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Pneumatic safety valve question

  1. Oct 18, 2016 #1
    I am developing a machine which consists of a horizontally mounted cylindrical drum, where the door is front mounted, top opening pneumatically actuated (Picture enclosed).
    The door is lifted up by the pneumatic cylinder.

    Now there is an obvious possibility of the door crashing down if the air supply to the cylinder is somehow disrupted. I have tried using a 5/3 Direction Control Valve & Pilot operated NRVs on the cylinder, but these do not help.

    I want to stop the exhaust of air from the cylinder if, for eg, one of the air pipes from either port on the cylinder, comes off. So the cylinder should stop where it is.

    Provision of mechanical stoppers is always a possibility. But I would like to leave it as a last resort.

    Any help would be great.
  2. jcsd
  3. Oct 19, 2016 #2


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    How about flow limiting the down stroke so even if the air supply is disrupted, the door drops down slowly?
  4. Oct 19, 2016 #3


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    Does the cylinder have to do all the lifting ? Isn't there a counterweight system ?
    Perhaps you can install an air braking system that is pressurized from the working end of the cylinder and brakes when the pressure falls away (as with trucks, trains and elevators).
  5. Oct 19, 2016 #4


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    I am with BvU. Counterweight it to hold it open and use the cylinder to hold it closed if that is safe (i.e. the cylinder does not spin and need to hold contents in).

    If that is not feasible then a gas strut to slow closure plus an alarm for low pressure would probably be sufficient to make it safe.
  6. Oct 20, 2016 #5


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    (1) Auxilliary cylinder to latch main cylinder in up position . Latch is spring loaded or otherwise self acting and has to be deliberately pressurised to unlatch .

    (2) Use a screw instead .

    (3) Open door sideways .
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