How to Reduce Hydraulic Pressure Variation? 3

[acspain]

Hello All,

What should I add to the hydraulic circuit to reduce the pressure variation?

We are running an endurance test of a component using hydraulic pressure ideally ramping from 0 psi to 1030 psi and back to 0 psi over the course of 30 seconds to complete a cycle.
The peak pressure is going as low as 1018 and as high as 1050 which is too much variation. The low pressure does not stoke the part enough and the high pressure causes too much stroke. I would like a ±5 psi tolerance.

The hydraulic circuit comprises of a variable piston pump driven by an electric motor generating the flow/pressure to a solenoid valve switching the part between the pressure line and the sump line. The pressure and sump lines have a metering valve set to ramp the pressure within the cycle time. The volume required between 0 and 1030 is fairly small at .25 cubic inch.

My suspicion is that the variation is coming from the on/off nature of the solenoid demanding flow/pressure or not from the pump and the electric motor adjusting to maintain rpm.

Thank you for your help.

 

[PNachtwey]

PNachtwey - Yes, we are not getting down to 0 psi which is fine. I am targeting pressure as that directly relates to deflection of the part. I am trying to stretch a bellows a fixed amount of distance for a number of cycles. The pressure variation is causing not enough stretch on the low end and too much stretch on the high end.

But you didn't answer my two questions.
1 what is the application.
2 are you really needing to control pressure or force.
I repeat, chances are it has been done before or something very similar.


Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/

IFPS Hall of Fame Member

 

[acspain]

Good Morning All,

PNachtwey - I completely agree with your last statement "chances are it has been done before or something very similar" which is why I am here on this forum. But all of us are aware of the challenges with lack of documentation, sharing of knowledge and the inability to find the needle in the haystack of available information.

I am choosing not to answer the application question clearly for proprietary reasons. It is sufficient to say it is a pressure application and for the bellows it is important that the pressure is balanced between the outside and inside.

Right now, I need to control pressure. The next time I specify this type of test, the approach should be controlling volume. LittleInch mentioned dead weight testing and hydtools mentioned controlling volume; both of which seems like a much better/easier way to control this type of test. I don't have resources for this level of reset.

Compositepro - Yes, springs can be used to augment the spring rate of the bellows and adjust the pressure to extend or compress the bellows. This is usually done at much lower pressures where gas charges become impractical and the bellows can handle the differential pressure between the outside and inside of the bellows.

Thank you for your help.

 

[LittleInch]

So are you going to change anything?

But thanks for coming back and letting us know.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

Your volume is so small, can you use a nitrogen tank and a precision pressure regulator to achieve your goal?

 

[acspain]

Good Morning LittleInch,

Yes, I am going to find a valve and add a circuit to enable the pump to continuously move fluid. Then when the solenoid switches and siphons off the small amount of fluid needed, the pumps reaction is going to much smaller and therefore the pressure variation should drop.

The next step (today) is reaching out to one of hydraulic component suppliers to identify and purchase a reasonable valve.

Have a good day!

 

[Null Full]

To reduce the pressure variation in the hydraulic circuit, you could consider adding a pressure regulator valve in the circuit. This valve can be set to maintain a constant pressure within the circuit, regardless of the fluctuations in demand caused by the solenoid valve. Additionally, you could also consider adding a pressure relief valve to protect the circuit from over-pressure conditions. Finally, you may want to consider using a proportional pressure control valve, which can adjust the flow of hydraulic fluid to the actuator more gradually and precisely than a solenoid valve, to help achieve your desired tolerance level.

Sonkit
Product Manager at Sonkit Industry, For Metal Ring Seal Solution,

https://www.sonkit.cn/en/

 

[TugboatEng]

Proportional regulating valves DO NOT maintain constant pressure!