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Permit to Work Systems

This Technical Measure Document refers to permit to work systems required to control work such as maintenance activities on chemical plant and so prevent a major accident.

See also Technical Measure Documents on:

The relevant Level 2 Criteria are and

General principles

The following aspects should be considered with respect to Permit to Work Systems:

The following issues may contribute towards a major accident or hazard:

Contributory factors for an assessor to consider concerning the Work Permit System

The Safety Report should address the following points:

Major hazards

Major hazards could arise from the following:

Guidance relating to permit to Work Systems

The following HSE publications can be used as guidance material relating to safety issues surrounding permit to work systems:

HS(G)5 Hot work : welding and cutting on plant containing flammable materials, HSE (Not in current HSE list).
Paragraph 3 refers to the precautionary measures needed when welding in areas that could be potentially flammable by planning and controlling the task using a work permit system.
Paragraph 72 refers to the importance of management controlling the work permit system.
Paragraph 73 refers to the principles that should be followed when operating a work permit system.

HS(G)48 Reducing error and influencing behaviour, HSE, 1989.
Paragraph 27 refers to conscious incompetence whereby an employee consciously refused to follow the work permit system to help an operator. A breathing line was not assessed and an operator inhaled nitrogen instead of air. Had the work permit system been managed properly then the event would not have occurred.

HS(G)51 Storage of flammable liquids in containers, HSE, 1998.
Paragraph 48 illustrates a permit to work system and summarises its expected contents.

HS(G)64 Assessment of fire hazards from solid materials and the precautions required for their safe storage and use, HSE, 1991.
Paragraph 28 refers to the need for a work permit system if a source of ignition is introduced such as welding, cutting or grinding. The system should contain any fire precautions necessary.

HS(G)65 Successful health & safety management, HSE, 1997.
The section called; `Devising Risk Control Systems RCSs' under Inset 11, illustrates the permit to work system as an example of a management control loop i.e. plan, do, check and act. It demonstrates how risks in the work place can be reduced if they are controlled and managed.

HS(G)77 COSHH and peripatetic workers, HSE, 1992
Paragraph 19 refers to the inclusion of a work permit system in a COSHH assessment. It highlights the importance of safeguarding against risk when carrying out work on a chemical plant.

Further reading material

The following publications are useful references relating to aspects of permit to work systems:

OIAC. Guidance on permit-to-work systems in the petroleum industry, Oil Industry Advisory Committee, HSC, 1997.

IND(G) 98 (Rev 3) Permit-to-work systems, Free copy available at HSE Books online ISBN 0 7176 1331 3, HSE, 1997.

Guidance on permit-to-work systems in the petroleum industry. ISBN 0 7176 1281 3, HSE, 1997 

Loss Prevention in the Process Industries: Hazard Identification, Assessment and Control. Frank P Lees 1996, 2nd Edition, vol 2 ch. 20 and 21. ISBN 0 7506 1547 8. Published by Butterworth Heinemann.

Case studies illustrating the importance of permit to Work Systems

Hickson and Welch Ltd Fire (22/9/1992)

Pasadena - Phillips 66 (23/10/1989)

San Francisco Natural Gas Pipeline Puncture (25/8/1981)