Burning Up the Fax Machine
Q: If you were running an underground line 120 feet to a free standing fire department connection, would you use more than one ball drip drain valve? If so, how many for 120 feet of 4" pipe?
A: One ball-drip assembly will suffice. And since that piping will always be dry, it only needs to be buried to a depth of 1 or 2 feet, and be sure that someone digs a pit beneath the ball-drip at the low point and fills that pit with #9 stone. I would pitch the whole run a minimum of 3 inches from the high end to the low point.
Q: Our firm is designing several schools that will all contain computer server rooms that take up about 2,700 cubic feet of space. Now that halon has been banned, what alternatives do we have in terms of fire protection, and what will they cost?
A: Of the most popular clean agents currently on the market, my guess is that an installed FM-200 system will run in the vicinity of $25,000 for this room, about $26,000 for Novec 1230, and somewhere in the vicinity of $29,000 if you go with Inergen. The advantage of using Inergen is that it is a very clean agent, has 0% ozone-depletion potential (ODP), and the clean-up following discharge is not a major ordeal. Inergen is not the most popular agent because it requires a large bank of Inergen “bottles,” which take up a substantial amount of floor space. And, due to the method of their tank construction, they must be pressure tested every five years. The task of refilling the cylinders is labor-intensive as they must be removed from the site to a shop where they blend 3 gases. This exercise puts the area in question out of service for at least one day. Also, propane is used to propel the gases, and propane speeds up your heart if you inhale it. You can breathe in FM-200 or Novec 1230 with virtually no problems.
In any case, we will be flooding a room with lots of gas so that oxygen is displaced. The reason some engineers still choose to go with preaction systems for these applications is that with the clean agents, one room can become over pressurized, and there have been instances in which the walls of a server room have been blown out during a discharge.
Probably because it was one of the main players that came on board following the phase-out of halon, over half of the server room installations today consist of FM-200, a very clean agent. Although the FM-200 tanks do not require periodic pressure testing, you would have to remove and replace those cylinders for re-charging following a discharge. The big advantage with Novec 1230 is that you can re-charge the tanks in the field. Like FM-200, it is also environmentally friendly, causes almost 0% global-warming problems, and does not require a lot of hardware. It has 0% ODP, but its tanks are a little more expensive. Prices for all these agents will very slightly because they are custom engineered for specific applications to achieve the most effective arrangement of storage and distribution of actuation and discharge components, valves, and electrical trim equipment.
A: If these hose stations each consist of one 1-1/2" hose valve (and no 2-1/2" hose valves), we are concerned with requirements applicable to a Class II service. What the code says (NFPA 14:1996, section 8-5.1) is that “the water supply shall be tested to verify compliance with the design. This test shall be conducted by flowing water from the hydraulically most remote hose connections.” Further (A-8-5.1), “the hydraulically most remote hose connections in a building are generally at a roof manifold, if provided, or at the top of a stair landing to the roof. In a multizone system, the testing means is generally at a test header at grade or at a suction tank on higher floors. Where a flow test at the hydraulically most remote hose connection is not practicable, the authority having jurisdiction should be consulted for the appropriate location of the test.” The wording of the code here underscores the need for rational minds making decisions in the field.
With regard to the points to be calculated and related pipe sizing, section 5-9.2.1 states that “for Class II systems, the minimum flow rate for the hydraulically most remote standpipe shall be 100 gpm. Additional flow shall not be required where more than one standpipe is provided.” The function of the test is to verify that there is adequate pressure at these hose valve outlets, but not too much pressure. Another issue to be ironed out is if what is being tested is indeed a standpipe, or more accurately a short and simple “fire protection supply riser.” If the entire mall is sprinklered, the NFPA standards don’t really dictate a minimum pressure requirement for the hose valves. But if their presence was required by the local fire department, then they are the ones who will most likely dictate specific testing protocol.
Q: In our shop, we have about 100 stainless steel flexible drops that are 9 feet in length and have been there for some time. They have never been used, but we are hesitant to install these because the ones we are seeing installed today are much shorter. Since there are no sprinklers attached to these flexible drops now, does it matter how old these fitting pieces are?
A: Flexible drops, first marketed in the mid-1990s, were originally U.L. listed in varying lengths (usually in 1-foot increments) up to 10 feet long. These components are designed for use in “center-of-tile” projects, and are to be piped horizontally from a 1” outlet on the side of a branch-line or cross-main. The new drop is bracketed securely to the suspended ceiling system.
The cost of a flexible drop actually exceeds the total aggregate material cost of a typical mutual (return bend) arrangement. The choice to use flexible drops, especially with contractors on the East coast, is based on an inherent savings in labor. In an installation where a fitter completes 8 to 12 traditional “return bends” daily, the same fitter may be able to install 50 to 60 flexible drops to new sprinkler locations.
I don’t believe those long flexible drops are manufactured anymore, but I don’t see any reason to prevent you from using them in an upcoming installation. It wasn’t a planned obsolescence. With the publication of the 2007 edition of NFPA 13 came section 184.108.40.206.3, stating that “where flexible sprinkler hose fittings exceed 6 ft. in length and are supported by a suspended ceiling, a hanger(s) attached to the structure shall be required to ensure that the maximum unsupported length does not exceed 6 ft.” Since no one is really interested in installing flexible drops that require a hanger, most manufacturers have ceased their production of those longer than 6 feet.
U.L. has dropped the longer listings although Factory Mutual still approves the longer ones. FYI, the most popular flexible drop lengths sold by manufacturers are (AquaFlex) 31 inches, (Flexhead) 36 inches, (Victaulic) 36 inches, and (Viking) 39 inches. The latest data from NFPA shows that in 81% of fires having occurred in structures containing an automatic wet-pipe sprinkler system, it was only necessary that one or two sprinklers opened (activated by the fire) to control or extinguish the blaze.