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Rated capacity indicator vs limiter: meaning and why it matters

Boom Angle editorial teamSources checked 3 min read

A rated capacity indicator measures the load and the crane's setup, compares them with the rated capacity and warns the operator as the limit nears. A rated capacity limiter does the same and also stops the crane motions that would make the lift worse. Neither one replaces reading the chart.

Two columns. The indicator measures load and radius, compares with the chart, warns the operator and leaves the operator to act. The limiter does the same and also stops the motions that would worsen the lift
Both read and compare. The limiter also acts.

What each device does

Both devices take inputs from sensors, such as the load on the hook, the boom angle, the boom length and the crane's configuration. They compare those with the chart stored in the device.

  • Indicator. Displays the load, radius and how close the lift is to the limit, and warns the operator with lights or a sound. The operator has to respond.
  • Limiter. Gives the same information and also prevents motions that would increase the load moment past the limit. It does not remove the need to read the chart.

Devices are sold under several names, including load moment indicator and load moment limiter. The wording in the crane's manual tells you which one you have.

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Operations

Which action creates side loading on a crane boom?

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Where they can mislead

Their protection is only as good as their setup. Common problems:

  • Wrong configuration entered. If the device is told the outriggers are fully extended but they are not, it compares the lift against the wrong table.
  • Wrong parts of line or counterweight. Same issue.
  • Block and rigging weights. The load shown on the display may or may not include the hook block and rigging. The manual says which, and that decides whether you still make the deductions yourself.
  • A failed or bypassed device. The operator must know the capacity without it.

OSHA 29 CFR 1926.1416 covers operational aids. Read the section for which are required and what to do when one stops working.

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Every answer comes with a full explanation.

Common mix-ups

  • "The device is green, so the lift is fine." It is only as right as its inputs.
  • Indicator and limiter are the same thing. A limiter acts. An indicator informs.
  • A device replaces the chart. The operator still needs the chart to plan the lift.
  • Deductions are always automatic. Check the manual.

On the NCCCO written exam

Core tasks 2.12 and 2.13 cover operator aids and what to do when they fail, in Operations, about 28% of the exam under the 01/25 handbook. Expect to explain what a device does and what an operator does if it stops working.

Practice it

The crane percent of capacity calculator computes the percentage a device displays, from load, deductions and chart capacity. Read two-blocking, another aid-related hazard, and load moment for the measurement behind the indicator. 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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