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Low Smoke Zero Halogen Cables from Prysmian Cables UK

Welcome

Low Smoke Zero Halogen Cables from Prysmian Cables UK

Welcome

Low Smoke Zero Halogen Cables from Prysmian Cables UK

Energy Cables with Low Fire Hazard
Posted: 19th December 2014

Energy Cables with Low Fire Hazard

Low fire hazard cables have a wide range of common names and a variety of British Standards to describe their performance during a fire. The cables are typically specified and required as general LV lighting and power distribution in occupied public buildings.

The current cable performance tests include:

Low Smoke Performance

Currently defined by BS EN 61034-2: 2005, the low smoke performance test measures light transmission inside a black 3m³ sealed cube with a pre-determined number of 1m sample lengths of cable. These are supported above a small steel bath containing one litre of ethanol. The ethanol is ignited inside the cube and the timer started. The alcohol produces a negligible amount of smoke so any smoke produced is a result of cable combustion only.

Over the period of the test a beam of visible light is shone across the cube and must not fall below the pass rate specified in the cable standard. PVC cables typically register 15% transmission and fail this smoke test. Low fire-hazard cables, also called ‘low smoke cables’ achieve in excess of 80% and pass.

Acid gas performance

Acid gas performance is currently defined by one of two standards; BS EN 50267-2-1 and BS EN 50267-2-2. Each of these uses a subtly different method to analyse the hydrogen chloride gas produced during the combustion of the cable sample. The first measures conductivity of the acid gas solution while the second test measures HCl concentration. A pass of either test corresponds to less than 0.5% hydrogen chloride produced.

PVC cables typically produce in excess of 25% during this test, while ‘zero halogen’ cables produce less than 0.5%.

Reduced flame spread performance

In many circles the characteristic least recognised, reduced flame spread performance is described by two separate tests BS EN 60332-1-2 for individual cables and BS EN 60332-3-24 for bunched cables. BS EN 60332-1-2 is used to measure single cable vertical flame propagation. This pre-dates the bunched cable test and is used to qualify PVC in low cable density environments such as houses or other dwellings.

Bunched Cable Test

The bunched cable test involves mounting a number of sample lengths of the cable onto a ladder rack to the density prescribed in standard. The ladder rack is oriented vertically into the test chamber with a propane and air gas burner aligned to 0.6m from the base of the rack.

The gas and air mixture is started, ignited and applied directly to the cable on the rack and the timer started. After twenty minutes the gas flame is extinguished and if the cable-flame has extinguished, the travel of the flame is measured and recorded.

A pass is awarded if the cable self-extinguished and the flame travelled less than 2.5m vertically beyond the burner position.

Next month we will look at energy cables with fire resistance and low fire-hazard

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