Members of the Institute of Architectural Ironmongers were treated to a fire test at Lorient UK‘s headquarters in Newton Abbot today. The furnace was fitted with two miniature hinged 30 minute fire doors (FD30s) each with reinforced vision panels. The door on the left was fully sealed with intumescent materials, which are designed to swell up under extreme heat – sealing the gaps and slowing the progression of the fire. The door on the right was unsealed.
With observers fully kitted out in safety glasses, at 3.22pm the gas furnace was switched on. Within 3 minutes the air temperature inside was approaching 500°C and wisps of smoke were seen emanating from around the frame of the unsealed door. There were occasional puffs from the bottom of the sealed door at this stage and indeed, the unsealed door stopped smoking for a while. A wide variation in results (up to 15%) is permissible under test conditions within the first 10 minutes of the test, but after that the door’s behaviour becomes more strictly monitored. There are a variety of intumescent materials depending upon the use; for the purposes of this test Lorient’s 10 x 4mm intumescent fire & smoke seals (made from sodium silicate) were morticed into the frame around the sides & top of the sealed door.
The hinges (Royde & Tucker HiLoad) were backed with intumescent hinge pads made from mono-ammonium phosphate (MAP). The glass vision panel was surrounded by intumescent glazing gasket made from a graphite compound. The unsealed door had none of these advantages and, sure enough, 22 minutes into the test at a temperature of 800°C it was well blackened at the top and smoking like a chimney – particularly from the top leading edge corner – opposite the hinge side. The glass panels in both cases had been crackling away periodically and had begun spitting a few tiny shards onto the floor.
Two minutes later flames began to flash outside the top half of the unsealed door but this itself is not considered “failure” – this comes when flames are sustained outside the furnace for 10 seconds – and in this test failure occurred for the unsealed door at 27 minutes. A Georgia Pacific gypsum board was attached over the blazing breach and edged around with Lorient intumescent sealant so the test could continue with our attention drawn to the sealed door. By now this poor door was really showing the strain, particularly around the vision panel, where the graphite was bulging and sooty grey smolderings were discolouring the top and frame. The room, part of Lorient’s high tech testing facilities snuggled in the lee of the Dartmoor countryside, was warm but not uncomfortably so – surely the furnace was nicely insulated and extracted – I had been warned that fire tests can become overwhelmingly hot for observers, so this pleased me. At 42 minutes and a temperature of nearly 700°C insistent flames began licking up from the lower hinge side of the frame – the sealed door surrendered to its fate and the test was over.