Ok. I’ll bite. This is all anecdotal, but I’ve seen the inside of pipe in several nearly 20 year old, -10 deg. F. freezer systems. The reason we were tearing into these systems was because of ice plugs. Pics from some of our systems were flying around FM as they were coming up with ways to solve the problem. Those methods eventually made it into NFPA 13 (2013) 7.9.2.7. I’ve also seen the inside of way too many plugged dry systems as you describe. I don’t remember corrosion ever being an issue in the freezers. Most of these systems were sched 10.
When we pulled the supply air from the cold area, and added isolation valves above the preaction valves for the trip tests, we solved most of the problem. Some customers went further and had us add regenerative desiccant dryers. While I have no experience with nitrogen systems, I suspect they’re the best solution for the dew point reasons previously stated. However, I’ve wondered how expensive they are to maintain when supplying large, loose systems. Most of the systems we dealt with also had in-rack sprinklers with pipe that was abused by forklifts. We believed that this abuse led to leaks – especially at the grooved couplings. We thought we solved that problem by replacing ‘older’ couplings with couplings with gap seal type gaskets rated for the cold. I’m guessing the ‘rated for cold’ was more important than the ‘gap seal’ part in these areas that never see above -10F. Based on my experience, corrosion wasn’t an issue and believe me, I’ve seen it all as far as mini-dammed sched 10 dry systems becoming plugged and ‘porous’. Many years ago on this forum, after preaching about the horrors of roll grooved mini-dams in dry systems, I received the nickname “Mini Dam Dave” from a frequent poster (miss you George!). For a ceiling only freezer system, even the big ones, I’d be comfortable with sched 10, proper gaskets in grooved coups, tank mounted air compressor, with sprinkler and air supply pipes per the diagrams in NFPA13. Should one become necessary, I’d spec provisions/room for the addition of a dryer or nitrogen generator. For a large system with IRAS, I’d spec the dryer/nitrogen up front. Dave Sornsin Formerly Fargo, ND Currently Kent, WA 701.371.0643 Sornsin Fire Protection FPS, LLC From: Sprinklerforum [mailto:[email protected]] On Behalf Of John Paulsen Sent: Wednesday, October 04, 2017 7:13 AM To: [email protected] Subject: RE: Schedule 10 vs Schedule 40 pipe Thanks guys, I DO find all of this helpful, but I was hoping to hear from someone that had experience with the “environmental” conditions of this freezer project and if they had noticed that the constant freezing conditions had inhibited corrosion in the pipes. I agree that under normal freeze thaw cycles, periodic trip testing and condensate water held in the pipe by roll grooves would best be controlled by all of the points mentioned in the thread. I have seen SO many horror stories in attics over the years with plugged lines from fine scale being compacted more at every trip test. I have no trouble explaining to clients why the internal inspection of their system is a critical “must do” maintenance item. But I would like to keep the pipe sizes on this project as small as possible in order to meet the trip times required by the CMSA head that we are using. If we spec schedule 40, it essentially increases the pipe size a diameter. If it’s justified I will do so. But I have this nagging doubt that the freezing temps will preserve the schedule 10… if the seams are fabbed on top of course… From: Sprinklerforum [mailto:[email protected]] On Behalf Of Andy Kaempfer Sent: Wednesday, October 4, 2017 9:36 AM To: [email protected]<mailto:[email protected]> Subject: RE: Schedule 10 vs Schedule 40 pipe Hi John, The most effective measure would be cut grooved sch. 40 black steel using Nitrogen as your supervisory gas instead of shop air. This will eliminate the dam effect at the joint. However, the biggest value for your customer will likely be roll grooved sch. 10 black steel and still using Nitrogen as your supervisory gas. Many arguments can be made about the CRR value which is nothing more than a comparison of the thickness of schedule 40 pipe under the first exposed thread. The “first exposed thread” is the minimum pipe thickness exposed to both interior and exterior corrosion. It occurs at the threaded joint at a line defined by the thread width just before the pipe engages the fitting. There are too many factors to consider when identifying corrosion rates and this ratio is very subjective. Strictly a comparison. As for using Nitrogen as a supervisory gas I think this is definitely the biggest “bang for your buck”. In your particular instance Nitrogen provides you with more than just a corrosion mitigation solution. In particular the low dewpoint of 98%+ N2. A typical refrigerated dryer will only get you somewhere around -40°F dew point and 98% Nitrogen will be somewhere around -60°F dew point (that’s a 50% increase in humidity reduction). Hope you find this helpful. Andy L. Kaempfer Senior Application Engineer – Fire Protection Systems Bull Moose Tube Company 1819 Clarkson Road Chesterfield, MO 63017 O: 636-812-9276 F: 636-530-5880 M: 314-306-2471 [BullMooseCorporateTagline-black] From: Sprinklerforum [mailto:[email protected]] On Behalf Of John Paulsen Sent: Tuesday, October 3, 2017 12:34 PM To: [email protected]<mailto:[email protected]> Subject: Schedule 10 vs Schedule 40 pipe Hello Forumites: We are working to develop a bid package for a pair of large freezers and coolers used for food stuffs storage on racks to 35’. The freezers are to be -10 degrees and the coolers will be 31 degrees. The sprinklers systems will be double interlock pre-action with Protecto-wire detection and CMSA sprinklers. My question: The owner is asking for a recommendation on whether to spec schedule 10 or schedule 40 piping. The concern is long term serviceability of the piping system. My initial thought is that due to the constant low ambient temperatures corrosion would be seriously inhibited for two reasons; any condensate in the pipe would be in frozen form and the low temps would inhibit microbial growth. So my thought is that schedule 10 pipe would last the 20 year expected service life of the system. However, I would like to get the thoughts of the forum participants, is the cost of schedule 40 warranted or would schedule 10 service just as well in this application? Thanks in advance for your responses. John Paulsen – SET Crown Fire System Design 6282 Seeds Rd. Grove City, OH 43123 P – 614-782-2438 F – 614-782-2374 C – 614-348-8206 Disclaimer The information contained in this communication from the sender is confidential. It is intended solely for use by the recipient and others authorized to receive it. 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