Load chain

The load chain of a chain hoist runs over a pocketed chain wheel into which every link has to fit exactly. It is therefore fine tolerance chain: pitch and link diameter lie within narrow limits. Such hoist chains are covered by EN 818-7.

A sling chain of the same nominal size is not built for this. Its tolerances are wider; it runs roughly in the chain wheel, climbs and wears out wheel and chain in a short time. Only the chain specified by the manufacturer for that unit belongs in a hoist.

EN 818-7 distinguishes several types of grade T chain. In simplified terms: chains for manually operated hoists, and chains with a hardened surface for power-driven hoists, where the bearing points are subject to more wear. The manufacturer determines which type belongs in a unit together with the mechanism classification.

The chain is designated by nominal diameter times pitch in millimetres. There are also corrosion-protected and stainless chains for food, wet and chemical environments. Some have a lower capacity and cannot simply be swapped for the standard chain.

A load chain wears at the bearing points, where link rubs on link. That is where the lubricant has to go – not onto the outer surfaces. The chain is therefore lubricated unloaded, so the lubricant can get between the links, and over its entire length including the section that rarely leaves the hoist body.

Lubricant and interval are stated in the operating manual. In dusty surroundings grease binds abrasion into a grinding paste; dry lubricants are the better choice there. A chain running dry reaches only a fraction of its possible service life.

Most chain damage is caused not by the load but by handling.

The load chain is replaced as a whole, never in sections. When it is changed, chain wheel and chain guide are checked: a new chain on a worn wheel wears quickly. Orientation and fixing of the chain end follow the manufacturer’s instructions. After the change the hoist is inspected before it works again. The limits at which a chain must be replaced are covered under discard criteria.