fixed pin hole; fixed pin includes tapered pin and cylindrical pin with anti-rotation parts. Such cross-head pin holes sometimes wear out abnormally. When the wear develops to the point that vibration will occur if it is not repaired, the pin holes should be repaired. Such pin holes can be repaired by brush plating. Before repairing the pin hole of the taper pin crosshead, check the contact of the pin hole and the displacement of the crosshead pin with the taper pin to determine the size of the taper surface to be brushed. Use taper pins to check the fit of the taper surface after brush plating (check with coloring method). Use wind grinding wheel or electric grinding wheel to grind, and gradually make the contact surface reach more than 70%. And check whether the axial position of the taper pin is correct to prevent the oil hole from being misplaced and affecting the installation and movement of the small end of the connecting rod. Check the verticality between the center line of the pin hole and the axis of the crosshead slide.
(3) 2) Repair of floating pin hole: When the design, manufacture and use are reasonable, the pin hole of the floating crosshead pin wears very slowly. When the pin hole is abnormally worn, the cause should be found first, and then the pin hole should be repaired. The original pin hole has a replaceable bushing with a bushing; if there is no pin hole, a bushing can be added. The bushing and the cross-head pin hole adopt an interference fit. After the bushing is inserted into the crosshead body, the inner circle of the bushing should be scraped so that the gap between the bushing and the pin is controlled to be about 1/5 of the gap between the pin and the connecting rod small head tile, and check the center line of the pin hole and the center of the crosshead slide The perpendicularity of the line. Finally, drill through the oil hole from the original slide plate to the cross head pin. Brush plating is not suitable for repair.
(2) Repair of connecting part with piston rod
The screw hole, the positioning plane or the flange clamp table are damaged due to the loose connection device in this part.
The threaded hole connected with the piston rod on the cast iron or ductile iron cross head is damaged, so that the strength is generally not suitable for repair.
The plane of the connecting part of the crosshead and the piston rod is punctured or crushed, which must be repaired. You can use a flat scraper to scrape and smooth. The plane here must be strictly perpendicular to the centerline of the crosshead slide plate. A little bit worse will have a great impact on the coaxiality between the piston rod and the centerline of the crosshead.
After repairing, connect the piston rod and the crosshead, tighten the connecting device, and use the piston rod as a reference to measure the outer circle runout of the full length of the crosshead slide; or use the crosshead slide as a reference to measure the full length runout of the piston rod. The runout value should not be greater than 0.03 mm over the full length of the piston rod. If this requirement cannot be met, the plane should be scraped until it meets the requirement.
After the crosshead is repaired, it should be inspected for cracks by ultrasonic testing or penetration testing.
2.1.4 Piston repair
After the piston of a small or micro compressor is abnormally worn, the piston is usually replaced.
The pistons of large and medium-sized compressors are worn out abnormally, mainly in the piston ring groove, outer ring bearing surface and piston rod bearing surface
(1) Wear of the piston ring groove; after the wear here, the gap may exceed the limit, causing abnormal vibration and noise (the double-acting piston is more obvious). Generally adopt the method of replacing the piston.
(2) Repair of the outer ring bearing surface of the piston: The outer ring bearing surface of the piston bears the weight of the piston and 50% of the weight of the piston rod, and it will wear out after long-term reciprocating friction. Two things will happen after wear:
(3) 1) The bearing surface is flush with the surface of the piston, the piston cannot be protected by the bearing surface, and the cylinder and the piston may be pulled up.
Due to the wear of the bearing surface, the centerline of the piston sinks, resulting in excessive clearance at the upper part of the piston, uneven force on the piston ring, and accelerated wear.
In the past, the piston bearing surface of large compressors was mostly cast with Babbitt alloy. When the babbitt alloy bearing surface is worn, the babbitt alloy should be re-poured. The babbitt alloy bearing surface is generally 1 to 1.5 mm higher than the piston.
Now large compressors mostly use PTFE support rings filled with carbon fiber powder, which are easier to replace after wear.
Experience has proved that after the bearing surface or support ring of the high-pressure piston is worn, the life of the piston ring will be greatly reduced when the center line of the piston sinks 1 mm
3) Repair of the piston support end surface; The piston support end surface and the piston rod support end surface cooperate with each other to ensure the correct position of the piston. After use and disassembly, this surface will change the surface and should be repaired before installation. This plane is required to be perpendicular to the axis of the piston inner hole, so it is better to scrape it with a flat scraper when repairing, and use the coloring method for inspection. During the inspection, the nut should be tightened to check the runout of the piston rod on the outer circle and end face of the piston. The value should not be greater than 0.015 mm. Use the coloring method to check the contact area, which should not be less than 70%.
When repairing, repair the end face of the piston rod first, and then repair the positioning end face of the piston based on the end face of the piston rod.
Some pistons and piston rods are fitted with a conical surface. When replacing the piston, check the contact area and coaxiality between the piston and the piston rod.
2.1.5 Cylinder repair
After the compressor is used for a long time, the cylinder will wear out. Some are normal bright wear, which is characterized by that the surface roughness of the mirror is still good, and it seems that there is no problem at a rough level. After measuring with an internal micrometer, the mirror surface is elliptical, conical or drum-shaped. If the deviation of the mirror cylindricity exceeds one thousandth of the cylinder inner diameter, it should be repaired.
Boring cylinder is a common method to repair the cylinder mirror surface. After boring the cylinder, the cylinder mirror surface should be honed on the cylinder honing machine. When there is no honing condition, try to make the cylinder mirror surface meet the requirements of the following table.
The cylindricity deviation should not be greater than 0.0001～0.00015 of the cylinder inner diameter.
The boring amount of the cylinder wall thickness is determined by: After the cylinder diameter increases, the piston force does not exceed the specified value. After the cylinder is bored and repaired, a hydraulic test shall be carried out. After the cylinder is bored, it should be matched with a suitable piston ring.
If the original is a cast iron piston ring, after boring the cylinder, it is not easy to buy a suitable piston ring, you can consider changing the cast iron piston ring to a filled PTFE piston ring, the height of the ring can be changed to twice the height of the cast iron piston ring , Rectangular cross section can be used.
If the cylinder mirror surface is damaged, it is not advisable to use the boring method to repair the cylinder, consider adding a cylinder liner after boring the cylinder to repair the cylinder. This method should understand the cylinder inner diameter wall thickness and the possibility of boring repair.
When the cylinder mirror is slightly strained in the longitudinal direction, the cambered oil stone can be used to grind the mirror horizontally until it is smooth and polished. And check whether there is any hard granular foreign matter embedded on the piston. If foreign matter is found embedded, clean it up. When the fuzz is severe, it should be repaired by honing or honing after boring the cylinder.
Adding SL lubricant anti-wear repair agent to the oil injection will gradually repair this kind of hair.
There are cracks in the inner diameter of the cylinder and the installation port of the valve, which should not be repaired; when there are cracks on the outer wall of the cylinder, if the crack is in the air cavity, it should not be repaired, and it can only be scrapped. When the crack is on the side of the water cavity, welding repair methods can be considered. After welding, the welding stress should be eliminated and a hydraulic test should be carried out. This patching method is only allowed for users.
