Hyd. Pressure Relief ??

[deerhunterf350]

Hello guys,

TC55DA w/18LA loader, I have 3 cast wheel wieghts on each side, and a 1200# 55 gallon barrel filled with concrete on the 3PH for ballast.

My question is.

Is the 3Ph HYD. lifting the 1200# and the Loader trying to curl/dig a heavy bucket load of Moist Clay , poping the pressure relief?

I sometimes here a Hissing sound when I am trying to curl a bucket full of Loose Clay.

I was thinking about changing the Hook up point on the Barrel. My thoughts are backup up to the Barrel, that is sitting on blocks say 1 foot off the Ground. Hookup , then lift the Barrel off the blocks and lower the 3PH so the Barrel is just hanging there 10 to 12 inches off the Ground.


I will try to check back throughout the week, but will be out of town on Business, so it may be next weekend before I am able to answer any questions.

Thanks

Dan

 

[Soundguy]

I installed my 3pt weight so that the hyds did not have to hold it up, but rather the load was supported by the arms at rest. This took the load off my hyds on my old ford 660 with an unloading type system, and only 1 system relief. i'm not sure how your new system is plumbed.. that is.. if the laoder has a seperate pressure relief.. say at 1500 psi or something, and thent he main relief at 2500 psi.. etc..

post more details..

Soundguy

 

[jinman]

Dan, I think your system only has one relief valve. The diverter valve routes pressure to both the 3PH and the loader at the same pressure. When you 3PH gets the 1200# load up, it goes open center and the load is held in place by a hydraulic lock. The system only has to work on that load if the valves or lift cylinder leak down. When the 3PH goes open-center, your loader has the full pressure. Most likely, you are just exceeding the relief pressure when curling your bucket in the moist clay.

Here's a little test you can do to check what I've suggested. As you curl the bucket under load, just drop your ballast load to the ground on the 3PH. That way it will not be supported at all by the lift arms. If you still get the hiss/relief sound, you'll know the 3PH is not contributing to the load. You may have to be a little careful the rear wheels don't come off the ground during your short test, but it should clear up any doubts you have about the way the system works.

 

[Doc_Bob]

I installed my 3pt weight so that the hyds did not have to hold it up, but rather the load was supported by the arms at rest. This took the load off my hyds on my old ford 660 with an unloading type system, and only 1 system relief. i'm not sure how your new system is plumbed..

I never thought of that approach, have the weight sit at the rest position so no load on hydraulics. Do you put (store the weight when not in use) the weight on a high enough platform so that when mounted, you lower it down?
Bob

 

[MadReferee]

The 3pt position control valve works somewhat like any other spool valve. Once the valve is in neutral (via the feedback linkage) the cylinder is locked and oil no longer flows to or out of the cylinder. Thus there is no load on the hydraulic system from the 3pt, regardless of how much weight is on the 3pt or in what position it is in (up or down).

Assuming the position control valve and feedback linkage are adjusted and working properly, the 3pt should have no effect on loader valve operations or the system or loader valve reliefs.

If the position control valve is defective or misadjusted, then all bets are off. When moving up or down oil is forced into the position control valve and poppets are opened and/or closed depending on the design of the valve and the direction of movement. A mis adjustment could cause fluid usage but since the loader is ahead of the 3pt in the hydraulic circuit, the loader would have priority.

My take on the problem is that the system or loader relief is set too low.

 

[Doc_Bob]

The 3pt position control valve works somewhat like any other spool valve. Once the valve is in neutral (via the feedback linkage) the cylinder is locked and oil no longer flows to or out of the cylinder. Thus there is no load on the hydraulic system from the 3pt, regardless of how much weight is on the 3pt or in what position it is in (up or down).

So, when I had a plow on my 3ph, I did not need to drop the plow to the ground when I had the tractor off to save wear and tear on the system? It just does not matter?
Bob

 

[MadReferee]

Of course it depends on the design of your 3pt position control valve (pcv) and cylinder. You have seals and springs that could fail or weaken. But for the most part, it is no different than keeping a loader raised. Once the cylinder is stopped, the hydraulic circuit (ie the pump flow) needs to do nothing to keep it there although the valve has to stay closed to keep fluid from leaking out.

 

[RickB]

A quick check of NH's online parts catalog for the TC55 reveals that there is no relief valve in the loader control valve. The main relief valve, located in the diverter valve housing should be checked and shimmed to the proper spec. Depending on the weight of the material you are trying to curl the valve may or may not be out of spec. The loader control valve has priority over rear remotes and 3PT for flow demands only. The relief valve will react to the function with the highest pressure demand regardless of where that function is in the system flow chart. That being said, any demand placed on the system by the load on the hitch will not affect the maximum PRESSURE developed at any pair of loader cylinders.

 

[Soundguy]

I never thought of that approach, have the weight sit at the rest position so no load on hydraulics. Do you put (store the weight when not in use) the weight on a high enough platform so that when mounted, you lower it down?
Bob

I have blocks I can set it on if i need to unlad the weight of fthe tractor tires.. however.. i use it often enough.. that I never take it of fthe tractor.. it is like pseudo power steering on that old 660 with loader.

soundguy

 

[Doc_Bob]

I have blocks I can set it on if i need to unlad the weight of fthe tractor tires.. however.. i use it often enough.. that I never take it of fthe tractor.. it is like pseudo power steering on that old 660 with loader.

soundguy

Okay, now post some pics!!!!
Bob

 

[Soundguy]

Of course it depends on the design of your 3pt position control valve (pcv) and cylinder. You have seals and springs that could fail or weaken. But for the most part, it is no different than keeping a loader raised. Once the cylinder is stopped, the hydraulic circuit (ie the pump flow) needs to do nothing to keep it there although the valve has to stay closed to keep fluid from leaking out.

Correct on paper.. but not always in practice.

True.. the valve holds the oil in the cyl and thus the pump is no longer having to support the weight.. however... let a few drips of oil leak past the rings in the lift cyl... then the piston moves back into the cyl a bit, thus triggering the regen cycle.. that is.. the unloading type system is once again under load to repressurize the lift cyl. On a system with a very small leak.. you may see multiple regens shown as the 3pt lift 'bobbing'. The leaks aren't bad enough to cause a problem.. or warrant repair.. but they do keep the hyd pump in the circuit to hold a load.. even if it is intermittant.

The lift cyl is a very small displacement in an old ford.. probably something like 10oz at max piston travel... it don't take much for enough oil to leak past rings or orings to let that piston move 1/8 of an inch and trigger a regen like I was talking about. At that point.. your hyd pump is pushing against that lift piston and whatever load ( like a huge concrete counterweight ).. PLUS whatever is int he laoder bucket.

small leaks aren't bad... large leaks can be more than the pump can keep up with.

9n/2n/8n/naa had about 2.8 gpm displacement with eng at 2000 rpm.. and most of the time people run their engine on these N at far less.. more like 1000-1500. The hundred series got a 4gpm pump.. again.. at 2000 rpm... etc.. easy to see how a few oz of leaks at a 50yr old worn lift cyl / piston.. or a bypassing spool valve could easilly overcome a low output pump.. etc.

That's why I made the statement about not knowing what type of hyd system his tractor had.. and then I made a comparison to my old hyd system on my example tractor.. etc.

Soundguy

 

[Soundguy]

Okay, now post some pics!!!!
Bob

I'm sure in t he vintage section there are plenty pics of my 660 with 1-arm laoder and 3pt counterweight. Just recently I used it to move a 800# round bale of hay.. etc.

Soundguy

 

[deerhunterf350]

Thanks for all the Replys, The Tractor in question is a 2005 NH TC55da with 45 hours. So hopefully there are now leaks causing is to go into Regen.

I will try Jinman test, ( Lowering Ballast ) .

DocBob,

I plan on setting the Barrel on Blocks for easy removal.

 

[Doc_Bob]

DocBob,

I plan on setting the Barrel on Blocks for easy removal.

Seems like a good idea.
Bob

 

[DieselMonk]

Does that 3 point hitch still surge like that with tractor equippment hooked up to it, besides that heavy ballast drum?

 

[joes_427_vette]

Bob; Did you have your dealer check the pressure on the hydraulic system ? I knew my 45 was low and the factory sets them lower than spec. My dealer shimmed the 55 as he stated it was way too low. There is a huge difference in the two with cycle time and lifting capacity.

 

[schmism]

how do you adjust it and were is the best place to blumb a guage to montor what your working pressures are?

 

[Soundguy]

On ~most~ systems you control overall system pressure by shimming the relief valve.. that is.. you set the pressure at whicht he valve will pop.. This may be a threaded spring adjustment.. or shims.. etc.

As for the gauge.. find a convienient point to tap in.. a plug.. remote.. etc..

Soundguy

 

[jinman]

how do you adjust it and were is the best place to blumb a guage to montor what your working pressures are?

On our Boomers, the relief valve is normally plumbed into the diverter valve on the right-hand side of the transmission case below the operator's platform. It can be identified by following your loader's input hydraulic lines back to the diverter valve body (if your non-oem loader does not use power-beyond). There will be a removable plug with the symbol of an open book beside it. They are telling you with the book symbol that you should refer to the maintenance manual for what is under the plug. It's kind of an "international symbol" meaning, "Don't mess with this unless you know what you are doing." I believe adding shims lowers pressure and removing shims raises it by about 200 psi per shim. Please don't hold me to this because I don't have my book in front of me.

The best way to measure hydraulic pressure is to plumb a 3000 psi or greater pressure gage into a male quick connect just like one on your loader attachments. Remove one of the loader hoses and put the gage in it's place. Start your tractor, raise the rpm to about 2000, and use the joystick to apply pressure. You can read maximum pressure on the gage. That's all there is to it. My tractor was exactly 2500 psi, just like the book said it should be.

 

[RickB]

I believe adding shims lowers pressure and removing shims raises it by about 200 psi per shim. Please don't hold me to this because I don't have my book in front of me.

Very good info in this post except for the effect of adding/removing shims. Add shims to increase pressure. Adding shims increases the spring rate; oil pressure has to overcome the spring to unseat the relief valve poppet. 200lbs/sq. in per shim is pretty close although ALWAYS check with a gauge of known quality.