The Grenfell Inquiry has started a new phase by hearing from a series of experts in fire engineering, who gave presentations on the fire safety regime.
Luke Bisbee, is a professor of fire and structures at Edinburgh University, explained a series of tests performed on materials used at Grenfell Tower. “These were some of the most shocking experiments I have ever witnessed. After about 15 years of working in these lab.”
He said the most dramatic results came from cladding panel manufacturers Arconic Reynobond PE is an aluminium composite material, made from two aluminium skin's sandwiching, a polyethylene core known as ACMPE. This is the cladding material that covered the whole of the exterior of the Tower. Shortly after ignition, Raynobond ACM produced a continuous stream of burning polyethylene droplets.
“It is perhaps a bit tricky to visualise a 100 by 100 millimeter square sample of Raynobond PE sample but to put it into perspective, this was the piece of Raynobond that we tested in that video. And that's about the size of a beer mat or drinks coaster, to put in perspective for you, so it's a piece of not very much material at all.”
Luke Bisbee told the inquiry: “It (Raynobond) had the largest potential to contribute to fire growth and spread. It accounted for as much as 59% of the total potentially available energy on any single floor of Grenfell Tower. And as much as 87% of the total potentially available energy within the architectural Crown of the four principal cladding products. Raynobond PE is comparatively slow to ignite. However, once ignited, it releases more energy more quickly than any of the other products.”
Luke Bisby tested the ACM panels paired with Kingspan K15 insulation. The materials were put onto a one meter high test rig, with a burner underneath to set it on fire. The burner was removed after four minutes. The cladding continued to burn and flames reached the top of the test rig, molten polyethylene dripped from the panel. Just over a minute later, the flows extended further above the rig. At between six to nine minutes, the aluminium surface of the cladding separated from the polyethylene, flames extended further and engulfed the rig.
“Even having witnessed this escalation in person. Now dozens of times, I still find it pretty shocking. Indeed, the comparatively small size of our experiments in general terms was dictated by the fact that these were the largest experiments that we felt we could safely perform within our purpose built fire labs.”