Pressurized Hydraulic Reservoir [1<P<5] psig

[jas165]

I am looking for an economical and reliable method to provide a small mobile hydraulic reservoir with a small amount of positive pressure. Looking for component recommendations for the following ideas.

1. Use air over oil volume as accumulator.
Tmin = 32F, Tmax = 150F.
System always draws oil from reservoir nominal.
Worse case system draw is 13 in^3.
Nominal air volume is 380 in^3.
Need vacuum breaker and relief device for safety??

2. System has access to pressurized air. Would need to filter and remove water from air.
Need regulator/relief to maintain pressure??

Other ideas include a bladder accumulator, but this is expensive. What about a small spring return pneumatic cylinder as an accumulator?

Any other ideas?

 

[ccfowler]

With the small pressure range that you state, friction may be a problem with spring-loaded cylinders, but you may want to take a look at "Bellowfram" products for some ideas. I've used Bellofram actuators because of their nearly friction free operting characteristics for relatively long strokes. I'm not sure how large a volume will be economically or physically practical for your situation, but it is probably worth your time to investigate the options available.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[MikeHalloran]

Use a filtered vent on an elevated reservoir.


Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

You may want to look at the spring-loaded rolling diaphragm reservoir from Eaton:

http://www.fpweb.com/Classes/Article/ArticleDraw.aspx?HBC=Issue&NIL=False&CID=44634&OASKEY=Issue

Ted

 

[kcj]

Pressure regulator always has a risk of failure. I for sure would put a 3 to 5 psi cracking check as tank relief.

'Mobile' equipment: Do you have turbocharger air pressure available? I have seen that several times.

Do you have to have guaranteed positive pressure on startup? If not, a simple pressure vacuum breather may work. The system pressure would build with heat. We use the Bruning, now Parker, -.3 psi to +3 psi I think.

I have an acquantaince who does undersea hydr stuff with pressurized small tanks. I will check with him.

We also use the Greer, also now Parker, KleenVent breather bag. Effective, but they are really big.

kcj

 

[subsearobot]

You want a spring energized rolling-diaphragm.

In the subsea industry, we call these items compensators. Several companies make them, including my own. Charge pressures tend to be a little higher than you prescribe- 7-15 psi is typical, but every manufacturer has a different standard. We just released a 1 gallon model with 4-5 psi pressure.

I am not sure about the policies of self promotion on this forum, so I'll give some references, including my own company.

DOER Marine (this is an older data sheet that does not list the new 5 psi availability)

http://www.doermarine.com/files/DOER_Compensator.pdf

Schilling Robotics (no direct link on their website, but I know they make them as we have one in our shop)

Perry Slingsby

http://www.perryslingsbysystems.com/assets/pdf/datasheets/compensator/PositiveCompensationUnit.pdf

Sound Ocean Systems

http://www.soundocean.com/legacy-products/miscellaneous/hc-1000

Technadyne

http://www.tecnadyne.com/Brochure/Pressure Compensator Brochure.pdf

A Google search will probably turn up more manufacturers.

I would be happy to offer opinions on features, if you like...