Smoke Beam Detection

Beam detection has become commonplace within large open warehouses. The product is cost effective when compared with using point detection and suitable for heights way above the operating limits of conventional smoke detection.

It all sounds too good to be true however, there are important factors to consider when selecting and installing beam detectors.

The operational range of a standard beam detector is 100M with coverage upto 15m Wide. Immediately we can see that covering 1500m2 with one pair of beam detectors is quite impressive. This also means that the beam must be connected to its own zone on a conventional fire alarm panel or its own software zone on an analogue addressable control panel. In the case of the latter a short circuit isolator will also be required as no zone can exceed 2000m2 under BS5839 part One:1988.

The next consideration must be sunlight. Certain manufacturers have produced "Solar Blind" beam detectors with the use of I.R. filters whereas others will be affected by sunlight pouring through roof lights into the beams I.R. receiver. In this case false alarms will often result at set times of the day and of course with seasonal fluctuation, low winter sun being a prime example.

Beam detectors spanning 100m are prone to movement. Steel framed buildings move. This is a normal occurrence, but when trying to hit a target approximately 100mm x 100mm from 100m away even a few degrees of movement can cause problems. Correct initial alignment is critical as is a solid & secure fixing to structural steel or brickwork. In many cases bracing and special bracketary may be required. Wiring is also critical particularly with loop driven devices where a clean earth is of paramount importance. This should be one of the first things checked when problems are evident.

Maintenance is also critical. Detector lenses become coated with dust and alignment will be affected by building movement over time. You should always re-align and clean all beam detector lenses once per annum to ensure reliability and performance.

Finally, birds! Often blamed for false alarms and faults. Is it a myth? Not necessarily, our own engineers have encountered a bird using a beam detector as a regular perch. The evidence it had been there was clearly visible however, this is by no means a regular occurrence and we would always suspect the other issues listed above ahead of the bird scenario.

If you have any problems relating to beam detection please don't hesitate to contact us for some free and impartial advice. We don't manufacture beam detectors and therefore have no bias towards a particular product.

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