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Air consumption Rate

  1. Feb 27, 2013 #1
    Hi all

    I am trying to set up a report showing the air consumption rate of my cylinder actuators on different valves. I am stuck at the very end where I should calculate the air consumption rate. All calcs are in metric units.

    Okay as an example lets use the following:
    Valve: SKG200 with closing thrust 1259kg at 10bar line pressure.
    Actuator size: D = 250 mm
    Valve stroke: S = 296 mm
    Cylinder rod diameter: d = 32 mm
    Available air pressure: P2_guage = 4 bar

    Now I calculated the total cylinder volume for the closing and opening strokes:
    V_open = ((D-d)/10)^2*∏/4*S = 8584.8 cm^3
    V_close = (D/10)^2*∏/4*S = 11290.1 cm^3

    So the total air consumption respectively:
    Air_open = V_open*(P2_guage+1)/1000 = 42.92 liter
    Air_closed = V_close*(P2_guage+1)/1000 = 56.5 liter

    And with a maximum operating speed of 25mm/s we calculate that the duration of the stroke is:
    t = S/25 = 296/25 = 11.84 sec

    So now that I have all this info, how do I calculate the rate of air consumption if I want to know what size compressor to buy... Thanks guys and I hope this is in the correct forum...
     
  2. jcsd
  3. Feb 28, 2013 #2

    CWatters

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    Are you saying:

    a) it uses 43L to move the piston one way and another 57L to move it back the other way? eg a total of 100L per cycle?

    or

    b) The cylinder volume changes from 43 to 57 L in one stroke and no air is used for the return stroke? (eg the load or a spring does the return).

    Is the duration of the stroke the same in both directions? eg The cycle time is 2 * 11.84 = 23.68 seconds?


    Assuming you mean a) then..

    The max consumption is going to be around...

    100L every 23.68 seconds
    or
    (100/23.68) * 60 = 253 L/min
     
  4. Feb 28, 2013 #3
    CWatters: Yes as stated in A it is a double acting actuator... Lets say that the duration of the strokes is the same so yes thanks, now you made that seem pretty obvious, haha...
    Thanks

    Now the other thing I started to have trouble with, say I do not want to place a spring for fail safe purposes (load is to big), I am recommending an air receiver.

    I however have to size the receiver accordingly. Lets say for only the closing stroke.
    I know I have to use Boyle's law: pV = k or p1V1 = p2V2

    I've tried a view solutions by now. I dont know what to use as V1 and V2? Do I use the 57 liters as V1 and say V2 = Vreceiver + V1? One of the engineers said that rule of thumb says multiply it by 4 so that gives 228L! But surely I can get to the answer using Boyle's law.

    Thanks for the help
     
  5. Feb 28, 2013 #4

    CWatters

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    I'm afraid that's outside my level of experience.
     
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