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Preparing for NICET Level III CBT Exam - Hydraulics

Preparing for NICET Level III CBT Exam - Hydraulics

Preparing for NICET Level III CBT Exam - Hydraulics

So after a few years of procrastinating to get NICET certified, I finally started taking the tests this year.  They changed to CBT at the end of last year which has certainly made the testing process smooth.  Now I'm ready to take level III, and I'm concerned about the hydraulics portion.

I have only ever performed calculations using software.  I started off using HASS and inputting each length of pipe, each node, etc.  After about a year of that we switched to SprinkCAD which spits the calculations out in seconds once the pipes and sprinklers are laid out and sized on AutoCAD.

I'm aware of how hydraulics work and the fundamentals, but with no hand calculation experience I'm concerned that I will be too slow without some practice.  I've practiced a couple times with small tree systems with my own calculations and the one in the back of NFPA 13.  I've never practiced with a gridded system though.  So here are my questions:

Would anyone have a recommendation for a good source(s) to study or practice?

Is there anything in NFPA 13 that details how to distribute the flow in a gridded system?

For those that have experience doing hand calculations, are there any shortcuts that you've ever used with the HW formula?

The only one I was thinking might help would be to setup a table that has already calculated the denominator using C's of 100, 120, and 150, and different pipe sizes and schedules.  I could at least see saving some time using something like that.  My main concern is knowing how to do the calculations, but failing to finish 25% of the questions because I took too long performing them.

RE: Preparing for NICET Level III CBT Exam - Hydraulics

For Level III, you only have to do a simple tree system.  You don't have to do a loop and/or compound loop until Level IV.  Just do a few practice runs and compare them to the results the computer gives you.

The biggest mistakes I saw when helping people study for it was forgetting to adjust the equivalent length of fittings for non sch 40 pipe.

Travis Mack
MFP Design, LLC

RE: Preparing for NICET Level III CBT Exam - Hydraulics

I am thankful I started my career in the mid 70's before the advent of the personal computer.  We were doing hydraulic calculations but everything we did was by hand.

Lots of loops and it was trial and error.  120 gpm this way and 140 gpm that way and see if the total head loss on each side balanced.  If it didn't then maybe 115 gpm that way and 145 gpm might work.

Got pretty good at guessing and we'd usually hit within 1/2 pound after three or four "iterations" taking maybe 20 minutes.

I would like to impress you saying I used Hardy Cross for grids but I wasn't that smart.  I always set the grid up to be center feed wherever possible and over sized both far and near main to minimize the loss making calculations easier.  

From here it was back to trail and error and I remember a k-mart store I did taking me 2 weeks to just do the calculations on three systems.  I had a callous on my writing finger you would not believe and it is still there 33 years later.  But this again was back in the days when we weren't NICET and worked 60 hours to earn half as much as a union fitter earned in 40 hours.

While Viking had tables in the back of their book (sch. 40 only) But I always made up my own set using N^1.85 graph paper.

You can actually get everything on one piece of graph paper.

Also works exceptionally well for visualizing loops.

RE: Preparing for NICET Level III CBT Exam - Hydraulics

Before computers I used to do this to visualize a loop is easy or even a feed to a system through three or four different mains of different sizes and lengths.


Flowing 1,350 gpm the 900 gpm is going to flow through the 6" pipe developing a friction loss of 25 psi which means 450 gpm will flow through the 4" developing the same 25 psi friction loss.  

Regardless of total flow 66% of the water will always flow through the 6" loop so if we needed 1,800 gpm total 1,188 gpm would flow through the 6" developing a friction loss of 43 psi while 612 gpm would make up the difference through the 4" developing the same 43 psi friction loss.  You could do this with a multiple of different mains and as long as they all connected at the same point it is accurate enough for our use.

RE: Preparing for NICET Level III CBT Exam - Hydraulics

I took an online course from Oklahoma State University.  It helped me out a ton.  It is called Hydraulic Caculation of Automatic Sprinkler Systems Online Course.  It is under the continuing education link on the web.

RE: Preparing for NICET Level III CBT Exam - Hydraulics

Thanks for the responses.  SD2, I think that I would be happier now if I had been forced to learn this stuff the hard way.  As it stands I feel way too dependent on the computer.  Now to get certified I will be forced to learn it one way or another.

After my initial post I dug through some older posts on this forum and found (another of your suggestions, SD2) the NFSA book so I ordered that and am studying from it.  I'll likely do my best studying from that for my exam in a couple weeks.  If it ends up being more than I can handle then I guess I'll have to look into the online course.

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