Hook blocks

A hook block is a component of a hoist used to suspend a load from a crane and move it in the vertical and horizontal planes. The device is used to form an assembly of a hook and rope for moving individual loads.

Design

A hook block consists of 4 components:

1. Guide pulleys rotating on a shaft.
2. Hook for securing the load.
3. Crossheads (traverses).
4. Limiting elements.
5. Gearbox.
6. Shafts.
7. Bearings.

Stationary pulleys are connected to the rope by a traverse and metal limiting plates. The mobile and fixed pulley, combined into a single unit, form a pulley block.

The device operates via an electric drive. Power units are supplemented with balancing mechanisms to improve operating performance.

For a shortened hook block, a traverse fitted with a thrust bearing, complemented by a hook, is used. The components are additionally mounted on an axle fixed to the traverse.

Classification of load hook blocks

Hook blocks are classified according to operating parameters:

1. Number of axles.
2. Dimensions of the block.
3. Material used.
4. Intended purpose.
5. Fixing method.
6. Hook type.

Materials

High-strength steel grades are used for crane hook blocks and bridge crane suspensions. Depending on the production method, they are cast, forged or stamped. Cast hooks are rarely used, since it is difficult to detect cavities in the metal structure.

Operating features

The block assembly on cranes allows the speed of moving the load or workpiece to be adjusted depending on its weight. According to regulatory documents, the weight of the hook unit must not exceed 20% of the rated load capacity, which ensures tension of the flexible rigging element.

An eye, swivel or fork is used to secure the hook. The choice depends on the weight and type of hook. According to regulatory requirements, the following hooks are used in hook blocks:

• Weld-on;
• Chain;
• Double-pronged (ram’s horn);
• Sling;
• Swivel hooks.

Models are fitted with an individual latch that meets standards and is manufactured according to a drawing. The rated load marked on the component must not be exceeded. Before use, the condition of the hook and the flexible rigging elements must be checked for defects or damage.

How to choose?

The selection of a hook block is based on the load capacity and the type of load to be raised or lowered. Additional factors to consider are the diameter of the wire rope or rope, the design features and manufacturing method of the hook, and the characteristics of the electric motor. For safety reasons, the load on the mechanism must not be exceeded. Therefore, a load-capacity margin regulated by GOSTs must be maintained.