Extended-coverage sprinkler technology dates back to the 1970s, and one of the most common applications is the horizontal sidewall extended-coverage sprinklers that you often see protecting hotel bedrooms. However, more recently, manufacturers have developed extended-coverage sprinklers for a wide range of commercial and industrial applications that can provide substantial cost savings.
In simple terms, an extended-coverage (EC) sprinkler, provides an extended area of coverage compared to a standard-coverage sprinkler. However, achieving this is not straightforward as, for instance, just increasing the pressure delivered to a standard-coverage sprinkler does not provide a uniform distribution over the extended area. This is because at high pressures, distributed water may mist before reaching the area to be protected, or the distribution pattern may collapse as the sprinkler deflector is effectively overwhelmed by the amount of water it is attempting to direct. An easy way to picture this is to imagine 1m2 (or 1ft2) collection trays completely covering a floor in a sprinklered room.
When any sprinkler operates, what should happen is that all the trays should, as near as possible, fill uniformly to the same depth in the same time. For EC sprinklers, this presents a special challenge, which is solved by using larger orifices (larger K factors) and deflectors specifically designed to extend a uniform distribution pattern.
A good example of how EC sprinklers can provide advantages to installers and end users is when protecting long corridors in buildings such as hotels, hospitals and schools. For these Light Hazard risks, standard sprinklers can be spaced up to 4.6m/15ft apart (and up to 2.3m/7.5ft from a partition or fire door). Extended-coverage long-throw sprinklers, such as a Reliable model LT56, can be spaced up to 8.5m/28ft apart (and up to 4.25m/14ft from a partition or fire door).
Another advantage to using a dedicated long-throw corridor sprinkler is that water is used more efficiently because, unlike standard sprinklers with radial distribution patterns, this type of EC sprinkler has an elongated deflector shape that means less water is wasted wetting walls.
Why don’t we see more EC sprinklers?
With a proven track record for over 30 years in the USA, it’s no surprise that EC sprinklers are relatively commonplace there, but in other areas, such as Europe and the Middle East, EC sprinklers are used less often. So why would this be? There are several reasons:
Firstly, EC sprinklers require a smooth, flat ceiling, so they are not always able to replace standard sprinklers.
Secondly, whilst EC sprinklers for Light and Ordinary Hazards have featured in NFPA13 since 1987, other design codes, such as EN12845 have yet to fully embrace the technology – so the options for designing with EC sprinklers may be limited when local codes don’t support their use.
Thirdly, EC sprinklers require specific minimum operating pressures that are detailed in manufacturers’ product bulletins, so the designer has to be competent with the full hydraulic calculation design method.
However, providing the installation contractor has the competency and the authority having jurisdiction agrees, EC sprinklers could be installed to NFPA13 rules anywhere in the world – resulting in some or all the following benefits:
- Significant opportunities for cost savings on labour (fewer sprinklers/flexible hoses or arm pipes and drops/fewer brackets).
- Potential for faster installation programs.
- Less pipework to coordinate = fewer potential clashes.
- A ‘greener’ solution – fewer pipes and fittings – potentially less water required.
- In long hotel rooms with very small ceiling voids, sometimes EC sprinklers are the only practical option.
A brief history of extended-coverage sprinklers:
1973 EC sprinklers were suggested by Rolf Jenson & Associates for use in hotels and apartments.
1974 Testing standards for EC sprinklers were proposed by Underwriters Laboratories.
1987 EC Sprinklers confirmed in NFPA13 as suitable for Ordinary Hazard
1994 EC Sprinklers approved by Factory Mutual
2003 BS5306 Part 2 TB35 – Ordinary Hazard Group 3 systems using Enhanced Protection EC Sprinklers
2009 CEA4001 – EC may be used in Light and Ordinary Hazard Group 1 applications
2016 SBF120:8 – EC Sprinklers used for Light or Ordinary Hazard according to NFPA classification
For more information, go to www.reliablesprinkler.com