Eliminate or mitigate is the mantra for health and safety professionals. If you can’t eliminate a hazard then mitigate its effects. It’s no different for those involved with fire as risk assessments underpin projects from start to finish. Some high risk industries will always struggle to eliminate, so how we mitigate is the challenge. The following case study may help others in their approach to new and challenging situations.

Performance standards are increasingly used instead of prescriptive design codes where high risk plant is involved. In any case, prescriptive standards don’t always keep pace with new technologies and at best lag well behind due to the testing regimes involved. Prescriptive standards have also been criticised for their one size fits all approach and, as was concluded in Lord Cullen’s report into the Piper Alpha incident, can be instrumental in the escalation of a particular incident.

The introduction of the Regulatory Reform (Fire Safety) Order (RRO) has formalised the approach but specialist advice is required for special risks. The end result will be arbitrated by the competent authorities such as the fire authority and insurers, but ultimately responsibility rests with the site operator in discharging their duty of care.

The introduction into the UK of Biofuel plants is a case in point and it follows that the risk assessment requires a hazard specific approach. The key point is that a fire hazard assessment should be qualitative and determines what recommendations are appropriate to reduce the risk to persons and the environment to as low as reasonably practicable, not to mention ensuring that the assets are protected to provide business continuity.

Even if one plant is deemed to be a sister plant to another the risk assessment process has to be individually tailored to the site conditions. For example, a Biofuels operation in one part of the country is going to have its own geographical conditions that will affect issues like firewater containment, immediacy of municipal fire cover and proximity to residential areas.

Let us take a specific scenario as a case study (not unique to ethanol process plant of course):

• Distillation area: the area will hold an inventory of ethanol. Processed at a maximum temperature of 120 0C and at a maximum pressure of 1.8 bar in the rectifier column. The flashpoint of ethanol is approx. 17 0C therefore any release in summer will be well above its flashpoint with danger of ignition.
• Flammable substances tank farm: let’s assume that the tanks will be fixed roof, vented to atmosphere via flame arrester and will neither be provided with frangible roofs nor explosion relief manholes. The expectation is of a vapour space explosion with subsequent rupture of tank and spill into bund. If multiple tanks are ruptured the bund would not normally be able to contain the entire product and would overspill outside the bund. Should ignition occur then not only would a tank bund fire threaten the other tanks by radiated heat and flame impingement but the ethanol that has been released from the tank bund could threaten other parts of the plant.
• Tanker loading area: numerous tankers a day would service a site of this nature. Despite the mitigating measures from ethanol cooling prior to storage, solar heating could take ethanol to within its 17 0C flashpoint in this area. The subsequent explosion or fire could extend to the tanker loading area via the local sump.
• The domino effect: an accident in one part of the plant can either escalate or effect other parts of the plant by one of the following methods (this list is not exhaustive) (i) A fire in part of the distillation area affecting parts of the area by radiated heat and/or flame impingement. (ii) An explosion in the distillation area affecting the distillation structure or other parts of the plant by debris, missiles and/or blast. (iii) A fire in the tank farm bund affecting other tanks by radiated heat and/or flame impingement. (iv) A fire in the closed tanker sump affecting a tanker or the tanker loading area by radiated heat and/or flame impingement.

Integrated risk management

This is a term used by the British fire service to describe its approach to modern day risks. The emphasis is correctly on the saving of lives mainly lost in residential fires and leads to a strategy to achieve these objectives. The outcome may well be that now and in the future, fire cover to industrial areas is reduced in favour of residential areas. It follows that industrial hazards need to be addressed without the comfort blanket of a local fire station resourced to deal with exceptional process plant incidents - if indeed they ever have been resourced to everyone’s satisfaction. New and existing plants need to address some key issues affecting their fire cover:

• Manning levels will be reduced to the most efficient level to run the plant, not to provide fire cover
• There is an understandable reluctance to expose even trained personnel to any hazard, fire or otherwise
• Insurance may seem like the best way of transferring risk from the business, however, it can be difficult to obtain cost effective cover in certain market conditions, sometimes impossible if the risk is too great or if the insurance market is “hard.” Besides, insurance cover is not normally able to replace the loss of customers to competitors during re building
• Municipal fire cover may well be retained (part-time) and may not have the resources to deal with large scale process hazards

The fixed fire protection options

The purpose of the fire hazard assessment and recommendations is to draw up a road map to both detection of the fire and the best way of dealing with the outcome.
Having identified the threats we now need to assess the methods of mitigating them. It’s a given that detection will be installed to comply with BS 5839 but in the case of a high risk industry, should be linked to a constantly manned monitoring station.

Given the external location of tanker off-loading and tank farm it is more appropriate to install combined UV/IR flame detectors configured to reduce false alarms by filtering out solar frequencies and reflections.

In buildings housing safety critical control panels serious consideration should be given to total flooding or local application gas systems, likewise transformer and cable void areas.

Fixed protection on plant and equipment that carry a risk of explosion are always at risk of damage from such explosions. Reliance should never be wholly placed on fixed equipment in such locations. Even if fixed protection is supposedly fully explosion protected, and even duplicated, it is not good practice to place 100 per cent reliance on such systems.

A suitable means of manual intervention should always be available. However, a much higher reliance can be placed on fixed protection that is not actually “on” equipment being protected but is suitably positioned and controlled to be able to provide the intervention needed.

Fixed foam/water monitors should be suitably positioned and remotely controlled from the control room via CCTV and via wireless joystick units at ground level. This will be the most appropriate form of fire protection for fires within sumps, bunds and structures. These monitors can deliver AFFF-AR to deal with both flammable liquid spills and provide coverage of vulnerable plant and equipment.

Additionally, they can be used to deliver water spray to protect from radiated heat or flame impingement and/or to dilute Ethanol and Methanol below their flammable limits. Nozzles can be fully adjustable between jet and spray and have a swivel capability of at least 210 degrees. Flow should not normally be less than 1800 lpm at a minimum pressure of 7 bar, however, their specification should ensure that their throw is adequate to reach all targets from where they are positioned. If the positioning of the monitors to the hazard is less than 30 m then a good spray pattern is ideal for cooling.
Looking at our case study it will follow that monitors would be located in the following ways:

• Between the tanker loading point and main internal road
• Between the tanker loading point and the tank farm
• Between the tank farm and distillation area
• Between the tank farm and clay bund
• Between the tank distillation area and the new tanks.

As each monitor will be able to deliver either foam or water and can be individually operated and controlled it will give great flexibility of use for firefighting, foam blanket laying, cooling and protecting vulnerable plant. Such control and flexibility is important so as to ensure, as far as reasonably practicable, that the bunds and sumps are not overtopped.

In conclusion the plant should be provided with a fire ring main and hydrant outlets at suitable positions. It should be underground or explosion protected. (Pillar hydrants are often preferred for process sites.)

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