A master link is a forged, closed steel ring sized to sit comfortably in a crane hook while the sling legs (chain, wire rope or webbing) are attached below it, either directly or through subsidiary rings in a master link assembly. Where several legs would otherwise all bear directly on the same section of a single ring — wearing a groove and crowding each other — an assembly adds smaller links so each leg has a defined, separate bearing surface.
Master links and assemblies are used across the full range of multi-leg chain and wire rope slings in general lifting, and are typically supplied and certified as part of the complete sling assembly rather than sold and rated as a stand-alone item.
Identification: the master link itself is normally stamped with the manufacturer’s mark and size; the working load limit that matters in practice is the one on the sling assembly’s identification tag, since it reflects the whole assembly (link, legs, angle) tested together, not the link in isolation.
What makes one unsafe:
- Wear grooves at the hook or leg bearing points, especially where a leg has been allowed to bear directly on the main ring instead of on its intended subsidiary link
- Deformation — the ring no longer round, or opened out from overload
- Cracks, nicks or gouges from mishandling or dragging on the ground
- Corrosion or pitting, particularly on assemblies used outdoors or near salt exposure, common in Norwegian coastal and marine work
- Mixing a master link from one assembly with legs or a hook from another without a matching certified rating
Before use: check the sling assembly’s identification tag and working load limit rather than assuming a rating from the link’s size alone, inspect the master link and any subsidiary links for wear grooves, deformation, cracks and corrosion, and confirm the hook or shackle connecting into the master link is itself rated for the full assembly load.
Standarder: EN 1677 (components for slings — safety; relevant parts cover forged ring and master link type components — verify the exact part for the specific product before citing it).