What Is a Hot Work Permit?

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Gary Melrose
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Project Manager with experience of delivering complex, multi specialist projects, leading multi discipline project teams to deliver whole lifecycle optimized solutions.

Specific experience in leading various hazard and operability studies to ensure both safety lifecycle (PM 84 and BS EN 61511) and RAM lifecycle (BS 6079 and BS 5760) deliverables are whole lifecycle optimized for current and predicted operational lifecycles.   Full Bio
Q:What are "hot work" and "cold work" permits? Where are they used, and how do they serve safety?

Hot work and cold work permits are both examples of preventing a fire by preventing one of the fire triangle requirements, here the ignition source, from being introduced by a work activity. 'Hot Work' is pretty universal involving control of ignition sources in an actually or potentially hazardous, flammable, or explosive atmosphere; 'cold work' less so, but two sides of the same coin.

As far as how they serve safety, or reduce risk, it's worthwhile taking a look at risk assessments for hazardous areas, which tend to be two phase:

  1. Static assessments, dealing with the normal process safety aspects and hierarchy of controls (eliminate/reduce or replace/manage or control/mitigate/recover). Primarily aimed at the 'equipment' and plant/process side of the O&M equation.
  2. Dynamic risk assessments, task specific and performed by appropriately competent personnel immediately prior to, throughout the duration of and following any specific planned task or intervention.

The first will require identification of any area which could carry a risk of a flammable, explosive, or otherwise harmful atmosphere. Depending on the size of expected release under normal working conditions, i.e.NOT fault or failure conditions, and the amount of time it is likely to exist, these are normally segregated into different zones of increasing residual or remaining risk.

Given that prevention and reduction have resulted in this residual risk, we have to rely on secondary protection measures to reduce risk to an acceptable level - we manage ignition sources, which includes the fuel, combustible material, the required air to sustain combustion, so all we can do is remove the third side of the triangle: the ignition source. We do this by installing appropriately designed equipment.

However, we also need to operate and maintain all of this equipment and often whilst both the fuel and air exist as a potentially flammable/explosive mix (full isolation, vent and purge not practicable), so we need to limit ignition sources, which may otherwise be introduced by the working party and/or by the task.

The permit system allows us to do this by specifying everything from the competency of the working party right down to the methodology and tools employed.

The permit also ensures we can delimit the work being done from operations and work in adjacent areas, so that one does not impact on the other. It also allows us to perform contingency planning to put in place suitable and sufficient mitigation measures to deal with any reasonably foreseeable incidents or events arising from the planned work (anything from provision of suitable PPE and fire extinguishers, identification of safe havens, detailed evacuation, rescue and recovery plans and on) depending on the risk.

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