What happens when the threat of fire is not properly recognised?
Consider this situation. A modern power generation plant in the Middle East has multiple subterranean cable tunnels connecting the various generating units, substations and switchrooms across the plant.
Inert gas fire suppression has been installed in all the electrical equipment rooms and within the gas turbine compartments. There are water deluge systems in the cable spreader rooms below the substations. Everything above the ground looks “best in class”.
The Risk Engineer is delighted with what she is seeing, until she descends down a ladder into one of the subterranean cable tunnels.
No fire suppression. Not even any fire detection. How could this be so when the rest of the plant is so well protected?
Modern society relies on cables for continuous power supply and data transfer, and many of these cables run in subterranean tunnels. These cable tunnels have a high fire load. Burning cables emit large quantities of black smoke and toxic gases. Cable tunnels are generally narrow, low and dark. Access is typically through small diameter manholes and then down a vertical ladder. An unwelcoming space if there ever was one.
Now imagine that a fire starts within a cable bundle. No firefighter in their right mind will don breathing apparatus and descend down a vertical ladder into a hot pall of smoke just to save some cables; lives perhaps, but not property. So without a fire suppression system in place, the fire will spread rapidly, unimpeded in its progress, bringing with it business disruption to all those who depend on these hidden lifelines.
Cable tunnel fires are relatively rare, but when they do happen they often escalate to the maximum possible damage level.
To grasp just how serious a cable tunnel fire can be, consider the fire which occurred in Holborn, London, in April 2015. The fire started in a cable but then escalated significantly when a gas main in the same tunnel ruptured due to the heat of the fire. The fire took 36 hours to put out. Five thousand people had to be evacuated at the beginning of the incident and the whole area lost power and gas supply. Once the fire was put out there was still major disruption in the area as the services were being restored. There was also major evacuation works to repair the tunnel, which caused traffic chaos in the area.
This has been a technically difficult incident to tackle. The reason that the fire is still burning is because the cable tunnel is hard to reach and although firefighters have been applying water through access points throughout the night, the complexity of the tunnel layout means that it will be some time until the fire is fully extinguishedLondon Fire Brigade assistant commissioner Peter Cowup
As recently as March of this year, a fire inside a 1 km long cable tunnel in Johannesburg cut the power to a significant part of the central business district for more than three days, disrupting the powerhouse of the South African economy.
The common barrier missing in both cases, and in most cable tunnel fires, is that there was simply no fixed fire suppression system installed, whilst at the same time it was next to impossible for firefighters to safely access the fire location. With increasing levels of electrification and our growing dependence on internet infrastructure, each of these invisible subterranean tunnels become more and more important to our lives.
Let’s return to our Middle Eastern power generation plant. A number of different excuses were offered up by the plant management for the fact that the cable tunnels were wholly unprotected. These ranged from a misunderstanding between EPC contractors during plant construction, to the NFPA codes not requiring it, to the lack of fire potential in such tunnels. The exact reason or reasons didn’t matter so much; what really mattered was that this revealed a failure of imagination on behalf of the plant management when it came to those fire hazards with major business interruption potential.
With organizational failures, the imagination is often at fault. We can’t imagine things going wrong, so we don’t plan for them. In this case it was assumed that if there was a cable tunnel fire that the site Fire Brigade would handle it. Even the most cursory of examinations of the situation would have rendered this line of thinking null and void. The Fire Chief would be highly reluctant to commit crew and equipment into tunnels via vertical ladders as they offer no lobby protection or fire separation from any incident, plus there would be limited telemetry and radio communications down there.
No cable tunnel, no power generation. And for a long time.
Installing a fire suppression system that avoids the need for humans to descend into the tunnel is the only realistic barrer to a multi-month business interruption claim, on top of a fairly large property claim. There are several fire fighting technologies available for the protection of cable tunnels, with conventional deluge systems and high pressure water mist often coming out with the optimal mix of extinguishing capability and installation cost.
In this case, the Risk Engineer recommended a water mist system (as water supply was limited in this desert location) plus a fiber-optic linear fire detection system. This critical weakness was news to the executive management of the company (and their insurers!) and the recommendation was soon approved, budgeted and implemented.
There are many other examples which we have seen this year where it was obvious that there was a failure of imagination in respect of firefighting. Here are just a few;
- In a combined cycle gas turbine power station in Sri Lanka, the four-storey control building had a 6.6kV switch room on the third floor. This was the only medium voltage switchroom serving the plant, and was therefore a critical node. It did not have automatic inert gas suppression, unlike the high voltage switchrooms at the plant, instead being protected only by hand-held 5kg CO2 extinguishers. As this switch room is on the 3rd floor of the building there are limited options for quickly carrying heavier extinguishers or dragging fire hoses into this area in the event of fire. Hand-held extinguishers are insufficient to extinguish a high energy electrical fire (discharge time ~15 seconds), so the First Responder would need to leave the incident area to fetch another one which would allow the fire time to re-establish. We recommended that the power station operator purchased at least 2 x 25kg trolley-mounted CO2 extinguishers, locating them at either end of the Switch Room, thus increasing the effective usage time to ~75 seconds.
- At a remote water pumping station in Saudi Arabia which supplied one of the largest cities in the country, the power transformers which run the huge transmission pumps had no active fire suppression systems. Furthermore there was no fire brigade within 40 km of this remote location, so if a transformer fire did begin there was no hope of controlling it before it destroyed the transformer and disrupted water supply to that city. Again, the interesting aspect of situation was that fire protection levels throughout the rest of the pumping station was actually very good, with this being the glaring discrepancy.
- In the industrial zone of Antwerp, Belgium, a tunnel runs beneath one of the canals that contains pipelines bringing LPG, chemicals, water and – notably – oxygen to the nearby industrial plants. Despite being only 220m long the tunnel was 47m below ground level, meaning that it was accessible only via long vertical tunnels on either end of the horizontal shaft. There were no fire detection or suppression systems installed. When the issue of firefighting was brought up by the Risk Engineer there was a lot of head scratching amongst the owner representatives. No plan to isolate or depressurise the pipelines. No consideration for stopping the ventilation system to stop air getting to the fire. No recognition that if the oxygen line ruptured during a fire that the massive increase in fire intensity would likely collapse the tunnel. Nothing.
All these are examples of a failure of imagination. If we fail to conceptualize potential catastrophic incidents, then we won’t install the right protective systems or develop the right intervention plans. Risk Engineering surveys are excellent ways to correct this blindness, to stimulate the imagination. [VRS]™ Virtual Risk Space lets you see more of these issues and intervene before it’s too late.
When one is unprepared for a disaster, it has a greater effect: shock intensifies the blow. No mortal can fail to grieve more deeply when amazement is added to the loss.seneca