|The effort involved in fire detection is justified by the need to protect valuable power assets
Combustible materials, dust and debris, and voluminous areas make fire detection for power stations challenging.
Solutions must be sensitive to danger and raise alerts early, but must not be prone to costly false alarms. This all amounts to another serious problem the power station safety officer or facility manager has to face.
In July of this year, the UK’s Ferrybridge power plant was affected by a fire widely reported in the media.When the nationally-broadcast images had begun to fade from memory, the cost to Ferrybridge’s owner, SSE, began to be calculated.
RBC Capital analysts estimated a loss in earnings of around à‚£35 million ($56 million). SSE will also have to factor in the cost of repairing the facilities (although insurance will cover much of the losses) and the transactional costs of buying back forward-contracted power that will now need to be sourced from elsewhere.
Just weeks ago Didcot B Power Station, also in the UK, suffered a major fire in its cooling towers. More than 25 fire appliances from as far as 30 miles away were called to the 1360 MW gas-fired plant, which is operated by RWE npower.
While the full costs of the damage are still being calculated, the impact on the UK’s power needs has generated much debate.
Peter Atherton, energy analyst at Liberum Capital, stated that the risk of blackouts this winter was now far higher due to the UK’s “meagre capacity” to absorb unexpected events.
As developed countries find power disruption an unacceptable situation, the extra capacity in the system should see the UK with the energy supply it needs over winter, providing that other major fires and incidents to power generation are avoided. But for a single power plant to make the possibility of power shortages a reality shows the importance of protecting these critical assets.
The sheer size of power plants makes fire detection a challenge: the huge ground area occupied, the ceilings often as high as 20 metres and the voluminous areas that must be monitored.
This presents difficulties in terms of the time it takes for smoke to reach detectors – and it may not reach them at all owing to smoke stratification. We can also factor in the need to provide a system that can cover large areas effectively – no easy task.
Turbines also present a very industry-specific issue: fire is initially hard to detect as the shell can obscure and contain flames for some time, impeding early detection.
Power generation environments are known for their high levels of dirt, grease, dust and oil. This, of course, means that any fire detection system needs regular maintenance.
Moreover, the combustible nature of oil, gas, coal and renewable waste makes plants vulnerable, and with the debris that can be kicked up there is the inherent danger of numerous false alarms. A balance needs to be struck between the required sensitivity and false alarms, which some fire services are now demanding visual verification for commercial properties before attending, while some levy fines for being called out for false alarms.
If suppressants are released, then for voluminous areas the cost can be substantial, certainly well in excess of à‚£100,000 for many sites. The attendant environmental impact such as wash-off running into water supplies also needs to be considered.
|VSD operator’s dashboard: Users can segment the video to concentrate on specific areas of greater fire risk
Fire detection technology
Visual Smoke Detection (VSD), Infra-red (IR) and Aspirating Smoke Detectors (ASD) are the principal options for power station operators.Each has advantages and drawbacks.
VSD uses motion system technology to identify and analyse the behaviour of smoke patterns and flames Visual monitoring at the point of fire danger is particularly suited to large areas and across distances.
Footage can offer visual verification (usually done on-site) and large area monitoring, and can direct the use of fire suppressants and emergency services.
Temperature sensing capabilities can be incorporated within the system, the latter being a new innovation in the market.
Infrared converts radiant energy in the IR into a measurable form. Detecting IR energy emitted by objects takes away reliance on visible light, so obscured conditions should not affect its effectiveness although thick smoke is an issue. Oil and grease can also be problematic.
IR gives much of the VSD solution, however the latter offers accompanying video, which provides better situational awareness in the event of a fire. It also helps determine the most appropriate action that should be taken, triggering an overall suppression system.
ASD is a highly sensitive technology. It can detect smoke before it is visible to the human eye, which is particularly valuable where a fire develops in obscured or difficult-to-access locations or environments containing dangerous and toxic substances. Yet the sensitivity to distinguish between smoke and dust in early-stage fires can be problematic in some facilities, although improvements are being introduced. Moreover, it requires that smoke hits detectors, which can be challenging if smoke stratification is a possibility.
Ferrybridge and now Didcot remind us of the costs of fire in power generation environments. Safety professionals must analyse their requirements against the solutions available, be it VSD, ASD, IR or another system. Fire detection for power stations requires planning, frequent maintenance and continual assessment, but the effort is justified by the need to protect these high-value assets.
Ali Aleali is Business Development Manager at FireVu, which works with power plants across the UK and Ireland. Please visit www.firevu.co.uk
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