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The Permit To Work System (PTW)

What Is Permit To Work

The permit to work (PTW) system is a safety program initiated for high risk activities.

PTW is a core element of integrated safe system of work (ISSOW) systems, along with risk assessment and isolation planning. It enables as low as reasonably practicable (ALARP) reduction of unsafe activities in non-trivial work environments. Permit to work adherence is essential in process safety management.

PTW is initiated at the planning phase of the job to cover all the safety necessities for a safe and successful completion of a high-risk task. Some jobs that requires permit to work include: Hot job, Work at height, Confine space entry, electrical equipment maintenance, etc.

Sometimes  jobs that requires PTW are signified as (Permit required). Example: Permit required confine space entry, etc.

It is recommended that the process of design and implementation of the permit to work should be carried out by a competent person.


The PTW contains a set of laid down structures (Checklist) that must be followed for the specified job.


Content Of A Permit To Work

There are necessary contents of every permit to work, these contents include:

  • The caption of the permit
  • The job to be done
  • Brief description of the job to be done
  • The inherent hazards in the job
  • Corrective measures in place
  • Location of the job
  • Time of the job; Start time and end time.
  • Responsible person
  • The equipment/ machinery involved
  • Emergency plan
  • Signatories (Permit supervisor and the plant/machinery supervisor), etc.

The aim of having a drawn-out permit to work check-list is to ensure that necessary controls are not omitted.

After a permit is designed, it can be easily implemented even with a less skilled professional; this is possible because almost all the necessities for the job has already been stipulated. What is needed is just to ensure that the stipulated conditions are met.

It is needful that the permit be followed through-out the task. At any point where any of the conditions stipulated in the permit changes, the permit has to be withdrawn and the task suspended. This withdrawal will be pending when all the conditions will be met.

“A permit to work is not a replacement for robust risk assessment, but can help offer context for the risk of work to be done. Studies by the UK Health and Safety Executive have shown that the most significant cause of the maintenance related accidents in the UK chemical industry was a failure of effective permit to work systems. Common failures in control of work systems are a failure to follow the permit to work or isolation management procedures, risk assessments that are not suitable and sufficient to identify the risks, and/or the control measures and a combination of the two”.



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