Experience in North America
|by George Anolik|
|In the very recent past, a fire broke out in a
motor room in the basement of an aluminum rolling mill, when electrical
arcing started from a motor panel and ignited some oil and residue on the
floor. From the floor, the flames spread to three tiers of cable trays,
then traveled thousands of feet down the cables and destroyed a 300-horsepower
The final cost of the conflagration was $300,000 in equipment damage. plus $1.5 million in lost revenue during the resultant shutdown. The insurance underwriters' investigation demonstrated unequivocally that had the basement been sprinklered, and had there been firestops in place in the cable tray penetrations, damage would have been minimalin the range of $3,000 as opposed to $1.8 million
A proliferation of similar case histories has resulted in the heavy emphasis that is placed today, within the construction industry, on the relatively new development of firestopping systems. But what is firestopping, and where has it come from? Why has there been no great emphasis on it until the recent past?
Firestopping is the process of systematically sealing the service penetrations and apertures in the walls and floor slabs of a building, thereby converting it into a series of fireproof boxes. It is totally concerned with containing firesand therefore controlling themand with preventing the spread of the lethal smoke and gases generated by the tire. When a fire-stopping system is in place, properly installed, a tire breaking out in any sealed unit of that building will be confined to that unit, securely contained, and unable to affect the other elements of the building.
Firestopping systems are not a brand new concepts although the excitement and interest surrounding the subject would tend to make it appear to be a sudden occurrence. It is an actuarial statistic that 23 percent of all building fires originate from electrical systems. In recognition of that, the first firestopping in North America was accomplished in the mid-1960s by means of a device called a multi-cable transit (commonly known as an MCT). The MCT was a grouping of individual electrical cables, all of which had been insulated against fire and assembled together so that they could pass safely and securely through walls or bulkhead penetrations to deliver power to various types of equipment.
Purely a mechanical device, the MCT bore little visible relation to the more sophisticated firestop systems in use to- daythe insulations, sealants, intumescent products, and expanding foams and grouts. But the MCT was a breakthrough, and it paved the way for today's firestopping industry.
The MCT was made up of a series of cast-iron frames and insert blocks. Each insert block held one individual cable, and the blocks were then assembled and clamped together by a cast-iron frame. The assembly was fastened in place by tightening down the bolts on the cast-iron framewhich provided a very tight compression fit around the electrical cables and the device was used each time the cables passed through a fire-rated wall or bulkhead, providing a safe and thoroughly effective seal.
The first of these MCT systems were installed in U.S. shipyards in 1966, and the results were so successful that the use of MCTs eventually spread to land-based construction projects. By 1970, the Fort Saint Vrain nuclear plant in Colorado had become the first of 30 U.S. nuclear plants to install and use MCTs for several reasons: the MCT was a tested and proven means of preventing fire from spreading from one area to another along electrical cables; it was also the only system available in North America that had documented results to substantiate the claim that it could prevent the propagation of fire along electrical cables. The MCT set the North American standard.
|George Anolik is manager of firestop systems for Fleck Bros. of Burnaby; British columbia. This article originally was published as Firestopping in British Columbia: The Practical Experience by the British Columbia Insulation Contractors Association. It is reprinted by permission.||
The Role of Nuclear Power
The MCT was designed in Sweden, where there had been an awareness, particularly in the ship-building industry, of the dangersand the costsinvolved when fires and smoke were able to spread through unprotected service penetrations. In North America. however, as recently as the mid- 1960s, the only industry that had shown any interest in firestopping was the nuclear power industry.
Significantly enough, the major factor stimulating that interest was the astronomical amounts of dollars involved for equipment replacement. The industry had previously experienced some really appalling situations. One such occasion occurred in an electrical room where penetration seals had been installed specifically for the purpose of preventing the passage of air and gaseous vapors from one area to another. Unfortunately, the material used to provide these seals was not fire-resistant. and the direct damage caused by the fire was in excess of $50 million.
Damage and losses of this magnitude led to the exploration of ways and means of containing and curtailing the spread of fire, and the first scientific testing methodology was inaugurated in North America when the Nuclear Energy Liability Property Insurance Association outlined the basic parameters for an acceptable fire-exposure test for mechanical and electrical penetrations. This information was published in a 1975 bulletin that was issued to the industry's agents and brokers, to architectural firms, and to the many other peopLe involved in nuclear plant construction. Shortly after the bulletin was issued, some of the nuclear power industry's dedicated manufacturers began submitting their products and systems to the testing agencies for evaluation.