residual pressure/k-factor
residual pressure/k-factor
(OP)
I am new in the water industry i just started work for an overhead fire sprinkler company in the design department. For the majority its coming fairly easy, but some of the "simpler" terms are confusing to me i still have not found a good explanation for k-factor and residual pressure. Any help would be much appeciated. Thank You





RE: residual pressure/k-factor
The k-Factor is simply a constant. It is related to the size of the orifice in the sprinkler. I assume it was derived from empirical data. If you are familiar with the ideal gas law, PV=nRT. R is simply the gas constant that was derived from empirical data.
Residual pressure is simply the pressure remaining in the piping system while water is flowing out of the system, whereas static pressure is the pressure in a piping system when no water is flowing.
I don't know if this helps or makes you more confused. Some of the more intellectual guys on here can probably give a better explanation. This is basically how it was explained to me many years ago when I started in fire sprinklers.
RE: residual pressure/k-factor
The larger the diameter of the discharge orifice, the larger the k-factor. The smaller the diameter of the discharge orifice, the smaller the k-factor.
K-factor is important because it used as the basis for calculating the flow of the sprinkler using equation:
Flow [Q] = (k) (square root of minimum discharge pressure)
K-factor is established by the manufacturer of the sprinkler and confirmed by the testing laboratory. The k-factor can be modified by the designer in cases where the diameter and length of pipe nipple is used as the basis for the calculations.
As to residual pressure, see the following answer:
http://www
RE: residual pressure/k-factor
RE: residual pressure/k-factor
Are your mentors having you perform hydraulic calculations by hand before they give access to a computer program?
For your sake I hope they are.
I first started hydraulic calculations back in the early 1970's before personal computers were around and, like many of my contemporaries, I got pretty good at trees (easy), loops (not all that hard) and even simple ladder grids (it is doable).
I know it is frustrating at first but down the road you will thank them many times over. Being able to calc a system using a $20 pocket calculator, a piece of ^1.85 graph paper and worksheets will benefit you in ways you can't imagine. The biggest benefit will be when you have a problem on a computer program you'll know right what to look for in finding a solution instead of haphazardly increasing pipe sizes until "something" works.
A while back I started a project ht
RE: residual pressure/k-factor
Related to sprinklers, if you continue on this field, don´t worry, you will soon be using this term as an expert, even if you don´t feel a real need to use it.
RE: residual pressure/k-factor
tony
RE: residual pressure/k-factor
I am a FPE and I just wanted to make sure everyone knows this statement can cause confusion. Anyone who knows even a little bit about water-based fire protection system hydraulics is aware that the available residual pressure at various flow rates is critical when engineering and/or designing the systems. An incorrect water flow test (which indicates the residual pressure is higher than the actual residual pressure for a given flow rate) can lead to SERIOUS issues down the road!
RE: residual pressure/k-factor
I've done a lot of jobs over the past 32 years and, like everyone with time in the trade, I've had a few problem jobs.
I've had to reroute main because of conflicts with duct work, I've hit steel beams I didn't pick up on the drawings and I have suffered sprinkler fitters who just didn't care about craftsmanship.
But the most challenging problems I've had to deal with is when the residual pressure I thought was there wasn't.
With a good residual water pressure you can overcome about anything but it takes what seems to be an unlimited supply of money to overcome a lower then expected residual pressure.
RE: residual pressure/k-factor
Thanks
RE: residual pressure/k-factor
RE: residual pressure/k-factor
The jockey pump controller should be set to come on at 155 psi and go off at 160 psi. The 21st floor pressure gauge will be about 69 psi(21 floors if 10' high per floor is 210' times .433 = 90.93 call it 91 psi - 160 psi = 69 psi.
RE: residual pressure/k-factor
CMurry
RE: residual pressure/k-factor
-residual pressure of the system (2.2bar? @ 60L/min in the most unfavourable sprinkler head if it stands alone? or 2.2bar? @ 40L/min x 2 =80L/min when two sprinkler heads are open in the most unfavourable branch of the system)
-2.2bar?
RE: residual pressure/k-factor
And give us a link for the UK standard. We are all from America and most are from a time zone that includes the phrase "you want me to do what?"
RE: residual pressure/k-factor
We are?
RE: residual pressure/k-factor
he is right!!!
the water flow information ( static, residual, and flow) are used to size the pipe
the k-factor is a ratio that is based on volume and pressure