Hydraulics question?

[eaglejay]

Hey, I'm in the local academy and trying to complete a hydraulics worksheet...I'm very comfortable w/ figuring out friction loss in our standard lines( 1" 3/4.....2" 1/2......and 3")....however tonite HW has a scenario involving a 4" line....Anyone know any equations which will help me complete this section?

[bobsnyder]

4" line has a friction loss coefficient of 0.20

The "equation" is the same for all hose:

FL = C * Q * Q * L

where:

C = FL coefficient for chosen hose/coupling size
Q = flow in 00s of gpm
L = hose length in 00s of feet

[eaglejay]

Thanks for the help...

[ALSfirefighter]

Bob pretty much summed it up.

Coefficient (c) Quantity (Gpm divided by 100, multiply that number by itself) Length (L) (Length divided by 100)

C x Q (squared) x L= FL

If you have any other questions like wyed or siamese lines. Please ask.

[eaglejay]

we were taught 2 ways to figure out friction loss...q squared method...but also gallonage...they just want us to know 1 way and to get it right!! they don't care which one we use...needless to say I have grown accustomed to the gallonage method...which left me in the dark to do the 4"...Although it worked out well for me and received a good quiz grade!!! Thanks for all help!!!

[Cmdr/3rdalarm]

Hey, just a quick reference. A 4 inch large diameter hose line has 10 psi friction loss per 100 ft for a flow of 1000 GPM!!!! Less than 5 psi flowing 500 GPM.

In other word vey low loss.

[bobsnyder]

we were taught 2 ways to figure out friction loss...q squared method...but also gallonage...they just want us to know 1 way and to get it right!!

If I get into situations I don't know off the top of my head, the method I actually use in the field most of the time is to pull out my handy Waterous pocket friction loss chart and look up the values I need. I'm not saying you shouldn't know how to do the actual math - because you should - but I would rather see people using a pocket chart than using one of these "rule of thumb" methods.