Fire sprinkler & deluge systems:
Published: 01 September, 2006
In use for well over a century now, sprinklers are required in all new highrise and underground buildings generally 75 feet (23 m) above or below fire department access, where the ability of firefighters to provide adequate hose streams to fires is limited.
Depending on the national legislation in a particular country, sprinklers are also required in hazardous storage spaces by building codes, or may be required by insurance companies where liability due to potential property losses or business interruptions can be reduced by adequate automatic fire protection.
Typically, each sprinkler head is held closed independently by heat-sensitive seals. These seals prevent water flow until a design temperature is exceeded by the individual sprinkler heads.
Seals may be broken by melting (fusing) of metals with a low melting point (often bismuth alloys) which breaks the seals - or systems may be activated by glass bulbs that break from pressure differences when heated.
Bulbs in sprinklers are colour-coded to indicate their operating temperature. Typical activation temperatures are 135 °F (57 °C), 155 °F (68 °C), 200 °F (93 °C), and 286 °F (141 °C), which correspond to the type of hazard the sprinkler system protects against.
Each sprinkler activates independently when the predetermined heat level is reached. This limits the total number of sprinklers that operate, thereby providing the maximum water supply available from the water source to the point of fire origin.
What’s available?
Standard commercial wet sprinkler systems are designed for 1,500 square feet (140 m2), and maximum water supplies of about 300 US gallons per minute (20 L/s). Other systems can include:
* Deluge systems - essentially pre-action systems which have open sprinklers - i.e. the fusible link is removed, so that every sprinkler served by the system will discharge water. These systems are used for special hazards where rapid fire spread is a concern.
Such pre-action systems are highly specialised for locations where accidental activation is unacceptable. Pre-action valves are connected to fire alarm initiating devices such as smoke detectors or heat detectors and virtually eliminate the possibility of accidental water flow.
* Some sprinkler systems used for industrial applications may have foam instead of water suppression agents for fire protection in occupancies with flammable liquids, such as airport hangars. ‘Clean agent’ gaseous systems, such as Argon/CO2/Nitrogen mixtures can be used in very small spaces where water cannot be used for suppression.
* Typical ‘wet’ systems are simple and passive. They have water already pressurised in the pipes held back by the sprinkler head. These systems requiring no manual controls to activate, so long as adequate water supplies are provided.
* Specialty systems called ‘dry’ systems, designed for unheated spaces, have a low ‘maintenance’ air pressure in the pipes. Water is feed into the system when the sprinkler ‘fuses’ allowing the maintenance air pressure to reach the minimum pressure point.
Getting a laugh from Hollywood
Just about every architect, builder and sprinkler engineer will probably enjoy watching Bruce Willis and other Hollywood heroes as they battle through some unsuspecting office tower or warehouse, only to have a fire start up and all of the sprinklers in the room go off at once.
It makes for wonderful special effects!
Fire professionals will know - of course - that 99% of fire sprinkler systems - especially those in industry, in office and public spaces - only sprinkle the area of the fire.
In fact, properly-installed sprinklers use up to 100 times less water than non-sprinkled fires where the fire department has to come in to douse the flames.
Sprinklers go offshore
During the construction of Elf Enterprise Caledonia Limited’s Claymore offshore oil platform a key element was the installation of an effective and reliable fire sprinkler system.
The company behind the construction of the free-standing accommodation platform, leading marine offshore engineering company, SLP Engineering of Lowestoft, UK, had to install 500 sprinkler heads covering 72,000 sq. feet, in a structure over seven storeys high.
Andy Bogg, a senior mechanical engineer at SLP explained: “A BlazeMaster Fire Sprinkler System was selected for its uncompromised safety and considerable cost savings compared to other systems commonly used in offshore platform installations.
“BlazeMaster products demonstrated a reduction
of 90% in installation costs when compared with
Cunifer,” he reports.
“Although this was the first time that we had used BlazeMaster products, we experienced no problems whatsoever with the installation. We found it to be cleaner, healthier to work with and more maneuverable even in confined spaces. We saved many hours on the project and the handling and assembly of the pipes and fittings could not have been quicker or easier.”
In the early stages of the project, there was some scepticism about the use of new materials in thistype of application. The BlazeMaster(r) system, for example, was then not approved for this environment in Europe - although it did have both Underwriter’s Laboratories (UL), USA approval, and provisional approval from the Loss Prevention Council (LPC).
By the time that the accommodation platform was completed, full approvals were obtained from the LPC, from Lloyds offshore and from the Health and Safety Executive (HSE). The system can now be used in process areas as well.
“The BlazeMaster Fire Sprinkler System was subjected to numerous fire tests as well as physical property and pressure tests,” said Jon Thomson.
“During the direct fire exposure, peak temperatures exceeded 500°C (930°F), and the system maintained operating integrity. The pipe has also been approved for continuous operating pressures up to 12 bar (175 psi) and 50°C (120°F) and has an excellent track record over the last 10 years.”
The Claymore accommodation platform contract includes over 500 concealed sprinkler heads. The pipes were manufactured by Harvel Plastics Inc. and the fittings by Spears Manufacturing Co. Inc.
The sprinkler pipes and fittings used are regarded as being much lighter than conventional ones, which is an important consideration, particularly for offshore rigs. The pipe and fittings are said to be easily solvent-weldable and to offer superior hydraulic results in offshore accommodation platforms.
Higher Impact and Tensile Strength
Spokesperson Judy Makowski commented: “BlazeMaster pipe compound has a tensile strength at least 14% greater than other CPVC material used in fire sprinkler systems.”
Similarly, tests show the BlazeMaster fitting compound can withstand three times the impact strength, as defined by ASTM D1784, of standard CPVC. The higher tensile strength also translates into higher burst pressure strength.
“With this higher impact strength professionals in fire protection and building trades can confidently install durable BlazeMaster fire sprinkler systems in a variety of applications. The higher impact strength allows the fittings to be installed on the construction site with fewer fractures, breaks and ultimately, a lower scrap rate,” reports Ms.Makowski
More information? www.blazemaster.com
