thread184-206768

[UFT12]

thread184-206768

Interesting to read. SprinklerDesigner2 hopefully you never had issues there.

One thing I would like to note though, mainly for my understanding, is that the 149 psi for a standard 2 1/2" hydrant butt (refered in post Nr 8) is understood as the pressure difference exerted on the hydrant alone, which means practically 149 psi in the input of the hydrant since always flowing to the atmosphere. In the 6th post however, it seems that the K factors cited are derived from the entire pressure loss between water supply and hydrant outlet, not just the hydrant itself and therefore the factors should not be directly comparable.

Am I getting it wrong?

 

[UFT12]

OK so after doing some research the k factors seem comparable since the residual pressure is measured on the hydrant just before entrance to the opening. Got confused by typical pump curves.

Side note, NFPA fire protection handbook has graphs of various orifices including those of fire hydrants and it seems the k factor for a 2 1/2" outlet hydrant comes to an around 180 for most of the pressure range shown. I guess relying on a fixed K factor for any 2 1/2 hydrant may not be the most reliable approach.

 

[cdafd]

https://www.akronbrass.com/media/pdf/HK_Instructions.pdf

Page 2 help you in any way

 

[UFT12]

Thanks cdafd

it did.

 

[SprinklerDesigner2]

I seem to remember FM once figured a k-factor at 260.

Actually I mistyped the 260 should have been 160.

Of course this number will go down under certain conditions. If we have a large circulating main we can expect numbers from 150 to 160 but let's assume we have the flowing hydrant on a 6" dead end main 800 feet from the static and residual hydrant then the K-Factor will be lower as we have to take in mind the friction loss from the test to flowing hydrant.

I should add I never use these for calculating a system but I do use it as a smell test. If I have a static of 60, residual of 55 flowing 660 gpm then something might be wrong. At 55 residual we can expect a flow of around 930 gpm so what's wrong?

 

[UFT12]

improper flushing I guess...