The UK Health and Safety Executive (HSE) has published the following safety alert covering two recent crane incidents in which the crane boom upper hoist limit systems failed to prevent the crane booms from being hoisted up too far and against the boom backstops. The continued hoisting resulted in the booms fully compressing the boom backstops, causing high loading on the boom upper main chords with the eventual catastrophic failure of the booms. Measures should be in place to verify the correct operation and the correct settings of all safety systems and limits on offshore cranes.
Pre-use checks on a diesel hydraulic crane fitted with a pneumatic control system failed to identify or question why the boom hoist upper limit system was not functioning in the manner detailed in the crane operation manual.
This malfunction was the result of an omission to fit a blanking plug in a pneumatic valve in the control system. A fault developed in the boom hydraulic pump actuator which allowed the boom to continue hoisting after the control lever was returned to neutral. This fault in the pneumatic control system allowed the boom to be hoisted beyond both the upper hoist operational limit and the upper hoist ultimate limit.
The boom upper hoist operational limit on an electric crane had been deliberately defeated to allow the boom to be hoisted up to a position which would allow the crane to be rotated through 360 degrees.
This activity may have been conducted on the basis that the boom upper hoist ultimate limit would provide protection.
Unfortunately, this ultimate limit had not been set to operate at the correct angle of the boom. The boom was therefore hoisted up too far and against the boom backstops, leading to the failure of the boom before this ultimate limit was activated.
The HSE alert suggests the following actions:
- Ensure that the inspection and the function testing of the safety systems on offshore cranes are sufficiently robust to verify that they operate in the manner described in the crane operation manual;
- Ensure that inspection and function testing includes verifying that the boom hoisting limits operate at the angles of the boom specified in the crane operation manual;
- Where cranes are fitted with ultimate boom limits advice should be obtained from the manufacturer or a suitably competent person as to the method and frequency of the tests required to verify the correct operation and setting of these limits. These tests – particularly if carried out by simulation – should be robust enough to ensure all operational components are tested and that the system operates at the correct angle of the boom.
The full alert can be found at hse.gov.uk/safetybulletins/crane-safety-systems.htm.
Members may wish to refer to Guidelines for lifting operations.
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