fire detection for power stations

Effective fire detection for power stations requires solutions that can overcome the challenges of wide open spaces as well as high ceilings, as illustrated by this turbine hall. Moreover, the challenge of smoke stratification is a key issue that any solution must address to be comprehensive.

Didcot B brought into sharp focus the consequences of power station fires.

While it was the most high profile power generation plant blaze in the UK of 2014, it was not the only one. Ferrybridge, while not having the same media impact, illustrated the financial aspects of a major power station fires: loss of production, damage to assets and cost of buying alternative supplies.

If we include mechanical breakdowns in addition to fire that have affected the UK so far in 2014, it includes at least six large power plants, representing nearly 12% of the country’s electricity generating capacity. While not yet critical, it still reduces the spare capacity to absorb more incidents, something that has raised high level concerns.

What can be done to lessen the risk of fire through more effective fire detection solutions?

FireVu, a specialist in the power generation sector, tells us more about the issues and the solutions in January’s issue of Modern Power Systems.

Didcot B raised many key issues, not least what happens when 1.3GWt of electricity is at risk at being removed from the national grid.
Ofgem warned recently that electricity-generating margins could drop below 2 per cent in the winter of 2015/16. This winter sees a higher risk of blackouts due to the UK’s “meagre capacity” to absorb unexpected events, according to Peter Atherton, energy analyst at Liberum Capital.
One can only imagine the effect of another major power station fire.
Moving to the subject on a business level, power station fires are costly and their impact is immediate for power generation companies.
While we don’t yet have any estimates of the cost of the recent incident at Didcot, we have more information about the Ferrybridge fire in July 2014.
RBC Capital analysts estimated a loss in earnings of around £35 million. We can also factor in the transactional costs of buying back forward contracted power that will now need to be sourced from elsewhere and the cost for repairing the facilities, which should be covered to a large extent by insurance cover.

Fire detection power plants – the challenges
Combustible materials, dust and debris, and the voluminous areas of plants make fire detection for power stations challenging. Fire detection solutions have to be sensitive to danger, raise alerts early, but not be prone to costly false alarms.

I don’t think I need stress further that power generation facilities are high risk environments that demand rigorous levels of fire safety. So I will move onto the particular challenges power plants present for fire detection.

Let’s start with the size of the plants: the huge ground area occupied, the high ceilings that are often reach 20m and the subsequently the voluminous areas that must be monitored. This presents difficulties in terms of the time it takes for smoke to reach detectors, or perhaps not at all owing to smoke stratification. We can also factor the need to provide a system that can cover large areas effectively – no easy task.

Turbines also present a very industry specific issue as fires can initially be 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, which 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 having the required sensitivity needed and false alarms.

Many fires services are now demanding visual verification for commercial properties before sending crews or levying fines for false alarms.

If suppressants are released (for false alarms), the cost for big voluminous areas can be substantial, certainly well in excess of £100,000 for many sites. The attendant environmental impact such as the wash off of foam and liquid based suppressants running into water supplies also needs to be considered.

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 their advantages and drawbacks. Let’s begin an overview with the VSD solution:

Power stations have a particular interest for me as our Visual Smoke Detection (VSD) technology was originally developed to satisfy the need to protect power station turbine halls in the 90s.

The voluminous spaces of the halls and the issue of smoke stratification (as mentioned above) were key challenges.

VSD uses motion system technology to identify and analyses the behaviour of smoke patterns and also flame behaviour. Visual monitoring at the very point of fire danger is particularly suited to large areas and across distances.

Footage can offer visual verification (usually done on site), 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 and 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, such as triggering an overall suppression system.

ASD is a highly sensitive technology.

It can detect smoke early, which is particularly valuable where a fire develops in obscured or difficult to access locations, such as a turbine, or perhaps in environments that have dangerous and toxic substances. Yet, the sensitivity to distinguish between smoke and dust in early stage fires can be problematic. Moreover, it requires that smoke hits detectors, which can be challenging and risky if smoke stratification is a possibility.

Conclusion
Ferrybridge and now Didcot B remind us of the costs of fire in power generation environments. Safety professionals have to 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 justifies the need to protect these high value assets. Effectiveness, not solution costs, is the driver for investment in fire detection and greater protection of the industry’s high value assets.

Many thanks to Modern Power Systems, which first published in January 2015, for its help and permission to reproduce the article; please note that there are differences between this version and MPS’, with changes in use of image, title, caption and design.