WorldWide Drilling Resource

60 NOVEMBER 2014 WorldWide Drilling Resource ® Water Can Hammer by Britt Storkson Owner, P2FlowLLC Often, people do not recognize the incredible forces of nature. The force exerted by falling water inspired dam- building, and power generation from tur- bines mounted inside the dam. Large quantities of water falling just 50 feet can contain huge amounts of energy. Marc Reisner, in his book Cadillac Desert, describes the 1975 Teton (Idaho) dam break that literally wiped several towns off the map. Flash flooding is a very real threat, throwing around cars and trucks like so many toys. This energy is expended by the inertia of the flow- ing water, and by the weight of the water. When designing water systems, one must consider the effect of “water ham- mer” on pipe and related equipment. While water can be a very real prob- lem, air in the water can be a much more serious problem in which the air compresses and stores energy until a critical point where it is released explo- sively...usually through the pipe as a break. To give an idea of just how much pressure is generated with water hammer, one formula used to calculate pressure rise during a water hammer condition is: P = 0.70 (VL/T) Where: P= Pressure rise (psi) above static pressure V= Velocity of flow (feet per second) L= Length of pipe (feet) on pres- sure side of valve T= Closing time of valve (in seconds) Calculations are shown for: 1-inch class 315 pipe Velocity of flow: 8.13 feet per second Static pressure: 160 psi [Formula is from Irrigation Technical Services, Lafayette, California.] So, if we have 100 feet of pipe and a valve closure time of 1 second: P = 0.70 (8.13 x 100) = 0.070 x 8.13 = 56.9 psi + 160 psi = 216.9 psi As you can see, even with small flow rates and pipe sizes, very significant pressure “spikes” are created from a 1- second valve closure. The “spike” is very short duration, but the energy dissipated has the potential to break pipe and fit- tings and make for a very bad day. Design accordingly. Britt Britt Storkson may be contacted via e-mail at michele@wwdr-usa.com In Memoriam James Emery Edwards (1961~2014) James Eme r y Edwards was born in Fresno, California, in 1961, living his entire life there. Sadly, he lost his battle with cancer on September 2, 2014. He had been an outside sales rep- resentative for Grundfos Pumps for 31 years. His daughter Ashley wrote: He was very dedicated to his job or anything he put his mind to. James is survived by his daugh- ter Ashley Edwards, brother Gary Wayne Edwards, sisters Janet Lee Majuta, Ovetta Cheryl Edwards, and his one and only beautiful granddaughter Isabela Edwards. The management and staff of WorldWide Dri ll ing Resource ® offer their sympathies to James’ family, friends, and colleagues.