Valve Tips

Discussion in 'Irrigation' started by Ron Wolfarth, Jul 22, 2014.

  1. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,367

    I'm pretty sure those ITT solenoids came directly from hydraulic or pneumatic control applications, which probably would have pre-dated lawn sprinkler diaphragm valves. So, with water instead of air or hydraulic oil, they performed differently.

    Speaking of water, I know there is a component I liked in old Rainbird diaphragm valves that would make today's irrigators say "Huh?" ~ I speak of the "Fluid Resistor"
  2. Ron Wolfarth

    Ron Wolfarth Sponsor
    Messages: 997

    A water hammer reduction strategy.
    Posted via Mobile Device
  3. SoCalLandscapeMgmt

    SoCalLandscapeMgmt LawnSite Silver Member
    Messages: 2,128

    I still have a ton if those in stock. Back in the day I used to tear down and rebuild brass RB valves on a regular basis!
    Posted via Mobile Device
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,367

    I didn't have too many to deal with. I know the first time I brought a diaphragm assembly to a job, was the first time I learned that there was a change in the design of the RB brass valve that made the part I brought with me unfit for the job. I know I spent some minutes looking at the two diaphragm assemblies, wondering what the design change achieved besides royally ticking me off. :realmad:
  5. SoCalLandscapeMgmt

    SoCalLandscapeMgmt LawnSite Silver Member
    Messages: 2,128

    Revenue increasing strategy for RB. It meant that you had to stock TWO different diaphragm assemblies and RB sold twice as many diaphragms! :dancing:
  6. Ron Wolfarth

    Ron Wolfarth Sponsor
    Messages: 997

    Why does water pressure influence the maximum wire run on a valve zone?

    In the charts Rain Bird provides customers that show the maximum wire run for different size wires there are multiple tables with the only difference being the water pressure at the valve. It is not very intuitive that water pressure would have an effect on electrical performance.

    When electricity is provided to the valve solenoid, the coil in the solenoid creates a magnetic field that magnetizes the metal core in the middle of the coil. This magnetized core acts on the metal plunger pulling it up off its seat where it has acted like a drain plug in a sink of water because, like our residential valves, our solenoids are ‘reverse flow.’ This means that the ‘plug’ is on the upstream side of the drain.

    In a sink of water, the deeper the water, the harder it is to pull the drain plug off the seat. The weight of the column of water above the plug is pushing against it. More work is required to lift that heavier column of water.

    The same thing happens in the solenoid. The more water pressure, the more pulling force is needed to pull the plunger off its seat.

    As water pressure increases, a stronger and stronger magnetic field is required. This is where the length of the wire run becomes a factor. The maximum wire run is determined by the minimum voltage required to operate the valve. We run tests to determine that minimum voltage. At higher water pressure, more voltage is required because a stronger magnetic field is required. The minimum voltage needed to operate the valve is reached in shorter wire length runs. Larger wire results in longer runs because there is less voltage drop in larger wire.
  7. Sprinkus

    Sprinkus LawnSite Silver Member
    Messages: 2,304

    Remember this from our good friends at WM? No other company that I contacted was willing/able to provide this information.

    Solenoid Inrush Measurement

    Inrush Current. It is the current required to generate sufficient magnetic force to pull the plunger or overcome the air gap.

    If there is any fluid inside the solenoid, the air gap is filled with water which exerts certain amount of pressure on top of the plunger.

    We need to know what is the force/pressure exerted on top of the plunger .


    P=water pressure
    A= Area of the Plunger where water pressure is exerted.

    F1= Force on top of the plunger.

    Now the Magnetic force required to pull the plunger is
    F= F1+FP

    FP= is the weight of the plunger.

    Based on the net force, which is the required magnetic force, use Maxwell force formula:

    F = ( Fm)2 μ0 A / (2 g2)

    In order to calculate this, you should know the magnetic permeability of the solenoid, material, number of turns in the coil, cross section of the coil ,or the magnet wire Inductance,etc.

    The INRUSH does depend on the water pressure and efficiency of the solenoid.
  8. Ron Wolfarth

    Ron Wolfarth Sponsor
    Messages: 997

  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,367

    I think you can even up those equations to include the characteristics of the fluid the solenoid is operating with.

    Now, is it true that a valve tip from several decades ago might read "Don't connect the Thermal Hydraulic valve wires to line voltage?" :p
  10. Ron Wolfarth

    Ron Wolfarth Sponsor
    Messages: 997

    Only if the wire gauge was as big as your little finger!

Share This Page