Fire Works

18/01/2015

A well designed, fully functioning and properly installed sprinkler system is the most important fire protection a warehouse can have. Experiments at full scale have shown that vertically stacked combustible storage results in rapid fire growth. In fact, fire grows three times faster in vertically stored commodities than those stored horizontally. This makes extinguishing warehouse fires extremely challenging because they spread quickly and have immense increases in heat release rates – or the measurement of a fire’s size and rate of growth – over a short period of time.

The good news is that years of fighting fires have produced a wide array of sprinkler systems specifically designed to control and mitigate warehouse blazes. The most important consideration when choosing a sprinkler system is that the design matches the hazard. For example, plastic content is the most likely storage characteristic to contribute to a class IV or V high-hazard commodity classification (which denotes the most flammable products). The system installed must meet that classification and address the particular challenges that storing those products present. Below are the most common systems used to prevent not only plastic fires but all other flammable product, too.

Wet pipe system
The most common and reliable fire sprinkler system is the wet pipe system. It is easily installed, maintained, modified and has a short downtime after a fire. This system consists of pipes where water is constantly stored, so when it activates, the water is immediately discharged. The disadvantage of this system is that it can have leaks if the pipes are damaged by impact (from forklifts, cranes or pallet transportation), and it is not suitable for cold storage with below freezing temperatures.

Deluge system
Deluge systems are also connected to a water supply through a deluge valve that is opened by the operation of a smoke or heat detection system. When fire or smoke is detected, the system is activated and water flows through the available sprinkler heads.

Early Suppression Fast Response (ESFR)
ESFR high output, high volume systems are located in ceiling spaces as with conventional fire sprinkler systems. They incorporate very large high-volume, high-pressure heads to provide the necessary protection without the need for in-rack sprinklers.

In-rack fire sprinkler system
In-rack fire sprinkler systems are specifically designed for the protection of storage rack in warehouses. This system will not prevent a fire from starting; in fact, they rely on the heat generated by the fire to trigger them, but they will help contain the fire to a specific area and extinguish it. This system is a somewhat more complicated to implement but it limits and reduces fire damage and loss of life. Compliance with fire safety codes is intended to provide a minimum level of safety. When designing a system, it is recommended to go with one capable of handling a high hazard classification – because once it’s installed, it’s very expensive to change.

Quell fire sprinkler system
The particular needs of cold storage facilities promoted the development of systems suited for application in these environments. The quell fire sprinkler system was created specifically for cold storage environments, such as frozen food storage facilities and unheated warehouses. It is a dry sprinkler solution that does not rely on in-rack components or anti-freeze, which are prone to damage and difficult to maintain. This system employs a “surround and drown” effect, preventing damage to the warehouse and the stored goods.

Dry pipe fire sprinkler system
The pipes in a dry pipe fire sprinkler system are filled with pressurized air or nitrogen instead of water. The disadvantages of this system include its complexity, lower design flexibility, higher costs and maintenance costs as compared to the wet pipe system. Also, with dry pipe, the fire response time is longer, and there is a potential for pipe corrosion.

The Ecological Five
Several catastrophic warehouse blazes have shown that fire defense strategies should consider the potential impact on the exterior environment. Among the environmental consequences to take into consideration, the noxious effects liquid runoff can have on nearby streams, rivers, lakes or below-ground drinking water aquifers stand as the most devastating. The toxic waste created by the contaminated water can poison water supply for a community and decimate the local flora and fauna. The fire plume carried on by the wind to nearby residential and business centers should also be considered. Smoke and ashes generated by the fire can cause an adverse reaction among the general population exposed to them.

Some fire extinguishing systems like the following five do not employ water to put out fires. Foam is used whenever there is a possibility of a liquid fire; the distribution of a foam blanket over a flammable liquid will snuff out a fire by eliminating the fire’s oxygen supply and providing a cooling effect on the burning fuel.

CO2 fire suppression systems are the preferred extinguishant for a multitude of critical facilities. Fast, efficient and adaptable to a wide range of hazards, the discharge of carbon dioxide (a low cost clean agent) is non-damaging to property and electrically non-conductive.

FE-13 fire suppression systems were developed by DuPont as a chemical refrigerant; its molecules at the flame front absorb heat from a fire in much the same way a sponge absorbs liquids. It is an ideal application for large rooms with high ceiling structures in low temperatures, such as unheated storage warehouses. It also has low toxicity, which lends itself to use in flood applications and in instances where people are present in the space during discharge of the system.

The chemical heptafluorospropane is a replacement for Halon 1301, which was deemed damaging to the ozone layer in the ‘80s. This system is waterless and provides an environmentally safe, non-toxic product that requires no clean-up and can be used in rooms storing art or history collections or any facility in which water damage from a sprinkler must be avoided at all costs.

Victaulic vortex fire suppression systems use both water and nitrogen homogeneously to extinguish fires. The foil technology creates unique nitrogen and water suspension, producing droplets less than 10 microns (0.01mm) in size, a regular drop is approximately 500 microns (0.5mm). This smaller water drop absorbs more heat, while the nitrogen reduces the oxygen feeding the fire. The smaller water drops mean that there is minimal wetting, dispersing just one gallon of water per minute per emitter in total flood applications, and the nitrogen is safe to use with people in the room.

Inegren is an environmentally green three-dimensional fire suppression agent. It is a blend of three naturally occurring gases: 52 percent nitrogen, 40 percent argon and 8 percent carbon dioxide. Inegren is safer than carbon dioxide systems because it reduces oxygen concentration only enough to suppress combustion while stimulating breathing efficiency. This gas produces no ‘fog’ during discharge, so escape routes remain visible. The blend is stored in cylinders and produces zero ozone depletion, no global warming and no atmospheric lifetime. It is also ideal for any storage that cannot be exposed to water.

Within the warehouse, allocation of certain flammable materials, such as trash or aerosol cans, need to be properly addressed with prompt and frequent trash removal and special handling and storage of flammable materials. The items stored in a warehouse are not the only components to take into consideration – equipment and supplies used within the facility are just as important. Products like aerosol cans present particular challenges as well, especially when in contact with nitrogen-based systems. During a fire, aerosol cans can propel themselves across a warehouse, carrying a trail of fire behind them in what is called “rocketing,” propagating fire at great speed along their path and presenting a danger to the workers trying to evacuate.

Designating floor storage and staging areas approved for stored materials will make it easier to enforce safety issues related to blocked aisles. As with any safety system, they are only as effective as the methods of communication used to educate warehouse personnel of their existence.