The maintenance and thorough examination of braking systems on offshore cranes

Introduction

1. This notice is to remind dutyholders of the requirement to ensure the continued integrity of crane braking systems by:

• operating a maintenance system that will ensure all braking systems remain in an efficient state, in efficient working order and in good repair;
• ensuring the thorough examination undertaken by a competent person is sufficient to ensure any deterioration in the braking system will be detected and remedied in good time.

With many offshore cranes now more than 20 years old it is vital to ensure both the maintenance activities undertaken and the content of the thorough examination continue to be appropriate.

[back to top]

Background

2. An incident occurred on a Priestman Sea Lion 60D diesel hydraulic pedestal crane manufactured in 1977. Crane lifting operations had been completed. However, as they were to be resumed, the crane boom was not lowered down onto the boom rest. The boom was instead placed directly above the boom rest at an angle of approximately 45 degrees. The crane operator switched off the diesel engine and as he was walking away from the crane the boom lowered in an uncontrolled manner, resulting in considerable damage to the boom when it made contact with the rest. The boom luffing winch unit, situated above the crane cab, was torn from its mounting pedestal, debris from the winch unit fell onto the deck below but the majority fell into the sea. The crane operator sustained minor injuries from the falling debris but the incident could have resulted in serious injuries or fatalities.

3. The winch units for whip hoist, main hoist and boom luffing are all situated above the crane cab. Two hydraulic motors power each of these winch units, driving Hamworthy reduction gearboxes mounted on each side of the winch drum.

4. Each Hamworthy gearbox incorporates a multi plate, oil immersed, friction disc brake. This brake is activated by a sprag clutch (roller clutch) which allows the gearbox to rotate in the direction of hoisting, however when it tries to rotate in the opposite direction it locks, bringing the brake plates into operation which hold and prevent rotation.

5. The luffing winch drum is fitted with an additional safety feature in the form of a luffing pawl. This is a spring applied, hydraulic release pawl/sprag which engages with a toothed ring on the drum barrel and prevents the lowering rotation of the drum.

6. The winch pedestals on this crane were manufactured from grey cast iron. It is unlikely that this material would be employed on load bearing components on modern cranes. Metallurgical examination, however, suggested the failure of the pedestal casting was a consequence of a sudden gross overload and it was not the initiating event for this incident.

7. It has not been possible to recover the luffing winch unit and identify the root cause of this incident. However, for the boom to lower, the brake in each of the two gearboxes must have failed to operate and the sprag/pawl failed to engage onto the drum.

[back to top]

Actions required

8. Dutyholders should review their maintenance routines for crane braking systems to ensure they cover all critical components in the braking systems. In addition dutyholders should:

• ensure that maintenance undertaken on the critical components in the braking system is sufficient and continues to be appropriate as the age of the crane increases;
• in the case of braking systems that employ sprag clutches, the maintenance activities undertaken are able to verify the correct operation of each sprag clutch independently so as to determine the presence of any unrevealed faults. Also, ensure that the instructions from the crane and gearbox manufacturer are followed, particularly regarding the grade of oil, oil condition monitoring/oil replacement, and any recommendations on intervals for gearbox or sprag overhaul;
• if a drum pawl/sprag is fitted then the examination and testing of the pawl is included in the maintenance routines. Particular attention should be paid to testing the time it takes to engage for all its operational situations, ensuring these are within those specified by the manufacturer or, in their absence, a competent person;
• ensure the maintenance routines include the testing of the crane hydraulic systems by a competent person to ensure correct setting and operation of these systems and the satisfactory condition of the components within the systems.

9. Dutyholders should discuss the scope of the thorough examination with their competent person to ensure it includes all items and parts of the crane braking systems that could, through deterioration, lead to a dangerous situation. Attention is drawn to the recommendations given in BS 7121-2

[back to top]

Relevant legal requirements

10. The relevant legal requirements are:

• the Provision and Use of Work Equipment Regulations 1998 (SI 1998/2206) (PUWER);
• the Lifting Operations and Lifting Equipment Regulations 1998 (SI 1998/2037) (LOLER).

[back to top]

References

11. You can find more relevant information in the following publications:

• Safe use of work equipment. Provision and Use of Work Equipment Regulations 1998. Approved Code of Practice and guidance L22 (Second edition) HSE Books 1998 ISBN 0 7176 1626 6
• Technical guidance on the safe use of lifting equipment offshore HSG221 HSE Books 2002 ISBN 0 7176 2100 6
• Code of practice for Safe use of cranes - part 2: Inspection, testing and examination. BS 7121-2 2003 British Standards Customer Services, 389 Chiswick High Road, London W4 4AL
• Code of practice for Safe use of cranes - part 11: Offshore cranes. BS 7121-11 1998 British Standards Customer Services, 389 Chiswick High Road, London W4 4AL

[back to top]

Further information

12. Any queries relating to this safety notice should be addressed to:

Health and Safety Executive
Hazardous Installations Directorate
Offshore Division
Lord Cullen House
Fraser Place
Aberdeen
AB25 3UB

Tel: 01224 252500
Fax: 01224 252629