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Relief valve for accumulator in a closed system?

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canmecheng

canmecheng

Mechanical
Joined
Feb 15, 2011
Messages
14
Location
CA
Hello,

what options are their for adding a relief valve for an accumulator? Is it a common requirement and practice to add a relief valve and empty reservoir to accumulator used for energy storage? Should the relief valve be provided for both the nitrogen and hydraulic side?

I have a closed circuit including an accumulator, ball valve and hydraulic cylinder being used to assist with gravity loads. We are operating at 1000 psi where the accumulator has a MOP of 3000. The maximum compression ratio (which is defined by the stroke of the hydraulic cylinder is 2.40). I don't see how the accumulator can be over-pressured as there is no source of power that can generate high pressures even with dynamic operations. I am able to set the relief valve such that the compression ratio does not become excessive.

Thanks
 
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If you install a relief valve to reduce the amount of fluid displaced into the accumulator, you will lose the volume of fluid available to move the cylinder resulting in loss of stroke.

A relief valve should only be used to prevent overpressure damage to components.

No need for a relief valve for the nitrogen charge.

Ted
 
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In many countries, it is a requirement to add a relief valve to an closed circuit with an accumulator. It is not a legal requirement, more of a directive for safe machine operation.

Likewise, there should be a method of safely releasing any stored pressure and there should be a method of isolating the accumulator for maintenance etc.

All of the above can be achieved by fitting a safety block to the fluid port on the accumulator.

If there is risk of fire, then the gas valve should be fitted with a thermal fuse. As Ted says, there is normally no need to add a pressure relief to the gas, but if there is a risk of a thermal event, then there must be a way of venting the gas if the heat rises. This is usually a plug filled with lead / solder that melts at a given temperature and allows the nitrogen to escape.
 
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