I. Pulleys and pulley sets

1. Pulley

A pulley is a rotating piece with one or several guide slots used to guide and/or change the direction of the wire rope (chain), and the force of the wire rope (chain) on the pulley does not change essentially.

(1) The type of pulley according to the pulley manufacturing process, can be divided into casting pulley, welding pulley, double plate pressing pulley and rolling pulley; According to the bearing type used, it can be divided into deep groove ball bearing type, cylindrical roller bearing type, double row full cylindrical roller bearing type and plain bearing type. The typical structure of the cast pulley is shown in Figure 1-4.

(2) Pulley according to the role can be divided into working pulley and balance pulley; According to the movement of the axis, it can be divided into fixed pulley and dynamic pulley. Working pulley is responsible for the main work of the pulley, there are fixed pulley and moving pulley. The fixed pulley is installed on the shaft in a fixed position and rotates around the shaft to change the direction of the movement of the wire rope or force, such as the guide pulley; The pulley is installed on the moving mandrel, which is lifted and lifted together with the traction load to achieve the purpose of labor saving, such as the pulley block of the hook head. A balancing pulley is a pulley used to equalize the elongation of a wire rope in a wire rope winding system.

2. Wheel selection group

The device composed of the wire rope successively bypassing a number of fixed and driven pulleys is called a pulley block.

The pulley block can pull a heavy load, not only open the road but also change the direction of the force. The block assembly equipped with a lifting hook is a lifting block. The multiplier of the block is the multiple of its labor saving. The multiplier of the double block is equal to half the number of branches of the rope supporting the lifting load.

3. Safety technical requirements and maintenance of pulley and pulley block

(1) The pulley should be able to rotate freely and provide sufficient support for the wire rope to avoid excessive bending stress, radial pressure and inertia of the wire rope.

(2) The pulley should have a device or structure to prevent the wire rope from slipping out of the rope groove. The gap between the side plate of the pulley cover and the circular top plate equal to the pulley body should not exceed 50% of the nominal diameter of the wire rope.

(3) Pulley blocks accessible by hands should be provided with pulley covers. For the pulley block that may fall to the ground, the pulley cover should have sufficient food strength and rigidity.

(4) The pulley and pulley set should be checked once a week, and the pulley lubrication should be carried out according to the instructions.

4. Scrap standard of pulley

The pulley should be scrapped in any of the following circumstances:

(1) Surface defects that affect performance, such as cracks or loose riveted pipes.

(2) The rim is damaged, and the uneven wear of the wheel groove is up to 3mm.

(3) The wall thickness of the wheel groove is worn to 20% of the original wall thickness, and the diameter of the bottom of the wheel groove is reduced by 50% of the diameter of the wire rope due to wear.

(4) The wear amount of the double plate pressing pulley rope liner exceeds 50% of the original thickness, the wear amount of the pulley shaft reaches 3% of the original diameter, and the rope liner and the pulley shaft should be scrapped.



Two, the drum

The drum is a rotating part, which is installed on the drum group, and its main function is to wind the wire rope driven by the motor to realize the lifting action of the lifting mechanism of the lifting machine, or the changing action of the flexible amplitude changing mechanism. Figure 1-5 shows the appearance of the drum.



1. Safety technical requirements and maintenance of the drum

(1) The wire rope should be arranged neatly in order on the reel. Winding only one layer of wire rope drum, there should be a rope groove; The drum used for winding redundant layers should adopt the rope arrangement device used or the flange guide structure which facilitates the automatic winding of the wire rope.

(2) The multi-layer winding drum shall have a flange to prevent the wire rope from sliding off the end of the drum. When the wire rope is all wrapped around the drum, the flange should exceed the outermost layer of wire rope, and the height should not be less than 1.5 times the diameter of the wire rope (for tower cranes, it should not be less than 2 times the diameter of the wire rope).

(3) The fixing device at the end of the wire rope on the drum should be safe and reliable and have anti-loosening or self-tightening performance, if the end of the wire rope is fixed with a pressure plate, the degree of fixing should not be less than 80% of the minimum breaking tension of the wire rope, and there should be two separate pressure plates clamping, and the bolt will be reliably fixed.

(4) Check the drum once a week, focusing on the fixing of the steel wire rope tail plate and bolts, and shall not be loosened.

(5) The drum shall be lubricated according to the instruction manual.

2. Scrap of drum

The drum should be scrapped when one of the following situations occurs:

(1) Surface defects that affect performance, such as cracks.

(2) Cylinder wall wear up to 20% of the original wall thickness.



Three, the reducer

The reducer on the crane is one of the important transmission components, and its role is to reduce the high speed of the motor to the working speed required by the various institutions and transmit torque.

1. Crane reducer varieties

The crane reducer base is an accelerator, a crane with three fulcrum reducer, a crane with a vertical reducer, a crane with a package reducer, a crane with a base type hard gear reducer, a crane with three branch hard gear reducer, a crane with a three-in-one reducer.

2. Structural type and lubrication requirements of crane reducer

The following only describes the structural types and lubrication requirements of the two types of retarders:

(1) Crane base type hard tooth surface reducer: including QY3D, QY4D, and QY34D three series of external engagement involute helical cylindrical gear reducer, mainly used in the crane related mechanisms.

According to the transmission mode, its structure can be divided into three-stage transmission type (QY3D), four-stage transmission type (QY4D) and three-stage and four-stage combination type (QY34D), as shown in Figure 1-6.



(2) Crane with three fulcrum hard gear reducer: including QY3S, QY4S, and QY34S three series of external engagement involute helical cylindrical gear reducer, mainly used in the relevant machinery of the crane.

Its structure type. According to the transmission mode, it can be divided into three-stage transmission type (QY3S type), four-stage transmission type (QY4S type) and three-stage and four-stage combination type (QY34S type), as shown in Figure 1-7.



The lubrication requirements of the above two retarders are as follows:

1) The horizontal installation reducer uses oil pool splash lubrication, and the vertical installation reducer uses circulating oil injection lubrication. The lubricating oil should be L-CKC220 or L-CKC320 industrial closed gear oil in accordance with the "Industrial closed Gear oil" (GB 5903-2011).

2) When the ambient temperature is below 0 ° C, there should be a lubricating oil heating device. When the oil pool splash lubrication is used, the reducer can only be started when the oil temperature is higher than 0 ℃. When oil injection lubrication is used, the reducer can only be started when the oil temperature is higher than 5 ℃.

3) When the bearing uses oil pool splash lubrication, the lubricating oil used should be the same as the gear lubricating oil.

4) Different grades of lubricating oil are not allowed to be mixed.

3. Inspection and maintenance requirements of crane reducer

(1) The inspection and treatment requirements of sealing and lubricating oil are as follows;

1) There should be no oil leakage or oil leakage, the amount of oil should meet the requirements, and it should be added in time when it is insufficient.

2) The lubricating oil should be replaced regularly according to the regulations, and the lubricating oil should be replaced in time when it is found that the deterioration of the lubricating oil is prohibited from mixing with each other.

3) The inspection of oil and oil level and the replacement of oil must cut off the power supply to prevent electric shock and wait for the reducer to cool down.

(2) Disassembly and installation requirements are as follows

1) When disassembling and installing the gear, bearing and other parts of the reducer, try to avoid direct tapping with tools such as hammers.

2) When replacing the gear, try to use the original parts and replace them in pairs; When assembling the output shaft, pay attention to the tolerance fit and protect the hollow shaft.

(3) Scrap standards for reducer gears and other transmission gears. If the drive gear scrap index is not provided in the operation and maintenance manual, it should be scrapped in any of the following cases

1) The peak or valley of the tooth surface caused by plastic deformation of the tooth surface is higher or lower than 20% of the theoretical tooth module (the module m refers to the ratio of the tooth distance r between the adjacent two teeth on the same side of the tooth profile and the PI PI, that is, m=t/π, the unit is mm. The greater the modulus. The higher the tooth, the thicker).

2) The tooth break is greater than or equal to 1/5 of the tooth width, and the tooth crack is greater than or equal to 1/8 of the tooth width (when the crack of the tooth does not reach the scrap standard, it should be tried to remove and stop the development).

3) The pitting area of the tooth surface is 50% of the working area of the gear tooth, or the maximum size of the pitting pit is more than 20% to 0.2 modulus, or the pitting pit depth of 20% of the lifting and non-equilibrium amplitude changing mechanism is up to 0.1 modulus, or the pitting pit depth of 20% of other mechanisms is up to 0.15 modulus.

4) The gluing area of the tooth surface is 20% of the working tooth surface area. And the depth of the gluing groove is up to 0.1 modulus.

5) The criteria for tooth surface stripping are the same as those for tooth surface pitting.

6) The sum of wear amounts on both sides of the root for lifting, non-equilibrium amplitude changing mechanism and tooth root reaches 0.1 modulus; For other mechanisms, the sum of wear on both sides of the root reaches 0.15 modulus.

7) Lifting hot metal or inflammable explosive and other dangerous goods lifting, non-balanced amplitude changing mechanism, the transmission gear tooth surface pitting area and tooth surface spalling up to 3), 5) of 50%, or root wear up to 6) of 50%

Figure 1-8 shows the gear teeth and their parameters





4. Reducer oil leakage causes and solutions Figure 1-8 gear teeth and parameters

(1) The causes of oil leakage are as follows

1) The structural design of the reducer has no ventilator, and the reducer can not achieve pressure balancing, causing oil leakage.

2) The pressure in the tank rises, and the oil seeps from the improper seal.

3) The amount of refueling is too much, and the lubricating oil accumulates in the shaft seal, the joint surface, etc., resulting in leakage.

4) During equipment maintenance. The dirt on the joint surface is not completely removed, the improper selection of sealant, the reverse direction of the seal, and the timely replacement of the seal will also cause oil leakage.

(2) Solutions for leaking oil are as follows

1) Specific solutions should be taken according to the cause of the leaking oil.

2) For the static sealing point leakage of the reducer, polymer composite materials and technology can be used to solve the problem.



Four, coupling

A coupling is a device that connects two shafts or shaft rotating parts and transmits torque and movement.

1. Type of coupling

Coupling is divided into rigid coupling, flexible coupling and safety coupling three categories. A coupling that cannot compensate the relative displacement of two axes is called a rigid coupling; A coupling that can compensate the relative displacement of two axes is called a flexible coupling; A coupling with overload protection is called a safety coupling. Figure 1-9 shows the toothed couplings of flexible couplings.



2. Coupling use and maintenance requirements

(1) The coupling is not allowed to have cracks, if there are cracks, it should be replaced.

(2) The coupling is not allowed to have more than the specified axis line skew and radial displacement.

(3) The bolt of the coupling shall not be loose and defective, and the key shall be fitted tightly and without loosening.

(4) If the elastic ring of the pin coupling and the sealing ring of the gear coupling are damaged and aged, they should be replaced in time.

(5) Gear coupling and cross slider coupling shall be lubricated in accordance with the instruction manual.



Five, brake

The brake is a device that slows down or stops the lifting mechanism, or prevents its movement.

1. Typical brake used by crane

(1) Electric hydraulic drum brake: Drum brake driven by electric hydraulic thruster, its structure is shown in Figure 1-10.

(2) Electric hydraulic disc brake: A disc brake driven by an electric hydraulic thruster, as shown in Figure 1-11.

(3) Electromagnetic drum brake: Drum brake with electromagnet as the driving device, its structure is shown in Figure 1-12. Electromagnetic drum brake has AC type electromagnetic brake, DC type electromagnetic brake, parallel excitation type electromagnetic brake, series excitation type electromagnetic brake.



2. Safety technical requirements for brake installation

(1) For power-driven cranes, the lifting, amplitude, operation, and rotating mechanisms should be equipped with reliable braking devices (except those driven by hydraulic cylinders); When the mechanism requires load support, a mechanical normally closed brake should be installed. In the special occasions where there is a self-locking link in the transmission device of the running and rotating mechanism, the brake can also be used if the movement or self-locking failure exceeding the allowable stress can be ensured.

(2) For power-driven cranes, when a large voltage drop is generated or when the electrical protection element is in action. It should be ensured that the actions of the agencies do not get out of control.

(3) For the hook crane, the braking distance of the lifting object during descending braking (the sliding distance from the brake power off to the lifting object stopping after the controller runs stably at the lowest descending speed and pulls back to zero) should not be greater than 1/65 of the stable lifting distance within 1min.

(4) The brake should be easy to check and adjust, the brake spring of the normally closed brake should be compressed, and the brake lining should be easy to replace.

(5) It is appropriate to choose a brake that has an automatic compensation function for the wear of the brake liner.

(6) Control device for operating the brake. Such as pedal, longitudinal handle, etc., should have anti-skid performance. The force exerted by the hand on the control handle of the control device shall not exceed 160 N, and the force exerted by the foot on the pedal of the control device shall not exceed 300 N.

3. Brake parts replacement or brake scrap requirements

The parts of the brake appear in one of the following situations. Parts should be replaced or brakes scrapped

(1) Drive device: electromagnet coil or motor winding burned, or thruster thrust does not meet the requirements of the release brake or no thrust.

(2) Brake spring: plastic deformation of the spring and the amount of deformation reaches more than 10% of the working deformation of the spring, or more than 20% of the surface of the spring corrosion or cracks and other obvious damage.

(3) Transmission components: serious deformation of components affecting performance; The main swing hinge has serious wear, and the wear causes the brake drive travel loss of more than 20% of the source drive travel.

(4) Brake liner: The wear amount of riveted or assembled brake liner reaches 50% of the original thickness of the liner, or the wear of the strip-backed brake liner reaches 2/3 of the original thickness of the liner, or the surface of the brake liner appears charring or stripping area reaches 30% of the surface of the liner, or the surface of the brake liner appears cracked or serious cracking phenomenon.

(5) When the brake wheel appears one of the following, it should be scrapped: defects such as surface cracks that affect performance; The moving surface of the brake wheel of the lifting and amplitude changing mechanism is 40% of the original thickness. The brake wheels of other mechanisms wear up to 50% of the original thickness; When the roughness of the wheel surface reaches 1.5mm, if it can be repaired, the thickness of the repaired brake surface should meet the relevant requirements.

4. Check and maintenance requirements of the brake

Inspection and maintenance shall be carried out in accordance with the requirements of the instruction manual, and cleaning and lubrication shall be done well. The daily inspection of each shift should focus on the following

(1) The brake works normally, the parts do not meet the replacement standard, and the brake does not meet the scrap standard.

(2) The actual contact area between the brake liner and the brake wheel is not less than 70% of the theoretical area, and the brake tile retreat meets the requirements and is uniform.

(3) The hydraulic brake has no oil leakage phenomenon, and the brake surface of the brake wheel has no oil pollution and other phenomena affecting the braking performance.