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The Theory and Practice of Variable Orifice in Automatic Sprinklers VOS

The Theory and Practice of Variable Orifice in Automatic Sprinklers VOS. Fire Protection Engineering Ltd Ralph R Mehr D.Sc. PE. Q=K*P ½. Q = The Flow [gpm] P = The Pressure [psi] K = A constant Coefficient [gpm/psi ½ ]. Q= V* P ½. 5.6 gpm/psi½ ≤ V ≤ 28gpm/psi½

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The Theory and Practice of Variable Orifice in Automatic Sprinklers VOS

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  1. The Theory and Practice of Variable Orifice in Automatic Sprinklers VOS Fire Protection Engineering Ltd Ralph R Mehr D.Sc. PE

  2. Q=K*P½ Q = The Flow [gpm] P = The Pressure [psi] K = A constant Coefficient [gpm/psi½]

  3. Q=V*P½ 5.6 gpm/psi½ ≤V≤ 28gpm/psi½ 7 psi ≤P≤ 175 psi

  4. V=a*Pb V=2.12*P1/2 Q=2.12*P

  5. The size of V as a function of the Pressure P

  6. V performance compare to K

  7. Add-on Devicestand-by position maximum pressure

  8. Special Sprinklerstand-by position maximum pressure

  9. Insert to a Large SprinklerThe Insert stand-by maximum

  10. Final Conclusions The Variable Orifice Sprinkler can operate within a wide range of pressures. The Variable Orifice Sprinkler demonstrates a high degree of flexibility, and can operate at all kinds of hazard occupancies from light hazard to extra hazard and special hazard, including storage etc. As the first sprinklers deliver much more water, it is expected that fewer sprinklers will be needed to control or even to suppress the fire, as a result, less water might be needed and less water damage is expected.

  11. Recommendations for additional research Determination of the optimal function of V in the basic equation (Q=V*P½) so that the first sprinklers will deliver the maximum possible water, while all sprinklers calculated will deliver a total amount of water, as required by the standard. As the insert type device seems to be the most cost effective, the insert should be designed to best comply with the optimal function of V. A full scale research to re-determine the minimum number of sprinklers needed for each occupancy hazard should be performed. Investigation to determine if the VOS fulfils the criteria of Quick Response Early Suppression sprinklers (QRES) as defined by the standard (Budnick & Fleming) which may improve the Fire Protection Level with much less water.

  12. Thank you Fire Protection Engineering Ltd For more information or a copy of the research please send an e-mail to mehr@fpe.co.il

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