FEL and Rear T&T Control Valve Flow Capacity Questions

[TX mower]

Questions relating to choosing control valves for FEL and Rear Top and Tilt applications for tractors like my Yanmar with constant-flow hydraulics (where control valves are in series with open center and power beyond / PBY) ....

1. It's been my understanding that control valves should certainly have rated capacity adequate to flow the tractor's rated pump GPM @ rated pressure, paying particular attention to pressure loss between the pressure input and the PBY out port to ensure good flow and pressure for other implements that may be in the hydraulic 'chain'.

Is that a correct understanding?

2. It's also been my understanding that using a valve with too much excess flow capacity usually means it'll be more difficult to achieve 'finesse' / 'fine control' of cylinders on the working ports of that valve.

Is that a correct understanding, and if so, is there any rule-of-thumb guidance for a 'target cutoff' for control valve excess capacity (say, as a % of tractor pump flow, like ~120%) above which one would expect the loss of 'fine control' to be meaningful?

3A. IF one finds they would like better 'fine control' for a given implement control valve and cylinder action (e.g. bucket tip, for 'feathering' dump of gravel while spreading), would inserting a inline flow-restrictor between the control valve working port and the cylinder for that action improve that situation (e.g. on the bucket-tip / bucket cylinder extension hose)?

3B. IF it would, are there other side-effects of adding a flow restrictor in that situation which should be considered?

- I realize that not all cylinders / actions need particularly 'fine control', but FEL bucket tip, and in the case of rear control valves both top and tilt are actions where it would seem desirable.

- And I realize there's more than just flow-capacity to consider when selecting control valves. Just wondering about this flow-rating aspect of the equation when making the expensive choice of valves and hoping to get the best result possible given all the variables / compromises that must be balanced.

TIA for any continuing education.

 

[majorwager]

Believe you already have an understanding of your hydraulic questions. I was taught that the flow rating of the pump capacity and the valve should match. That said, last year I read a post with the scenario I describe.

A poster purchased a prince valve from surplus center that I was also considering. The spec noted it was rated at 25 gpm so it was eliminated from my list. The poster had a pump capacity similar to mine, about 9 gpm. He stated it worked flawlessly. I found that hard to believe but that is what he wrote. The valve was also huge in size which he found to be an issue, but he mounted anyway. It was a double spool w/ an additional 3 rd function spool.

I believe he had no feathering ability at all but he reported the contrary. I question why you need a restrictor valve. One exists on most compacts, it is a screw type that regulates the speed drop of the rockshaft cylinder.

This function can be accomplished w/ the pressure valve but since the rockshaft cylinder is NOT power down, most folks are careless w/ the lever and just dump the oil into the reservior too quickly. (A single acting cylinder)

If the function you are employing is power up and down (double acting), , you should be able th feather the stroke absent a separate in-line restrictor. This presumes valve and pump are matched in capacity output.

Kubota factory rear remote valves are famous for by-pass. I did not know this at the time I installed my top link. I believed the cylinder was the culprit. I installed restrictor in-line valves to offset the cylinder creep. They work but w/ a cab, I must exit and open them to operate the top link. Not worth the effort.

Should go w/o noting, pump pressure rating and the valve must also match or a pressure regulator is required. Constant use of the pressure regulator likely will overheat and FOAM your oil.

 

[TX mower]

OK, thanks for validating my understandings about basic rules for sizing.

If the function you are employing is power up and down (double acting), you should be able [to] feather the stroke absent a separate in-line restrictor. This presumes valve and pump are matched in capacity output. ....

Fair enough, but my question about using a flow restrictor is for mitigating the situation where the valve has significant excess capacity relative to the pump.

I question why you need a restrictor valve. One exists on most compacts, it is a screw type that regulates the speed drop of the rockshaft cylinder. .....

My Yanmar has a fast/slow return valve but it seems to only affect the 3PH ("rockshaft"?). As far as I can tell both from tweaking it while using my FEL and from looking at the hydraulic circuit diagrams it has no effect on valves/implements connected to the tractor's divider block such as FEL and Rear Aux valves.

Disclosure:
My tractor has a pump rated at 8.4GPM with main pressure relief at 2050-2200 psi.
I recently installed a replacement FEL control valve rated at 'nominal' 10GPM which is giving very satisfactory feathering control for all functions - no worries or problems there. (the ~35 year-old OEM valve had several issues including lack of available rebuild parts).

I'm still searching for a control valve to add T&T (where I'd like 'fine control') and a box-blade ripper-drop / flail mower side-shift cylinder (fine control not so important) .... that's the reason for my questions as I'm having a bit less luck finding a 3-spool monoblock or stack valve that offers all the features I'd like along with closely-matched capacity. I'll keep looking, I may end up with multiple separate valves instead of a monoblock or stack.

Just working toward a setup that's a bit more operator-easy as I'm aging and my tractor has, I hope, lots more life left in it as I do

 

[MtnViewRanch]

TX mower, I provide these valves for all tractors up to 12 GPM. ZERO issues reported. These are an excellent quality control valve with several different functions available.

 

[majorwager]

Another source is surplus center. They will send you a catalog which provides valuable reference. Do you have a rear remote valves currently?

If you feed an additional valve from the loader valve be sure the power beyond port is activated.

 

[TX mower]

Brian, thanks for that Bucher HDS11 sectional valve link, definitely another to add to the list of possibilities.

I see on your pricing page reference is made to "flow restrictors" included with some kits and available separately.

With apology if I missed it on your Tutorial or FAQ pages, would you explain when, why and how those flow restrictors are used in conjunction T&T systems?

majorwager, yes, I've been reviewing Surplus Center's control valve options rated at nominal 14 GPM also, thanks. I'm a bit disappointed that given 10 business days Surplus Center still hasn't responded to some specific product questions submitted by email to their product tech questions contact address but so it goes, I've written that off.

I'm currently running an FEL valve with a PBY Port since that's required to route back to my tractor's Divider Block for the 3PH operation, as well as a hose from FEL Port "T" out to the transmission case (system tank) for low-pressure relief return. No modification to the existing FEL valve is required, just a re-route of the FEL PBY Out hose to the added valve P In.

A blind plug is required inside the Yanmar Divider Block to enable the external valves hydraulic circuit, obviously that's already been done for the FEL.

I understand that the added Rear Valve will be inserted in series to the system as follows (black being what's there now, red being what will be added):

Tractor P Out > FEL P In > FEL PBY Out > Rear P In > Rear PBY Out > Tractor PBY In (actually a "P In" but Yanmar calls it "PBY In")

I'll add a "TEE" fitting at the transmission case port to allow the relief flow from both the FEL and added Rear valve to return to the tank there (that being a LP parallel, not HP series, return circuit, the Yanmar Powershift transmission case / hydraulic tank being at atmospheric pressure).

 

[Fallon]

I assume those Bucher valves MtnViewRanch mentioned are the same ones i got from him for my 3 spool & TnT install I did on my former L3200. They worked well. Several days to leak down. Not quite as good as the Kubota loader valves, but way better than current Kubota rear valves.

You put restrictors on your TnT cylinders to slow the cylinders & make them easier to control prescisely. They are way too twitchy without restrictors.

 

[majorwager]

TX
Surplus Center is a high volume merchandiser. When I have questions, I call and speak to their technical dept. Most often, responses are satisfactory.

Smaller businesses offer individualized attention more readily, but there is a COST. Folks familiar w/ hydraulics navigate the surplus center catalog and purchase what they need.

In today's market, difficult to serve all masters. Businesses have operated under lean economic conditions in recent years and customer service to assist the novice has suffered. Current economic expansion is beginning to recover but the business community is cautious.

You seem well enough informed to confirm your own project goals. I would offer an opinion, I do Not generally employ stand alone restrictor values.

If I need precision feathering, it is usually for a hyd motor and Use of a valve w/ built in flow control does the trick.
Example : Brand Hydraulics, surplus center product # 9-7497-30.

Case and Deere offer an Industrial Tractor w/ an integral box blade / with a 5 section double spool valve bank. This tractor is popular with driveway contractors in the South. There are no flow restrictors on the factory machines. Watching an experienced operator navigate those box blades is akin to a piano player spanning 3 octaves at once. It is all in experience, and a feeling for the valve control.

The same w/ a road grader. The dexterity of those operators is amazing, many can repeatedly adjust the cutting blade to a fraction of an inch, all second nature.

 

[TX mower]

.... You put restrictors on your TnT cylinders to slow the cylinders & make them easier to control prescisely. They are way too twitchy without restrictors.

Gotcha. So do they install at the cylinder or at the hose-end where it mates to the tractor rear couplers, or does it matter?

I assume that there's no real concerns about fluid heat buildup, cavitation, etc just because of the way that T&T is typically used .... they aren't subject to a lot of full-stroke back-and-forth actuation in normal use like loader cylinders are, is that correct?

 

[majorwager]

TX,

Your question to fallon, believe you made a proper assumption. Heat, cavitation not likely. I equate restrictor valves to training wheels on a bicycle.