Need the opposite of a relief valve
Need the opposite of a relief valve
(OP)
I need a valve that functions in a manner that is opposite of a relief valve: a valve that closes when pressure gets above a setpoint.
The application is at the outlet of an air cylinder that is to slow movement of an arm if the actuator lifting the arm fails. The outlet of the air cylinder is ported through two parallel openings, a small orifice and a larger opening. If the load is "dropped", I want the larger opening to close so that the air cylinder drops slowly.
Another possibility: a check valve that allows a certain amount of low pressure leakage before it is forced shut.
The application is at the outlet of an air cylinder that is to slow movement of an arm if the actuator lifting the arm fails. The outlet of the air cylinder is ported through two parallel openings, a small orifice and a larger opening. If the load is "dropped", I want the larger opening to close so that the air cylinder drops slowly.
Another possibility: a check valve that allows a certain amount of low pressure leakage before it is forced shut.





RE: Need the opposite of a relief valve
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Ted
RE: Need the opposite of a relief valve
The smallest one is still a bit large, though, and may not respond fast enough. Maybe if I use a larger cylinder...
RE: Need the opposite of a relief valve
RE: Need the opposite of a relief valve
You could try a safety excess flow check valve.
Ciao,
RE: Need the opposite of a relief valve
RE: Need the opposite of a relief valve
I still need to spar with the old school guys who want something 100% mechanical. At least this is getting me out to learn a few new things.
I can almost picture a device that could work, like a swing check or diaphragm valve with a spring to counter light pressure. Not actually finding such an animal.
RE: Need the opposite of a relief valve
Check out this link http://www.metalgoodsmfg.com/excess.htm, a purely mechanical device (quite symilar to your description). You can couple this up with a pressure switch to signal line failure.
Ciao
RE: Need the opposite of a relief valve
The idea of itascot is pretty good. Take a look at the link below (specific for air).
www.rego
No need to design a new item, just evaluate the flow rate corresponding to your pressure threshold in order to have an idea of the most suitable item for your application.
RE: Need the opposite of a relief valve
Ted
RE: Need the opposite of a relief valve
RE: Need the opposite of a relief valve
In answer to your question on reaction time, need to know what size cylinder & what pressures are involved.
Ciao,
RE: Need the opposite of a relief valve
This sort of system works much better when the damping fluid is a liquid.
Mike Halloran
Pembroke Pines, FL, USA
RE: Need the opposite of a relief valve
The simple solution is as previous postings have suggested.
Ciao,
RE: Need the opposite of a relief valve
They were good to work with.
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