Introduction and background:
This Alert is to remind duty holders of the requirement to have measures in place to verify the correct operation and the correct settings of all safety systems and limits on offshore cranes.
Two incidents have recently occurred on offshore pedestal cranes when the crane boom upper hoist limit systems have 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.
In the first incident the inspection and maintenance activities together with the crane operators pre use checks on a diesel hydraulic crane fitted with a pneumatic control system had 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. When a fault developed in the boom hydraulic pump actuator which allowed the boom to continue hoisting after the control lever was returned to neutral the 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.
In the second incident which involved an electric crane the boom upper hoist operational limit 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.
Duty holders should ensure:
- 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.
- The inspection and function testing should include 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 crane 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. As it will be expected these tests will only be undertaken by simulation then they must be sufficiently robust to ensure all operational components are tested and that the system operates at the correct angle of the boom.
Relevant legal documents:
The relevant legal requirements are:
- The Health and Safety at Work etc. Act 1974
- The Provision and Use of Work Equipment Regulations 1998 (SI 1998/2306) (PUWER)
- The Lifting Operations and Lifting Equipment Regulations 1998 (SI 1998/2307) (LOLER)
Any queries relating to this safety alert should be addressed to:
Health and Safety Executive
Energy Division (Offshore)
Lord Cullen House
Tel: 01224 252500
Fax: 01224 252629
This alert sheet contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.
Article source: http://www.hse.gov.uk/safetybulletins/crane-safety-systems.htm