1、 Inspection of surrounding environment of crane
The operating environment and track are directly related to the safe operation of the crane, so they are also essential for the safety inspection of the crane. The inspection points are as follows:
1. Check whether there are power lines (especially high-voltage lines) in the crane operation section. The crane shall keep enough safe distance from it during operation. Otherwise, corresponding measures shall be taken to limit the operating range of the crane.
2. Check whether the surrounding buildings and temporary facilities hinder the normal operation of the crane, and whether the jib, counterweight and other parts will collide with it. Special attention shall be paid to inspection when the crane is running on the track or when the fixed crane moves up and down. For the tire crane and truck crane, it is also necessary to check whether the position of its feet is sufficient, whether there is a hole in the ground and the size of the ground bearing capacity.
II. Inspection of crane track
1. Whether the rail clamp or iron shoe is lost: it shall be specially checked for its firmness on the track and whether there is a safe distance of 1-3m from the end of the track.
2. Check whether the anti-collision devices at both ends of the track are missing or loose, and whether the installation position is correct. At the same time, check whether the travel switch has a suburb and whether the position is correct.
3. Check whether the pressing plate, connecting plate, track timber, track nail, etc. of the track are complete, and whether there are obstacles hindering the operation on the track.
4. Pay attention to whether there is rail gnawing. Serious rail gnawing will grind the inner and outer sides of the track into bright band marks, accompanied by difficult starting and increased running resistance. In the long run, the drive motor will be overloaded and burned, and the wheel and track will be quickly worn. In addition, the crane itself and gauge shall be further inspected to eliminate rail gnawing in time.
5. The gap between the rail joints shall be kept between 2 and 6mm. The positions of the two rail joints shall be staggered. The staggered distance shall not be equal to the base distance between the front and rear wheels of the crane. If it does not meet the requirements, large vibration will be caused when the crane runs to the joint.
III. inspection of crane traveling part
1. Check whether all open gears and couplings are equipped with protective covers.
2. Check whether the joint surfaces of open gears and couplings are excessively worn.
3. Check the running wheel tread. Since the tread has to bear a great contact stress of the track, if the surface hardness quality is poor, the massive peeling phenomenon can be seen in the inspection.
4. Check whether the oil hole of the traveling axle is unblocked. If the oil path is blocked and no butter is added, the bearing bush will be dry ground, and then the bearing bush will be crushed into fragments and run out, so that the four supporting points of the crane will be unequal in height, the structure above the trolley will be deformed, and the stress concentration will be caused to the main structural welds and the main connecting parts. The wheel without bearing bush will move left and right during operation, and the whole track will be polished.
5. Check whether the fixing foundation bolts of the gearbox are loose. Due to the frequent traveling of the crane and the huge inertia kinetic energy vibration, the foundation screws are easy to be loosened. If it is not tightened in time, the screw hole at the bottom foot of the gearbox may be torn, thus affecting the coupling and causing deterioration of the crane operation;
IV. inspection of crane metal structure
1. Plastic deformation of metal structure. Due to factors such as overload, thermal radiation and over frequency use, the upper camber of the main beam will disappear or even produce downward deflection deformation. Therefore, the upper camber of the main beam is the key part of the crane structure inspection. In addition, whether the main limb of the boom is bent or twisted; Whether the padeye of the pin at the root of the arm and the balance arm is cracked; Whether the welding seam between the main beam web and the lower cover plate of the bridge crane is cracked shall be inspected.
2. Check the connecting bolts of main structures. The connecting screws of important parts such as the boom of the crane, the tower body of the tower crane, the base of the crawler crane, the slewing center bearing seat of the portal crane may become loose after a period of movement. In use, we also found that the bolts at the above positions may even break from the root under the combined action of tensile stress, shear force and torsion force. It should be carefully checked.

V. inspection of main mechanism and parts of crane
1. Check the reducer to see whether it leaks oil. If there is abnormal noise in the box during operation, open the box cover for inspection. Generally, it is caused by bearing damage, excessive gear meshing backlash and serious tooth surface wear.
2. Check the performance and condition of the brake. The brake is an important part of the crane, which directly affects the accuracy and reliability of the movement of each mechanism. Therefore, it is necessary to carefully check the condition of the brakes of the lifting and luffing mechanisms, and observe the opening of the brake shoe and the wear of the friction element brake shoe. For the belt brake, pay attention to check whether the steel backing of the brake belt is cracked, whether the brake transmission is flexible, whether the brake frame is intact, and whether the elasticity of the main spring and the auxiliary spring meet the requirements.
3. Inspection of steel wire rope. The inspection of wire rope shall focus on the observation of broken wire, wear, kink, corrosion, etc. the positions with serious wear and broken wire but not exceeding the standard shall be marked so as to focus on tracking and re inspection. Pay attention to check whether the safety stopper of the steel wire rope in the drum is effective, whether the steel wire rope pressing plate on the drum is pressed and whether the number of pressing plates is appropriate.
4. Inspection of pulley. The focus is on whether the wear at the groove bottom exceeds the standard and whether the cast iron pulley has cracks. For the balance wheel of the hoisting mechanism pulley block, it is easy to be ignored because it does not act under normal conditions. Therefore, it is necessary to check the flexibility of rotation before installation, otherwise, the length and tension of the left and right steel wire ropes during the installation cannot be automatically adjusted by the balance wheel, which increases the difficulty of adjusting the hoisting rope at high altitude and the degree of operation risk.
5. Check whether each coupling is loose or even "rolling key". Focus on checking whether the elastic rubber ring of the elastic pin coupling has abnormal wear, and pay special attention to the gear ring wear of the gear coupling. Due to poor installation accuracy, when there is a large offset between the two shafts, the whole gear ring will wear out quickly in a short time. In case of such situation in the lifting mechanism, serious accidents are likely to occur.
Vi. inspection of hydraulic transmission part of crane
For tire type and truck type cranes, hydraulic transmission is generally used for lifting, slewing, luffing and outrigger expansion and contraction. The key points of hydraulic transmission inspection are as follows:
1. Mark and check whether the telescopic boom oil cylinder can maintain the extended length of the boom and whether there is leakage.
2. Check whether the luffing oil cylinder and outrigger oil cylinder have leakage, and whether the sinking and retraction amount meet the requirements under the rated load. Whether the outriggers have "soft legs".
3. Check whether the hydraulic oil is deteriorated and polluted, whether the liquid level of the oil tank is not lower than the lower limit of the normal mark, and whether the high pressure pipes and joints are leaking.
4. Check whether the oil pumps, valves and hydraulic locks operate normally; Whether the action is sensitive and reliable; Whether there is abnormal vibration and noise; Whether the performance of the seal is good, and whether there is internal leakage and leakage of hydraulic oil.
VII. Electrical inspection of crane
Electrical equipment is a more complex part of the crane. It is easy to break down when operating under the conditions of impact, vibration and swing. Especially in the harsh environment of high temperature, dust and humidity, it is more likely to break down and may cause accidents. Therefore, the main items of safety inspection for the electrical parts of the crane are as follows:
1. Check whether the insulation resistance of the motor is within the normal range, whether there is abnormal noise during operation and whether the temperature rise is normal; Check the slip ring, brush and wire connector for obvious cracks, wear, looseness and adhesion of carbon powder during shutdown;
2. Check whether the current collector and power sliding wire are deformed and worn, whether the tensioning device is normal, and whether the sliding wire and the slider are in good contact. If the power is transmitted by cables, check whether the cable insulation layer is aging, whether the cable guide device is flexible and whether the cable is flexible.
3. Check electrical components and control system. Check whether the shell of each switch is damaged, whether the pressure of the contact part is appropriate when closing, and whether the capacity of the fuse meets the requirements; Whether the main contact and auxiliary contact of the contactor are singed, whether the pressure between the contacts during contact is sufficient, and whether the contact is completely disconnected; Whether there is any attachment on the attraction surface of the moving and static iron core of the contactor, whether there is abnormal sound during the attraction, and whether the arc extinguishing cover is in good condition; And whether the relays on the distribution cabinet work normally, and whether the terminals and wiring screws are fastened. In the cab, check whether the action direction of each master controller is connected correctly, pay attention to check whether there is zero position protection, especially check whether there is an emergency power-off switch on the console, and confirm that the power can be effectively cut off in case of emergency. Similarly, pay attention to check the sensitivity and reliability of overload limiter, torque limiter and travel protection devices.
VIII. Conclusion
This article describes some main aspects of professional inspection of cranes, including some inspection contents that should be done before daily operation of drivers. It is within the scope of the driver's responsibility to do a good job in the safety inspection of the crane before the shift, which cannot be replaced by the regular professional inspection of the crane. Therefore, an important part of the crane safety management is to strengthen the safety education for the crane operators and urge the drivers to consciously do a good job in the daily inspection and maintenance of the crane. Only the combination of daily inspection and professional inspection can ensure the safe operation of the crane.