Crane, Rigging, Equipment, and Struck-By Case Lab

Crane, Rigging, Equipment, and Struck-By Case Lab

Scenario

A mechanical contractor is setting a rooftop air handling unit with a mobile crane. The unit arrived late, so the lift slid into the afternoon while concrete trucks, telehandlers, and roofers stay active nearby. The crane pad sits over a recently backfilled utility trench. The rigging crew has a spreader bar, synthetic slings, and shackles, but one sling tag is unreadable and sharp metal edges show on the load frame. Overhead, a 12 kV distribution line crosses near the boom path. Two supervisors are giving hand signals from different sides of the building.

First Priorities

The CHST should focus on high-energy struck-by, electrocution, and crush exposures. The lift must not proceed until the lift director or responsible competent person confirms the plan. Conflicting signals are an immediate stop — OSHA permits only one designated signal person, and the operator must stop for any unclear signal or for an emergency stop from anyone (1926.1419). A suspended load path over workers or active traffic is unacceptable. The unreadable sling tag and unprotected sharp edges require correction first.

A practical sequence:

1. Pause the lift and keep the load on the ground.
2. Establish and enforce swing-radius, load-path, and landing exclusion zones.
3. Confirm one signal person, a communication method, and stop-signal authority.
4. Verify load weight, crane configuration, radius, capacity, ground support, line clearance, and weather limits.
5. Inspect rigging; remove questionable components.

Power Lines and Ground Conditions

Under 29 CFR 1926.1408, when operating near energized lines the employer must maintain a minimum clearance of 10 feet for lines up to 50 kV, adding 4 inches per additional 10 kV above 50 kV — so the 12 kV line requires the 10-foot baseline, or de-energizing/grounding and a dedicated spotter. The crane may have ample chart capacity yet still be unsafe if the surface cannot carry outrigger loads. Recently backfilled trenches, voids, soft soil, and slopes undermine support. The plan must verify matting/cribbing, outrigger extension, level setup, and access path; a pad crossing a trench needs engineering or competent evaluation before continuing.

Rigging and Equipment Controls

Rigging selection is not guesswork. Slings, shackles, hooks, and spreader bars must be rated, inspected, and compatible with hitch type and geometry. 1926.251 requires a legible identification tag stating rated capacity; a missing or unreadable tag removes the sling from service until a qualified person evaluates it. Synthetic slings need protection from sharp edges and heat, and a basket hitch with the legs not vertical reduces capacity by the sling-angle factor (a 60° leg angle yields about 86% of vertical capacity; 30° yields only 50%). Equipment traffic matters too: concrete trucks, telehandlers, and pedestrians should not share an uncontrolled route with crane setup or landing. Backing alarms, spotters, barricades, and high-visibility clothing help but do not replace physical separation.

Emergency Response, Communication, and Documentation

The lift plan should address rising wind, lost communication, line approach, a shifting load, structure contact, or a person entering the zone. Everyone needs authority to give an emergency stop. After a dropped load or struck-by event, preserve the scene when life safety allows, secure the equipment, call EMS as needed, and block restart until investigated. Resist solving a near miss by telling workers to be careful — conflicting signals are a planning failure, an over-people load path is a coordination failure, and an untagged sling is an inspection and procurement failure. The pre-lift meeting covers weight, pick/set points, configuration, roles, signal method, exclusion-zone boundaries, weather stop criteria, tag-line use, and emergency stop, and affected subcontractors get the same briefing.

Qualified Roles and Critical Lifts

Subpart CC defines the roles the exam tests. A crane operator must be certified by type and capacity through an accredited program. A qualified rigger is required whenever workers are within the fall zone hooking, unhooking, guiding, or doing initial connections. A signal person must be qualified, know the standard hand and voice signals, and understand the crane's operations and limitations. The lift director plans and supervises the lift. A critical lift — generally one exceeding a percentage of chart capacity (often 75–90%), multi-crane picks, or lifts over occupied structures — requires a written plan reviewed by a qualified person before work begins.

Exam Judgment

In struck-by and crane items, eliminate any option that keeps people in the fall zone, follows two signal sources, uses untagged rigging, or sets up on unverified ground. The correct answer keeps people out of the line of fire, confirms qualified roles, verifies capacity and clearance, and holds the load until conditions are controlled. After a delay, restart planning must reconsider changed conditions: wind, lighting, fatigue, traffic, ground disturbance, or a revised load path.