Aqueous fire
suppression system

Bund fires are often caused by leaking flanges or valves at the base of tanks, damaged or cracked pipe work, and sometimes because of spills as a result of maintenance work.

For a long time fixed foam systems have been used to protect fuel storage tanks, but traditionally firefighters have relied on portable branchpipes or monitors to protect the bunded containment areas surrounding the tanks.

Both portable branchpipes and monitors have distinct disadvantages for protecting this risk. In the case of portable branchpipes firefighters may have to enter the bund to apply foam to the fire thereby putting themselves at risk. Monitors are designed to project a stream of foam long distances at high velocity e.g. tank roofs or jetty protection. In the case of bund protection their application can be too forceful, plunging the foam into the burning fuel causing fuel/foam mixing, or splashing the fire over into other areas. They have the added disadvantage of applying low expansion foam – which can be slow to cover large areas to a sufficient depth compared with a medium expansion foam blanket.

High expansion foam systems represent the most effective protection for such specialised and severe cryogenic risks as LNG (Liquified Natural Gas) and LPG (Liquified Petroleum Gases). Angus Fire’s LNG Fixed Turbex Systems meet the extremely demanding performance requirements for this high risk application.

Engineered to the highest standards for exceptional reliability and minimal maintenance, the FT1- 500P/LNG and FT2-500P/LNG Fixed Turbex Systems feature a foam making net and fan, which benefit from a special boiler grade of stainless steel designed to withstand continuous high temperatures without a reduction in material strength or risk of intergranular corrosion. The complex structure of the foam making net is specially supported to avoid distortion and the tubular support frame has holes drilled to prevent moisture build-up and relieve air expansion when heated. Special glass rope lagging insulates the water turbine and three lifting lugs are provided to assist with site installation. Rugged construction and careful choice of materials provides exceptional corrosion resistance against highly saline, humid and high temperature environments.

The high efficiency design of the Angus LNG Fixed Turbex System has enabled these units to exceed the severe requirements of the National Fire Protection Association NFPA 11A Fire Exposure Test. Performance is unaffected even after exposure to temperatures up to 1000°C during the 5 minute pre-burn period of this test.

Turbex LNG Skids are the proven high expansion foam systems solution to provide a fast and effective answer for LNG (Liquefied Natural Gas) spills in contained areas, whether vapourising or on fire.

Turbex LNG skids provide all the specialist features needed for LNG including a specially engineered skid base, LNG Turbex high expansion foam generator, plus discharge hood designed to protect the Expandol foam from wind and direct it downwards into the pit of LNG. Each LNG Turbex Skid is engineered from high performance 316 stainless steel and gunmetal materials.

Common to all fixed foam fire fighting systems is the need for a suitable induction/proportioning system to mix a pre-determined amount of foam concentrate with the fire mains water to produce a foam solution. The foam solution is then supplied through the fire system pipework to a finished foam generator or other delivery device.

The selection of the correct proportioning system is of paramount importance to ensure foam is delivered at the required application rate to extinguish the fire.

In most cases a foam induction/proportioning system will consist of one of the following types:

Where the foam solution demand is constant:

• Inline inductors
• Helijector system
• Self-inducing foam generators ( such as Angus Anderson Pourers or Fixed Turbex Skids)

Where variable foam solution demand over a wide range may exist:

• Balanced pressure proportioners matched with either
• Bag/bladder tanks
• Balanced valves

Constant flow systems are where the demand of the foam generator or delivery device for foam solution is constant, either because they are protecting a single risk or because all systems will operate simultaneously.

Variable flow systems include those where the demand of the delivery devices for foam solution varies over a significant range. These systems are ideal for more complex multi hazard systems were some but not all of the foam delivery devices or systems are on, and the number may vary. At the same time these variable flow systems must retain the capacity for all systems and devices to be activated at the same time if required. Examples of a variable flow system might be a zoned sprinkler system in a process area where just 1 zone, 2, 3 or all 4 zones may be required to operate at any time.

Sprinkler systems are generally fitted to protect large floor areas as well as protecting areas where fire can start unnoticed such as floor ducts and roof spaces. In a sprinkler system only the heads in the vicinity of the fire open and discharge water hence reducing the water used and potential water damage.