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Shock loading: meaning and why it matters

Boom Angle editorial teamSources checked 3 min read

Shock loading is the extra force that a sudden start, stop or jerk puts on a crane, rope and rigging, beyond the weight of the load. A load that is snatched, dropped onto slack line or stopped hard briefly pulls much harder than it weighs, so chart limits can be exceeded with a load well under capacity.

A line graph of the force on the hook over time. It sits level at the load's weight, jumps to a sharp peak at a sudden stop, then settles back to the weight
A sudden stop briefly puts more force on the hook than the load weighs.

Static and dynamic

A load hanging still pulls down with its weight. A load that is speeding up, slowing down or swinging pulls with its weight plus the force needed to change its motion. The faster the change, the larger the extra. A jerk is a very fast change.

Charts rate a load handled smoothly. They do not tell you how much extra force a snatch adds, because it depends on the speed, the stiffness of the line and how suddenly the motion stops. All you need to know is that it can be much higher than the weight, and that the printed capacity assumes you do not create it.

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Operations

Which action creates side loading on a crane boom?

Choose an answer to begin

Common causes

  • Taking up slack fast. A slack sling or line snaps taut under power.
  • Starting or stopping a hoist or swing suddenly.
  • Stopping a swing with the controls instead of letting it ease out.
  • A load breaking free from the ground, mud, ice or another object, so that it springs up.
  • A load dropped a short distance and caught. A free fall that ends abruptly is a shock.
  • Wind gusts on a large load.

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Every answer comes with a full explanation.

Habits that prevent it

  • Take up slack slowly and stop when the load just comes off the ground.
  • Use smooth control motions, with gentle starts and stops.
  • Slow down near the end of a travel.
  • Use the signals that call for slow motion. The standard "move slowly" signal asks for a slower motion alongside another command.
  • Avoid pulling a stuck load free with the crane. See side loading.

OSHA 29 CFR 1926.1417 covers operation under the manufacturer's procedures and limits.

Common mix-ups

  • A light load cannot be a problem. A snatch can make a light load pull hard on the rigging.
  • Shock only hurts the crane. Slings, shackles and lifting lugs take it too.
  • Shock is the same as two-blocking. They are separate hazards, though a sudden stop against the tip makes both. See two-blocking.

On the NCCCO written exam

Dynamic loading is named in Core tasks 2.16 to 2.19, with side loading, deflection and weather, in Operations, about 28% of the exam under the 01/25 handbook. Expect to pick the action that avoids a shock, such as easing the swing to a stop.

Practice it

Signals set the pace of a lift, and the crane hand signals drill trains you to name all the standard signals, including the ones that ask for slower motion or a stop. Read two-blocking and side loading next. The crane terms glossary lists the set.

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Sources

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Facts checked 25 October 2026 against the sources listed above. If something has changed, tell us and we will correct it within 2 business days.

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