What is Permit to Work Systems (PTW)

Permits to Work (PTW)

A permit-to-work system is a formal written system used to control certain types of work that are potentially hazardous. A permit-to-work is a document that specifies the work to be done and the precautions to be taken. Permits-to-work forms an essential part of safe systems of work for many maintenance activities.

They allow work to start only after safe procedures have been defined and they provide a clear record that all foreseeable hazards have been considered. A permit is needed when maintenance work can only be carried out if normal safeguards are dropped or when new hazards are introduced by the work. Examples are entry into vessels, hot work, and pipeline breaking.

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.

Safe systems of work are crucial in work, such as the maintenance of chemical plants where the potential risks are high, and the careful coordination of activities and precautions is essential to safe working. In this situation and others of similar risk potential, the safe system of work is likely to take the form of a permit-to-work procedure. 

The permit-to-work procedure is a specialized type of safe system of work for ensuring that potentially very dangerous work (e.g. entry into the process plant and other confined spaces) is done safely. 

Although this procedure has been developed and refined by the chemical industry, the principles of the permit-to-work procedure are equally applicable to the management of complex risks in other industries. 

The fundamental principle is that certain defined operations are prohibited without the specific permission of a responsible manager. This permission is only granted once stringent checks have been made to ensure that all necessary precautions have been taken and that it is safe for work to go ahead. 

The people doing the work take responsibility for following and maintaining the safeguards set out in the permit, which will define the work to be done (no other work being permitted) and the timescale in which it must be carried out. 

To be effective, the permit system requires the training needs of those involved to be identified and met and that monitoring procedures ensure that the system is operating as intended. 

Purposes & Objectives of a Permit To Work

The PTW system has been developed for the following purposes:

• To protect employees from exposure to risks that could result in injury, ill health, or death
• To protect the public from risks that could result in injury, ill health, or death
• To protect the environment from risks that could result in damage
• To ensure that work is carried out safely and in accordance with legal requirements.
• To ensure that risks are identified and assessed before work activities are undertaken
• To ensure that appropriate controls are put in place to minimize these risks
• To ensure that work is carried out safely and in accordance with legal requirements
• To ensure that employees, the public, and the environment are protected from potential hazards associated with work activities.

When Is A Permit To Work Required?

A permit to work is required when there is a potential for serious harm to workers or the environment. This includes work that involves:

• Hazardous materials
• High voltage equipment
• Working at heights
• Excavations
• Confined spaces
• Working with machinery

It is important to note that this is not an exhaustive list, and there may be other circumstances where a permit to work is required. If you are unsure whether or not a permit is required, you should always check with the relevant authority.

Permit-to-work procedures 

The permit-to-work procedure is a specialized type of safe system of work, under which certain categories of high-risk-potential work may only be done with the specific permission of an authorized manager. This permission (in the form of the permit to work) will be given only if the laid down precautions are in force and have been checked.

The permit document should specify the following key items of information:

• the date, time, and duration of the permit;
• a description and assessment of the task to be performed and its location;
• the plant/equipment involved, and how it is identified;
• the authorized persons to do the work;
• the steps which have already been taken to make the plant safe;
• potential hazards which remain, or which may arise as the work proceeds;
• the precautions to be taken against these hazards;
• the action to be taken prior to the task being started, such as the isolation of sources of energy and outlets; emergency procedures and equipment; ensuring the competency of those involved; communication arrangements; and reference to any other relevant documents.
• the equipment to be released to those who are to carry out the work.

In accepting the permit, the person in charge of doing the authorized work normally undertakes to take/maintain whatever precautions are outlined in the permit, such as:

• solation of the area;
• carrying out atmospheric monitoring;
• the provision and use of personal protective equipment;
• the provision of suitable equipment including lighting and tools;
• ensuring an adequate level of supervision; and
• arrangements for any extension to or handover of the permit.

The permit will also include spaces for: 

• signature certifying that the work is complete; and
• a signature confirming re-acceptance of the plant/ equipment.

Permit to work Principles

Permit systems must adhere to the following eight principles: 

1. Wherever possible, and especially with routine jobs, hazards should be eliminated so that the work can be done safely without requiring a permit. 
2. Although the Site Manager may delegate the responsibility for the operation of the permit system, the overall responsibility for ensuring safe operation rests with him/her. 
3. The permit must be recognized as the master instruction, which overrides all other instructions until it is canceled. 
4. The permit applies to everyone on-site, including contractors. 
5. Information given in a permit must be detailed and accurate. It must state: (a) which plant/equipment has been made safe and the steps by which this has been achieved; (b) what work may be done; (c) the time at which the permit comes into effect. 
6. The permit remains in force until the work has been completed and the permit is canceled by the person who issued it or by the person nominated by management to take over the responsibility (e.g. at the end of a shift or during an absence). 
7. No work other than that specified is authorized. If it is found that the planned work has to be changed, the existing permit should be canceled and a new one issued. 
8. Responsibility for the plant must be defined at all stages. 

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 workforce;
• Unconscious and conscious incompetence;
• Objectives of the work permit system;
• Types of work permit required; and
• Contents of the work permits.

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

• Failing of the site safety management system;
• Failure to recognize 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 minimize a potential human failing during the 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 fulfill the requirements of the work permit system;
• Whether the employees responsible for the control of the maintenance work are identified within the work permit system and that the work is properly authorized 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:

• The wrong type of work permit was used;
• Wrong information about work required on the work permit;
• Failure to recognize the hazards where work is carried out (e.g. flammable substances);
• Introduction of an ignition source in the 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 the plant in a safe condition on completion of work/canceling of a work permit;
• Unauthorized staff performing work permit functions;
• Poor management of the work permit system; and
• Insufficient monitoring of the work permit system.