NFPA 13, 2016 Chapter 11 and Chapter 23 provide information on systems that were designed as a Pipe Schedule System (as defined in Section 3.4.9). Section 11.2.2 and 23.7 provide information regarding "Ordinary Hazard" pipe schedule systems, but the storage capabilities in NFPA 13 are based on specifically Ordinary Hazard Group 1 and Ordinary Hazard Group 2 (specifically referencing chapter 13 in this situation for Miscellaneous storage).
I am working in an existing building with an "Ordinary Hazard" pipe schedule system, what are the storage capabilities of the existing system (assuming it does not adequately calculate)?
I did try hydraulically calculating the system just to see if it would work, but there wasn't enough pressure for the existing pipe configuration. A few people I have talked to agreed to stick to OH1 storage capabilities without any upgrades, but I am looking for formal guidance if anyone knows of any.
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10/12/2020 08:41:58 am
Let's not forget the OH3 curves. The old curves used to be ".1" ".18", ".24", & ".30" for the 1500 square foot design areas (understanding that this isn't a hydraulic question but Ordinary Hazard had a third option for a time).
10/12/2020 10:10:07 am
Hey Dan, good questions. The occupant of the space is changing and the new occupant intends on storing a different commodity in a different configuration than the previous occupant. The AHJ typically makes us verify the existing system is adequate for a new occupant when they pull a building permit with new rack plans.
10/12/2020 10:32:17 am
Yes, with no info the OH1 (Class 1 to <12' & Class 2 to <10' - nothing else) approach would be the safest with the caveat that you provide something in the letter stating that hydraulic calculations to current standards would be in the best interest of all parties and that your review/conclusion is only at a basic level of compliance as to the original design intent and per NFPA (site sections and adoption year).
10/12/2020 10:48:14 am
If you are saying you calculated the system for OH1 and there wasn't enough pressure, why would you stay with OH1 storage capabilities. You now have prior knowledge of an inadequately designed system for a new/changed occupancy.
10/12/2020 12:15:26 pm
Dan has some great info and good points and I would definitely approach it as Mike is suggesting. I have done a number of these and you have to put on your lawyer hat first. You do not want to be sitting on the stand being grilled by a lawyer 5, 10, 30 years down the line for something you did or did not do. My letters always state the info I received, where I got it from, the date I got it, and the 2nd part of my letter is analyzing existing storage (hopefully classified by owner, you don't want to do that for them if at all), 3rd part is analysis of what the system is capable of doing, and then the last part is the conclusion of if it works, or if it doesn't. Be very clear that water supplies can and do change over time, any information supplied by others is assumed accurate, and that you will not be liable for changes in occupancy/storage heights/storage types/storage scenarios, that could affect the system's capability of proper protection. In my opinion, this is not something you want to half A do. Be very clear of your scope, what you are doing, and then be very detailed. Or wash your hands early and put it back on owner. Don't get caught playing in the middle of the road on something like this. You should always assume its not if there is a fire event, but when will there be a fire event at this location.
10/13/2020 10:45:43 am
I fully agree with Mike's comments.
10/13/2020 12:10:47 pm
NFPA 13, 2016 section 220.127.116.11 allows pipe schedule methods for additions or modifications to existing pipe schedule systems. If the water supply requirements of Table 18.104.22.168 are met, why would the system need to be modified if the maximum storage is kept to the OH1 storage limitations. NFPA 13, 2016 doesn't provide any guidance on upgrading existing pipe schedule system based on hydraulic calculations except for Extra Hazard occupancies. I hear what you're saying from an insurance perspective, but that sounds like an opinion above and beyond the standards of NFPA 13, 2016 since there is nothing that recommends doing that. The hydraulic calculations were for the owner, but doing calculations doesn't change the fact that pipe schedule systems are allowed. My understanding is that most pipe schedule systems don't work hydraulically. If the intent is to upgrade a system every time someone decides to try a hydraulic calculation (knowing that it probably won't work), why would NFPA 13, 2016 22.214.171.124 allow the pipe schedule method to be permitted?
10/13/2020 12:41:22 pm
I would have to agree with Franck as well on this. The question is how many pipe scheduled systems have not had any changes on what is being stored, how its being stored, the height, etc... it comes down to who has asked for this "analysis" and why. Also remember that an ordinary hazard occupancy is not the same as a storage occupancy using ordinary hazard density and area for protection. There are some nuances there that you should be very careful of making from Chapter 11 to Chapter 13, or vice versa. Like 126.96.36.199 water supply requirements mention light or ordinary hazard occupancies, they don't mention storage occupancies protected by ordinary hazard design requirements. Little bit of a rabbit hole there. Now that you have proof that the system doesn't work hydraulically (even if you didn't do an analysis of storage type, height, arrangement, etc..) you are in a precarious position.
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