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Doctor's orders

09 February 2017

Dr Carl Hunter outlines the need for mathematicians to help calculate fire fire engineering designs

THE FIRE industry calculates fire-engineering designs based on formulas that its technicians have no way of understanding or verifying are accurate. The industry needs a resident mathematician to ensure that the formulas it uses are correct. Fire engineers do not always understand the physical properties of the clean agents they use. Some do not wholly appreciate the impact of temperature on the state of an agent, or its pressures. 

Novec 1230, for instance, is an organic compound, which, if poorly handled and stored, deteriorates quickly to a point of non-effectiveness. This problem, and many more, can be solved by the application of fundamental scientific and engineering principles. But they can only be proved by the application of the mathematics involved. 

CO2 is permanently under 720 psi or 49 bar of pressure, which is nearly 50 times atmospheric pressure. As temperatures increase, it changes state to one that is neither a liquid nor a gas. Gases under pressure are often considered by the industry, from the perspective of post-installation monitoring, as single and passive cylinder columns of solid material. But because they are under pressure and constantly change according to temperature they should be considered as active and dynamic systems and, as such, they require constant monitoring.

A data centre is expensive to build and maintain and it generates significant heat. Every high-street bank with a branch network relies on hundreds of them. They are high-value facilities, but the cost of their inability to sustain business continuity is far higher. Nevertheless, insurers are asked to underwrite them and the fire industry to deliver protection for them at the cheapest price. Who, today, in the security industry would consider installing an alarm system without monitoring its status? Who would build a ship or offshore platform and fit it with power-generating auxiliary machinery without installing emergency power systems, or monitoring their condition states? These are basic engineering principles. 

All good engineering demands the monitoring of dynamic structures, and a highly pressurised cylinder is a dynamic structure. It is designed to protect a critical infrastructure or asset. Without constant monitoring, a risk is generated in the very environment in which risk is designed to be reduced. The risk is not only to the asset but to the people who work in the asset. Their ability to enable business continuity in the high-value asset is also at risk. 

Room integrity monitoring is essential under ISO 14520, according to which gaseous extinguishing systems must be designed in relation to the discharging-agent hold-time (if the room cannot hold the agent because of leaks the agent will disperse and not extinguish the fire) and discharging-agent peak pressure (if the pressure is too high for partition walls or suspended ceilings they will be blown apart or damaged, possibly destroying the room integrity). 

At the design stage of a fire-extinguishing system, rooms are tested for integrity by being positively pressurised; the escaping pressure is then detected. This is to verify that the room, into which the gaseous extinguishant discharges on actuation, can both hold the agent after its discharge and hold its pressure on actuation. Subsequently, however, there are few further tests on room integrity; the cylinders are merely hydrostatically tested to ensure they can cope with their design pressure limits. How can one be sure, therefore, that, on actuation, the room will hold the discharged agent to extinguish the fire, and that its partitions and ceilings are capable of withstanding the pressure of the agent on discharge? 

The fire industry’s customers depend on it to deliver fire-engineering solutions to protect them from risks, while insurance companies underwrite that risk. But there are high consequences for failure ‒ whether in the application and understanding of the formulas used to calculate design concentrations of gases and flow rates, or in the deployment of fundamental engineering principles to protect dynamic pressurised systems.

Dr Carl  Hunter is CEO of Coltraco Ultrasonics and he will be a keynote speaker at the Fire Safety Event at 1pm on 22 March at the Birmingham NEC. Carl’s session is titled ‘Constant monitoring of gaseous and room integrity’. You can reserve your seat now for this, or any other keynote session, for FREE by visiting, www.firesafetyevents.com

For more information on Coltraco Ultrasonics, visit www.coltraco.com