You can either calc it by hand using the formula and procedure as outlined in NFPA 13 or use one of the multitudes of computer programs available for calculating fire sprinkler systems.
Hi Travis
I thought I'd browse around the codes before I replied, but I'm quite familiar with them and have NFPA online also.... search as I may I find little help when consulting 13, 13R or 13D regarding the calculation of looped systems. I can calculate it as a closed end system like normal and then just qualify it by saying something about a safety factor being built in by looping it.. And of course I could purchase the software to do it for me... but I'd like to know how to calculate it myself really.
The only time I have had to do loop calcs by hand was when preparing for the NICET examinations. There are several study guides for the NICET exam that detail the process for doing the hand calculations for the looped systems.
the AFSA website for study material. However, I am not sure you want to buy the study material (Level III - IV study book) just to get that calc information.
This does it, I am going to create a website giving detailed instruction on doing hand calculations.
Looking over the archives there are a number questions on performing sprinkler calcs.
Any designer worth his salt should be able to calculate a system using a cheap (under $20) scientific calculator, yellow legal pad, a pencil and table of pipe size/ID'S.
I did my first hydraulic calculations in 1976 well before the advent of computers. Trees were simple, loops were not hard to do and grids were not defined so starting out we didn't do those.
But you should be able ot do simple ladder grids by hand.
We also didn't have the 1.2 and 1.4 * sq rt. of design ereas either. What we did was calculate the entire branch line. If you had a branch line with 9 heads one side and 8 on ther other you calculated all 17 sprinklers down through the riser nipple.
I have always been thankful for the eight years I did hand calculations it taught me how to balance a system and how, just by having one head at a higher elevation then another, a system could end up being really screwed up.
I must agree with you that starting out with hand calcs has made the understanding much deeper. I didn't get started until 1989 and we had computers, but the guy I worked for made me do hand calcs on trees for the 1st 6 months I worked in design. It really lets you get a handle on what the computer is doing when you put in all of the information.
I must admit that I did not have to hand calc any loops by hand until my NICET testing. And, based on doing those test problems, I don't want to go back to a day of doing hand calcs again
It has also been evident to me that guys starting a couple years after me and did not have to do hand calcs do not have a good understanding of the process. They can only input numbers to the computer and if it doesn't work, make the pipe bigger. It blows them away when it may actually make a system work to decrease pipe sizing ;-)
I look forward to seeing the web page if you get a chance to develop it.
"It blows them away when it may actually make a system work to decrease pipe sizing"
I often tell new designers bigger is not always better.
Your old boss served your interests well and while hand calcs are tedious at best, took me 10 years to get the callous off my middle finger, I've never regretted the insight it brought me.
New designers should not be allowed to touch a hydraulics program for the first six months.
I love you guys. Sometimes I sit at the dining room table with my fluid dynamics notebook and make sure I can still do the math. So many designers play "plug & chug" with the software and declare they are the master designers.
And I appreciate your efficency regarding pipe diameters. I had an inspector call me one day to tell me that a feed main diamater changed from 8 to 6 inches and it wasn't right. I pulled the drawings and the calculations and confirmed it was perfect acceptable. He had such a hard time understanding that smaller pipe is allowable.
From a plan review perspective I wish the software designers would at least generate consistent outputs. You must be an expert in the software's output to perform a reasonable plan review. I've become a sudo expert between Hass, SprinkCalc and some of the other less known packages in the market place. And I am still a pain in the a__ on equivalent lengths. Many a designer hates me for it but it has such an additive effect and with the new pipe diameters available, a lot of folks don't recognize this.
Stars for both of you.
Travis, we're happy your going to become Texan. Do you want to help me on a new ICC book on high piled storage?
With all due respect... though this is an engineers forum per se, it is a valuable tool for those who respect it for what it is... an excellent source of information with perspectives from both the engineers and AHJs point of view. I dare say many who frequent this site are not the seasoned veterans some of you obviously are. And I for one am a Journeyman sprinkler fitter / business manager, not an engineer. Our core business is fire protection service, dealing with everything from clean agent systems to FA panels. When I need an engineer I have several I generally use out of the south (Alberta... I'm in Yellowknife Northwest Territories).... But too, I've always gone looking for how to figure it out myself first. I hope my questions and presence here is not looked down upon. As for such a website SD2. I would love to see that also.
Your presence here is not looked down upon at all. Having a fitter's point of view is great when it comes to putting a project together that is both code compliant and practical for installation.
Welcome to the site! I hope you stick around and participate.
