REPRODUCED FROM A FULL ARTICLE IN FSMATTERS, JUNE 2019.
“The new proposed regulation expands the need to avoid the risk of entanglement from escape routes to all areas. The new proposed regulation (521.10.202) does not just apply to cables in escape routes, but any cable that is subject to premature collapse. Premature collapse may occur for a number of reasons, but typically heat from the fire can cause plastic fixings to fail.”
Darren Staniforth, Technical Development Manager, NICEIC.
This is Important – there are other ways Premature Collapse occurs in a fire event which need to be taken into consideration.
So let’s consider all of them.
1. EXTREME HEAT
There are 3 critical events in a fire which cause premature collapse of cabling. EXTREME HEAT is the one everybody in the industry is focusing on. NATURALLY, BECAUSE THIS CAUSES PLASTIC FIXINGS TO FAIL AND ENTANGLEMENT BECOMES A REAL THREAT.
Firefighters still move around in a building where the temperature at ceiling height exceeds 400 C but by crawling at ground level the temperature may still be such that firefighters can operate with the correct PPE. At this temperature the plastic SUPPORTS have melted and that’s when following a collapse of the cables entanglement becomes a real risk.
2. HIGH WATER PRESSURE
70mm dia Fire hoses operate at 5 bar or 70psi at ground level and 5 times higher in high rise blocks and water running down walls into apartments below can cause the ceilings to collapse. A sweep of pressurised water of this kind will strip most walls and ceilings bare. It is essential that fixings used to support cables from Premature Collpase are up to the job, both today, tomorrow and way into the future.
40% of fires in industrial units and 60% of fire in domestic situations result in an explosion of some kind. At home it could be a scent bottle, an aerosol spray can or a tin of baked beans. Fixings used in installations MUST be able to support cables in this kind of event.
In industrial situations it can be pressurised canisters, inflammable fluids, chemicals or bottled gas. The explosions tend to be larger in industrial fires because of the collective storage of multiple units, however smaller explosions bring higher risk of premature collapse because substrate stays intact – and they can occur anywhere on a site. Again, it is the fixings used which can help prevent Premature Collapse in this instance.
THIS IS WHY THE USE OF CONCRETE SCREWS IN FIXING METAL CLIPS IS SO IMPORTANT
Fire Safety Clips could be in a building that is partially on fire and subject to percussive shock by explosion and water spray without high temperatures. So Fire Safety Clips must hold in other than high temperature circumstances.
The best fixing for offering protection from Premature Collapse (TRIPLE THREAT) under 18th Edition of BS7671 is a CONCRETE SCREW. Here is why.
- Strength and Long Life retaining of cables particularly in the event of Fire is the most important feature of ANY fire safety cable retention clips.
- A Concrete Screw acts as a mechanical Lock, holding everything in place in the widest range of substrates, under the most trying of conditions – providing Strength and Long Life retaining of cables. In ceilings, we do not recommend installing ANY clip of any brand directly into plasterboard. Joists must be used for anchorage because in the event of exposure to water the plasterboard will fail.
- The design of a Concrete Screw is such that every twist provides additional resistance to pull-out load. This is why a Concrete Screw provides the highest level of pull-out load of any fixing currently available. Pull-out load is the relevant loading here. SHEER load merely holds a weight in place at 90 degrees so you could stick your finger in a hole in substrate and dangle a bag of cement from it. In Premature Collapse (Triple Threat) it is pull-out load which is relevant.
This is why Firefly clips and cleats are installed with Concrete Screws. They offer the highest protection against pull-out loads in any circumstances and are the only method of fixing we can recommend in the event of Premature Collapse (Triple Threat).
MALCOLM BROOMFIELD SAFETY CONSULTANTS
JUNE 4, 2019