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Monthly Archives: November 2018

Fire Protection Hydraulics of Grid Sprinkler Systems

Do you Peak?

Fire Sprinkler Grid Systems that is. How do you hydraulically peak your automatic sprinkler system? Do you depend on the program you use for fire protection hydraulic calculations and just trust it implicitly? I have learned not to!

The basic premise of hydraulically peaking a gridded fire sprinkler system is that the hydraulically most remote area of operation will be on the most remote branch lines between the primary and secondary cross mains. The branch lines furthest away from the point where the feed main connects to the primary cross main.

The programs I used did a great job of calculation as long as you understand the assumptions and limitations. Many hydraulic calculation programs assume that the system is a box with a common sprinkler head spacing and elevation. Then they just shift the remote area by adding the distance between heads to one side and subtracting it from the other. This is perfectly acceptable if the spacing is typical, but this is not always the case. So unless the system is spaced evenly, I peak manually. I just use the automatic peaking feature to give me a starting point.

Yes, I know what your saying. It’s Hard, and the Building Department, Fire Marshall or other Authority Having Jurisdiction are approving my calculations now. Well, That’s only because they assume several things. First, that since a computer was used it’s correct. Second, that you know what you are doing. But the day when the AHJ stops making these assumptions is coming. They have been learning!

Will the remote area be between the mains or will out board heads be involved. Many programs assume the remote area will always stay between the mains. But that depends on how many outboard heads the system has.

How many outboard heads can I have? The easy answer is one half the number along the line in the remote area. My experience is that as long as you follow this rule, even if the remote area should include outboard heads, the difference is marginal. However if design considerations mean that the secondary cross main has more heads outboard, then a calculation should be done using the outboard heads.

Will the remote area be on the end grid lines. Right now everyone assumes this is the case, but there are situations where it will not be. I have seen calculations where the end line was sized larger than the rest of the grid to make it work. But then the remote area actually will shift across the lines and not parallel to them. Most programs assume peaking is parallel to the lines. Also, if the grid is not typical, but has different spacing along the lines due to steel, or changes in ceiling grid, the remote area will not necessarily be on the end branch lines.

So be careful. Computer programs are great tools, but you are still the one in the hot seat.

Fire Sprinkler Legislation and Education

H.R. 1194: Fire Sprinkler Incentive Act of 2009

As an old timer in the business, I am a firm believer in educating people to be able to make informed choices. I tend to resist using the heavy hand of government to force the issue. But the Fire Sprinkler Incentive Act is not brute force, but an incentive. It changes the tax codes to change how sprinkler systems are defined as property for the purpose of depreciation. Those who know me will know that I am not a fan of the current unfair tax code. But it is the way things are for now. So as such I support this bill, H.R. 1194 and any companion bill the Senate may introduce.

But it is not going to be easy. This bill has been stuck in committee since February and not been presented for a vote. A similar bill has been presented at least 6 times before and all have died. Please contact your representative and indicate your support.

Additional information can be found here:

http://www.nfsa.org/fsia/fsiahome.html
http://www.govtrack.us/congress/bill.xpd?bill=h111-1194
http://www.opencongress.org/bill/111-h1194

The History of Automatic Sprinkler Protection, Part One

Part 1 – The Beginnings, Perforated Piping Systems

The forerunners of the automatic sprinkler system were the perforated pipe and open sprinkler. The perforated pipe system, as its name implies, was simply a series of small perforated pipes attached to the ceiling and divided into sections.

In 1806 John Carey filed a patent in London for a perforated pipe concept for fire protection systems, but the system never gained acceptance. The world’s first recognizable sprinkler system was installed in the Theatre Royal, Drury Lane in the United Kingdom in 1812 The apparatus consisted of a cylindrical airtight reservoir of 400 hogsheads fed by a 10 inch water main which branched to all parts of the theater. A series of smaller pipes feed from the distribution pipe were pierced with a series of ½” holes.

From 1852 to 1885, perforated pipe systems were used in textile mills throughout New England as a means of fire protection. The Providence Steam and Gas Pipe Company, later to become the Grinnell Company, was a major installer of these systems.

James B Francis was one of the first to develop a system of perforated pipes and his system was installed many New England mills. Other systems were the Whiting system, Hall system and Grinnell system. Each system having a different spacing ,and sizes of holes in an attempt to effectively distribute the water. The Hall system is notable in that it used galvanized sheet metal piping. It was soon removed from service as unreliable.

These early systems did establish some basic design concepts, Such as spacing of lines, and sizing of the pipes. One early rule was that the sizes of the pipes were of such size that the area of the orifices would not exceed 50 per cent of the area of the pipe that fed them.

Frederick Grinnell’s first patent, on March 12, 1878, concerned perforated “sprinkling-tube” that had the holes bushed with a non-corrodible material such as brass. This indicates that potential clogging of the perforations due to oxidation of the iron pipe was a major problem.

The success of perforated sprinkler piping was short lived. It is evident that with this system there was a great waste of water, and probably poor distribution. Furthermore, the systems were not in any way automatic. They were manually activated by the building occupants. By discharging water over the entire area of the room where there was no fire, the water damage usually greatly exceeded the fire damage. The lack of automatic operation was the main problem as nearly all of the highly destructive fires occurred at night when there was no one in attendance.

Next – The First Automatic Sprinklers

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