Article Archive
EXPLOSION PROOF
Today's gas detectors limit risks to workers while giving operators enough flexibility for safety & efficiency
Volume 23, No. 3

In the wake of several highly publicized explosions and fires in the refining and fuel storage industries where vapor leaks were followed by ignition, management is asking how can safety measures be improved to prevent mobile equipment operating under hot work permits or within the fringes of the classified areas from creating another disaster?

Heavily regulated by governments throughout the world, refineries and similar energy industries have a responsibility to ensure that any explosion risk is kept to a minimum. Within the US, refineries have been required to comply with 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, adequate levels of regulations and worker protection have not been established. This means that workers at many refineries today still remain at risk.

To start a fire and/or explosion requires three constituents to come 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 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 the control of mobile equipment movement.

Before examining how to better manage the movement of mobile equipment under work permits or in "low" risk areas, we should agree in areas formally classified as an explosive hazard, the equipment used should be designed and certified to operate safely in those areas. Again referring to 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 used 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-ton 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 generator sets operating inside the refinery perimeter 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 a risk management processes. In most cases the person(s) responsible for issuing the work permit have the relevant experience and the authority to manage the risk involved with the task at hand.

How can you limit the chances of the hazard and the ignition source from coming together?

When diesel powered equipment is used, it is common to insist that an engine over-speed 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 electro-static 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 or van 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 handheld gas detector. But who or what procedure ensures that the gas detector has been specifically calibrated against the gases and vapors that could potentially 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 handheld gas detector relies on an operator to 'kill' the equipment before the equipment 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 that 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 ring fenced by dedicated gas detectors that will automatically shutdown 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 shutdown from being restarted before it is safe to do so?

Relying on engine over-speed valves, fixed gas detectors and handheld 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 over-speed valves and the limitations of relying on handheld gas detectors being held by infallible workers does not appear the way to improve facility safety going forward.

Today's pro-active gas detection technologies limit the risks to workers and at the same time allow the operator the flexibility they need to perform their job safely and efficiently by:

  • Ensuring that the equipment which is operated has its own integral gas detection system that will only allow the equipment to function when the immediate area surrounding the equipment is free of flammable gas or vapor.
  • Ensuring that before the operation begins the equipment performs a forced automatic gas test to ensure it is calibrated correctly.
  • Ensuring that equipment which is operated has its own integral gas detection system which 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 that if shutdown does occur that 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.

Even though the technology is available for those who need it, it is the safety culture and corporate mindset that needs adjustment. Appointing the appropriate budgets and implementing new safety programs are fundamental to accomplishing real change. With the right mindset, some investments, minor equipment modifications and fine tuning of the site process & permit schemes, significant progress in equipment safety can be made in relatively short time. This will not only reduce the risks of fire and explosions, but also protect people, their investments and our environment.

 
 

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