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Multi-rope friction hoist

2024-02-19

Selection of skip for multi-rope friction hoists:
The skip is a single-purpose hoisting container designed exclusively for lifting coal or ore. In China's coal mines, fixed-bottom discharge skips are widely used due to their advantages: the gate mechanism is simple yet highly reliable, with minimal impact when closing upward. Moreover, once the coal bunker is full and unloading is complete, the skip itself has an extremely low risk of rope failure. The skip’s discharge gate is primarily opened by the pressure exerted by the coal itself, which means the force transmitted to the unloading curved rail during unloading remains relatively low—significantly improving the stress conditions on the shaft frame. However, this design does have a notable drawback: if the locking mechanism fails, the gate could inadvertently open on its own due to vibrations or impacts within the shaft. Not only would this result in coal being dumped directly into the shaft, but it could also damage the shaft’s equipment. For this reason, thorough and regular inspections of the locking system are absolutely essential.

Floor-mounted multi-rope friction hoist

[Floor-Mounted Multi-Rope Friction Hoist]

Determining the lifting deceleration for multi-rope friction elevators:
The free-gliding deceleration method works as follows: At the start of deceleration, the motor is disconnected from the power grid, allowing the container to move toward the unloading position solely by the system's inertia—its natural momentum—while gradually slowing down. Since this method relies neither on electric traction nor on braking mechanisms, it’s known as the Baishan Gliding Deceleration System.
Static anti-slip: Multi-rope friction hoisting operates entirely on the same principles as single-rope friction hoisting—specifically in terms of traction, kinematics, and dynamic calculations. Crucially, whether there is sufficient friction between the steel wire ropes and the friction lining directly determines the reliability of the friction hoisting system.

[Shaft-Type Multi-Rope Friction Hoist]

When the ratio of the actual tensions on the two sides of the multi-rope friction hoist—specifically, F₁/F₂—exceeds the value specified on the right-hand side of the equation, relative slippage will occur between the wire ropes and the friction sheave. In practical engineering applications, to prevent such slippage, the actual tension ratio on both sides must remain below its limiting value, ensuring an adequate safety margin. From the equation F = F₀ * μ^(θ/180), where F₀ represents the maximum frictional force generated between the wire rope and the friction lining under ideal conditions (i.e., when the rope just begins to slip on the friction pad), it’s clear that the frictional force—directly determining the lifting capacity of the multi-rope friction hoist—is influenced by three key factors: the tension in the wire ropes, the wrap angle of the ropes around the drive sheave, and the coefficient of friction between the ropes and the friction lining. If the frictional force decreases—for instance, due to wear or improper maintenance—there is a heightened risk of the wire ropes slipping along the drive sheave, potentially leading to catastrophic consequences. Therefore, to ensure safe operation and prevent slippage during hoisting, it is essential to rigorously verify the anti-slip safety factor. This verification typically involves three critical assessments: static anti-slip checks, as well as safety-brake-based anti-slip analyses.

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