A full scale fire test of a Rubb building with 28 oz/sy PVC coated polyester membrane demonstrates the fire safety advantages of the Rubb system. The Rubb membrane fabric… “will not propagate flame or sustain combustion when exposed to a severe fire”. The test report also discusses fire sprinkler performance in a Rubb building and the ability of the structure to self-vent. In an actual fire the fabric cladding melts away from the flame or heat source allowing heat and smoke to escape the structure. This lowers the risk for people within the building and for fire fighting personnel.
It also helps avoid the risk of structural collapse which can occur in other types of construction. Read the full report below and view our fire video for more information on Rubb fire safety.
At 3am on a November morning in 1999, a fast spreading fire engulfed one of the Rubb storage sheds at the Merrill Marine Terminal in Portland, Maine. A stray spark caused hundreds of bales of scrap paper to ignite and fire swept through the 28.5m wide x 36.5m long Rubb building.
Amazingly, the storage facility was back in service in less than a week. This was due in part to the fact that the structural membrane melted away where exposed to the fire, thereby releasing heat and smoke. The fabric used for the membrane passed stringent flame tests and was proven flame retardant, self-extinguishing and did not propagate flame. Due to the self-venting release of heat, there was no structural damage to the hot-dipped galvanized steel frame and a new membrane was quickly fabricated and installed by a Rubb field service crew.
As Rubb’s client Mr. P.D. Merrill commented after the event, “Any other building would have been a total disaster – a total loss. We simply put a new fabric on the building and it was back in service in less than a week.”
The Client was delighted with the six-day turnaround in repairing his storage facilities, but that came as no surprise to Rubb employees. The situation merely served to reinforce the results from an earlier full-scale fire test. This was conducted on a 12m wide x 15m long x 7m high tension supported membrane structure located in the 18m ceiling site of the Factory Mutual Research Corporation (FMRC) Test center, located in West Gloucester, Rhode Island.
The test structure consisted of a galvanized steel tube frame set on I-Beams anchored to the floor. The covering was 950g/m2 polyvinyl chloride-coated polyester fabric tensioned over the framework. For this test, instrumentation was used to measure fire signature data and to obtain information regarding fire detection response. Inside the structure, ceiling ionization and photoelectric smoke detector pairs were installed at two ceiling locations and fast-response and standard-response sprinkler pairs were installed at four sprinkler stations. The sprinklers were unconnected to a water supply and were used only to obtain information regarding sprinkler actuation times.
The fire was set in one corner of the test structure utilizing the fire source prescribed by the FMRC Approvals Division Building Corner Fire Test protocol. The first smoke detector (ionization type) actuated at 24 sec. after ignition and by 1 min. 7 sec, all installed smoke detectors had actuated.
First sprinkler actuations occurred at 4 min. 59 sec. and 5 min. 34 sec. for fast-response and standard-response sprinklers, respectively. After severe exposure of the test structure to the fire source for a 15-minute duration, the fire test was concluded with no apparent self-sustained propagation of the fire by the fabric covering, and no fire damage to structural support members.
This required a 1.5m high, 340 Kg pile of hardwood pallets, 17 in total, as an exposure fire for evaluation of wall and ceiling building materials, and was positioned in the southeast corner of the test structure. Although the fire penetrated the closest wall before the first sprinkler actuation, all installed sprinklers actuated before flames burnt through the adjacent south wall and the ceiling over the fire source location. Crucial to the continued life of the steel structure was that once burn-through had occurred in the south wall at around 9 minutes after ignition, the building vented and interior temperatures were significantly reduced. This was exactly the experience of the Merrill fire, thus saving the steel structure for a new membrane cover.
Although four ceiling sprinkler stations were installed inside the test structure, they were not connected to a water supply for test reasons, however, had the first sprinkler that was located closest to the fire source actually discharged water, the fire may well have been sufficiently controlled to prevent subsequent sprinkler operations.
In addition, laboratory scale flammability tests were also performed on the membrane fabric to measure heat release and ease of ignition properties. In their conclusion, the Factory Mutual Research Corporation commented, “Fabric used for construction of the tension supported membrane structure evaluated during this program will not propagate flame or sustain combustion when exposed to a severe fire. Only the fabric immediately adjacent to the flaming fire source became involved in the fire.”
Smoke detectors will provide early warning against fire prior to burn-through or venting of the structure. If a severe fire occurs in close proximity to walls, burn-through of the exposed walls is likely before a sprinkler can actuate. However, sprinklers would most likely actuate prior to burn-through of the ceiling fabric.
Only last year the components of Rubb buildings were analyzed in further stringent fire tests in the U.K. Rubb products have now been accredited with BS 7157 as further proof in satisfying current building regulations.
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