Hoisting and Rigging

Why Hoisting and Rigging Matters

Hoisting and rigging is one of the highest-consequence activities in construction, general industry, maritime, and energy work. When a load is suspended, gravity is working against every component in the system, and any failure point (a worn sling, a miscalculated angle, an unlevel crane, or a worker standing under the load) can produce a fatality in a fraction of a second. OSHA and BLS data consistently show that crane and rigging incidents account for dozens of worker deaths per year in the United States, with the leading causes being struck-by falling loads, electrocution from power line contact, crane tip-overs, and boom collapses. Beyond the human cost, a single dropped load can destroy millions of dollars of equipment and shut down a project for months.

For the BCSP Associate Safety Professional (ASP) exam, hoisting and rigging falls under the Safety Programs and Concepts domain because it brings together nearly every core skill a safety professional must have: hazard recognition, regulatory knowledge (OSHA 29 CFR 1910 and 1926, ASME B30 standards), applied math (load weight estimation, sling tension, sling angle factors, mechanical advantage), inspection programs, training and qualification requirements, and lift planning. Expect multiple questions on this topic, often involving calculations.

What Hoisting and Rigging Is

Hoisting refers to the mechanical equipment and process used to lift and move a load vertically and horizontally. This includes mobile cranes, tower cranes, overhead and gantry cranes, derricks, hoists, chain falls, come-alongs, and block-and-tackle systems. Rigging refers to the hardware and techniques used to attach the load to the hoisting equipment: slings, shackles, hooks, eyebolts, spreader bars, turnbuckles, wire rope clips, and the hitches used to connect them.

The governing standards you should know include:
- 29 CFR 1926 Subpart CC (1926.1400 to 1926.1442): Cranes and Derricks in Construction, including operator certification (1926.1427), signal person qualification (1926.1428), power line safety (1926.1407 to 1926.1411), and inspections (1926.1412).
- 29 CFR 1926.251: Rigging Equipment for Material Handling (construction).
- 29 CFR 1910.179 (overhead and gantry cranes), 1910.180 (crawler, locomotive, and truck cranes), and 1910.184 (slings) for general industry.
- ASME B30 series: B30.5 (mobile cranes), B30.9 (slings), B30.10 (hooks), B30.26 (rigging hardware), and B30.2 (overhead cranes). These consensus standards define inspection frequencies and removal-from-service criteria that OSHA often incorporates by reference.

Key Terminology

- Rated Capacity / Working Load Limit (WLL): the maximum load a component is designed to handle in service. It must never be exceeded.
- Design Factor (Safety Factor): the ratio of breaking strength to WLL. Typical values: wire rope slings 5:1, alloy chain slings 4:1, synthetic slings 5:1, hooks and shackles typically 5:1 (shackles sometimes 6:1), and running ropes on cranes 3.5:1.
- Load Chart: the manufacturer document showing crane capacity at a given boom length, boom angle, radius, and configuration (outriggers extended, counterweight, over-the-side vs over-the-rear). Capacity decreases as radius increases.
- Radius: horizontal distance from the center of rotation to the center of the hook. This, not boom length, is the primary driver of capacity.
- Gross Load: the weight of the load plus all rigging, the hook block, and any attachments. Load charts are based on gross load.
- Center of Gravity (CG): the point where the load would balance. The hook must be positioned directly above the CG or the load will tilt and shift when lifted.
- Shock Loading: a sudden application of force (jerking, dropping onto a sling) that can multiply the effective load several times.
- Two-Blocking: when the hook block contacts the boom tip, which can snap the hoist line. Anti-two-block devices prevent this.
- Critical Lift: typically any lift exceeding 75 percent of the crane rated capacity, lifts using more than one crane, lifts over occupied structures or process equipment, lifts of personnel, or lifts of high-value or hazardous loads. Critical lifts require a formal written lift plan.
- Competent Person: capable of identifying hazards and authorized to take corrective action. Qualified Person: possesses a recognized degree, certificate, or extensive knowledge and demonstrated ability. Subpart CC uses both terms in specific places; for example, assembly/disassembly must be directed by an A/D director who is both competent and qualified.

How It Works: Sling Types and Hitches

Sling materials:
- Wire rope: durable, heat resistant, good for abrasive or rough loads; susceptible to kinking, bird-caging, and broken wires. Classification such as 6x19 or 6x37 refers to the number of strands and approximate wires per strand; more wires means more flexibility but less abrasion resistance.
- Alloy steel chain: Grade 80 and Grade 100 are the only grades permitted for overhead lifting. High temperature tolerance, resists cutting, but heavy and vulnerable to shock loading.
- Synthetic web and roundslings (nylon, polyester): lightweight, flexible, protect finished surfaces; vulnerable to cuts, abrasion, UV, heat (do not use above about 194 F / 90 C), and chemicals. Nylon is attacked by acids; polyester is attacked by alkalis. Roundslings have a colored cover; exposed red core yarns indicate immediate removal.
- Metal mesh: used for hot or sharp loads in specialized applications.

Hitch types:
- Vertical (straight) hitch: one leg, full rated capacity. The load can rotate.
- Choker hitch: sling wraps around the load and back through itself. Capacity is reduced to roughly 75 to 80 percent of vertical because of the bend at the choke; capacity drops further if the choke angle is less than 120 degrees.
- Basket hitch: sling passes under the load with both ends on the hook. At a true vertical (90 degree) configuration, capacity is double the vertical rating, but the capacity drops as the legs angle inward. Loads in a basket hitch can slide if not balanced.
- Bridle (multi-leg) hitch: two, three, or four legs. For rating purposes, a four-leg bridle is often treated as having only three load-bearing legs unless the legs are adjustable, because rigid loads rarely distribute weight evenly.

How It Works: The Math You Must Know

1. Estimating Load Weight. Weight = Volume x Unit Weight. Common densities: steel 490 lb/ft3, concrete 150 lb/ft3, aluminum 165 lb/ft3, water 62.4 lb/ft3, hardwood about 45 lb/ft3. A steel plate 10 ft x 4 ft x 1 inch thick is 10 x 4 x (1/12) = 3.33 ft3 x 490 = about 1,633 lb. For cylinders, volume = pi x r2 x length. Always add rigging and block weight to get gross load.

2. Sling Angle and Tension. As the angle between the sling leg and the horizontal decreases, the tension in each leg increases dramatically. Formulas:
- Tension per leg = (Load / number of legs) x (Sling Length / Vertical Height), or equivalently
- Tension per leg = Load / (number of legs x sin of the horizontal sling angle).
Sling angle factors (multipliers) to memorize: 90 degrees = 1.000, 60 degrees = 1.155, 45 degrees = 1.414, 30 degrees = 2.000. Example: a 2,000 lb load lifted with a two-leg bridle at 30 degrees from horizontal has 2,000 / 2 = 1,000 lb per leg x 2.000 = 2,000 lb in each leg. This is why the industry recommends never rigging below 30 degrees and preferring 60 degrees or more. If an exam question gives sling length and vertical height, use the L/H ratio; if it gives the angle, use the sine function or the factor table.

3. Load Share on Unequal Legs. When the hook is not above the CG, the leg closer to the CG carries more load. Leg 1 share = Load x (distance from CG to leg 2 attachment) / (total distance between attachments). Combine with the angle factor for total tension.

4. Mechanical Advantage. For block and tackle, the mechanical advantage equals the number of rope parts supporting the moving block. A system with four parts of line lifts a 400 lb load with roughly 100 lb of pull (ignoring friction). Note that the lead line running off the fixed block to the operator does not count unless it comes off the moving block.

5. Percent of Capacity. Percent = Gross Load / Chart Capacity x 100. If the result exceeds 75 percent, treat it as a critical lift. Never plan a lift at 100 percent of chart.

How It Works: Power Line Safety (Subpart CC)

Electrocution is a leading cause of crane-related fatalities. Before any work, the employer must identify the work zone and determine whether any part of the crane or load could get closer than 20 feet to a power line. If it could, the employer must choose one of three options: (1) de-energize and ground the line, (2) maintain a 20 foot clearance using encroachment prevention measures (dedicated spotter, proximity alarm, range limiting device, insulating link, or elevated warning line), or (3) determine the line voltage and maintain the Table A minimum clearance. Table A key values: up to 50 kV = 10 feet; over 50 to 200 kV = 15 feet; over 200 to 350 kV = 20 feet; over 350 to 500 kV = 25 feet; over 500 to 750 kV = 35 feet; over 750 to 1,000 kV = 45 feet. Within these distances, additional requirements include a planning meeting, tag lines that are non-conductive, and treating all lines as energized unless confirmed otherwise by the utility.

How It Works: Inspections

Inspections are tiered by frequency and depth:
- Initial: before first use and after any modification or repair.
- Frequent (daily to monthly): visual check before each shift of controls, wire rope, hooks, latches, brakes, hydraulic leaks, tires or tracks, outriggers, and safety devices. Under 1926.1412, the shift inspection does not require documentation, but the monthly inspection does and records must be retained for 3 months.
- Periodic (annual / comprehensive): performed by a qualified person, includes structural members, wire rope detailed inspection, and function tests; records retained for 12 months.
- Slings and rigging: must be inspected before each use and at least annually by a designated person (more often in severe service). Chain slings and synthetic slings require documented periodic inspections.

Wire rope removal criteria (ASME B30 / 1926.1413): in running ropes, 6 randomly distributed broken wires in one rope lay or 3 broken wires in one strand in one lay; in standing ropes, 3 broken wires in one lay or 2 at the end connection; one outer wire broken at the point of contact with the core; wear of one-third the original diameter of outside individual wires; kinking, crushing, bird-caging, core protrusion, heat damage, or reduction of rope diameter beyond nominal tolerance. Wire rope clips must be installed with the saddle on the live (load) end (never saddle a dead horse), with the number of clips and spacing based on rope diameter, and re-torqued after initial loading.

Alloy chain removal criteria: cracks, gouges, nicks, stretch (measure the reach and compare to the original), wear exceeding manufacturer limits (commonly around 10 percent of link diameter), bent or twisted links, heat damage, missing identification tag.

Synthetic sling removal criteria: missing or illegible tag, holes, tears, cuts, snags, burns, melting, broken or worn stitching, acid or alkali damage, knots, excessive abrasion, exposed red core yarns on roundslings, damaged or distorted fittings.

Hooks: remove if throat opening increased more than 15 percent (some sources use 10 percent for wear), twist exceeds 10 degrees from the plane of the unbent hook, cracks, or a damaged or missing safety latch where required.

Identification: every sling must bear a legible manufacturer tag showing rated capacity for each hitch type, material, and manufacturer. No tag means no use.

How It Works: Personnel Qualifications

- Crane operators (1926.1427): must be certified by an accredited testing organization or qualified through an audited employer program, and additionally evaluated by the employer as competent to operate the specific equipment. Certification is by type (and optionally capacity).
- Signal persons (1926.1428): must be qualified through a third party evaluator or employer qualified evaluator and know the standard hand signals, crane dynamics, and limitations. A signal person is required when the point of operation is not in full view of the operator, when the operator view is obstructed, or when site-specific concerns exist. The operator must obey a stop signal from anyone.
- Riggers: a qualified rigger is required during assembly/disassembly and whenever workers are in the fall zone and hooking, unhooking, or guiding a load.

How It Works: Safe Lifting Practices

- Conduct a pre-lift meeting and complete a lift plan for critical lifts: load weight, rigging selection, crane configuration, radius, percent of chart, ground conditions, swing path, exclusion zones, communication method.
- Verify ground conditions: firm, drained, graded, and able to support crane and load. Use outrigger pads or cribbing; outriggers must be fully extended or set according to the chart. The crane must be level (typically within 1 percent).
- Never allow workers under a suspended load; establish and control the fall zone and swing radius (barricade the rear swing area of the counterweight).
- Use tag lines to control load rotation (non-conductive near power lines).
- Protect slings from sharp edges with softeners or corner protectors.
- Do not side-load the boom or drag loads; keep the hoist line vertical.
- Never shorten slings with knots or bolts. Never use shackles with the pin in the running position where it could unscrew; mouse the pin or use a bolt-type shackle for long-term use.
- Check the hook latch is closed and the load is centered in the bowl of the hook, not on the tip.
- Perform a test lift: raise the load a few inches, check balance, brakes, and rigging before proceeding.
- Account for wind; most manufacturers specify maximum wind speed (often around 20 mph) and sail area of the load increases hazard.
- Personnel platforms are prohibited except where conventional means are more hazardous or impossible, and then require a trial lift, proof test at 125 percent, and a 50 percent derating of crane capacity (1926.1431).

Exam Tips: Answering Questions on Hoisting and Rigging

1. Draw the geometry. For any sling angle or tension problem, sketch the triangle. Identify whether the angle given is measured from the horizontal (the standard) or from the vertical. If measured from the vertical, convert (90 minus the angle) before using the sine.

2. Memorize the four angle factors (90 = 1.0, 60 = 1.155, 45 = 1.414, 30 = 2.0). These appear repeatedly and let you solve without a calculator in many cases. Remember that lower angle means higher tension, so a correct answer will always be greater than the load divided by the number of legs.

3. Divide the load by the number of legs first, then apply the angle factor to get tension per leg. Then compare the result to the sling WLL for the hitch type in use. A common trap is giving you the vertical WLL when the question uses a choker, so apply the choker reduction before comparing.

4. Always compute gross load. If the question lists the weight of the load, the block, spreader bar, and slings, add them all. The answer that uses only the load weight is a distractor.

5. Know the power line numbers cold. The 20 foot trigger and the 10 foot Table A clearance for up to 50 kV are the two most tested values. Also recall that de-energizing and grounding is the preferred option and that the utility, not the contractor, confirms voltage.

6. Distinguish OSHA from ASME. If a question asks what OSHA requires, answer with 1926 or 1910 language; if it asks about consensus standards or best practice, ASME B30 is the source. Inspection frequency terms (frequent vs periodic) come from ASME B30 and are adopted into Subpart CC.

7. Wire rope removal criteria are frequently tested. Remember 6 in one lay or 3 in one strand for running ropes, and one-third wear of outer wires. If the question describes a standing rope, the numbers change to 3 and 2.

8. Watch for competent vs qualified. Frequent inspections are by a competent person; annual/comprehensive inspections and lift plan engineering are by a qualified person. Operators must be certified and employer evaluated; signal persons and riggers must be qualified.

9. Hierarchy of correct behavior. When a scenario asks for the best immediate action, the answer that stops the lift, removes defective equipment from service, or gets people out of the fall zone is almost always correct. Any option that continues the lift with a workaround is a distractor.

10. Critical lift threshold is 75 percent. If you calculate percent of chart capacity and it is over 75, the question is probably testing whether you recognize the need for a written critical lift plan.

11. Density values and unit conversions. Practice converting inches to feet (divide by 12) and recognize 490 lb/ft3 for steel and 150 lb/ft3 for concrete. A frequent error is forgetting to convert thickness in inches before computing volume.

12. Mechanical advantage counts supporting parts of line. Count the lines attached to or passing over the moving block. Do not count the line going to the operator unless it leaves the moving block.

13. Synthetic sling chemistry. Nylon is damaged by acids; polyester is damaged by alkalis. Neither should be used near temperatures above about 194 F or exposed to prolonged sunlight without inspection.

14. Read the whole question. ASP questions often embed two conditions (for example, a choker hitch at 45 degrees). You must apply both the hitch reduction and the angle factor. Eliminate answers that only account for one.

15. When in doubt, be conservative. The exam rewards the safest defensible interpretation: round load estimates up, round capacities down, assume lines are energized, assume a tagless sling is unusable, and assume a four-leg bridle shares the load across three legs.

Mastering this topic means combining regulatory recall with simple, repeatable calculations. Practice ten to fifteen sling tension and load weight problems until the angle factors are automatic, and review the removal-from-service criteria for each sling type the night before the exam.