- Jerry Schultz, P.E.
Put the Blue Stuff on the Red Stuff
Every now and then, something happens in the world and you end up scratching your head and saying, “Why didn’t I think of that”. Some people refer to this as the Aha moment which I was surprised, has been defined by Merriam-Webster as a moment of sudden realization, inspiration, insight, recognition, or comprehension. (I was also surprised to find out that the first known use of the term Aha moment was in 1939). We, as a fire protection community, are in an Aha moment right now and one should take the time to recognize it and appreciate it. I strongly recommend reading this blog prior to the 2016 NFPA Conference & Expo because there is an opportunity for those of you attending the conference to gain some additional insight into this moment.
As we discussed in the very first blog, the criteria that appears in NFPA 13 for rack storage was based on over 100 fire tests conducted in the 1970s. At that time, the “industry standard” sprinkler was a standard orifice sprinkler, that was standard response and rated for ordinary temperature. Note that the use of standard is not me being repetitive but was the industry term. It was basically a k5.6, non-fast response, 165F rated sprinkler. Of course, since this was the industry standard at the time, this was the sprinkler that was tested and set the criteria that we are following to this day.
Sprinkler technology evolves, improves, and comes at us in various ways. The addition of the fast response sprinkler concept came from fire tests done in residential occupancies. The introduction of the Early Suppression Fast Response (ESFR) sprinkler in the 1980s took the fast response link that originated in the residential testing and applied it to a larger orifice. The purpose of this sprinkler was to achieve “Early Suppression”. The introduction took us from controlling the fire to suppressing the fire. The use of the word control still appears in NFPA 13 and is defined as holding the fire in check through the extinguishing system until the commodities involved are consumed or until the fire is extinguished by the extinguishing system or manual fire suppression measures. This was the criteria set forth in the 1970s tests, not necessarily to extinguish or suppress but to control. At the time, it should be noted that the ESFR sprinkler achieved suppression (not control) without the need for in-rack sprinklers for the commodities being tested.
And now the Aha moment. What if, instead of the industry standard sprinkler in the rack, we provide quick response sprinklers? What if instead of a k5.6 sprinkler, we provide a larger orifice and use a k25.2? Seems kind of obvious in hindsight. Get an in-rack sprinkler that will respond quicker, put out a whole bunch more water from one sprinkler, and limit the fire spread. In this way, we get away from control into suppression of the fire. We are no longer dependent upon manual fire suppression measures and thereby are protecting the individuals within the facility along with those fighting the fire. By default, we’re also protecting the contents and the building in a more effective manner.
The rationale behind this concept should be obvious. Back in 2007, my company, The FPI proposed a protection scheme using quick response sprinklers in the racks and ran successful full scale fire tests that were incorporated into NFPA 13. FM Global is expanding the concept with the introduction of larger orifice sprinklers along with the fast response concept, and seeing where this leads us. Basically the concept looks at the traditional in-rack sprinkler protection method that has been around for the past 40 years based on the (at the time) industry standard sprinkler and uses a large orifice, quick response sprinkler within the rack (ESFR sprinklers within racks). If you haven’t read it, I would strongly suggest that you read Weston C. Baker’s article entitled Rack Rate that appears in the March/April 2016 NFPA Journal (http://www.nfpa.org/newsandpublications/nfpa-journal/2016/march-april-2016/features/rack-rate). Mr. Baker is with FM Global and he writes about an in-rack sprinkler research project that FM Global undertook in 2011. One quote from his article that jumps out at me states:
“This approach demonstrated that by using larger orifice sprinklers and higher water flow rates the number of in-rack sprinklers needed for an installation could be greatly reduced. This could lower the cost of an in-rack sprinkler installation by an estimated 40 percent, as well as reduce the likelihood of damage to sprinklers and stored products.”
Read that again—“lower the cost… reduce the likelihood of damage”. As Mr. Baker points out in his article, FM Global is achieving satisfactory results with less in-rack sprinklers by getting a quicker responding sprinkler and using a larger orifice. This results in a lower installed cost (less sprinklers being provided) and a corresponding decrease in the likelihood of damage due to fewer sprinklers likely to be hit when loading the rack. The best of both worlds here. His numbers provided in the article state that if one provides the older, traditional design, the total cost of the installation in his sample building is $3,570,200 while if one provides the newer design, the cost of the installation is $2,111,200. This is obviously significant.
The simple rule of sprinkler design is to “Put the blue stuff on the red stuff” (my adult kids still go nuts when I use this phrase.) This Aha moment states “Put more blue stuff (from an individual sprinkler) on the red stuff, quicker!”
In the opening paragraph of this blog, I state that this blog should be reviewed prior to the NFPA Conference which is taking place in Las Vegas on June 13 through 16, 2016. The aforementioned NFPA Journal article should also be read as Mr. Baker will be presenting some of the above research results on Monday June 13, 2016 at a presentation entitled “In rack Sprinkler Design Options for Warehouse Locations, A Case Study”.
The design theories that he is espousing have to make their way into NFPA 13 to be thoroughly accepted in the industry. I am sure the designs will be given a detailed vetting by the committee, but this is truly an Aha moment.
As always, I welcome your comments: firstname.lastname@example.org