Human factors: Permit to work systems

Why are permit to work systems important?

Instructions or procedures are adequate for most work activities, but some require extra care.  A 'permit to work' is a more formal system stating exactly what work is to be done and when, and which parts are safe.  A responsible person should assess the work and check safety at each stage. The people doing the job sign the permit to show that they understand the risks and precautions necessary.

Permits are effectively a means of communication between site management, plant supervisors and operators, and those who carry out the work. Examples of high-risk jobs where a written 'permit to work' procedure may need to be used include hot work such as welding, vessel entry, cutting into pipework carrying hazardous substances, and work that requires electrical or mechanical isolation.  It is also a means of coordinating different work activities to avoid conflicts.

It should be emphasised, however, that a 'permit to work' is not a replacement for robust risk assessment, but can help bring the risk assessment 'to life', at the sharp end, where it matters.

There are many human factors aspects of permit-to-work systems, including competence, procedures, and communications.  Wider guidance on permit to work systems can be found in HSG250.

Key principles in permit to work systems

  • The issue of a permit does not, by itself, make a job safe.
  • Roles and responsibilities - is it clear who is in charge, and who does what - with no important gaps or overlaps?
  • If the job cannot be finished in one shift, ensure that it will be left in a safe state and that clear instructions are available for the next shift (see Shift Handover topic);
  • The Permit should contain all relevant information, be correct, and presented in a suitable format (eg not overly complex or ambiguous, a single-sided A4 permit might suffice - see Procedures topic);
  • Ensure end-user involvement in the design of the permit system, and the document design process;
  • Communicate all relevant information (including hazards and controls) to all personnel involved;
  • Ensure that other people are aware of what maintenance staff are doing and vice versa;
  • If there are a number of permits, they should be displayed at an appropriate location, in a systematic arrangement that enables staff to check which equipment is eg isolated or undergoing maintenance;
  • Make links between related permits – consider simultaneous tasks and interdependent activities;
  • Consider the balance between communicating 'routine' safety information on a Permit (eg PPE, housekeeping), and issues specific to the task in hand, including process safety information where relevant;
  • The permit system should have a process for hand-over of plant on completion of work;
  • Train all users in the PTW system and provide information to other persons affected by it;
  • Make arrangements to manage non-compliance eg where there may be overload of permits at the beginning of a shift;
  • Plan work to smooth out the distribution of PTWs, or provide more PTW authorisers at busy times;
  • If you are considering introducing an electronic permit system, assess the risks from the changeover from a paper-based system.  Use good interface design, and train personnel in the PTW process, not just use of the software interface.  See HSG250, p.16.
  • Ensure effective management and review of the work permit system.

More information on permit to work systems

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