Unprotected diesel engines fuel explosion risk offshore
  by: OilOnline
  Wednesday, May 07, 2008

Most oil and gas companies operate safely offshore, or at least that is the intention.  By managing the risk of explosion correctly, it is likely that the oil company will maintain the flow of oil without incident.  However, lack of specific safety education concerning diesel engines and ‘over-riding procedures' in some oil regions is common and a cause for concern as sources of ignition find their way close to the wellhead.

"A diesel engine should not be used in a hazardous area on an oil and gas installation unless it is suitably protected" explains Rob Double who is responsible for upstream operations for explosion protection specialist Pyroban.  "A standard diesel engine is riddled with ignition sources that could cause an explosion if they come into contact with a flammable hydrocarbon, for example, the surface and exhaust gas temperatures, sparks from the exhaust or electrical equipment, flashback through the air inlet, static discharge or engine overspeed."  Yet why are so many engines being operated offshore with inadequate protection?

Diesel engines are used to power all types of oilfield service equipment such as CTUs, pumps, compressors or cementing units which are typically specified 6-12 months prior to its required operational date. Most units will be built to order, requiring parts and components sourced from all over the world and it is at this point that the safety specification is usually addressed.

The operating company that owns or runs the installation will typically specify which ‘Zone' the equipment will be used in.  The Zone reflects the hazard, which in simple terms is the distance from the wellhead where there could be a release of flammable hydrocarbons. 

As a basic rule Zone 0 is 0m to 1.5m, Zone 1 is 1.5m to 7.5m, Zone 2, 7.5m-15m and Rig-safe/not zoned 15m and beyond, however this is open to interpretation, and every operation is different. Diesel powered oilfield service equipment will typically be required for operation in Zone 2 or Rig-safe areas.

Rob Double who is based at Pyroban's headquarters in the UK explains "Education about Rig-safe and Zone 2 is where the problems lie.  When the contract is agreed, the company that builds the package may be sold a safety system which they think is Zone 2, or they simply believe that Rig-safe is Zone 2.  They may also not have the budget."

Engines built for operation in Zone 2 require significant modification and additional components including a water cooled exhaust system, temperature sensors, air inlet shutdown valves, flame arrestors and spark arrestors on the exhaust system.  Every possible source of mechanical or electrical ignition found on today's mechanical and electronically controlled engines are eliminated by Pyroban. The complete unit will be certified for use in Zone 2 to strict local standards or the internationally recognised European Directive ATEX*.

Because the risk is lower in Rig-safe areas, typically only 8 modifications are made to the engine such as a valve on the air intake, anti-static fan belt and an air starter package leaving many other sources of ignition exposed.  Rig-safe is a basic level of protection and therefore not a solution for Zone 2 operation.

"Operating a Rig-safe unit in a Zone 2 area is potentially disastrous, placing personnel and the installation at undue risk" continues Double.

The problems also occur at the point of delivery. If a Zone 2 unit was originally specified and 6 months later a Rig-safe unit arrives at the dock waiting for despatch, a chain of events occurs depending on the education and awareness of the personnel, controls that are in place and the urgency of the unit. In some oil regions such as the UK, the unit will not leave the port.  Elsewhere however, personnel may think that Rig-safe is Zone 2 and let the equipment operate. Alternatively, if procedures are in place and the unit arrives as rig-safe, it may be urgently needed, so a dispensation will be issued.  These scenarios all result in unprotected units operating for long periods in zone 2 areas.

Pyroban supplies Zone 2 explosion protection solutions globally, working with engine manufacturers such as DDC, Caterpillar, Volvo, Iveco and Cummins and packagers to ensure that equipment required for operation offshore is specified correctly around the world. For more information visit http://www.pyroban.com/ or Tel +44 (0) 1273 466200, info@pyroban.com

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