hydraulic safety valves...suitable replacements?
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Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=73071
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Topic: hydraulic safety valves...suitable replacements?
Posted By: doctorcorey
Subject: hydraulic safety valves...suitable replacements?
Date Posted: 07 Jul 2013 at 7:24pm
| Hello, again. Corey in Lincoln, Mo. here. I'm looking at possibly replacing the bulldozing safety valve on my HD7G, and as I know no AC part is available new (at least below the national debt) , I'm wondering if any of you geniuses know of a suitable replacement, maybe cat or JD. I think it's 3/4 pipe mount (correct me if I'm wrong, please) and length is not a factor. I get the symptom of the bucket just folding under if I try to doze with it, and it takes little force to acccomplish this, although it seems to have pretty good power in tipback. I always thought that if the dozing safety valve was leaking, then you would get leakdown on the bucket creeping down in the hold position. Maybe the safety valve spring is sacked or broken, and just shows up bad when you're pushing something? I'm going to try to get some guages on it but I don't yet own a flow meter. Appreciate any advice. I took the side case off the shovel reservoir and remove the suction screen: I'll post a pic tomorrow of all the crap that was in that screen. Mostly some sort of fibrous stuff that was burgundy color and looked like the red stuff you peel off of baloney before you eat it. Lots of dirt and old crap as sediment. I flushed with diesel and then wet vac'd it. All clean now. |
Replies:
Posted By: Coke-in-MN
Date Posted: 07 Jul 2013 at 8:36pm
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IF your bucket is folding under , I would say it is the valve body and not relief valve , either that or bad cylinder seals on piston. Relief valve should only be in system for overpressure or over load when valve body is open to cylindres. Once valve body is in neutral the relief valve would bypass any overpressure from pump but have no control of load . Check your cylinders roll cylinder all the way back , then - remove one hose (dump side) and plug line, and with pump pressure apply pressure to roll - back side of bucket - If you get flow out of dump side you have bad cylinder seal. Do each side separate to isolate bad unit. ------------- Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something. "Challenges are what make life interesting; overcoming them is what makes life meaningful." |
Posted By: doctorcorey
Date Posted: 07 Jul 2013 at 10:57pm
Coke,  OK, but what could be wrong in valve body to cause that much fluid slippage? Are not the outlets hoses to lift and dump blocked off by valve spool in the hold position? Or the bucket spool check valves dirty of sticking. The bucket seems to be real strong while backdragging. I can buy a valve body here locally, but it's a second or third design. Do you suppose it would fit?
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Posted By: Coke-in-MN
Date Posted: 08 Jul 2013 at 10:57am
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Changing out the valve body ? Unsure as the flow rate of pump has to be considered in it's design. Seems the leakage has to be downstream from the valve . When dozing with my HD5G I do get a little drift down with bucket but not enough that it is not affected with a slight pull on control. I set bucket angle and then control depth and cut with loader lift frame control. As oil between the dump cylinders is fed off common manifold to both cylinders I still think the cylinders is where the problem is - oil bypassing in the cylinder from lift to dump side. ------------- Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something. "Challenges are what make life interesting; overcoming them is what makes life meaningful." |
Posted By: dadsdozerhd5b
Date Posted: 08 Jul 2013 at 8:05pm
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does the bucket drift when it is above the ground? if it does, it is definitely the packing. coke's test will provide you with the info you need to pinpoint the issue. it should not roll under when grading. good luck and I want to see those pics. ------------- HD5B, HD5G, (2) FARMALL A's, CUB. DO IT RIGHT THE FIRST TIME, IGNORE THE LAUGHTER. FLANNEL IS ALWAYS IN STYLE. |
Posted By: doctorcorey
Date Posted: 08 Jul 2013 at 8:22pm
No, dads, it doesn't drift down. With a load of dirt, it doesn't , but if you drop the bucket bottom vertical to the ground and then roll the machine forward, the bucket rolls under easily and pulls the rams out of the cylinders. I've got to get a gauge on the bucket circuits and see how much pressure the pump can make before the slippage or the dozing safety valve "pops". I'm going to run the packing tests this weekend as well. The machine still digs good and can move a lot of dirt, but is hard to contro the bucket for scraping. Kinda like a poor mans excavator......
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Posted By: HD6 Merv
Date Posted: 09 Jul 2013 at 2:54am
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Theyre called bucket line relief valves, designed to 'let go' before something breaks from a external load, like bulldozing with the bucket. Don,t know there pressures but are about 300lb above normal main system relief valve pressure on a 941 cat. I usually found it was better to bulldoze with the bucket flat; once the bucket half fills with dirt it acts the same and just pushes the dirt, sure it runs around the outside but that happens with a narrow dozer blade too. 4/1 bucket open the clam abit and use it like a carpenters plane, works fantastic, wider the clam=more bite. my 10c worth anyway, cheers M ------------- tits tyres and tracks they all cost you money |
Posted By: doctorcorey
Date Posted: 09 Jul 2013 at 7:58am
| Yeah, Merv, on this machine, the safety valve for the bucket cyl tail end is 2900 psi, made to relieve pressure from dozing when the spool is in the hold position. A bucket can work pretty good even if this valve is weak, as the working pressure rarely exceeds 12-1500 ( main relief pressure) psi, but fail when really pushed. If my packings are good, I'll be looking for a broken spring on that valve. Thanks |
Posted By: Coke-in-MN
Date Posted: 09 Jul 2013 at 1:55pm
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Dose that circuit have a return to level circuit in it ? If so that could be the area of problem also . My old HD5G just has straight control from spool with a relief valve on lift. ------------- Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something. "Challenges are what make life interesting; overcoming them is what makes life meaningful." |
Posted By: doctorcorey
Date Posted: 09 Jul 2013 at 3:13pm
| Well, Coke, it has no return to level thing, but it does have a diverter valve under the main valve body for the ripper. |
Posted By: doctorcorey
Date Posted: 10 Jul 2013 at 9:41am
The only filter on this machine I never checked, until now. Geeeeez....
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Posted By: doctorcorey
Date Posted: 10 Jul 2013 at 9:43am
| Notice the baloney peel looking strips. Maybe the end packing of old filters? |
Posted By: doctorcorey
Date Posted: 21 Jul 2013 at 9:05pm
| Well, I repacked all the rams yesterday. Pretty straightforward except the lift packings were TIGHT! But now, no more creep-down on the boom. I retested the backdragging and bulldozing holds and now I only have roll-over when dozing. That's why I always ended up digging holes instead of scraping dirt. I'm going to attack that dozing safety valve after I test it's yield pressure. I'm getting close to having this machine fully cured. |
Posted By: doctorcorey
Date Posted: 04 Aug 2013 at 9:49pm
Just a follow-up on my project. After repacking the rams, I now have dead-steady control on the boom and bucket. Now I don't tear everything up just trying to push brush piles around. I put a 3000psi gauge on the tip-back circuit, rolled the bucket almost over and pushed against a large cedar stump in low gear. The gauge flew up to about 2800psi and popped the dozing safety valve as advertised (2900 factory setting) Tipping back bucket against the stops shows around 13-1400 psi main relief valve setting. Now, I'm reading this gauge under duress so I don't expect calibrated readings, but they;re close so I'm happy. I'll check steering brake pressure next. I just need to buy my decel linkages (hint, hint, DMILLER) and I'll be done. Now I'm obsessed with backhoes, so.....
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Posted By: Coke-in-MN
Date Posted: 05 Aug 2013 at 12:43pm
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Still have my AC 615 backhoe attachment I had on my HD4. 14' hoe with 24" bucket, that drops into toolholder which mounts to back of machine . It is 2 stick valve body setup, with stabilizer legs Was thinking of mounting it on my HD5G or the FD5 but with the 715B I don't need 2 hoes. ------------- Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something. "Challenges are what make life interesting; overcoming them is what makes life meaningful." |
Posted By: doctorcorey
Date Posted: 06 Aug 2013 at 10:07am
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Coke-in-MN wrote:Posted By: Coke-in-MN
Date Posted: 08 Aug 2013 at 1:28pm
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Looking for about $2500 for the hoe , is a 14' dig and present bucket is 24" - pin size to bucket is 1 1/4" - where my AC715 uses 1 1/2" pins. Right now I have one of boom cylinders on my 715 as I have a problem with piston on that. All the cylinders between the two hoes are interchangeable. The 615 hoe uses a Cessna swing rotary piston where the 715 uses 2 cylinders. Unsure of what the GPM was on the HD4 but seems the 25 GPM was about right. The hoe has it's own valve body and relief valve built into controls. ------------- Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something. "Challenges are what make life interesting; overcoming them is what makes life meaningful." |
Posted By: Froggieo
Date Posted: 08 Aug 2013 at 2:06pm
| After the bucket rolls back, if lift the buck up does it roll forward to original position. It sound like you may have air trapped in cylinder which will let it roll when extreme pressure is on the bucket, but it should spring back when the load is removed. |