Author Topic: Another booster pump (Read 6664 times))

Jmorris · « **on:** May 30, 2015, 08:21:31 PM »

My check valves came in today and it looks like it's going to work.

Uses a 2.5" x 8" stroke pneumatic cylinder, and 1" tubing with an aluminum piston.

i have a video but am too new to post external links.

sixshootertexan · « **Reply #1 on:** May 30, 2015, 08:26:46 PM »

Interesting. I'd like to see the whole thing.

majorm · « **Reply #2 on:** May 31, 2015, 12:55:48 PM »

I would like to see more of it too. I would really like to build one myself.

moorepower · « **Reply #3 on:** May 31, 2015, 01:16:07 PM »

So far this thread is like putting a single Cheeto in front of me. I need more!

Jmorris · « **Reply #4 on:** May 31, 2015, 02:36:31 PM »

If someone can post a link to the YouTube video send me a PM, the forum won't allow me to.

I made it as simple as I could, there really isn't much to it. The LP part is a 2.5" bore 8" stroke cylinder I had sitting around. The HP part is 1" seamless tube, I just machined an aluminum piston about .006" smaller than the bore ID.

Instead of machining a manifold where the tube needed to be precision aligned and such, I just turned groves into the cylinder end for the o-ring and let the tube "float" if you will.

With no pressure the HP end can be lifted up off the LP ram, like this.

When you apply the pressure to be boosted to it, the piston drives to the top and tube to the bottom like this. Energizing the solenoid that feeds the LP cylinder at this point will pull the piston in the HP cylinder down, compressing the gas.

A hole drilled just above the O- ring at the bottom of the HP tube and an 1/8" NPT bung welded on. A "T" fitting with an "in" and "out" check valves completes it.

rsterne · « **Reply #5 on:** May 31, 2015, 03:58:26 PM »

About the only issue I can see is if the lower O-ring failed, the tube and check valve assembly could launch off the piston rod.... otherwise a great design....

Bob

Jmorris · « **Reply #6 on:** May 31, 2015, 04:17:45 PM »

Quote from: rsterne on May 31, 2015, 03:58:26 PM

About the only issue I can see is if the lower O-ring failed, the tube and check valve assembly could launch off the piston rod.... otherwise a great design....

Bob

The top of the HP cylinder is completely open, no way to build pressure above the piston.

If the lower o-ring fails, it just leaks.

For any "launching" to take place you would need pressure above the piston or if the 5/8" rod itself broke, the rod and piston could come out (not likely as at 4500 psi there is only about 315 lbs of force on the HP piston, a 1/4" rod could hold that).

With all the pressure below the piston you eliminate the possibility of flying parts. Would just leak from the gap between the two.

A keen eye will spot the set collar clamped to the top of the LP cylinder, I was going to add another to the top cylinder in order to limit upward movement but didn't after I thought about it and realized it couldn't go anywhere.

rsterne · « **Reply #7 on:** May 31, 2015, 04:26:48 PM »

OK, if you're sure.... I'd remove the bottom O-ring and try (carefully) pressurizing the HP cylinder to see what happens.... I think the air exhausting out the bottom might scoot the cylinder upwards like a rocket.... Perhaps because the inner bore is parallel that might not happen.... I realize the space above the piston is at atmospheric....

Bob

moorepower · « **Reply #8 on:** May 31, 2015, 06:01:48 PM »

I have a dumb question. If you have 1 88ft tank, using this, can several tanks, "88cf.", be filed by the one tank?

rsterne · « **Reply #9 on:** May 31, 2015, 06:15:36 PM »

No, because all you do is boost the pressure from whatever is in the HPA tank to a higher pressure.... The main idea is to use air from, say, a SCUBA tank that might be at 2000 psi and boost is to 4500 psi to fill a smaller tank or gun to that pressure.... You use a shop compressor to supply the low pressure air to run the large cylinder to supply the power to boost the HPA pressure....

Bob

moorepower · « **Reply #10 on:** May 31, 2015, 06:24:49 PM »

Kind of knew that, but had to ask! I have about 9' of 5" thick walled aluminum tubing wanting to find a use, other than scrap, of ebay.

Jmorris · « **Reply #11 on:** May 31, 2015, 06:28:11 PM »

Bob,
you were right it will move without the o-ring on the bottom but it is more like a hovercraft than a rocket, just enough gap for the air to escape and makes a lot of noise.

Moorepower,
No, device doesn't "make" anything just takes something at a lower pressure to a higher pressure.

Idea is that if you want to fill to say 2500 psi and your tank is at 3000 psi to start with your going to get a certain number of fills before tank pressure below 2500 psi as you only have a 500 psi window.

The thing I built will allow the window to be much larger but can't do what your asking.

rsterne · « **Reply #12 on:** May 31, 2015, 06:32:29 PM »

At least it's safe....

Bob

Jmorris · « **Reply #13 on:** June 01, 2015, 12:10:11 AM »

I hope so.

I looked into building something like the shoebox compressor but from the thread you posted about yours locking up I decided to go with something as simple as I could.

Not much chance I would be lucky enough to build something from scratch that was better than a design that has had a few years of R&D.

I figured if it only took an hour to build it in the first place, only has one piston and 5 o-rings there couldn't be too much down time to rebuild it.

Even if I had to scrap everything and start over. A lot less parts than the SB and all of my compressors are reciprocating anyway.

I should have a few 4500 psi tanks in a week or so and I we will see just how viable it is as an option to the other methods.

rsterne · « **Reply #14 on:** June 29, 2015, 01:09:12 AM »

I am thinking of making a similar booster, but I have a question about the lower O-ring that seals against the shaft and rides in a groove in the tube.... In your second photo in the original post, it looks like there is a lot of O-ring exposed between the tube ID and the piston rod OD, possibly 1/16" or so?.... How is it that the O-ring doesn't extrude out through that large gap?.... The pneumatic cylinder I have has a 25mm shaft (0.980"), and the tube I was going to use is 1.50" OD x 0.188" wall CrMoly, so the ID is 1.124"....That leaves a gap between the Rod OD and the tube ID of 0.072".... I would think that the O-ring would just blow right out of there, no?.... As you said, when you pressurize the tube with 2000+ psi, it pulls the rod and piston up, and pushes the tube down until it hits the end of the pneumatic cylinder.... When the tube stops, the O-ring will try and keep pushing, right?.... At full pressure, there is 4500 psi pushing on that O-ring, trying to force it through the gap between the tube and piston rod....

Bob

Jmorris · « **Reply #15 on:** June 30, 2015, 11:01:08 AM »

There will be 4500 psi on the O-ring but it won't have 4500 lbs of force on it because the area of the O-ring is a fraction of a square inch.

The gap between my shaft and bore is about .030". Your gap being double, you might need a harder O-ring that will resist extruding (you can get them made from a wide range of things).

A better idea would be to machine an insert that could be threaded into the bottom of your tube that houses the O-ring, with an ID only a few thousands larger than the OD of your shaft.

Gippeto · « **Reply #16 on:** June 30, 2015, 04:33:50 PM »

Might be worth a look....

http://www.sealanddesign.com/category/Extrusion-Limits/611.html

For the sake of comparison....the cylinder wall/piston clearance in my booster is .002" (.004" total difference in diameters) and I still used backer rings..likely a contributing factor as to why it still has the original 70D Buna N o-rings in it...have 90D Urethane for when the Buna N eventually does fail.

Al

rsterne · « **Reply #17 on:** June 30, 2015, 06:05:52 PM »

Yeah, I've seen that chart before.... which is why I was wondering how you can get away with a 0.030" gap at 4500 psi.... I wonder if the O-ring is moving into the gap and laying against the end of the ram casting?....

Al, how big a gap do you think you can tolerate with 90D backer rings at 4500 psi?....

Bob

Jmorris · « **Reply #18 on:** June 30, 2015, 06:41:29 PM »

Quote

I wonder if the O-ring is moving into the gap and laying against the end of the ram casting?

That's a good question, that I don't have the answer to, just know it works. If it worries you that yours might not work you can machine an insert or make a complete lower manifold that has ID and OD seals, check valves and inlet/outlet ports all in one. I just went the quick and easy way to see if it was going to work.

Gippeto · « **Reply #19 on:** July 01, 2015, 09:24:09 AM »

Bob, anti extrusion rings or backers essentially reduce the clearance to zero as far as the o-ring is concerned. I would imagine that material choice for the backer would be the deciding factor as far as its ability to withstand applied forces....Peek might be more tolerant than Buna N.

I could guess at a max clearance, but manufacturers are pretty good about providing information on their products. As a suggestion...go with maximum extrusion gap for no backers...then put them in anyway.

Al

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Another booster pump

Author Topic: Another booster pump (Read 6664 times))