Permit to Work Systems

Permit to Work System (PTW) is where proposed work is identified as having a high risk, strict controls are required. The work must be carried out against previously agreed safety procedures, a ‘permit-to-work’ system.

The PTW is a documented procedure that authorises certain people to carry out specific work within a specified time frame. It sets out the precautions required to complete the work safely, based on a risk assessment. It describes what work will be done and how it will be done; the latter can be detailed in a ‘method statement’.

The permit-to-work requires declarations from the people authorising the work and carrying out the work. Where necessary it requires a declaration from those involved in shift handover procedures or extensions to the work. Finally, before equipment or machinery is put back into service, it will require a declaration from the permit originator that it is ready for normal use.

General principles

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

  • Human factors;
  • Management of the work permit systems;
  • Poorly skilled work force;
  • Unconscious and conscious incompetence;
  • Objectives of the work permit system;
  • Types of work permits required; and
  • Contents of the work permits.

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

  • Failing of the site safety management system;
  • Failure to recognise a hazard before and during maintenance;
  • Failure to comply with the work permit system in hazardous environments; and
  • Communication failure during the use of a work permit system.

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

The Safety Report should address the following points:

  • Whether staff have been sufficiently informed, instructed, trained and supervised to minimise a potential human failing during operation of the work permit system;
  • Whether the work permit system includes sufficient safety information, maintenance instructions, correct PPE and equipment for use;
  • Whether the work permit contains sufficient information about the type of work required (Equipment removal, excavation, hot/cold work, repairing seals, vessel entry, waste disposal, isolation);
  • Whether there is sufficient provision available to fulfil the requirements of the work permit system;
  • Whether the employees responsible for control of the maintenance work are identified within the work permit system and that the work is properly authorised by a responsible person;
  • Whether the work permit system is managed, regularly inspected and reviewed;
  • Whether all work permits are kept on file;
  • Human factors (stress, fatigue, shift work, attitude);
  • Whether sufficient precautions are taken prior to initiating a work permit (isolation, draining, flushing, environmental monitoring, risk assessments, communication, time allotted for the work);
  • Whether staff are aware of the type of environment they are working in during the operation of a work permit (flammable, corrosive, explosive, zones 0, 1 & 2, electricity supplies);
  • Whether the person responsible for operating the plant is aware of the type of maintenance involved and how long it is likely to take; and
  • Whether the work permit system involves a formal procedure whereby the maintained plant or equipment is handed back to operation.

Major hazards

Major hazards could arise from the following:

  • Wrong type of work permit used;
  • Wrong information about work required on the work permit;
  • Failure to recognise the hazards where work is carried out (e.g. flammable substances);
  • Introduction of ignition source in controlled flameproof area (e.g. welding, non spark-proof tools, non-intrinsically safe equipment used in intrinsically safe zones);
  • Terms of work permit not adhered to (e.g. failure to isolate plant and/or drain lines of hazardous substances);
  • Failure to hand-over plant in safe condition on completion of work/cancelling of work permit;
  • Unauthorised staff performing work permit functions;
  • Poor management of the work permit system; and
  • Insufficient monitoring of the work permit system.