Pressure inside a bladder when subjected to an outside liquid pressure

  1. If I have a bladder (or balloon) that is charged with 300# of a nitrogen gas at a normal atmospheric pressure outside the bladder, and I then enclose the bladder and subject that bladder to a liquid pressure of 25# on it's outside surface area but inside the enclosure. Assuming a constant temperature, does the inside pressure of the bladder increase due to the 25# of liquid pressure, or does it take more than 300# of liquid pressure on it's outside surface area to get the pressure inside the bladder to increase? This is not a homework problem, but a problem with a system I am trying to understand at my work place. Thanks in advance for any insight you can provide.
     
  2. jcsd
  3. russ_watters

    Staff: Mentor

    Depends on if you want gage, differential or absolute presssure. Is this an expansion tank?
     
  4. It also depends on the design of the bladder. Is the bladder elastic? If so, the pressure inside may well increase. If the bladder is not elastic however, the pressure inside will remain at 300 pounds (per square inch? per square foot?) until the outside pressure exceeds the inside pressure.
     
  5. Russ Watters, cjl, and anyone else who can provide info. - This is a pulsation dampener for a liquid dye pump. The bladder is elastic. The pressure inside the bladder is 300 psi of nitrogen. I am looking for gage pressure inside the bladder when the outside of the bladder is subjected to a lower liquid pressure. If the liquid pressure is something less than the 300 psi inside bladder pressure, will it compress the nitrogen gas and increase the pressure inside the bladder, or will it take more than 300 psi of liquid pressure to change the pressure inside the bladder? Thanks, again, for any help you can provide.
     
  6. I have an elastic bladder that is charged with 300 psi gage pressure of a nitrogen gas inside the bladder, at atmospheric pressure outside the bladder. This is being used as a pulsation dampner for a liquid dye pulsing pump. If I subject that bladder to a liquid dye pressure of 25 psi gage pressure on it's outside surface area, assuming a constant temperature, does the inside pressure increase, or does it take more than 300 psi of liquid pressure on it's outside surface area to compress the bladder and get the nitrogen gas pressure inside the bladder to increase?
     
  7. I have an elastic bladder that is charged with 300 psi gage pressure of a nitrogen gas inside the bladder, at atmospheric pressure outside the bladder. This is being used as a pulsation dampner for a liquid dye pulsing pump. If I subject that bladder to a liquid dye pressure of 25 psi gage pressure on it's outside surface area, assuming a constant temperature, does the inside pressure increase, or does it take more than 300 psi of liquid pressure on it's outside surface area to compress the bladder and get the nitrogen gas pressure inside the bladder to increase?
     
  8. russ_watters

    Staff: Mentor

    This is basically an expansion tank, so the bladder itself holds 300 psi of gauge pressure due to its own internal strength. If you add external pressure to it, that increases the pressure inside the tank with respect to the atmosphere, but decreases the pressure "felt" by the bladder itself. The exact resulting pressure will depend on the properties of the bladder and can probably be found by looking at the manufacturer's documentation.
     
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