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Found my next ex-customer

Discussion in 'Irrigation' started by DanaMac, Oct 16, 2010.

  1. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Really? Provide the quote ... or is this another case of you putting words in my mouth?

    I think it is more like you are ignoring how water hammer is reduced by a slow closing valve. If you worked the equations it would become abundantly clear.

    Perhaps, since you obviously can't work the equations, find a ball valve, put in a pressure gage upstream of the ball valve, a flow gage downstream and record the variation in pressure and flow as you test different closing speeds. If that does not make it crystal clear for you .... then you will never understand.

    I don't locate irrigation valves to prevent water hammer Pete. I pick a location that is relatively central to the zones being irrigated, with consideration to the source location. I have stated this on many occasions.

    But since you insist, locating the valve closer to the hydraulic grade line and main water source (reservoir) would a be more effective location to minimize the effects of water hammer due to a closing solenoid valve than locating the valve further from the source.

    Why?

    1. You eliminate long runs of pipe to the valve.
    2. You are closer to a larger body of water which will dissipate any resultant hammer much quicker. For resi/comm irrigation that means the POC.
    3. You are not adding to the hydraulic head like you would be by placing the valve at the lowest point of the site.

    If I must have a long run of pipe to valves, and there is a risk of significant water hammer .... then I will spec an appropriate master valve (griswold or actuated ball valve) close to the source in order to minimize the potential for hammer. Just in case you weren't aware Pete .... actuated ball valves don't slam shut.
     
  2. If the zone valve slams shut before your slow closing master valve not sure the cost was worth it. Maybe you have a controller that shuts the MV 10 seconds before the last zone valve.

    My reference to putting the valve at the bottom was in response to putting the valve at the top. One would create a noticeable hammer the other would not. I explained in detail that I would center the valve and set it lower than the initial lateral line. The valve is described as having two chambers but I see it as having three chambers. The one above the diaphragm, the inlet port from the main line, and the chamber the water flows into after the valve opens. Making sure water is not leaving that chamber faster than it is being replaced when the valve closes is important. the reverse can be true as well. Too much back pressure into that chamber from a low valve. Centering it and lowering it below the initial lateral always assures that chamber will be full of water when the valve closes and assure the water will not be going through the valve at a greater speed than 5fps assuming that was the designers intention. Water is a much better shock absorber then air.

    My other guess is you have given very little thought to installation caused water hammers. In a flat terrain with 1" valves that is probably no big deal. Get into 2" plus valves on a hilly terrain (golf courses come to mind) and you better think about it.

    I don't think we will be seeing any 1.5" ev avb combinations sticking up in rows anytime soon.
     
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,415

    Sure they slam shut, only very slowly :p
     
  4. We aren't dealing strictly with the equipment 99% of us use that's for sure.
     
  5. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Thing is .... I didn't say anything about valve placement until my last post .... so what exactly were you "responding" to? Furthermore, why are you certain it will create a "noticeable" water hammer? I have seen plenty of installations that are within 2 feet of the buildings water service entrance that operate with no "noticeable" water hammer.

    Care to show that "logic" mathematically? :dizzy:

    It is? Air is compressible .... water is essentially incompressible. Guess you have never seen air filled shock absorbers before. Perhaps you would care to explain this jewel of logic?

    What part of adding to hydraulic head and keeping the valve closer to the hydraulic grade line did you not understand?
     
  6. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    You have never used a master valve? :rolleyes:
     
  7. Explode a bomb in air and see how far it travels. Explode a bomb under water and see how far it travels. I can assure you nobody wants a car shock situation in their irrigation system.

    A valve next to a house in a level terrain is no big deal. A valve next to a house that slopes downward is different. The more steep the slope the more one needs to take into consideration.

    Your avg irrigator isn't putting his systems in with a slide rule. He's putting it in with common sense and experience. When one needs to take extra precautions and when one doesn't is an experience factor. To my knowledge I have never created a water hammer situation but I've repaired many of them.
     
  8. Used many a mv but never a Griswold or ball actuated as 99.9% of other irrigators.
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,415

    Griswold valves were featured in National Lampoon Vacation movies :)
     
  10. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    No comment .....

    What does this have anything to do with a closing valve?

    Only boots uses a slide rule.

    Perhaps because you think there must be a noticeable condition for water hammer to exist?

    You do realize how bad of a contradiction this statement is .... don't you? Guess that means you have never installed a solenoid valve then.
     

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