Detect the bright sparks

Published:  02 April, 2009

Cranes, access platforms, forklift trucks and numerous other types of mobile equipment are used every day in refinery and petrochemical operations.
Malcolm Davis from safety company Pyroban explains that explosion prevention is possible and financially viable – even for short term use.

Mobile plant equipment have one thing in common. Unless suitably protected, they may be riddled with sources of ignition that could cause an explosion in a potentially explosive atmosphere. However, when businesses claim that it is not possible to make mobile equipment such as cranes and vans suitable for operation in such environments, they are placing their staff, and the business at significant risk.

In the last few years we have seen several explosions and fires in the refining and fuel storage industries – most as a result of vapour leaks followed by ignition. How can safety measures be improved for mobile equipment operating under hot work permits, in zoned areas or within the fringes of the classified areas?

Heavily regulated by governments throughout the world, industries have a duty to ensure that any explosion risk is kept to a minimum. Within Europe companies would be required to comply with the ATEX 1999/92/EC directive. However the equivalent level of regulation and worker protection is not in place everywhere and in many operations workers remain at risk from mobile sources of ignition as can be found on cranes, vans, forklift trucks, pumps and generators.

Businesses can plan the processes and prepare most equipment to limit wherever possible the chances of a hazard being in contact with a source of ignition. 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 practice.

Referring to European law, if an area is classified as Zone 1 then only equipment certified to Category 2G under the ATEX 94/9/EC equipment directive should be used. For Zone 2 areas, equipment certified to both 2G and 3G would be suitable. Pyroban can convert almost any type of equipment for such operations. However the majority of conversions are on forklift trucks, with an increasing trend from Zone 1 to Zone 2 operation, as business reduces its cost by improving its safety practices.

Insisting on ATEX-only equipment being allowed into a refinery or similar sites is often neither practicable nor desirable. Imagine insisting that a 100-tonne mobile crane required for a maintenance operation being made fully explosion proof before being permitted on site. I doubt any hire company can afford to keep an explosion proof crane on standby for the occasional job. Or the personnel carriers, vans, tractors, tankers, mobile compressors and gen-sets operating inside a refinery perimeter not permitted into formally classified areas without first being made fully explosion proof.

In such applications the operation often relies on the use of hot work permits and risk management processes. The person(s) responsible for issuing the work permit should have the relevant experience and the necessary authority to manage the risk involved. But how do they limit the chances of the hazard and the ignition source coming together?
When equipment powered by diesel engine is being used it is common to insist that an engine over-speed air shutdown valve and exhaust spark arrestor is fitted. Provided these components are correctly fitted and correctly serviced (in the case of the over-speed valve typically every three months) they should alleviate a couple 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, 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 for hot surfaces causing auto-ignition? Who is checking that the over-speed valve has been correctly calibrated before the operation begins? And in such cases the operator of the crane, truck, van etc has no knowledge of whether the area immediately surrounding his equipment has come into contact with gases or vapor at explosive levels. There is massive scope for human error.
Another common practice under the permit to work approach is for the operator to carry a handheld gas detector. But has the gas detector been specifically calibrated against the gases and vapours that could be released into the operating area? Does the gas detector always remain with the equipment and its operator throughout the permit process? The handheld gas detector relies on the operator to “kill” the equipment before the equipment’s ignition source ignites the explosive atmosphere, but it is an undeniable fact that most accidents are caused by human failure.

We could rely on gas detection systems monitoring the site but we would need to ensure sufficient gas detector points cover all areas where mobile plant 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 genset or compressor but if this is mobile plant such as a crane or vans the process is impracticable. And how do you prevent equipment that has automatically shut down only being restarted when it is safe to do so?

Relying on engine over-speed valves and handheld gas detectors may have been the traditional protection of yesterday. With today’s diesel engines relying on electronics, the use of over-speed valves and the limitations of relying on handheld gas detectors being held by infallible workers is not the way forward.
It is possible to limit the risk to workers and at the same time allow the operator the flexibility needed to do the job.

The installation of Pyroban’s Gascheka system on mobile equipment can ensure that equipment to be operated has its own integral gas detection system which will only allow it to function when the immediate area is free of flammable gas or vapor. Gascheka ensures that before the operation begins, the equipment has an enforced automatic gas test to ensure it is calibrated correctly. Pyroban’s gas detection system automatically shuts down the equipment it is protecting well below explosive limits and if shutdown does occur any restart is controlled by a person in authority.

Gascheka is simple to fit, simple to use, simple to maintain and most importantly designed to isolate the many ignition sources from an explosive atmosphere. Gascheka has been installed onto all types of equipment and is in use at refineries, petrochemical and chemical sites and in aviation, pharmaceutical, logistics and food and drink operations.

The technology for safety is available for those who need it especially for aging fleets of equipment operating in many of the refineries around the world. But it is the safety culture that needs most attention and the necessary budgets for implementing safety are fundamental to change. With the right mindset small changes to sites processes/permit schemes can significantly reduce the risk of an explosion and improve the safety of workers.

  • Operation Florian

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