Permit To Work (PTW) systems are used in hazardous industries to request, review, authorise, document and most importantly deconflict tasks to be carried out by frontline workers.
PTW is a core element of ISSOW systems that along with Risk Assessment and Isolation Planning, enable As Low As Reasonably Practicable (ALARP) reduction of unsafe activities in non-trivial work environments. PTW adherence is essential to achieve Process Safety Management.
PTW implementations usually utilise incompatible operations matrices i.e. preclude one workgroup welding/grinding in the vicinity of another venting explosive/flammable gases. The PTW system is for work being performed in accordance with preapproved procedures and that has been macro scheduled, the purpose is to deconflict short term activities of different frontline workgroups to prevent mutually hazardous interference.
Once a PTW has been issued to a workgroup, a tag-out or lock-out system is used to restrict equipment state changes such as valve operations until maintenance is complete. Since the PTW is the primary deconflictation tool all work activities in high risk environments should have a PTW, specific hazardous operations will then have a second permit for activities such as Confined Space or Hot Work. Here the Hot Work permit is minimising the risk of the individual task, the PTW is minimising the risk of simultaneous activities.
PTW system permit authorisation and its trace-ability are crucial if it is to be beneficial. Ideally one person should be delegated with this responsibility at any one time and all workers at that facility should be fully aware of who that person is and when the responsibility is transferred.
== Generic PTW form contents〔http://www.eig.org.uk/eig2002/documents/permit.htm〕 ==
* Specifies the work to be done, the equipment to be used and personnel involved
* Specifies the precautions to be taken when performing the task
* Specifies other workgroups to be informed of work being performed in their area
* Authorisation for work to commence
* Duration permit is valid
* Method to extend permit for additional period
* Witness mechanism that all work has been complete and the worksite restored to a clean, safe condition
* Actions to be taken in an emergency
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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