Fire-Stop Seal for Poke-Throughs
A fire-stopping sealant system has been developed for conduit and cable poke-throughs in fire-resistant industrial and commercial buildings.
The new system is based on silicone elastomer foams developed jointly by Dow Corning Corporation, Midland, Mich., and Brand Industrial Services, Inc. (BISCO), Elk Grove Village, Ill. The foams are applied by specially designed equipment.
The new material, Dow Corning Q3-6548 silicone RTV foam, is injected into dammed penetrations. The foam-in-place material quickly expands approximately three times the volume of its liquid constituents to form an air and watert ight , fire-resistant seal. Once cured, the foam maintains a pressure against the walls and pipes to provide an air and watertight fire barrier.
The material sets in three to four minutes, after which the dams may be removed and the foam trimmed with a knife.
Although the material will char, it will not support combustion. Tests have shown that its products of decomposition are Si02 (sand), CO2 and traces of incompletely burned carbon products.
Depending upon the temperature of the fire, the exposed foam surface forms either a char or glass-like clinker that protects the material beneath and limits the amount of burning possible. Furthermore, the silicone foam will seal tighter when exposed to a high temperature due to the expansion of gases within the foam cells.
The new silicone foam has been firetested in both wall and floor cable penetration seals at National Gypsum and witnessed by Factory Mutual Research. It has also been fire-tested by TVA, BISCO, Chemtrol and others.
The Factory Mutual test, the wall test made in March 1975, and the floor test made in October 1975, followed the ASTM-E-119-73 furnace test procedure. A 12-inch-thick concrete block wall and an 8-inch-thick, precast, reinforced concrete floor were used.
The penetrations, which enclosed electrical conduit, cable trays, individual wires and cables, piping and tubing, were sealed with silicone foam from 3 to 12 inches thick. One side of the wall or floor was then exposed to direct flame from a gas-fired furnace with the exposure following the standard time-temperature curve. Flame exposure was maintained for five hours on the wall and three hours on the floor.
Factory Mutual Research Report 24963 on the wall test stated: “After five hours, all seals remained in place and did not allow passage of fire or smoke.”
BISCO’s experience is that the installed cost of a silicone foam penetration seal is approximately half that of a foamed concrete or composite seal. Although the silicone is more expensive than concrete or composite materials, the labor is far less.
To put a new cable or pipe through the penetration seal, an undersize hole can be cut or drilled out and the pipe or cable pushed through. The silicone foam exhibits a spring-back characteristic to reseal the opening. Larger openings can be sealed with additional silicone foam or Dow Corning 96-081 silicone sealant.