Maintenance knowledge of several typical lifting machines
1、 Bridge crane inspection and maintenance system
Due to the large number of components of the bridge crane, according to the different technical characteristics of each component, we divide the maintenance and inspection cycle into weeks, months and years. The specific contents of each cycle are as follows:
1. Weekly inspection and maintenance
Maintenance and inspection shall be conducted once a week. The contents of inspection and maintenance are as follows:
1) Check whether the nuts, cotter pins and positioning plates on the brake are complete and loose; whether the lever and spring have cracks; whether the pin bolts and buffer washers on the brake wheel are loose and complete; whether the brake is reliable. When the brake is opened, the opening of the brake pad shall be less than 1.0 mm, and the distance between the brake pad and both sides of the brake wheel shall be equal, and each axle pin shall not be stuck.
2) Check whether the safety protection switch and limit switch are positioned accurately and work flexibly and reliably, especially whether the rising limit is reliable.
3) Check whether the steel wire rope winding on the drum and pulley is normal, whether there is any phenomenon such as groove dropping, grooving, knotting and twisting, whether the bolts of steel wire rope pressing plate are fastened, and whether there is double nut anti loosening device.
4) Check whether the fastening screws on the coupling seal cover of the lifting mechanism are loose or short.
5) Check whether the transmission of each mechanism is normal and whether there is abnormal noise.
6) Check the lubrication condition of all lubricating parts.
7) Check whether there are foreign matters on the track that hinder the operation of bridge crane.
2. Monthly inspection and maintenance
Maintenance and inspection shall be carried out once a month. In addition to the weekly contents, the inspection and maintenance also include:
1) Check that the wear of the brake pad pad pad should not exceed 2mm, and the contact area between the pad and the brake wheel should not be less than 70%; check the installation and fixation conditions, wear and lubrication conditions of each pin shaft. The wear amount of each pin shaft should not exceed 5% of the original diameter, the wear amount of the small shaft and spindle should not be more than 5% of the original diameter and the ovality should be less than 0.5mm.
2) Check the wear of the wire rope, whether there is broken wire and other phenomena, and check the lubrication condition of the wire rope.
3) Check whether the hook has cracks, whether the wear of dangerous section exceeds 5% of the original thickness; whether the locking device of hook nut is complete; whether all parts on the hook group are complete and reliable. The hook shall rotate flexibly without jamming.
4) Check all bolts for looseness and shortage.
5) Check the bolt fastening condition of motor, reducer and other bases, and tighten them one by one.
6) Check the lubrication condition of the reducer, the oil level should be within the specified range, and measures should be taken to prevent the oil leakage.
7) Lubricate the gears.

8) Check the wear of the steel wire rope at the balance pulley, and lubricate the pulley and pulley shaft.
9) Check the condition of the pulley to see if it is flexible, whether it is damaged or cracked, and pay special attention to the wear of the fixed pulley shaft.
10) Check the brake wheel, the concave convex unevenness of its working surface shall not exceed 1.5mm, the brake wheel shall not have cracks, and its radial circular runout shall be less than 0.3mm.
11) Check the coupling, the upper key and keyway should not be damaged or loose; the axial displacement of the transmission shaft between the two couplings should be 2 ~ 7mm.
12) Check the running conditions of large and small cars, and there should be no rail gnawing, three fulcrum, twisting and swinging when starting and stopping. Check the wear condition of wheel flange and tread. The wear condition of wheel flange thickness shall not exceed 50% of original thickness, and the wear condition of wheel tread shall not exceed 3% of original diameter of wheel.
13) Check the condition of the crane track to see whether the bolts are loose and short, whether the pressing plate is fixed on the track, whether the track has cracks and fractures; whether the gap at the joint of two rails is 1 ~ 2mm (in summer) or 3 ~ 5mm (in winter), and whether the dislocation of joints is more than 1mm.
14) The crane shall be thoroughly cleaned to remove the dirt on it.
3. Half year inspection and maintenance
The maintenance and inspection shall be conducted once every six months. In addition to the monthly inspection contents, it shall also include:
1) Check the gear engagement and wear of all reducers. The pitting damage on the tooth surface should not exceed 30% of the meshing surface, and the depth should not exceed 10% of the original tooth thickness (fixed chord tooth thickness); the percentage of the wear amount of the gear tooth thickness to the original tooth thickness should not exceed 15% ~ 25%; check the condition of the bearing; replace the lubricating oil.
2) Check the condition of large and small wheels, lubricate the wheel bearings, and eliminate rail gnawing phenomenon.
3) Check the main welding seams of main beam and end beam for open welding and corrosion. The corrosion shall not exceed 10% of the original plate thickness, and whether the main stress-bearing parts have fatigue cracks; whether various guardrails and supports are complete; check the bolts of main beam and end beam and fasten them once.
4) Check the deformation of the main beam. Check the condition of trolley track. Under no-load condition, the downward disturbance of the main beam shall not exceed 1 / 2000 of its span; the inward horizontal side bending of the main beam shall not exceed 1 / 1500 of the measured length; the track of the trolley shall not be jammed, and the wear (single side) of the track top and side shall not exceed 3 mm.
5) Check the condition of the drum, the drum wall wear should not exceed 20% of the original wall thickness, rope groove convex peak should not be strain sharp.
6) Tighten all connecting bolts and fastening bolts on the crane.
4. Lubrication of overhead traveling crane
Lubrication is one of the important measures to ensure the normal operation of the machine, prolong the service life of parts, improve efficiency and safety in production. Maintenance personnel should fully understand the importance of equipment lubrication, regularly check the lubrication of each moving point, and regularly add lubricating oil (grease) to each lubricating point.
4.1 main lubricating parts of bridge crane in Danjiang power plant
① Hoist of bridge crane; ② various bearings; ③ gear coupling; ④ reducer; ⑤ wire rope; ⑥ hinge point on brake.
4.2 lubrication precautions
1) Keep the lubricating oil (grease) clean;
2) Different brands of lubricating oil (grease) can not be mixed;

3) Select suitable lubricating oil (grease) for lubrication according to the specified time;
4) The pressure grease injection method (with oil gun or oil pump, screw cap type oil cup) is used to add grease, which can squeeze the grease onto the friction surface and prevent it from entering the friction surface when wiping by hand;
5) Sodium based grease is not suitable for wet area because of its strong hydrophilicity and easy failure;
6) If there is no oil filling point in the rotating parts of each mechanism, a thin oil pot should be used regularly in each rotating gap to reduce friction and prevent corrosion.
2、 Maintenance contents of portal crane
1. All safety settings of rack drive luffing driving device of portal crane shall be sensitive and reliable. Because the rack is easy to be worn during operation, there will be impact when starting and braking. If the safety setting is not reliable, the boom will fall over the stroke.
2. The hydraulic transmission luffing driving device of portal crane has the characteristics of compact structure and can bear two-way force, but its piston, cylinder barrel and push rod have certain accuracy, so maintenance should be strengthened.
3. The torque wrench should be used to install the connecting bolts, so that the pre tightening force is more uniform. Since the portal crane is easy to vibrate in operation, it is necessary to regularly check whether the bolts are loose.
4. For hydraulic driven brake, the quantity of hydraulic oil should be checked frequently, and if it is insufficient, it should be supplemented appropriately. Check whether there is hydraulic oil leakage or air entering the oil cylinder at the oil pipe joint. If there is air in the oil cylinder, it should be eliminated in time.
5. The operating mechanism and brake should be checked frequently, especially whether the electromagnet of the crane brake is stuck due to vibration, and whether the coil of the electromagnet is damped.
6. The type of hydraulic oil in the oil pump should be selected according to the local temperature. In order to prevent the oil pump from sucking in air in the process of working, it is necessary to check and discharge it regularly.
7. Due to the self weight of gantry crane, the bearing of balancing trolley should be added with calcium base grease once a week to ensure that the friction surface does not appear dry friction.
3、 Safe use and maintenance of crawler crane
1. Operation points of crawler crane
1) All joysticks must be in the neutral position when the engine is started. After starting, check the indication value of each instrument and listen to the engine running condition, and then start to work after confirming that it is normal.
2) Before operation, test run should be carried out to check whether all mechanisms work normally and reliably. Especially when working after rain and snow, the crane should be retried and the work can be started only after the reliability is confirmed.
3) There shall be no obstacles affecting the operation of the crane. No one is allowed to stay or pass under the boom when working. It is strictly forbidden to use crane to carry personnel.
4) The safety protection devices such as amplitude indicator, moment limiter and travel switch of crane shall not be adjusted or removed at will. It is strictly forbidden to use the limit device to replace the operation. For the crane without lifting limit device, the maximum elevation angle of boom shall not exceed 78 °.
5) The crane must operate according to the specified lifting performance, and it is not allowed to overload or lift objects with unknown mass. It is strictly forbidden to use the lifting hook to pull or lift.
6) When lifting with full load, the crane must be placed on a solid horizontal ground. First, lift the heavy object 20-50 mm away from the ground. Check and confirm the stability and braking reliability of the crane before continuing to lift. The action should be stable, and it is forbidden to carry out two actions at the same time.
7) In case of heavy objects that must be lifted by two cranes, the weight shall not exceed 75% of the total allowable lifting capacity of the two cranes. Attention should be paid to the average distribution of load in binding, so that the load of each crane does not exceed 80% of the allowable load of the crane. Under the unified command and close cooperation, the hook pulley block of the two machines should be basically kept vertical.
8) The crane driven by hydraulic and pneumatic pressure shall operate according to the specified pressure and speed. It is forbidden to meet the construction requirements by means of increasing the pressure and speeding up the speed.
9) For the luffing mechanism driven by worm and worm gear, it is forbidden to pull the jaw clutch into neutral before the boom stops stably.
10) When the crane moves with load, the crane arm shall be parallel to the crawler, and the heavy object shall be tied with a pull rope. Do not turn too fast when walking. Do not turn when the road is rough or uneven.
11) When the crane runs without load on the ramp, the elevation angle of the boom should be reduced when going up the slope, and the elevation angle of the boom should be enlarged when traveling down the slope, so as to balance the center of gravity of the crane. It is forbidden to slide down the slope.
12) In case of strong wind, heavy snow, heavy rain or fog, the lifting operation shall be stopped and the boom shall be turned to the downwind direction.
2. Crawler crane transfer transportation
1) Long distance transfer should be transported by railway. If concave flat car is used for transportation, it can be loaded as a whole, and only the operation equipment needs to be removed. If the ordinary flat plate is used for shipment, the shed and working device shall be disassembled and divided into two wagons, which shall be handled according to the rules for the transportation of out of gauge goods.
2) The platform trailer with corresponding load capacity can be used for transportation in the city. During transportation, the jib and counterweight should be removed, the slewing brake should be braked, and the bolt should be fixed firmly. The two ends of the track should be padded and bound firmly. In order to reduce the height of the crane, lower the upper A-frame of the crane.

3) When a short distance is transferred by self-propelled method, it should not exceed 10km in general. Each part of the walking mechanism should be checked and lubricated every hour to avoid excessive wear and tear.
4、 Daily maintenance of tower crane
1. Maintenance of mechanical parts: check the brake of each mechanism, the operation of each mechanism, the fastening of connecting bolts of various parts, and the steel wire rope of each part. In case of any fault, it shall be timely eliminated. Check the working conditions of connecting bolts, welds and components of each mechanism, and fix and paint them regularly.
2. Maintenance of hydraulic system: add or replace the hydraulic oil on time, and check the oil pipe and its joint, safety valve, hydraulic pump and hydraulic cylinder, and deal with the problems found in time.
3. Maintenance of electrical system: wires and cables shall be free from damage, travel switch of safety device shall be reliable, and grounding protection resistance shall meet requirements.
4. Lubrication: the lubrication condition of each part of tower crane shall be checked regularly, and the lubrication shall be added or replaced on time.
5. In order to ensure the normal operation of tower crane and the safety of human and machine, the daily maintenance work centered on inspection, adjustment, cleaning, fastening, lubrication and replenishment must be done well.
5、 Maintenance of suspended crane
1. Check and fasten the transmission shaft seat, gearbox, coupling and shaft chain.
2. Check and adjust the clearance between the brake and the brake wheel, especially the evenness and uniformity of the clearance between the synchronous driver and the brake wheel of the crane, and it is required to be sensitive and reliable.
3. Check and adjust the wire rope, winch drum, hook and pulley for broken wire, crack and wear.
4. Check whether the brake is sensitive and reliable.
5. Check the oil level and oil quality of the gearbox, add new oil as required, and inject proper amount of grease into bearing seat, brake frame and coupling.
6. Check whether the limit switch is sensitive and reliable, whether the conductive frame is safe and reliable, remove the singed part of the electrical box, replace the contact, and check whether the protective device is complete and effective.
7. Check whether the signal light and telex are effective and reliable.
8. Wipe the appearance of the crane to ensure that there is no accumulation, oil dirt and rust, supplement the fasteners of each part and keep the equipment clean and intact.