Fireray Reflective Beams shine in open area smoke detection

 

FFE’s Fireray reflective beam smoke detectors have proven themselves to be fully capable of protecting an application where a competitor’s detection system had
frequent problems.

KEY FACTS:

  • A revitalised shopping centre required state-of-theart smoke detection for a series of glass atria as part of an overhaul of its fire protection system.
  • An imaging smoke detection system was initially installed, but several weeks of trials demonstrated repeated faults due to sunlight and building vibration.
  • A series of Fireray reflective beam systems were fitted instead and these have provided trouble-free smoke detection for many months.

When the services in a building have been allowed to deteriorate over time, sometimes it is easier and more cost-effective to start again from scratch rather than try and work with what is already there. This was the situation that confronted Pacific Security Systems Limited, a London and Kent-based fire and security company, when they were hired to recommission the fire protection system in the St Nicholas Shopping Centre in Sutton, in the south of London. The original system, which had been installed many years previously, had gradually failed over time and much of it was shut down, including the smoke detection components. The new owners of the centre wanted to fit an entirely new fire protection system that met modern standards. In particular, they were concerned about protecting a series of glass atria that forms the centrepiece of the public shopping area.

Given the large and relatively complex geometries of these atria, some of which were octagonal in shape, optical beam smoke detection was seen as the ideal choice. Initially, Pacific decided to install an open area smoke imaging detection system. These systems, which have emerged on to the market in recent years, typically consist of an emitter and receiver, similar to the well-established end-to-end infrared beam systems. The particular system selected by Pacific for this application used an imager to target and track the beam emitters. This was designed to assist with aligning the components and maintaining this alignment in service.

As these systems were relatively new to Pacific, their Operations Director decided to install two beams in the shopping centre on a trial basis. The emitter and imager were fixed to the concrete structure of the centre, just underneath the glass lantern at the top of the atrium. As recommended by the manufacturer, the components were roughly aligned using a tool containing a laser, after which the imaging software was activated to find and lock on to the emitters. This alignment process wasn’t quite as straightforward as the manufacturers had indicated, but eventually the systems were ready for testing.

At the end of the initial trial period of two weeks, the system log was downloaded to evaluate the performance. The log revealed a problem with sunlight apparently giving spurious alarms. A shield was fitted over the lenses on the imagers and a further week’s trial was performed. Thistime the log showed that, although the sunlight issues had been resolved, false alarms and faults were stilloccurring, which the manufacturer attributed to “building vibration”. A new version of firmware was installed in the components, but another week’s testing showed no significant improvement; in fact, there now seemed to be numerous faults being generated by several different causes.

It was at this point that Pacific made the decision to reject the imaging system as unsuitable for this application. They were becoming concerned that it was taking too long and costing too much to run the trials without seeing any improvement in performance. They also couldn’t think of any way of resolving the vibration issues that seemed to be the main cause of the faults, as they were already using the building’s concrete frame as a solid base for supporting the components and nothing more robust was available.


A TRIED AND TESTED SOLUTION

The trial systems were removed, and Pacific elected to replace them with FFE’s Fireray Reflective Beam Smoke Detectors. There were several reasons for this
selection:

  • A reflective beam solution was appropriate in this case because there were no obstructions or reflecting surfaces in close proximity (≤ 0.5 m) which could block or deflect the beam.
  • Reflective beam systems require electrical cabling to be laid to only a single component of each infrared beam (the detector), with a simple reflector being mounted on the opposite side of the area being protected. This significantly reduces installation costs and timescales.
  • With an operating range of up to 120 m, the Fireray was more than capable of protecting the largest atrium in the shopping centre, which was 25m in length.
  • Pacific had many years of positive installation and servicing experience with these products.

 

The detectors were mounted on the same concrete surfaces that had been used for the imaging system components previously. Three beams were set up across the largest atrium, an octagonal-shaped lantern at the heart of the centre which contained the main escalators between the floors. These beams could be arranged to cross each other without affecting performance, because the detectors were spaced sufficiently far apart to avoid any reflection from neighbouring beams. Further beams were set up to protect the atria in each of the smaller pavilions and above the connecting malls.

Next came the all-important alignment stage. In the imaging system, a laser is used to roughly pre-align the emitter and imager; the smoke-detecting beam plays no part in the alignment. Therefore, it must be assumed that the detecting beam is completely parallel to the laser; any deviations from this could increase the sensitivity to building movement, which was the cause of many of the faults seen in the trials.

In contrast, the Fireray solution uses the reflected infrared beam to align the detector and reflector perfectly. Pacific reported that the beams were easily set up using the feedback given from the indicator LEDS on the front of each unit, without the need for any additional equipment.

Once installed and aligned, the Fireray detectors use an in-built drift compensation routine that regularly monitors the received infrared beam signal and automatically compensates for any change. This maintains performance if the lenses gradually become contaminated with dust, increasing the time intervals between servicing visits. In addition, Fireray detectors feature Building Movement Tracking that re-aligns the beam to compensate for small changes in building position due to settling. This maximising the Fireray’s tolerance to building movement, with the system operating accurately with up to ± 5° misalignment of the beam at the reflector.

The Fireray Reflective Beams installed in the St NicholasShopping Centre have now been operating for many months without any issues being reported. Neither fluctuating levels of sunlight nor building vibration have generated any false alarms or fault signals. Pacific’s Operations Director commented that the systems are also easy to service and adjust as needed to maintain optimum performance.

“The reflective beam detectors from FFE are a robust and reliable solution for a variety of applications, and they have certainly proven themselves in this case. We’ve always found them to be excellent products that we have used many times in the past and would not hesitate to do so again.”

Do you have an interesting project with FFE detection? Contact us at [email protected] and we can help write and publicise it.

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