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10-12-2011, 07:34 AM #1
counterbalance recharge central ct.
I need to get the counterbalance on my vf-2 recharged, it's at about 600psi now.
It is alarming out because the pressure on the counterbalance is low. I've had the unit replaced once and recharged once. Haas will not recharge it and wants me to buy a new one so l was wondering if anyone around here re charges them. Any leads on independents in the Connecticut area that do this would be great.
10-12-2011, 08:59 AM #2
Why does Haas refuse to charge the system? My guess is that is leaking, which means that is needs to be repaired. If it is leaking then you have a potentially dangerous situation that can happen at any time.
Most common place for them to leak is with the seals in the couterbalance cylinder at the Z-Axis but unfortunately there are no rebuild kits available so replacement is the only option.
Get this fixed ASAP!
10-12-2011, 09:37 AM #3
Nitrogen was added about 4 years ago because the pressure was a little low. The service guy told me they will only add nitrogen once, then they won't do it again and said the next time i need to have it replaced.
10-12-2011, 09:53 AM #4
I made up equipment to charge mine about a year ago. It was down to about 550 to 600 and with the servos off the head might drift down. I put it back to 750 and it is still at 750, not moving.
My old VF-4 went down a little while it was under warranty and my dealer charged it back up. It never went down again in four years.
10-12-2011, 10:09 AM #5
we got a small nitrogen tank from the welding supply store and i believe we got the hose from haas? and we charge ours every few months. it's been replaced a couple times and charged a couple more times. i can't remember what the service call price was but the tank and hose payed for itself on the first re-charge.
10-12-2011, 10:16 AM #6
Make sure you get the proper nitrogen tank. Needs to be "dry nitrogen," rather than standard nitrogen.
10-13-2011, 09:59 AM #7
This time of year is the peak for machines needing charged due to fluctuations in day/night temperatures affecting how well the seals in the cylinder work.
Recharging 1-2 times a year in my book is perfectly acceptable. If they don't want your money, then as others have said, do it yourself and save lots of money, down time, and most importantly keeping your machine safe to work around.
Go to a welding shop and get all the parts you need or you may be able to order the hose with connectors from your HFO. Be sure to get dry nitrogen as previously mentioned and fill it sloowwllyy; it really is very easy to do.
Remember though, these cylinders can be charged up to 3000 PSI so be careful.
10-13-2011, 12:47 PM #8
I got a bottle of medical grade nitrogen (it's what they recommended for my ap) and this set up http://www.hydracheck.com - Accumulator charging kit, Schrader, Tobul
I'll charge it up and monitor it for leakage. If I see the rate of leakage accelerating I'll have the system replaced.
If anyone in the area needs theirs re-charged pm me and I will hook you up, literally .
10-18-2011, 03:00 PM #9
The counterbalance system contains both oil and nitrogen. If the counterbalance system looses enough oil, just filling the system with nitrogen would not be effective. Due to the difficulty of removing the oil from the tank, measuring the oil and refilling the tank, it is common practice to just replace the tank with one that was built and filled (oil) by the Haas factory. I would also like to add that the loss of nitrogen indicates that there is a leak in your system. This needs to be repaired. Low nitrogen, a leaking counterbalance system or incorrect oil level can all lead to an unsafe machine.
A Haas Factory Outlet may decide not to charge a nitrogen system based on the fact that the system is leaking or there is a significant loss of oil.
Please provide me with a serial number and I can look into this for you. I am a service engineer for Haas Automation, Inc.
Jason_S liked this post
10-19-2011, 07:55 AM #10
10-19-2011, 09:16 PM #11
I add to one of my machines twice a year, spurt, and good again.
09-26-2012, 12:33 PM #12
First forget about the nitrogen, if you are to the point of leaking nitrogen it's too late for a simple fix.
You are probably not leaking nitrogen, you are leaking hydraulic fluid. The pressure will drop slowly until the hydraulic fluid is gone then it will leak very fast when it gets to the nitrogen(like in less than a week).
I got a grease gun that would also work for hydraulic fluid and a shreder fitting that attaches to the valve by the guage under the tank on the column.
You have to pump a while but the pressure will come back up and will work fine.
I did mine 6 months ago to 1150 psi on my Haas vf3 and it seems to have healed itself.
I would say this method is safe if you are not below about 600 psi for a vf3. Below that pressure you may be into the nitrogen.
Make sure it's a 3,000 psi grease gun
If it's leaked all the way down you will have to pump in the right amount of hydraulic fluid and then charge it with dry nitrogen to the right pressure.
This works for slow leaks. Obviously if you have a serious leak then forget what I just said.
09-26-2012, 02:28 PM #13
09-26-2012, 05:07 PM #14
I know that if the pressure is too low the machine won't start, but if the pressure drops while running, will the machine stop where it is? If so, I don't see how it's all that dangerous a situation. Not that I think this would save the whales or anything, but I don't see a MAJOR crash happening. Is there something I'm missing (other than common sense).
09-26-2012, 05:18 PM #15
The nitrogen is in a steel pressure vessel upside down so it can't get out until the oil is gone.
So add oil to bring the system pressure up and it will remain in balance.
once the oil is gone the pressure will drop a lot faster. Don't ask how I know this.
09-26-2012, 05:23 PM #16
The head won't drop if it's under power. I ran a machine for a while with low pressure and except for a little higher z servo load it was fine.
But I lost power once while machining like this and it was fairly noisy.
09-27-2012, 07:39 AM #17
It's been about a year since I topped off the Nitrogen tank. I checked the gage and I'm about 725 psi at the top of the travel, so I lost about 25 psi in a year. I don't think that's bad at all. If it gets to a point to where it's losing pressure rapidly I'll have the counter balance replaced.
09-27-2012, 11:17 AM #18
I have personally drained many systems and I always do so leaving most of the oil in the tank. Sure I lose some while doing it, but I certainly do not loose all of the oil before I drain any gas. Perhaps you are not properly trained at doing such task.
Blindly adding oil to the system to increase pressure without knowing how much you have in it can damage your system if you put to much in it. I would never advise anyone to add hydraulic oil to the system without knowing how much was needed. Only way to know that is to completely drain it and refill with proper amounts.
09-27-2012, 11:19 AM #19
Your right 25 psi in a year is nothing. Mine was leaking 50 psi a month. I had lost so much oil that adding oil was my only option.
It fixed itself after I added it. I'm guessing there was seal conditioning additives in the hydraulic fluid I added.
But whatever the reason it has held it's pressure for about a year now(I said 6 months in a previous post but it's a year or so) and runs fine.
At the time I had no money, so I had to be creative.
Last edited by piotech; 09-27-2012 at 12:58 PM. Reason: wrong info.
09-27-2012, 11:51 AM #20
What do you think the odds of developing a leak in the bottom of a hydrostaticly tested pressure vessel are. Not as high as developing a leak at the moving seal on the counterbalance cylinder I'm guessing. and if you develop a leak in the seal then most of the oil will be pumped out of the system through this seal.
You actually can tell how much oil is in the system at any time with a little math.
you can calculate it from the rate the pressure changes from the bottom of travel to the top of travel. less oil will make the pressure change less and too much oil will make the pressure go up faster because the volume of gas is smaller therefore the ratio of change is more severe. This holds true regardless of the pressure because you are looking for the ratio.
find out how much the pressure changes on a machine with a properly function counterbalance and compare it the leaking one and you will know if you're low on oil or nitrogen.
There is a decent margin of error if you add oil slowly and travel the machine up and down and watch the pressure change. too much oil will make it start to spike some and you can stop and replace the cylinder or whatever you decide.
It's pretty obvious that things are going amuck and it happens slowly. It takes 40 pumps on the gun to put 1 oz. of oil in so it is not a speedy thing. you can sneek up on it slowly.
I am not advocating anyone doing this, I'm just stating what worked for me