This calculator will produce the results based on the parameters entered. Velocity change, pipe run, material and sizing all are functions that influence the resultant surge. These calculations are based on water (62.4 lb./ft3) and transmission within irrigation systems.
| • Basis of Calculation • |
- A - Wave velocity is the speed of the pressure surge/wave through the pipe. The constant of 4660 used, is the velocity (ft./sec.) of sound in water at 72 F.
E - Modulus of elasticity, in tension, of the pipe materials.- 400,000 = PVC
- 150,000 = HDPE
- 17,600,000 = Brass/Copper
- 30,000,000 = Cast Iron
K - Bulk Modulus of elasticity, of the fluid in the pipe.- Water = 300,000 psi.
Tc - Critical Valve Close Time is the minimum time needed for the valve to reduce the actual flow of water, without producing a surge.- TYPICALLY, IN ELECTRIC VALVES MORE THAN 80% OF FLOW (VELOCITY) IS REDUCED IN THE LAST 30% OF THE TIME. (FROM THE 'CLOSE' SIGNAL TO ZERO FLOW)
V - Velocity change, of the fluid within the system. Generally, flow velocity *LESS* than 5 feet per second, is considered to be *SAFE*. Higher velocities may be used in cases when the operating characteristics of valves and pumps are known so that sudden changes in flow velocity can be controlled.
| • • • • Caveat • • • • |
The information and calculations provided are based on data which we believe is reliable. Expert4PVC Consulting, however can not take responsibility for the information or data contained herein and no warranty of performance for any specific purpose or particular installation of any product is expressed or implied from this calculator. Results based on the equations shown and parameters entered.
