Rigging
1.5 hours
Learning Objectives
- •Apply wire rope inspection and removal criteria per OSHA 29 CFR 1926.1413 to 3A equipment
- •Calculate the effect of sling angle on the tension in each leg of a two-leg bridle hitch
- •Identify the correct hardware components — shackles, hooks, blocks, and sheaves — used in pile driving and derrick rigging
- •Describe the daily rigging inspection required before pile driving and derrick operations
Topics Covered
- •Wire rope construction: strands, wires, core (IWRC vs. fiber); designations such as 6×19 and 6×37
- •Wire rope inspection: mandatory before each shift; look for broken wires, corrosion, kinking, bird-caging, core failure
- •Removal criteria (OSHA 1926.1413 / Subpart CC running ropes): 6 randomly distributed broken wires in one rope lay, or 3 in one strand in one lay
- •Standing/pendant rope removal: more than 2 broken wires in one lay beyond end connections; more than 1 at an end connection
- •Rope diameter reduction: remove from service if diameter is reduced by more than 1/3 of the nominal diameter (per ASME standards)
- •Sling types: wire rope, chain, synthetic web, round sling — each with rated capacities
- •Sling angle effect: as the angle from horizontal decreases, tension in each sling leg increases; at 30° the load per leg is approximately 2× the load at 90°
- •Shackles: bolt-type vs. screw-pin; load rated in tons; pin must be moused or secured when under load
- •Wire rope clips (Crosby clips): U-bolt over the dead end, not the live end; "never saddle a dead horse"
- •Blocks and sheaves: sheave diameter must match wire rope diameter; worn grooves cause accelerated rope wear
- •Load block (running block) vs. head block (fixed block): understanding reeving arrangements
- •Guy wire inspection: daily inspection of tension, condition, and anchor security per 230 CMR 6.00 and OSHA 1926.1436
- •Anti-two-block devices: prevent the load block from striking the head block; required by Subpart CC for equipment where provided
- •Pre-lift rigging check: verify load weight, center of gravity, rigging rated capacity, and clear lift path
Resources
Self-Check Questions
Question 1: Under OSHA 1926.1413, how many randomly distributed broken wires in one rope lay of a running wire rope require removal from service?
- A. 3
- B. 6(correct)
- C. 10
- D. 12
Show Explanation
Explanation:
6 randomly distributed broken wires in one rope lay (or 3 in one strand in one lay) is the removal threshold for running ropes under Subpart CC. This is one of the most frequently tested wire rope facts on hoisting exams.
Question 2: When installing a wire rope clip, the U-bolt of the clip must be placed over which part of the rope?
- A. The live (standing) end of the rope
- B. The dead (short/tail) end of the rope(correct)
- C. Either end — orientation does not matter
- D. Wire rope clips are not approved for use on pile driving equipment
Show Explanation
Explanation:
The U-bolt bears the bending stress, so it must go over the dead end. "Never saddle a dead horse" is the memory aid: the saddle (base plate) sits on the live end. Reversed clips can reduce rope strength by up to 40%.
Question 3: A two-leg wire rope bridle is used to lift a load. As the included angle between the sling legs increases (legs spread further apart), what happens to the tension in each leg?
- A. Tension decreases as the angle increases
- B. Tension increases as the angle increases(correct)
- C. Tension is not affected by sling angle
- D. Tension increases only if the load weight exceeds 1,000 lbs
Show Explanation
Explanation:
As sling legs spread apart (larger included angle = smaller angle from horizontal), each leg must exert more force to support the same load. At 30° from horizontal, each leg carries nearly 2× the load vs. 90°. Always minimize sling angle spread.
Question 4: During a daily guy wire inspection before derrick operations, you find one guy has significantly more sag than the others. What should you do?
- A. Proceed — slight variation in guy tension is normal
- B. Stop operations and correct the guy tension before use(correct)
- C. Reduce the load to 50% of rated capacity and proceed
- D. Use only the remaining guys and remove the slack one
Show Explanation
Explanation:
OSHA 1926.1436 requires daily guy tension verification. Unequal tension means the derrick mast is not properly supported — proceeding risks overloading the tight guys and destabilizing the structure. Correct tension before any lifts.
Question 5: What condition in a wire rope is called "bird-caging"?
- A. Broken outer wires that are visible on the surface of the rope
- B. Separation and expansion of the strands and wires caused by a sudden shock load or overload(correct)
- C. Corrosion visible at the contact points between strands
- D. Reduction in diameter along a section of the rope
Show Explanation
Explanation:
Bird-caging occurs when the rope's outer strands separate and flare outward — often caused by a sudden release of tension or shock load. A bird-caged rope has permanently distorted geometry and must be removed from service immediately.
Question 6: Before any lift with a derrick, the operator should verify which of the following?
- A. The load weight, center of gravity, rigging rated capacity, and that the lift path is clear(correct)
- B. Only that the rigging hardware is free of visible cracks
- C. Only that the load is within the maximum rated capacity shown on the load chart
- D. The weather forecast for the next 12 hours
Show Explanation
Explanation:
A proper pre-lift check covers: confirmed load weight, estimated center of gravity, rated capacity of all rigging components, and a clear lift path with no personnel underneath. All four elements are required — missing any one creates a serious hazard.