Proactive Protection in Classified Areas

How can safety measures be improved to prevent mobile equipment operating unsafely under hot work permits or within the fringes of the classified areas?

• By Robert Zuiderveld
• Jul 22, 2008

Several highly publicized explosions and fires in the refining and fuel storage industries have resulted from vapor leaks followed by ignition. Heavily regulated by governments throughout the world, refineries and similar energy industries have a responsibility to ensure any explosion risk is kept to a minimum.

Within the United States, refineries have been required to comply with the codes and regulations for the use of powered industrial equipment in explosion hazardous areas.However, due to code interpretation and explosion hazardous areas rating variances, equivalent levels of regulation and worker protection have not been established. This means many refineries workers remain at risk today. To start a fire and/or explosion takes three constituents coming together: an oxidizer, a hazard (gas/vapor), and an ignition source.While it is not possible to eliminate the oxidizer (air), it is possible to plan processes and protect equipment to limit, wherever possible, the chances of the hazard’s getting in contact with an ignition source. However, it is a matter of fact that when it comes to the control of mobile equipment,many responsible for site operations lack the experience, site discipline, or budget to enforce safe and acceptable practices in terms of control of the equipment’s movement.

Before examining how to better manage the movement of mobile equipment under work permits or in “low” risk areas, we should agree that when in areas that are formally classified, the equipment used should be designed and certified to operate safely in those areas.Again referring to the codes and regulations, if an area is classified as Class 1, Division 1, or Zone 1 certified, then only equipment certified to EX Class 1, Division 1, or Zone 1 codes and regulations should be used in those areas. For Division 2 or Zone 2 hazardous areas, equipment should at least be tested and certified according to the codes and regulations applicable to equipment in those areas.

Insisting that only Division 1, Zone 1, Division 2, or Zone 2 certified equipment can be allowed to operate in the refinery is often neither practicable nor desirable. Imagine insisting that a 100-tonne mobile crane required for a maintenance job must be converted to fully explosion proof before being permitted to operate on site. I doubt any rental company can afford to keep an explosion- proof crane on standby for the occasional job in an explosion hazardous area.The same thing applies to personnel carriers, vans, tractors, tankers, mobile compressors, and gen-sets operating inside the refinery perimeter and not being permitted into formally classified areas without first being made fully explosion proof. In these situations, most refineries rely on the use of hot work permits and risk management processes. In most cases, the person(s) responsible for issuing the work permit have the relevant experience and the necessary authority to manage the risk involved with the task at hand.

Limiting the Risk through Gas Detection
How do we limit the chances of hazard and ignition source coming together? When diesel powered equipment is used, it is common to insist that an engine overspeed air shutdown valve and an exhaust spark arrestor are installed.Provided these components are correctly fitted and correctly serviced, they should alleviate some of the many ignition sources to be found on a forklift truck, crane, tanker, compressor, or gen-set. But what about the other ignition sources, such as electrostatic releases, flame flashback through the inlet system or flame emission (not sparks) from the engine exhaust, and sparks from any electrical equipment, such as alternators, lighting, instrumentation, or engine management systems? What about the potential of hot surfaces’ causing auto-ignition? Who will ensure that the over-speed valve has been correctly calibrated before the operation begins? And if so, how will the operator of the crane, truck, van, etc. know whether the area immediately surrounding his equipment has reached an explosive gas or vapor level? Besides working under a hot work permit, it is common practice for the operator to carry a hand-held gas detector. But who or what procedure ensures the gas detector has been specifically calibrated against the gases and vapors that could be released into the operating area? Does the gas detector always remain with the equipment and its operator throughout the permit process, or does the operator stray away from the equipment? A hand-held gas detector relies on an operator to “kill” the equipment before it ignites the explosive atmosphere that has developed unexpectedly. Unfortunately, it is an undeniable fact that most accidents are caused by human failure or response time.

One could rely on gas detection systems monitoring the site, but it would be necessary to ensure sufficient gas detector points cover all areas where mobile equipment is operating— because, if not, the hazard and ignition source may combine before appropriate action can be taken.

A better approach may be to have the equipment and its ignition sources ringfenced by dedicated gas detectors that will automatically shut down the gen-set or compressor when flammable gases or vapors are detected. However, if the equipment is mobile, such as cranes or vans, the process becomes rather impracticable. Besides that,how do you prevent equipment that has automatically shut down from being restarted before it is safe to do so?

Relying on engine over-speed valves,fixed gas detectors, and hand-held gas detectors may have been the traditional reactive protection methods of yesterday. However, with today’s powered industrial equipment relying on sophisticated electronics, the use of overspeed valves and the limitations of relying on hand-held gas detectors being held by fallible workers does not appear the way to improve facility safety going forward.

Today’s proactive gas detection technologies limit the risks to workers and at the same time allow the operator the flexibility he needs to perform his job safely and efficiently by:

• Ensuring the equipment that is operated has its own integral gas detection system that will allow the equipment to function only when the immediate area surrounding the equipment is free of flammable gas or vapor.

• Ensuring before the operation begins, the equipment performs a forced automatic gas test to ensure it is calibrated correctly.

• Ensuring equipment that is operated has its own integral gas detection system that shuts down the equipment automatically and immediately when an unexpected increase in flammable gas or vapors is detected in the immediate area surrounding the equipment.

• Ensuring if shutdown does occur, any restart is controlled by a person in charge of facility safety.

• Installing protection systems that are simple to fit, simple to use, simple to maintain and, most importantly, designed to isolate most of the ignition sources from explosive atmospheres.

This article originally appeared in the July 2008 issue of Occupational Health & Safety.