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How much weight is required?

  1. Nov 6, 2013 #1
    I have a large vessel that I would like to add a 10 psi purge to. There is a relief valve on it that is set to lift at 0.5 psi (essentially a flat circular plate 1 ft in diameter), so I am simply looking to keep this closed so that I can build up 10 psi inside the tank (don't worry, the tnak is rated for that pressure). Trying to figure out how much weight I'd need to do this, but doing the calc gives me a circular area of ~113 square inches, which would then provide a force of (113)(10) = 1130 lbf. I highly doubt I need 1130 pounds to hold this closed, so I must be missing something obvious here. Any insight would be greatly appreciated. Thanks
  2. jcsd
  3. Nov 8, 2013 #2

    You need a pressure of 9.5psi to keep the valve shut (difference in pressure). Using F = P*A and W = F/g I get a weight of around 1075lbs. Seems a lot but it's quite a straight forward calculation - you have a large area that the pressure is acting on.
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