Redirects
Rigging blocks & pulleys
Sheave diameter, WLL and a sound attachment decide what a block can take — and shock loads multiply everything.
Safety features explained
Large sheave with bearings
A sheave at least 4x rope diameter protects rope strength and reduces friction heat; bearings keep it turning under load.
Stamped working load limit
Marked WLL and design factor are the only legitimate basis for planning a pick.
Captive, load-rated attachment and swivel
A shackle or becket that cannot come unclipped and, where used, a swivel that stops the block from rolling over.
Daily inspection checklist
- 1Spin the sheave — smooth, no wobble, no grinding, no flat spot in the groove.
- 2Check the shell/plates for cracks, spreading, bending and weld damage.
- 3Inspect the axle, bolts, keepers and becket; look for elongated holes.
- 4Check the sling, shackle or strap that hangs it for cuts, heat and deformation.
- 5Verify markings are legible and the block is not overloaded for the planned piece.
Out of service now
- Cracked or spread shell, elongated axle hole, bent plate.
- Seized or grinding sheave, or a groove worn sharp.
- Illegible WLL or unknown provenance.
- Any component that has been shock loaded beyond the design factor.
Operating best practices
- Choose a block rated well above the estimated piece weight, and account for the doubled load at the anchor.
- Rig the block on a sound anchor above the piece so the line never crosses the stem or bark.
- Use a low-friction ring only where its lower efficiency and heat are acceptable.
- Keep a straight, clean line run to the friction device and watch the fleet angle.
Standards & compliance
- ANSI Z133: rigging hardware is used inside its WLL and inspected before use.
- Keep sheave and hardware diameters at or above 4x rope diameter to protect line strength.
Summarised for field use. The current ANSI Z133 standard, OSHA rules and the manufacturer's manual are the controlling documents.
Resource & video hub
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