Operating Pressure Vs Residual Pressure
Operating Pressure Vs Residual Pressure
(OP)
Is there any difference between operating pressure & residual pressure of sprinkler head. When NFPA 13 says operating pressure of sprinkler = 25psi what does it mean?





RE: Operating Pressure Vs Residual Pressure
http://www.eng-tips.com/viewthread.cfm?qid=193757
RE: Operating Pressure Vs Residual Pressure
RE: Operating Pressure Vs Residual Pressure
I take it that is the minimum pressure any head in the system is required to have to work properly
cannot address the high pressure, as long as you are not over 175 on the system, there is nothing extra needed
what they said again:::
http://www.eng-tips.com/viewthread.cfm?qid=235664
can I ask what you do for a living???
RE: Operating Pressure Vs Residual Pressure
You system demand at the base of the riser will be >y in almost all cases, unless your base of riser is far above your sprinklers.
Example: K17 ESFR at 44' elevation. The minimum sprinkler demand pressure is 52 psi. 44' of elevation is going to add 19 psi. You will likely have somewhere around 30 psi of friction losses, depending on pipe sizes. So, the base of riser pressure would be 101 psi. There would be extra pressure requirements if you have a backflow preventer or other devices in the riser assembly.
Hopefully this makes sense.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: Operating Pressure Vs Residual Pressure
Cdafd, M mechanical Engineer working in Middle East.
Travis, Your example raises one more question. How you have minimum sprinkler demand pressure as 52 psi. It depends on total no. of sprinkler. right? If you consider 20 sprinklers then the pressure will go much higher than what you described.
RE: Operating Pressure Vs Residual Pressure
RE: Operating Pressure Vs Residual Pressure
If it is for the most remote sprinkler then the pressure at the inlet riser will be too high which is surely wrong.
If it is for all the 20 sprinklers ( 50psi for 20 sprinklers) then the last sprinkler will not get minimum operating pressure. Travis already gave one example but number of sprinklers there are not clear.
I hope I am clear with my question this time and am waiting for your responses.
RE: Operating Pressure Vs Residual Pressure
1. Determine Density / Area requirements
2. Evaluate Possible Hydraulically Remote Areas
3. Measure out the area of operation
4. Measure out each sprinkler area
5. Calculate flow at remote sprinkler Q = density x area
then use Outlet formula to determine Pressure at that point
6. Follow a path from the remote head to the supply point for each pipe along that path:
a) Use pressure at pipe start point to calculate flow from any sprinkler
b) Add sprinkler flow to previous pipe flow
c) Use dia, length, accumulated flow and roughness to calculate friction loss
d) Use elevation differences between pipe ends to calculate elevation pressure
e) Calculate pressure at other end of pipe: P 2 = P 1 + P e + P f
RE: Operating Pressure Vs Residual Pressure
21 to 33
http://aucache.autodesk.com/au2011/sessions/5517/n...
RE: Operating Pressure Vs Residual Pressure
This is a CMSA design so it does not use the conventional discharge density/design area method. Also, it is inappropriate to reference some dribble out of an Autocad manual when the governing criteria is NFPA 13.
In this case the designer determines the 20 most hydraulically most remote sprinklers and calculates the design so that each of the 20 sprinklers has a minimum discharge pressure of 50 PSIG. This is a more demanding design because it is based on a minimum pressure rather than flow rate.
RE: Operating Pressure Vs Residual Pressure
RE: Operating Pressure Vs Residual Pressure
Maybe find a fire protection engineer near you to design or help with the design
I read you need whatever the manufacture says is the minimum pressure for the head to work per its listing
RE: Operating Pressure Vs Residual Pressure
Maybe looking at the manufactures design criteria might help answer your questions
http://www.vikinggroupinc.com/databook/sprinklers/...
RE: Operating Pressure Vs Residual Pressure
Travis Mack
MFP Design, LLC
www.mfpdesign.com