It must be recognized by all who perform hydraulic calculations, NFPA 13 does not require a separate or distinct “cushion” to be provided on the sprinkler system’s calculations. (Some people will use the term safety factor, hydraulic buffer or safety margin. Whatever term is used, this refers to a pressure margin below the water supply curve. The remainder of this document will use “cushion” because a safety factor to me implies it should be present.) In fact, NFPA 13 does allow one to design to the water supply curve. In fire protection, the Law of Supply and Demand can be stated as “The supply must be equal to or greater than the demand” or vice versa “The demand must be equal to or less than the supply”.
Recently this universal law has come under question and in the last NFPA 13 code cycle, there was a submittal requiring one to determine and apply a cushion to the water supply. This change did not make it into the 2016 edition of the standard; however, it appears that this is becoming a concern in the industry. The issue is so critical to 13 that the Fire Protection Research Foundation recently published a report entitled “Quantification of Water Flow Data Adjustments for Sprinkler System Design.” (http://www.nfpa.org/research/fire-protection-research-foundation/projects-reports-and-proceedings/suppression/other-sprinkler-protection/quantification-of-water-flow-data-adjustments-for-sprinkler-system-design)
The stated goal was “to identify the variables in water supplies that affect hydrant flow tests, which are used in the design of water based fire protection systems. The results of this research are intended to be used to establish recommendations for adjustment to water supply data to be used for the design of fire protection systems. Adjustments would be necessary to ensure that data used for design of fire protection systems represents the actual water supply system conditions during peak demand, accounting for parameters such as tank level during testing and normal system operations.”
A pretty ambitious goal! In reviewing the goal further, it seems like the conclusion is built in. The goal is to establish recommendations for adjustment to water supply data. Should not the initial goal of such a study be to determine if there is a need for adjustments? I keep going back to Chet Schirmer’s question as chair of the 13 committee whenever a change was proposed—“Where is America burning?” (For those of you not familiar with Chet Schirmer, he was a previous chair of the 13 committee and one of the individuals who developed the initial criteria for rack storage.) As they say in Missouri, the Show Me state, show the industry where the lack of adjustments to the water supply is causing system failure. Whatever happened to the adjustments to the water supply that I was told had to be done for any design? It was hammered into me during my early life as a designer—Perform the flow test then adjust for seasonal low pressure, then adjust for time of day low pressure. If we do all this, then why is there a need for additional cushion? From the discussions during the writing of NFPA 13, it appears this is not being done. One is just taking the water flow test at any time of the day or year and using it in the calculations. If the fire occurs on that day, at that time, I guess we are covered.
The other item hammered into me is there are natural safety factors built into hydraulics that one should recognize. These factors include:
• What is the likelihood that the fire will occur when we are experiencing the seasonal and time of day low pressure? • What is the likelihood that the fire will occur at the hydraulically most remote part of the building? • What is the likelihood that the fire will grow 1.2 times bigger in the direction of the branch lines? Or better yet, how does the fire know which way the branch lines are running? • What, in actuality, is the hose stream allowance? • When the first sprinkler discharges, what density is it putting out? The initial sprinkler doesn’t discharge at a rate of 0.1 gpm per square foot. • What is the impact of velocity pressure on the system demand? Velocity pressure will normally lower the demand but is not frequently considered. • How many fires actually reach 1,500 square feet? In 1970, NFPA Fire Journal published an article entitled Automatic Sprinkler Performance Tables which showed that 7 or less sprinklers on a wet pipe sprinkler system operated in 85.2% of fires. (Seven was used as the value because this represents the minimum number of sprinklers in a light hazard occupancy design.) • How accurate is the Hazen Williams formula in calculating pressure drops? The Hazen Williams formula was developed for low flows in large pipes. It is conservative when applied to sprinklers. There have been numerous studies presented to the 13 committee arguing for the use of Darcy-Weisbach formula.
With all the safety factors built in, I would pose the question again—is an adjustment necessary? I would also amend the question to state “Is an adjustment necessary when the pressure is already adjusted for seasonal and time lows?”
As outlined in the Research Foundation report and as any contractor can tell you, many municipalities require a cushion to be provided. The supply curve shall be reduced by 5 psi or the supply curve shall be reduced by 10%. I came across one where the statement was made that the initial sprinkler discharge pressure shall be increased by 10%. This compounded itself every step of the way. US Department of Energy 1066 Standard required 10 psi safety margin from the water supply curve. FM Global limits velocity pressure to 20 fps which effectively builds in a cushion.
If you are in a jurisdiction and uncomfortable with a design to the curve, then by all means, mandate a cushion. But please make the required cushion apply to all projects and write it as an amendment to the standard so that the contractor is aware of it and can design accordingly. This appears to be what the NFPA sprinkler committee is trying to decide. Determine if a cushion should be required and then come up with a method so that one can design an appropriate system keeping in mind that the “purpose of this standard shall be to provide a reasonable degree of protection for life and property…” If we didn’t care about costs, we would mandate a private tank and fire pump for all systems.
The last item to discuss can be summarized with one line—“I measured with a micrometer and cut with a chain saw.” To those of you who have done flow tests on a cold day in January, you know that the accuracy of the test is inversely proportionate to the temperature of the air. The colder it gets, the quicker I can read the gauge. The gauge that is flickering as I gently locate the pitot tube by hand, ½ the diameter into the stream coming out of the hydrant, ½ the diameter away from the hydrant. That flickering gauge sets the water supply and is the criteria that determines the entire design of the sprinkler system. Maybe this is the reason for cushion—people are finally recognizing that there is an inherent inaccuracy in the flow test itself that one needs to compensate for.
Next month I plan on talking about some serious deterioration in water supplies that I have observed and go back to NFPA 25 once again.
As always, I welcome your comments: j.schultz@the-fpi.com
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: j.schultz@the-fpi.com
Today, let’s talk about NFPA 25, Standard for the Inspection, Testing and Maintenance of Water Based Fire Protection Systems and discuss one of the biggest gaps in the industry. I believe that most people in the fire protection industry, understand and accept this gap but does that make it right and how can the fire protection industry deal with such a large gap in ensuring proper protection? Several years ago, there was a round-table discussion organized by NFPA that took place in Chicago where the gap was a key point in the discussion. It was decided at that point, 25 was not going to address the issue and the issue would have to be addressed in another manner.
The gap which I speak of is, who inspects the sprinkler system for adequacy? Who reviews the building to assess changes? Who evaluates the protection in the building and comes up with the conclusion that the system is adequate and that the building is properly protected? It clearly states in the Appendix A.1.1.3.1 of NFPA 25 that it is the property owner or designated representative’s responsibility to evaluate the adequacy of the design. There is some merit to this argument. For example, an AHJ in Illinois can require, per the Professional Engineering Act, a technical submission by a registered engineer developing the fire suppression system’s criteria for a facility. The layout of the fire suppression system has to be done by either a licensed engineer or a NICET Level 3 individual. During the initial design, there are attempts to ensure that the system being provided is adequate for the hazard.
It is after the initial design that the gap starts to appear. In a typical commercial office building, where reconfiguring of offices is routine, one would not anticipate the fire hazard to significantly change. The firm doing the inspection may notice sprinklers missing from rooms due to wall reconfiguration or similarly sprinklers too far from walls. In a warehouse however, the occupancy can have significant changes occurring. Storage creeps higher, racks are introduced in lieu of general storage, racks are reconfigured so that aisles are narrower and perhaps the biggest one, the commodity itself changes. This can be as simple as the “plasticization” of society. Everybody knows that plastics will burn “hotter” or more severely than ordinary combustibles. “Everybody” knows this, but is the warehouse manager aware of the implications? I cannot forget telling an owner that their sprinkler system was under-designed for the hazard when their domestic garden hose reels went from all metal to all plastic. I had to deal with three comments, all from the same client—
What are you talking about? I am still selling hose reels.
I want that previous inspector because he never cited me.
How can you say I am under-designed? I have not had a fire here in 20 years!
As I stated in the beginning, NFPA 25 clearly indicates that adequacy is not part of the inspection process. Starting in Chapter 1:
1.1.3.1 This standard does not require the inspector to verify the adequacy of the design of the system.
The burden is placed on the owner (or designated representative) to watch what is being stored and how it is being stored in Chapter 4.
4.1.6 Changes in Occupancy, Use, Process, or Materials. The property owner or designated representative shall not make changes in the occupancy, the use or process or the materials used or stored in the building without evaluation of the fire protection systems for their capability to protect the new occupancy, use, or material.
To further amplify that 25 never meant to have the assessment of the adequacy be part of the Inspection, Testing and Maintenance it states in Section 4.1.6.1 that the evaluation above is not part of the normal inspection required by NFPA 25 but does go on to say what it should address including occupancy changes or process changes.
And then NFPA 25 goes one step further (Section 4.1.7.1) and tells what the owner should do to address changes in the hazard including promptly taking steps to evaluate the adequacy and if the evaluation reveals the system is inadequate, the owner shall make the required corrections.
If the issue is still not clear, the committee makes it extremely evident with Annex comments:
A.1.1.3.1 The requirement to evaluate the adequacy of the design of the installed system is not a part of the periodic inspection, testing, and maintenance requirements of this standard. However, such evaluation is the responsibility of the property owner or designated representative as indicated in 4.1.6 and 4.1.7. A.4.1.6 The inspections and tests specified in this standard do not address the adequacy of design criteria or the capability of the fire protection system to protect the building or its contents. It is assumed that the original system design and installation were appropriate for the occupancy and use of the building and were approved by all applicable authorities having jurisdiction. If no changes to the water supply or to the building or its use have transpired since it was originally occupied, no evaluation is required. If changes are contemplated, it is the owner’s responsibility to arrange for the evaluation of the fire protection system(s). Where the inspections and tests specified in the standard have been contracted to a qualified inspection provider or contractor, it is not the role of the inspector or contractor to determine if any changes have been made or the subsequent evaluation of the fire protection system. The evaluation of any building changes should be conducted before any proposed change is incorporated and should utilize the appropriate installation standard and input from applicable authorities having jurisdiction. Fire protection systems should not be removed from service when the building is not in use; however, where a system that has been out of service for a prolonged period (such as in the case of idle or vacant properties) is returned to service, it is recommended that a responsible and experienced contractor be retained to perform all inspections and tests.
The gap should be obvious. The owner is paying for the Inspection, Test and Maintenance of his sprinkler system. He is hiring a licensed qualified contractor and is not being told that his sprinkler system is under-designed. We expect him to recognize the change in the hazard and take steps to evaluate it. This from an individual who may have been convinced by Hollywood that when the sprinkler system actuates, all sprinklers will begin to flow. (It must be understood that this comment does not apply to clients of The FPI.)
If not the owner and not the contractor, then who (or whom)? The insurance company? They are setting insurance rates on buildings based on the adequacy of the system. If a system is inadequate, they may just adjust the rates. In addition, certain insurance companies do not have a qualified fire inspection program. The building inspector? In most municipalities they don’t have the time to do follow up inspections. The consulting engineer? They have to be retained to do this (speaking as a consulting engineer it would probably make sense to make it a mandatory law that consulting engineers should inspect each building annually and write a report on the adequacy, but alas, not many people agree with me.)
Without the requirement that a consulting engineer be involved, how can a municipality be comfortable that the system is still adequate for the hazard? One way that seems to be gaining momentum is through a high-piled storage permit process. Certain municipalities require an annual application for a high-piled storage permit. Table 1.12.8(a) in the 2015 edition of the NFPA Fire Code (NFPA 1) and Section 105.6.23 of the International Fire Code requires an operational permit to “use a building or portion thereof as a high piled storage area exceeding 500 square feet”. It is this permit, if done properly, that can be used to evaluate the existing sprinkler system. This should not be a fundraiser for the municipality (submit your fee and we will file your drawings) but should be a way to evaluate what is present and if it is adequate. Certain municipalities require a drawing to be submitted identifying the storage arrangement, commodity classification and protection provided such that a knowledgeable individual can review the information and reach a decision if a problem warranting further investigation is necessary.
There are several key steps in using a high-piled permit in this way. These steps include:
The high-piled permit request form must clearly state what information is required. This information must include:
Commodity classification
Storage arrangement (racks-single, double-row, multi-row, shelf storage, pallets, etc.)
Aisle widths
Encapsulation
Solid shelving
Storage height
Sprinkler criteria
In general sufficient information to review and assess the adequacy.
A qualified individual working for the city must review the criteria and assess the design.
Random follow up inspections should be done to ensure that the information provided is correct.
The owner spends money buying a properly designed sprinkler system for their building. It is necessary that some form of evaluation be done to ensure that as conditions change, the system is still capable of controlling the fire. John R. Hall reports in the document U.S. Experience with Sprinklers, two reasons for sprinkler system failure are: Not enough water discharged to control the fire; and inappropriate system for type of fire. Both of these reasons can be reduced by the review of the adequacy of the system.
As always, I welcome your comments: j.schultz@the-fpi.com
