I wouldn’t agree that it isn’t a real-world issue. Years ago, I had a deluge system in an air craft hanger bend the hangers/supports on the risers during the trip testing. Bracing against the impact forces is strongly recommended.
I’ve even seen wet pipe systems mains that shifted out of position, due to the client wheeling open control valves and filling them to quickly. Larry Keeping From: Sprinklerforum <[email protected]> On Behalf Of Skyler Bilbo Sent: March-12-19 10:56 AM To: [email protected] Subject: Re: Water hammer in Dry or deluge systems Craig, I have run into a very similar scenario. I had a real concern with so much water hitting every change in direction and dead end with a lot of force. All of the deluge valves that I know of go from being closed to open full bore, as quickly as the clapper can open (fast). Also, it is important to realize that the water will not move through at the designed minimum flow rate, but probably much faster. In our case, we installed seismic bracing at every elbow and near any dead ends. This wasn't engineered, as I'm not aware of any guidelines or requirements for designing this bracing. It seems to me that this is a similar concept to thrust block design for underground piping (where the forces in a 6" elbow can easily exceed 5,000 lbs and substantially higher than this in larger sizes), but there are definitely some differences. If nothing else, the braces provided me with some peace of mind. I felt it was important to make sure that the braces were installed and oriented correctly. I also made sure that no one entered the area when we did the startup testing, and everything went well. The bracing definitely helped. Thinking about this more - hopefully someone will chime in... The total pressure (velocity pressure + normal pressure) should never exceed your initial static pressure. If you design braces to handle this full initial static pressure times the area of whatever size pipe you have (pi * r^2), I would think this would be a safe calculation. Again, I hope someone chimes in on this. I have been wrong more than once, so don't just take my word for it. I just read Roland's response. It's good to know it hasn't been a real world issue. I know that I was pretty nervous about it when my name was attached to it. The cost of the braces was worth it to me. - Skyler On Tue, Mar 12, 2019 at 8:59 AM Prahl, Craig/GVL <[email protected]<mailto:[email protected]>> wrote: So, I’ve got an FPE and ME questioning about water hammer in a deluge system. We have a unique installation where we have two levels of hose connections (one array at 12 ft AFF and one at 60 ft AFF) for manual firefighting in an unconditioned assembly building which is 145 ft high. Due to the non-heated condition, one proposed concept for a semi-automatic system is to use an electric release deluge valve to charge the system from manual pull stations. Flow rate will be 1,000 gpm at somewhere near 150ish psi though 600-800 ft of pipe inside the bldg. The FPE and ME are concerned with water hammer in the piping when the deluge valve opens based on how fast the valve opens. Has anyone dealt with or had to provide calcs for this? NFPA 13, 14, etc. are fairly silent on the issue. Is it even an issue? I’ve never had this brought up before on an interior system. Anyone have any data on how fast a solenoid operated deluge valve opens? Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | [email protected]<mailto:[email protected]> | www.jacobs.com<http://www.jacobs.com/> ________________________________ NOTICE - This communication may contain confidential and privileged information that is for the sole use of the intended recipient. Any viewing, copying or distribution of, or reliance on this message by unintended recipients is strictly prohibited. If you have received this message in error, please notify us immediately by replying to the message and deleting it from your computer. _______________________________________________ Sprinklerforum mailing list [email protected]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
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