Free MA Hoist
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Operating Hazards & Safe Procedures

2 hours

Learning Objectives

  • •Identify two-blocking and explain why it is catastrophic on friction winch cranes
  • •Apply the swing radius exclusion requirements of OSHA 1926.1424
  • •Explain the hazards of operating a crane near power lines and the clearance distances under OSHA 1926.1408
  • •Describe the free-fall prohibition under OSHA 1926.1426 and conditions for controlled load lowering

Topics Covered

  • •Two-blocking: the load block (bottom block) contacts the boom top (upper block) — the hoist line goes slack and the load free-falls
  • •Two-blocking on friction drums: particularly dangerous because the clutch can re-engage before the block is seen to contact
  • •Prevention: anti-two-block device (required on lattice boom cranes post-November 8, 2011); visual spotters; marking hoist line
  • •OSHA 1926.1424 swing radius hazard: the rotating superstructure, boom, and counterweight can strike workers
  • •Control measures: control lines, warning lines, railings, or barriers marking the swing/crush zone boundary
  • •Counterweight swing zone: the counterweight extends beyond the carrier and rotates — workers must be kept clear
  • •OSHA 1926.1408 power line safety (up to 350 kV): minimum clearance 20 feet unless the utility has confirmed a lower safe distance
  • •Encroachment prevention plan: required before operating within the Table A distance from power lines
  • •OSHA 1926.1418 — authority to stop operation: the operator has the right AND obligation to stop if a safety concern arises
  • •OSHA 1926.1426 free fall prohibition: equipment must not be used to free-fall loads except in specific conditions
  • •Controlled load lowering: the load must be lowered using the friction drum brake under positive operator control at all times
  • •No side-loading: the boom must not be used to drag or pull loads sideways — this is an operational prohibition under OSHA 1926.1417
  • •Load swing hazards: tag lines used by a ground person to control load rotation and prevent swinging into structures
  • •Boom angle limits: operating outside the manufacturer's minimum and maximum boom angle range voids load chart ratings and risks boom failure
  • •Operating on slopes: manufacturer specifications govern maximum allowable side slope and fore-aft slope during operation

Resources

OSHA 1926.1408 — Power line safety (equipment operations)

osha

Required

OSHA 1926.1424 — Work area control (swing radius)

osha

Required

OSHA 1926.1426 — Free fall and controlled load lowering

osha

Self-Check Questions

Question 1: What is two-blocking and why is it especially dangerous on friction winch cranes?

  1. A. When the boom contacts a power line — dangerous because the drum cannot be stopped quickly
  2. B. When the load block contacts the boom top sheave — on friction drums, the rope can go slack and the load falls(correct)
  3. C. When two cranes lift the same load simultaneously without a critical lift plan
  4. D. When the hoist drum is blocked by a mechanical brake failure
Show Explanation

Explanation:

Two-blocking occurs when the load block is hoisted until it contacts the upper block or boom tip. On a friction winch crane, the hoist line goes slack above the contact point, allowing the load to fall freely. The operator's clutch and brake have no effect on the falling load once rope tension is lost.

Question 2: Under OSHA 1926.1408, what is the default minimum safe distance from a power line (up to 350 kV) when operating crane equipment?

  1. A. 5 feet
  2. B. 10 feet
  3. C. 20 feet(correct)
  4. D. 50 feet
Show Explanation

Explanation:

OSHA 1926.1408 Table A establishes a default minimum approach distance of 20 feet from power lines up to 350 kV. A reduced distance may be permitted only after the utility owner confirms the specific safe distance in writing. The 20-foot default applies to all parts of the crane — boom, load, rope, and load.

Question 3: You are operating a crane and see a worker enter the counterweight swing zone while you are rotating. What must you do?

  1. A. Sound the horn continuously and complete the swing
  2. B. Slow the rotation and warn the worker verbally
  3. C. Stop rotation immediately — do not resume until the area is confirmed clear(correct)
  4. D. Ask the signaler to wave the worker out; continue rotating slowly
Show Explanation

Explanation:

OSHA 1926.1424 requires stopping all rotation when workers are in the swing/crush zone. A crane counterweight can weigh tens of thousands of pounds and cannot stop instantaneously. The only safe action is to stop immediately and wait for the area to be confirmed clear.

Question 4: Under OSHA 1926.1418, who has the authority to stop crane operations when a safety concern is identified?

  1. A. Only the site safety officer
  2. B. Only the project manager or general contractor
  3. C. The crane operator, who has the right and obligation to stop operations(correct)
  4. D. OSHA inspectors only, who must be called to the site
Show Explanation

Explanation:

OSHA 1926.1418 specifically grants the operator authority to stop operations when they believe a safety concern warrants it. This is not optional — the operator has both the right and the obligation to stop. No employer directive may override this safety authority.

Question 5: A flagman is directing the crane operator to swing the boom. The flagman's view of the load is blocked by a building. What must the operator do?

  1. A. Proceed slowly based on the flagman's last known position
  2. B. Stop and do not resume until the signaler has a clear view of both the operator and the load(correct)
  3. C. Switch to radio communication for this portion of the lift
  4. D. Ask another worker to relay the flagman's signals
Show Explanation

Explanation:

The signaler must be able to see both the operator's control zone and the load at all times. If the signaler's view of the load is obstructed, signals cannot be given safely. The operator must stop until the signaler is repositioned with a clear view, or a secondary signaler is designated for the obstructed zone.

Question 6: OSHA 1926.1426 prohibits the free-fall of loads on cranes. What does "free fall" mean in this context?

  1. A. The load falling faster than the boom can be lowered
  2. B. The uncontrolled descent of the load — hoist drum spinning freely without brake or clutch engagement(correct)
  3. C. The load swinging freely on the hook without a tag line
  4. D. Lowering the load faster than 50 feet per minute
Show Explanation

Explanation:

Free fall means the hoist drum spins without positive brake or clutch engagement — the load descends under gravity alone, uncontrolled. OSHA 1926.1426 prohibits this mode of operation. On friction drum cranes, the operator must maintain positive brake control throughout any load lowering.

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