Ropes, Chains and Hardware

Wires are wound into strands (usually 6), and the strands are wound around a core. A steel core resists crushing and is stronger than a fibre core.

• Larger outer wires → more abrasion-resistant.
• More wires and strands (smaller wires) → more flexible and more fatigue-resistant in bending — the trade-off against abrasion resistance.

Lay

= twist direction; lay length = distance for one strand to make a full turn.

Right regular lay

is the most common: wires twisted left in the strand, strands twisted right.

Lang lay

wires and strands twisted the same way — more flexible and wears longer, but does not resist crushing.

Telling the lay by eye: strands that spiral like a right-hand thread make a right-lay rope. Outer wires running roughly along the rope = regular lay (wires and strands twisted opposite ways); outer wires crossing it at a slant = Lang lay.

Preformed

rope has the helix pre-set: it doesn't fly apart when cut, and broken wires lie flat.

• Classification = diameter · number of strands × wires per strand · steel grade · core, e.g. 1″ 6×19 improved plow steel, IWRC (6 strands of 19 wires each).
• A kink is a defect to look for when inspecting wire rope.
• Watch the fleet angle (θ in the drawing: the rope's angle off the sheave's centreline, largest at the drum flanges, and drawn much larger than a real one). An excessive fleet angle causes severe abrasion.
• Salt water → galvanized rope; corrosive or acidic environments → stainless.
• Lubricate regularly — lack of lube causes embrittlement, corrosion and wear.
• Storing wire rope: clean and lubricate it, wind it on a reel off the floor, and keep it dry, covered and ventilated, away from heat and chemicals. Rope left damp without lubricant rusts from the inside, out of sight; a tarp outdoors only traps condensation against it.

• Natural fibre rope: manila.
• Synthetic fibres: nylon and poly.
• Reverse-twist construction: fibres twisted right → yarn, yarns left → strand, strands right → rope = a right-lay rope.
• The alternating twists lock the rope together: each stage's urge to unwind pulls against the next, so the rope holds its shape under load instead of unlaying.
• Soft-laid rope has the greatest tensile strength but wears poorly over sheaves.

Nylon

strong, elastic, great for shock loads; resists oils and greases.

Snap-back

a rope under load stores energy, and stretchy synthetic rope stores far more than wire. If the rope or a fitting fails, both ends fly back along the line of pull, hardware and all: stand well to the side, never in line with a loaded rope at either end.

Poly

ropes are cheaper and buoyant — used for water work.

Synthetic fibres melt at temperatures a slipping rope easily reaches. A rope that slipped on a capstan or winch drum and now has a hard, glossy or fused section is heat-damaged: take it out of service. Cooling, brushing or derating can't restore melted fibres.

• Chains break without warning — one link failing drops the load.
• Lifting chain must be alloy steel (fittings forged alloy steel). Alloy chain is graded and marked: Grade 80 (marked 8 or 80; older chain tagged “T” or “8”) or Grade 100 (marked 10 or 100). The tag gives the serial number, maximum vertical load and date of issue.
• No tag, no lift: a sling whose tag is missing or unreadable comes out of service until the maker or a qualified person identifies it and fits a new tag. A grade mark on the links names the chain, not the sling's rated load.

A hoist's load chain is heat-treated alloy chain made to the exact pitch of its pocket wheel. A stretched or damaged link means replacing the whole chain with the hoist maker's chain: weld heat ruins the heat treatment, and a connecting link won't run through the pocket wheel. Then the hoist is inspected and load-tested.

• Space the clips about 6 × the rope diameter apart (exam formula sheet), equally along the turn-back; apply tension and tighten the nuts, and re-torque the nuts after the rope has been in use.
• Clip order: the clip at the dead end of the rope (farthest from the thimble) goes on first and is torqued fully; next the clip nearest the thimble, then any between, nuts only snug until light tension pulls the rope straight. Torqued before that, the inner clips would trap slack between them. Tighten a clip's two nuts in turn so it seats square.

Hooks

forged alloy steel, fitted with a safety catch (except grab/sorting hooks).

Mousing

= wiring the hook throat closed.

• Cutting wire rope with a cutting torch makes the first 6″ unsafe.
• Cutting back a damaged rope: seize both sides of the cut first, in sound rope past the damage, then cut with a wire-rope cutter or abrasive cut-off saw. Strands cut before seizing spring apart and unlay. On a hoist, at least two full wraps must stay on the drum with the hook at its lowest.
• Lang lay ropes are not used for hoisting with single-part lines.
• Fibre-rope sheave diameter = 8 × rope diameter.
• Inspect before each use, on a regular schedule based on use, by a qualified person.
• Measure diameter with calipers across the crowns of opposite strands, at several points (across the flats between strands gives a low reading). One short section thinner than the rope either side of it means broken inner wires or a failed core, even if the outer wires look sound: have it closely inspected, and retire it if past the limit.