Interlocks for drill floor machinery

  • Safety notice:02/2006
  • Issue date: December 2006


1 There have been several serious incidents related to deficient interlocking on drilling machinery and pipe-handling equipment. This notice outlines the actions that should be taken to prevent such incidents.


2 Remotely controlled movable equipment is often used to assist in pipe handling, drilling and related activities. However, while such equipment may eliminate certain types of incidents, it may also introduce new hazards.

3 Collisions may occur between equipment and personnel, between equipment and structures, or between different items of drill floor equipment. Dropped objects are a further hazard arising from collisions.

Actions required

4 Owners and operators of drilling equipment should ensure that clear lines of responsibility are established for maintenance and inspection of drill floor equipment.

5 With guidance from the equipment suppliers, or another suitably competent person, those responsible for the equipment should: -

  • Ensure an up to date risk assessment is in place which has reviewed the operation of the drill floor equipment. All potentially dangerous interactions between the equipment, structures and personnel should be considered, and the means to prevent such interactions identified.
  • Ensure that interlocks to prevent collisions or protect personnel are regularly tested and maintained. Note that it may be necessary to update interlock settings to take account of changes to the position of other equipment or structures.
  • Ensure that suitable verification, validation and change control procedures for all interlocks are in place. This means that there should be version control to ensure that the modification history is clear and to prevent unauthorised modification. This is particularly important when interlocks are implemented in software.
  • Ensure that appropriate management and 'permit to work' controls are in place to ensure that equipment interlocks are neither defeated or overridden unless:
    • an appropriate risk assessment has been undertaken;
    • all reasonable precautions have been taken;
    • the assessments and overrides are properly authorised and recorded;
    • the overrides are removed as soon as practicable.
  • Verify, where the equipment undertakes lifting operations, that the 'thorough examination' addresses all relevant interlocks, including those implemented in software. The dutyholder should also ensure that the scope of the 'thorough examination' remains appropriate as the age of the equipment increases.

Relevant legal requirements

Employer duties

Provision and Use of Work Equipment Regulations 1998/2306 (PUWER) - Regulations 4, 5 and 18

Lifting Operations Lifting Equipment Regulations/1998/2307 (LOLER) - Regulations 9 and 10

Management of Health and Safety at Work Regulations 1999/3242 (MHSWR) - Regulation 3

Manufacturer/supplier duties

Health and Safety at Work etc 1974 - Section 6

Suppy of Machinery (Safety) Regulations 1992 (as amended)


BS EN62061:2005 Safety of machinery – Functional safety of safety-related electrical, electronic and programmable electronic control systems

BS PD 5304:2005 Safe use of machinery

BS EN 954-1 1997 Safety of machinery 

BS EN 1037:1996 Safety of machinery: Prevention of unexpected start up

BS EN 60812:2006 Analysis techniques for system reliability. Procedure for failure mode and effects analysis (FMEA)

Technical guidance on the safe use of lifting equipment offshore HSE HSG221 ISBN 071762 1006

Further information

Any queries relating to this 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 252648

This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance as illustrating good practice

Updated 2024-02-09