Core Adjustment Parameter Comparison Table
|
Parameter indicators |
Bridge/Gantry Crane (Block Brake) |
Tower Crane (Normally Closed Brake) |
Electric Hoist (Taper/Disc Brake) |
Remarks |
|---|---|---|---|---|
|
Brake clearance |
0.5 - 1.0 mm (unilateral) |
0.6 - 1.0 mm (unilateral) |
0.1 - 0.3 mm (Type CD) / 0.5 - 1.5 mm (Universal) |
Too small a gap can cause overheating, while too large a gap may lead to hook slippage. |
|
Braking torque |
1.5 - 2.0 times the rated torque |
1.5 - 2.0 times the rated torque |
1.25 - 1.4 times the rated torque |
The crane has stricter requirements for braking torque and must prevent hook slippage. |
|
Electromagnet stroke |
3.0 - 4.4 mm (Rated torque multiplier) |
25 - 30 mm (Long stroke) |
1.5 - 2.0 mm (Tapered rotor) |
The stroke must match the clearance to ensure complete brake release. |
Specific adjustment points for different models
Bridge / Gantry Cranes (Block Brakes)
This type of crane typically uses YWZ series electric-hydraulic brakes or MZD series electromagnetic brakes.
Clearance adjustment: The unilateral clearance is usually controlled within 0.5-1.0mm. When adjusting, a feeler gauge should be used for measurement to ensure that the clearances on both sides are uniform (the difference ≤ 0.1mm), preventing uneven force on the brake wheel and resulting in uneven wear.
Braking torque: It is achieved by adjusting the compression amount of the main spring. The standard requires that the braking torque should reach 1.5 to 2.0 times the rated load torque to ensure reliable braking under full load.
Electromagnetic stroke: The stroke of short-stroke electromagnetic brakes (MZD1 series) is relatively small (for example, the stroke of MZD1-100 is 3mm). When adjusting, it is necessary to ensure that the armature is fully engaged; otherwise, the brake release may not be complete.
Tower cranes (normally closed brake)
The hoisting mechanism of tower cranes usually adopts YWZ5 series or disc brakes, with extremely high safety requirements.
Clearance adjustment: The unilateral clearance is usually 0.6 - 1.0mm. The working environment of tower cranes is harsh, and the clearance needs to be checked regularly to prevent excessive clearance and failure due to dust or wear.
Braking torque: The tower crane must not have the "hook run" phenomenon. The braking torque must be large enough, usually reaching 1.5 to 2.0 times the rated torque, and a static load test (suspended at 1.25 times the rated load for 10 minutes without sliding down) must be conducted.
Compensation stroke: For hydraulic push-rod type brakes (such as YWZ5), the compensation stroke (hb) needs to be adjusted. For instance, the compensation stroke of YWZ5-250/50 is 30 ± 2mm, ensuring that the gap can be automatically compensated for after the brake lining wears out.
Electric hoist (conical rotor / disc brake)
The electric hoist has a compact structure, and the brake is usually integrated inside the motor.
Clearance adjustment: For the common CD/MD type electric hoist, the braking clearance is very small, usually controlled within 0.1-0.3mm. During adjustment, the adjusting nut at the tail end should be rotated to change the spring pressure, causing the rotor to have an axial displacement.
Braking torque: According to the standard, the brake should be capable of stopping 1.25 times the rated load. During adjustment, the "tighten and then back off" method is usually adopted. For instance, after tightening the adjusting nut clockwise, it should be loosened counterclockwise by 1 to 2 turns to leave an appropriate gap.
Braking distance: Under no-load conditions, the braking sliding distance is generally required to be no more than 80mm. If it exceeds this value, the gap needs to be readjusted or the braking surface cleaned.
Adjustment Precautions
Safety First: Before making the adjustment, the power must be cut off and a "Do Not Close" warning sign must be hung.
Clean the brake surface: Before adjusting, it is necessary to remove the oil, water stains and rust from the surface of the brake wheel (disc). Otherwise, the braking effect will be severely affected.
Uniform contact: After adjustment, manual rotation of the wheel is required for inspection to ensure that the contact area between the brake pad and the brake wheel is no less than 70%-80%.
