Standard for Scrap of Crane Spare Parts

 

Crane refers to a multi-action lifting machinery that lifts vertically and horizontally within a certain range. Also known as the crane. It belongs to material handling machinery. The work of the crane is characterized by intermittent movement, that is, the corresponding mechanism of taking material, migration, unloading and other actions in a working cycle is alternately working, and the development and use of the crane in the market is more and more extensive. For such a heavy lifting machinery, such a composite movement will naturally cause a lot of damage to its parts, so we have to understand the scrap standard of each part in detail, timely replacement of parts, so as to make the crane more safe and efficient work.

 

Scrap standard for pulleys

(1) The wall thickness wear of the pulley rope groove is 20% of the original thickness

(2) The radial wear at the bottom of the pulley rope groove exceeds 50% of the diameter of the rope or the uneven wear exceeds 3㎜

(3) Cast iron pulley found more serious cracks

(4) The wheel rim of the pulley is seriously damaged

 

Scrap standard for brake wheels

When the scratch depth or radial wear of the working surface of the brake wheel reaches 1.5㎜, it should be re-turned and heat treated. When the wear of the brake wheel of the lifting mechanism exceeds 40% of the original thickness, it should be scrapped; When the wear of the brake wheel of the operating mechanism exceeds 60% of the original thickness, it should be scrapped.

 

What are the contents of the overhaul of the bridge crane?

Overhaul includes

Mechanical part:

all the mechanisms are decomposed, including the reducer, coupling, drum group, wheel group and pick-up device, etc., replace the scrapped parts, clean and reassemble and lubricate. Replace wire rope and brake.

 

Electrical part:

The motor should be broken down, dried, assembled and lubricated. Replace the damaged motor, replace the brake opening device, replace the damaged controller, repair or replace the protection cabinet, replace the wiring of all lines, reinstall the wiring, and replace the control board of the lighting signal system.

 

Metal structure part:

the main beam that appears downwarped and sidebent is corrected and reinforced, and the whole crane should be cleaned and painted with anti-rust paint twice.

 

Crane main beam scrap standard:

Crane after many overhauls, the main beam after two downtorsion repair and serious downtorsion or multiple cracks, marking the end of the safe service life. After appraisal by the competent department and the safety technical department, the vehicle can be applied for scrap renewal. The downwarping deformation and crack of the main beam of the qualified bridge crane are fatigue damage, which is the linear cumulative damage gradually formed by the local cyclic slip and yield of the material structure under the action of alternating stress. Therefore, repeated severe downtorsion or multiple cracks mark the end of the safe service life of the main beam.

 

In general, the most heavy clamp crane, grab crane, electromagnetic crane, etc., the safe service life is about 20 years; Loading crane, rake crane, etc., about 25 years; Forging crane, casting crane in more than 30 years, general bridge crane for 40-50 years. The actual service life depends on the specific use conditions, which may be long or short.

 

Scrap criteria for wheels

When the wheel appears one of the following circumstances should be scrapped: (1) there are cracks; (2) The thickness of the rim is worn up to 50% of the original thickness; (3) Tread thickness wear up to 15% of the original thickness; (4) When the running speed is less than 50m/min, the line profile reaches 1mm; Or when the running speed is higher than 50m/min, the line profile reaches 0.5mm; (5) pitting occurs on the tread, when the wheel diameter is less than 500mm, and the pitting diameter is greater than 1mm; Or the wheel diameter is greater than 500mm, the pitting diameter is greater than 1.5mm, and the depth is greater than 3mm, the number is more than 5.

 

When the hook is placed in the lowest position, how many coils of wire rope should be retained in each of the two rolls? Why?

(1) When the hook is placed in the lowest position, the wire rope on both sides of the drum should be retained at least two rings or more;

(2) Because the wire rope is fixed on the drum by the pressure plate, only by retaining more than two circles can the wire rope and the drum produce a great friction force, reduce the tension of the pressure plate, and prevent the wire rope from being pulled out from the pressure plate or the screw of the pressure plate from breaking when the load is lifted.

 

The causes of rapid running-in of gear coupling gear and the measures to improve its service life

Reasons: 1) the installation accuracy is poor, the offset of the two axes is large, the internal and external teeth are not meshing, and the local contact stress is large.

2) Lubrication is not good, because it is a connection form without relative motion, the oil can not be automatically supplemented after being extruded, so it may be in a dry friction state to transmit torque, thus accelerating the wear and damage of the tooth surface.

3) Working in a high temperature environment, the lubricating oil is dried, and the lubrication state is deteriorated, which accelerates the wear and damage of the tooth surface.

4) Violation of operating rules, often bother the car brake, accelerated the damage of the gear teeth.

 

Key measures to improve the service life of gear couplings:

Improve the installation accuracy of each component, strengthen daily inspection and regular lubrication, but also comply with the operating procedures, improve the operation technology.

 

Causes of motor vibration:

Internal reasons: rotor mass eccentricity; The stator core is not firmly installed in the casing; The shaft head of the motor is bent or the brake wheel mounted on the motor shaft is eccentric; Motor anchor screws loose; The rotor circuit contact is poor, or the stator winding turns short circuit, resulting in unbalanced electromagnetic torque; Bearing wear, clearance exceeds allowable range.

 

External reasons: the motor is different from the driven reducer; The reducer vibrates and is transmitted to the motor connected with it; The steel structure of the motor base is not rigid enough.

 

Scrap standard of brake wheel:

Have cracks; The roughness of the wheel surface reaches 1mm or the friction damage depth of the wheel surface reaches 2mm; Lifting mechanism brake wheel rim wear up to 40% of the original thickness; The brake wheel of the operating mechanism is worn to 50% of the original thickness

 

To what extent should the reducer gear be scrapped?

Tooth breakage and crack; When the gear wear on the first shaft of the lifting mechanism reducer reaches 5% of the original thickness, when the gear wear on the other axes reaches 20% of the original tooth thickness, when the gear on the first shaft of the operating mechanism reducer reaches 10%, and when the gear on the other axes reaches 30-40%; The pitting area of the tooth surface should not exceed 60% of the tooth height and width.