PDA

View Full Version : Best way to bleed new hydraulics?



CCWKen
02-21-2005, 12:12 AM
Getting ready to fire up the grader I've been building. Well, maybe by next weekend--Still working on the wiring harness.

What would be the best way to bleed air from the new cylinders and lines? With the engine (pump) off, could I just open a control valve and manually operate the cylinder to fill it and the lines with HF?

OR... just fire it up and work the valves a few times? http://bbs.homeshopmachinist.net//eek.gif

wierdscience
02-21-2005, 12:36 AM
Crack the fittings open at the cylinders and shoot oil to the line that's on the colapsed side of the piston.When you get fluid there tighten it and run the cylinder on out to the other end then tighten that line.

You will still have a little air in the system,but it won't hurt anything.It will just diffuse into the oil and come out when it returns back to the resv.

Oh,you may have to re-fill the resv. when you fill the cylinders full during purging.

Oh,and don't do like my buddy did,he forgot to include a breather in his resv.,made a loud hissing noise and splat!Oil all over the place http://bbs.homeshopmachinist.net//biggrin.gif

CCWKen
02-21-2005, 12:55 AM
<font face="Verdana, Arial" size="2">...he forgot to include a breather in his resv...</font>

Thanks, I'm glad you mentioned this. The reservoir is the transmission! I'll have to open the dip stick cap, I guess. I don't think there's a vent.

chief
02-21-2005, 03:50 AM
A leech.

Tinkerer
02-21-2005, 02:08 PM
I don't know if I'd use the transmission as a reservoir. AFT fluid can deteriorate packing in the cylinder and pump causing leaks. Not only that but you could starve the trans of fluid if such a failure happens causing major headaches. Just take a piece of 4 or 6" pipe bevel cut one end to about 15º for bottom weld some plate and place a fitting 2" up from end. Weld a cap on top end along with a couple of fitting one for return and other for vent to allow thermo expansion. Just take a pipe nipple and cut some slits and wrap with screening for the vent tube. Run line to pump and controls ect.

Tim

catman
02-21-2005, 02:54 PM
What type of grader is this?

What type of transmission are you using?

Most of the farm tractors made in the last 40 years used the transmission for the hydraulic reservoir. Bulldozers used a separate hydraulic tank, mainly due to the higher flow hydraulic systems compared to farm tractors. If you are using an automatic transmission I would recommend a separate reservoir, however on the same token John Deere has a “power shift” transmission that uses a planetary gear system that can be shifted under load, and uses tractor hydraulic oil for its shift pack.

If you have the pump located lower than the oil reservoir and you have an open center system the air will work its way out of the system no problem. Just start up the engine and let the system sit making sure that there is plenty of oil in the reservoir while the main lines are filling up.

If you have two way hydraulic cylinders, removing the air is also not really a problem just work the cylinders back and forth and the air will generally be forced out by the oil moving in and out of the cylinders.

rumutt
02-21-2005, 03:31 PM
CCWKen

If you use the 'crack the line' method just becareful, wear at least leather gloves and a welder's jacket. I have many hydraulic specialists friends that are missing part or all of at least one finger due to the hydraulic fluid being injected under the skin of the fingers when cracking a line. Hydraulic fluid is bad enough on your skin but under the skin it really can cause problems.

Bruce

Sandy H
02-21-2005, 03:43 PM
Air is compressible. An unfortunate side effect of this is the cylinders are pretty uncontrolled if there is a large amount of air in them. Bleeding then can be dangerous. Unsupported loads are a complete 'no-no.'

Check out this link for some good information and if you're in the mood, read some with actual photos instead of drawings. It may well change the way you think of hydraulics.

http://www.fluidpowersafety.com/fpsi_sftyalerts.html

Sandy.

fixxit
02-21-2005, 04:05 PM
Great link !
What a collection of real life horror stories...

Check out saf-004

I've never worked with hydraulics, but this convinced me to get some real training before I do.



[This message has been edited by fixxit (edited 02-21-2005).]

crewchief
02-21-2005, 06:58 PM
<font face="Verdana, Arial" size="2">Originally posted by Sandy H:
Air is compressible. An unfortunate side effect of this is the cylinders are pretty uncontrolled if there is a large amount of air in them. Bleeding then can be dangerous. Unsupported loads are a complete 'no-no.'

Check out this link for some good information and if you're in the mood, read some with actual photos instead of drawings. It may well change the way you think of hydraulics.

http://www.fluidpowersafety.com/fpsi_sftyalerts.html

Sandy.</font>sandy h
i think it would be a good idea for every one here to go to this site and see how dangerous fluid power
really is,we were testing hydraulics on a blackhawk helicopter when main gage on the rig blew off 3000 psi, it went through the hanger roof,some one had repaired stainless tube on the gage with silver solder,lucky no one was killed or injured.
cc

C. Tate
02-21-2005, 07:04 PM
Leeches?

CCWKen
02-21-2005, 08:16 PM
<font face="Verdana, Arial" size="2">What type of grader is this?</font>

It's a homebuilt with parts from a Kubota G3200. Mainly the diesel engine and the front axle. Some of the sheet metal and hardware was also salvaged. The frame and blade have been scratch built. The grader blade is fully controlable in that each side will move up/down independently and the blade will pivot. The blade is controled by electro-hydraulics. ("Drive by wire")


<font face="Verdana, Arial" size="2">What type of transmission are you using? </font>

It's an Eaton Model 7 hydrostatic coupled to a Peerless Model 2500 two-speed axle drive. The Eaton has an auxilary hydraulic pump that will lift/lower the front tiller. The spec on the pump puts the pressure around 500psi but that's enough to control the tiller.

I've also made provisions to add a front-end loader. I've got the loader frame built but not the bucket. I put that on the back burner. I need the tiller and grader NOW! http://bbs.homeshopmachinist.net//biggrin.gif

The trans/pump/axle are direct-coupled so I don't have much choice about reservoir tanks. The pump draws directly from the axle sump, pumps to the control valve then returns to the trans via a filter. The trans then has an internal drain to the axle. The fluid is constantly being circulated through the filter (open center valve).

IOWOLF
02-21-2005, 08:30 PM
PICS. PICS. PICS. WHEN you get around to it.

CCWKen
02-21-2005, 08:43 PM
IWOLF, The fit and fab process was boring and I didn't take any pics. I basicly set the engine and trans in place then built the frame and all the bracets around them.

I started taking pictures at the point I had the frame ready for paint. I've been taking pictures as I "re-assemble" all the parts. (All 35mm though) I get the film on CD and try to post pics when the roll is done. http://bbs.homeshopmachinist.net//frown.gif

CCWKen
02-21-2005, 08:54 PM
How does this relate to a Machinist's Forum, you ask? Dang; I had to machine so many special pins, bolts, bushings and brackets I nearly wore-out my machines.

I also Went through a tank of gas and two 10lb. rolls of mig wire. Not to mention 20lbs. of stick welding rod.

I haven't weighed the beast but the frame alone is about 400lbs. Add the engine, trans and the rest and I'm guessing it'll tip at about 1200+lbs. Beefy for a sub-compact tractor!

wierdscience
02-21-2005, 11:22 PM
"Jimmyed up carnival ride"! http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//tongue.gif http://bbs.homeshopmachinist.net//biggrin.gif

CCWKen
02-21-2005, 11:39 PM
Hey, you're stealing my line! http://bbs.homeshopmachinist.net//biggrin.gif

Oh yea, I remember now. That was your truck, wasn't it? http://bbs.homeshopmachinist.net//biggrin.gif

[This message has been edited by CCWKen (edited 02-21-2005).]

wierdscience
02-22-2005, 12:03 AM
Yep! Have to talk to Neil about publishing a "Jimmyed up junkpile" book! http://bbs.homeshopmachinist.net//biggrin.gif

Chapter one should be titled "Sewed up with a grape vine and painted with a pine top" http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

CCWKen
02-22-2005, 12:13 AM
I just did a search on that line. Gosh, that was nearly a year ago. You have a good memory or you're making a list of "get backs". http://bbs.homeshopmachinist.net//biggrin.gif

Obviously you didn't electricute yourself. Is that truck still running? http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

I'm almost ready to tackle that L.V. wood. Had to fix my engine hoist to get it off the back porch though. http://bbs.homeshopmachinist.net//biggrin.gif

Sandy H
02-22-2005, 08:35 PM
I posted that link because a shop supervisor backhanded me when I was reaching around some hydraulic piping, looking for that mysterious leak that had developed on a machine we were starting up. I was livid and I'm bigger than he is (but, without question, he would have handed me my own butt if I would have tried anything). We yelled a bit back and fourth and he basically said I could lose my hand etc.

Being the guy I am, I went back to the front office and googled for a while to prove it wasn't a problem. After finding that site (and a few more gruesome) I walked back out and shook his hand.

My version of logic didn't see any real danger, but his experience said BS! Since that time, I have seen a few assemblers running a unit at pressure, tightening fittings etc. If I'm around, I E-Stop the unit and take them back to my office to see some pictures and read a line or two. Each time, they simply stood back and were surprised.

We build machines for the metal forming industry. The particular machine I got 'educated' while troubleshooting was running at 8500psi at the time I was reaching around the piping. It also had a 48" main ram, which yields just over 7500 Tons of force. I would have kicked a guys butt for reaching into the press while it was running, but in reality, the chance of losing the use of ones hand was much greater playing around a leaky fitting than reaching in to the slow moving ram.

That's what education does. It shows some of the dangers, but common sense is still mandatory.

I'm happy to say, that since I've been a bit of an ass with a few guys on the E-stop thing around the HPU's, they all tighten fittings with the dump valve open. In the end, hitting an E-stop is a bit less aggressive than a smack to the head, but I still say he did the right thing to me.

Now, if only I could get one particular guy to quit sticking his head under 75 ton machines to move the dunnage, when being lifted by our 50 ton crane with a 50 ton mobile helper, I'd feel pretty good. That one might take a good backhand, but I'll leave that to Mike!

When it comes to losing function of body parts, I tend to err on the side of safety. My conscience wouldn't allow otherwise.

Be safe with the loader! Control and air in a hydraulic system are true enemies!

Sandy.

wierdscience
02-22-2005, 10:18 PM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:
I just did a search on that line. Gosh, that was nearly a year ago. You have a good memory or you're making a list of "get backs". http://bbs.homeshopmachinist.net//biggrin.gif

Obviously you didn't electricute yourself. Is that truck still running? http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

I'm almost ready to tackle that L.V. wood. Had to fix my engine hoist to get it off the back porch though. http://bbs.homeshopmachinist.net//biggrin.gif</font>

Yep,the old truck is still running,sort of,I had rebuilt the carb,bout 2years ago,she ran like a top,but then I let my brother use it and he dumped 5 gallons of dirty gas in it and stopped up one side of the carb,it is right now a v-4.Got to do it again,plus the radiator has a leak.Other than that I am almost finished improving it http://bbs.homeshopmachinist.net//biggrin.gif

Guess I should have exanded on the bleeding post,just long enough on the handle to see fluid,then shut down and tighten.Not hang on the handle like a chimp till the sump runs dry and you need high water pants http://bbs.homeshopmachinist.net//biggrin.gif Course you already knew that http://bbs.homeshopmachinist.net//wink.gif