Common Failure Causes and Daily Maintenance Preventive Measures of mine hoist disc Brakes

1、 Introduction to disc brakes

The oil cylinder rear mounted disc brake (hereinafter referred to as "disc brake") is a new type of high-performance brake and the development direction of mechanical brakes today. Its main advantages are: small size, light weight, low inertia, fast action, good adjustable performance, high reliability, high universality, simple structure, easy maintenance and adjustment, etc.

Disc brakes can be used for various machinery such as mine hoists, belt conveyors, overhead cableways, and ship lifts.

The disc brake is used for working braking and emergency braking on the mine hoist, and its drive and control are completed by a separate hydraulic station. The braking torque of a disc brake is generated by the brake shoes pressing against the brake disc along the axial direction from both sides. In order to prevent additional deformation of the brake disc and prevent the main shaft from bearing additional axial force, disc brakes are used in pairs, each pair being called a pair of disc brakes. According to the required braking torque, each hoist can be equipped with multiple sets of brakes.

Disc brakes are used to achieve working braking and safety braking as needed. The maximum braking force distance of the braking device during working braking and safety braking shall not be less than three times the actual maximum static torque. The mechanical strength of each component of the brake should have a sufficient safety factor. Can work safely and reliably in various situations. The disc brake is controlled by hydraulic pressure, using disc spring braking and hydraulic pressure to open the brake. The response is rapid, and the idle time is not more than 0.3 seconds. Braking is safe and reliable, with even distribution of braking force. Good braking torque adjustment performance. The braking force transmission efficiency is high, close to 100%, with smooth braking and minimal wear. The brake must not leak oil or stain the brake surface.

7. Adjust the nut 8. Brake body 9. Pressure plate 10. Brake shoe 1 with simplified lining plate 12. Butterfly spring

2、 Analysis of Common Failure Causes of Disc Brakes

The failure of disc brakes is mainly divided into two forms: release failure and braking failure. The failure of the brake release is generally caused by cylinder jamming, insufficient working oil pressure in the hydraulic station, and other reasons; Brake failure is generally caused by various reasons such as brake shoe quality problems, scratches on the brake disc surface, reduced friction coefficient due to overheating, hydraulic cylinder oil leakage, and oil circuit blockage.

The specific analysis is as follows:

1. Failure of disc brake release

The failure of the disc brake to release the brake, commonly known as "unable to open the brake", is mainly caused by:

The brake cylinder is stuck or the cylinder is too tightly matched, and the working oil pressure of the hydraulic station cannot overcome the resistance of the cylinder movement.

The working oil pressure of the hydraulic station is insufficient to overcome the resistance of the brake cylinder piston movement and spring pressure.

2. Disc brake failure

The failure of disc brakes, also known as "inability to brake the car", is commonly caused by:

? Quality issues with brake shoe products (material too soft), insufficient friction coefficient μ of brake shoes;

? Quality issues with brake shoe products (hard material), with scratches on the surface of the brake disc, resulting in excessive roughness and affecting the contact surface;

Long term high-speed operation caused overheating of the brake shoes due to prolonged working temperature, resulting in a decrease in the friction coefficient μ of the brake shoes;

Brake hydraulic cylinder oil leakage, oil pipe welding, loose joints oil leakage, and aging of piston sealing rings inside the hydraulic cylinder cause oil leakage, and the surface of the brake disc or brake shoe is contaminated by hydraulic oil;

Oil circuit blockage causes excessive residual pressure in the brake system, resulting in insufficient positive pressure output from the brake;

The aging of the piston sealing ring and hydraulic oil leakage cause an increase in piston movement resistance, resulting in insufficient positive pressure output from the brake;

The brake disc spring experiences fatigue or fracture due to repeated stretching and compression, resulting in insufficient stiffness of the disc spring and insufficient output positive pressure of the brake;

Excessive deflection of the brake disc or excessive wear of the brake shoes can cause a large gap between the brake shoes and the brake disc, resulting in insufficient positive pressure output from the brake;

The large bolt connecting the lining plate cylinder and the piston has become loose, causing a decrease in the pre compression of the disc spring and resulting in insufficient positive pressure output from the brake.

Incorrect installation of the brake body or loose brake foundation bolts can cause excessive clearance between the brake shoes and brake discs, resulting in insufficient positive pressure output from the brake.

3、 Daily prevention and maintenance suggestions

Disc brakes are an important guarantee for the safe operation of elevators. The maintenance and upkeep of the hoist is of utmost importance and must be given sufficient attention. Conditional mines have begun to entrust this work to specialized maintenance service companies.

1. Maintenance of hydraulic system

Thoroughly clean the hydraulic station casing and valve assembly once a year.

Filter the hydraulic oil every six months to ensure its cleanliness.

Check the hydraulic oil level in each shift to ensure sufficient supply.

2. Oil leakage inspection and treatment

Check the oil leakage of the brake hydraulic cylinder in each shift, including oil pipe welding, loose joint oil leakage, and aging of the piston sealing ring inside the hydraulic cylinder, to prevent the brake disc or brake shoe surface from being contaminated by hydraulic oil. If oil stains are found, stop the vehicle in a timely manner to maintain a good friction coefficient between the brake shoe and the brake disc.

3. Gap management of gates

The gap between the gates should be kept at around 1mm and not exceed 2mm. When it exceeds the specified value, it can automatically alarm or cut off power. After adjustment, the positioning bolts need to be locked.

4. Complete equipment configuration

Old equipment without installed gap protection devices should be promptly configured.

5. Install an automatic detection device for brake disc deflection

When the brake disc deflection is greater than 1mm, flame method or turning method should be used to recalibrate it to ensure that the deflection is ≤ 1mm, meeting the requirements of the regulations.

6. Component inspection and replacement

Regularly check the remaining thickness of the brake shoe and replace it immediately if it is less than 6mm.

Regularly check the idle time of the brake, and repair it immediately if it exceeds 0.3s.

According to national standards, the service life of disc springs should be replaced if the number of actions exceeds 500000 times.

7. Braking method and performance testing

When lowering heavy objects, power braking should be applied to avoid relying solely on the brake disc to brake, which may cause the brake shoes to overheat and deform, affecting the braking force.

Regularly inspect the performance of working and safety braking, verify the braking torque, and determine the speed of safety braking.

4、 Supplementary suggestions

Professional training: Provide professional training to operation and maintenance personnel to improve their skill level and safety awareness.

Establish archives: Establish detailed maintenance archives for each brake, recording the situation of each maintenance and overhaul.

Regular inspection: Develop a regular inspection plan to conduct a comprehensive inspection of all components of the brake.

Emergency preparedness: Develop emergency plans to ensure that measures can be taken quickly in case of emergency situations such as brake failure.

Disc brakes play an important role in the mechanical field, especially in equipment such as mine hoists. Understanding their performance, failure causes, and daily maintenance and preventive measures is of crucial importance for ensuring the safe operation of equipment and improving production efficiency. In practical applications, it is necessary to strictly follow the relevant requirements for operation and maintenance to ensure that the disc brake is always in good working condition, effectively preventing accidents and providing reliable safety guarantees for production operations.

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