What type of rope is intended to be used with these snatch blocks?

They are specifically designed for natural or synthetic fibre ropes, not steel wire ropes.

What is the proof load for the snatch block?

The block must be tested to withstand a proof load equal to twice its Safe Working Load (SWL) without showing any permanent deformation.

Why are specific materials recommended for the sheave?

Materials like aluminum alloy or gunmetal are specified to provide a smooth, non-corrosive surface that minimizes friction and abrasive damage to the fibre ropes.

IS 939

: 1977

Specification for Snatch Block for Use with Fibre Rope for Fire Brigade Use

CurrentSpecializedSpecificationFire Safety · Fire Fighting

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This standard lays down the specifications for materials, dimensions, workmanship, and testing of snatch blocks specifically designed for use with fibre ropes. It is primarily used by fire brigades for rescue and general lifting operations.

Specification for Snatch Block for Use with Fibre Rope for Fire Brigade Use

Quick Reference Values

Proof load test2 x Safe Working Load (SWL)

Minimum factor of safety4 for load-bearing components

Sheave groove requirementMust be smoothly machined to prevent abrasion of fibre rope

Practical Notes

Always ensure the snatch block sheave groove size matches the specific diameter of the fibre rope to prevent rope flattening or excessive wear.

Verify the locking pin or mechanism is fully engaged before applying any tension to the rope.

Do not use snatch blocks specified under this standard with steel wire ropes, as the sheave material and groove profile are only rated for fibre ropes.