Hyd. Pressure Relief ??

[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.