Log Lift Valve Help, Please.

[Rocosil]

Inspired by the excellent posts about log lifts here, I'm building one onto my splitter. I'm planning to use a Dinoil (Bondioli & Pavesi) valve I've had sitting on a shelf for a while. The manufacturer's website gives me no info about this valve - older model I suppose - but with the help of a hydraulics tech I've come to understand that it has a power beyond feature and retract, neutral, extend, and float positions.

I had first meant to put this valve inline after the splitter valve (Prince, detent from Northern T. & S.), eliminating the power beyond by taking the plug out, but the hydraulics tech tells me that the back pressure it would create that way would interfere with the proper operation of the splitter valve. He recommends that I put the log lift valve inline first, ahead of the splitter valve, making use of the power beyond feature. He also tells me that, if I do that, the float position wouldn't work. I'm a bit hesitant to follow his advice because I just put on a bunch of new hoses (I raised the H beam), and positioning the valve as he suggests would mean that several of the new hoses would be too short. Two questions:
1) What do you think of the hydraulics tech advice? I ask because it doesn't seem to jibe with the info I've picked up from some of the posts here.
2) What would the float position do for me on the log lift? (This shows the depth of my ignorance about hydraulics.)

Thanks in advance for your input,

Bob

 

[Mike Van]

You don't need the float pos. Bob, my lift [and all others I know of] are double acting, power up, power down. The way he said to put the valve is the correct way, however, on my splitter I have 3 valves just plumbed in series, pressure in, out goes to the next valve, and so on. A log turner I built for my mill has the same setup. I've never had a failure, I use 2 valves at the same time sometimes [cly. is retracting & I lower the loglift] The PB valve first is supposed to eliminate a possible pressure buildup by porting it back to the tank -

 

[drmiller100]

your hydraulic tech is giving you great advice.

another idea is to buy a 2 spool valve and replace the valve you have.

 

[Rocosil]

Thanks, Mike Van. That was my initial idea: pull the PB plug and plumb the log lift valve in series, as you describe, after the splitter valve, but if putting it first in series with the PB doing its thing works just as well, or maybe better, I'll follow the technician's advice. I have found a mounting spot that will allow me to use my new hoses by just getting some different couplings. BTW, pardon my ignorance and idle curiosity, but what is "float" actually supposed to do, let's say, in a different application, if it's not needed for a log lift?

Bob

 

[Rocosil]

your hydraulic tech is giving you great advice.

another idea is to buy a 2 spool valve and replace the valve you have.

Glad to hear that. I hate disagreeing with an expert, especially when I don't know what I'm talking about. Buying a two-spool valve would certainly be neater, but being the cheapskate I happen to be, I prefer to make do with the valves I already own. To illustrate the extreme to which I'm carrying that principle: I'm scavenging the metal for the lift from from an old snow plow blade.

Bob.

 

[Mike Van]

The float position would be like on a front end loader, the bucket would scrape along the ground, but float up or down as it needed to. Kind of like a single acting cyl. in the down position. Snow plow would be another use.

 

[Rocosil]

Thanks for the education, guys.

Bob

 

[drmiller100]

so lets say you have a log lift. and you lift the log half way.

from there you can power up further, you can power down, or you can "float".

float lets the weight of the log drop the log to the ground. again, not needed.

 

[kevin j]

VALVES IN SERIES OR POWER BEYOND

Assuming this valve is large enough for full pump flow of course.

Float is usually a 4th position, past the ‘down’ position. Usually detented to hold in float. Scraping with a loader bucket is a common application.

With a log lift, the valve could be accidentally pushed in past ‘down’ (controlled flow) to ‘float’ (uncontrolled wide open) causing a sudden drop. I doubt that matters here, as the lifter is probably already down as the spool passed through full speed down on it’s way into float. You could remove the detent balls, put shims in there, tap a setscrew into the cap, anything that limits spool travel so it can’t go to float. Personally, I’d just use it as is.

One thing you don’t want is to reverse the hoses and have ‘float’ past the ‘up’ direction. If you went past ‘up’ into float, it would suddenly drop like a rock as A & B are connected to tank.

I would put the power beyond valve first, using the PB port to the second valve as intended. Valves can be plumbed in series, even those not intended to be used that way, and many people here have done it with no apparent problems, but there are several potential issues:

-The outlet port of the first valve sees full system pressure when the downstream valve is loaded. The casting of the first valve needs to be strong enough to take that.

-Sometimes the end caps are connected to tank line (usually not on manual valves) for leakage, and that can blow the end caps or seals.

-Load pressures are added up and can’t exceed the relief valve setting of the pump. Say the RV is 2500 psi. Lifter could have 2500 psi by itself. Splitter could have 2500 psi by itself. If both are together, the loads add. 2000 psi on lift only leaves 500 psi on splitter. 1000 on splitter leaves 1500 psi for lift, etc. Not likely an issue here, but keep in mind for circuits that are loaded at the same time.

-Most significantly, the relief valve in the first valve in series can be defeated and not work at all. RV does not control pressure in absolute psi readings, but only so many psi above its reference port. Usually, reference is the outlet or tank line, so with a spring of say 2500 psi, the pump gauge reads roughly 2500 psi when relief valve is venting to outlet (tank) line. However, if the outlet port of the valve sees 2000 psi from the downstream loads, the RV will be seeing that on its reference port. If a load is put on both valves, the pump could see 2000 + 2500 = 4500 psi. If the load is totally on the downstream second valve, the RV will never open at all and pressure is uncontrolled. RV is out of the picture because any reference or any relieving just goes downstream against basically a plugged line.
If you go series valves, add a separate RV in the line before the first valve, venting to tank.

-There can be a situation with cylinders in series called ‘intensification’. Depending on bore/rod ratios and direction of load (push vs. pull, and resisting vs. overrunning) the downstream valve can see pressures much higher than the pump RV setting. Basically cylinder 1 acts as a pump and adds energy to the downstream fluid. With the PB feature, the first cylinder returns to tank, and the second cylinder returns to tank, and they won’t intensify pressure. Beyond the scope of these boards, just be aware of it.

k

 

[drmiller100]

valves in series that aren't intended for it have one more issue.

if you mount a hydraulic motor off the first valve, then try to run both valves at the same time, your odds are pretty good on blowing the seals on the motor.

 

[kevin j]

if you mount a hydraulic motor off the first valve, then try to run both valves at the same time, your odds are pretty good on blowing the seals on the motor



good point on motors. Same cause: the shaft seal/case drain is internally connected to the downstream port of the motor and expects a low pressure. When that outlet port is pressurized, it can either blow the shaft seal, blow the motor case from pressure, blow the front bearing because of twice the amount of thrust forces in some motors. Even if not fail right away, the lip seal is pressureized and gripping the shaft really tight and will probably fail and score the shaft.
If you want a motor in series, check the mfr maximum outlet port pressure, and connect a separate 1/4 inch case drain hose back to tank.

k

 

[Rocosil]

VALVES IN SERIES OR POWER BEYOND

Assuming this valve is large enough for full pump flow of course.

Float is usually a 4th position, past the ‘down’ position. Usually detented to hold in float. Scraping with a loader bucket is a common application.

With a log lift, the valve could be accidentally pushed in past ‘down’ (controlled flow) to ‘float’ (uncontrolled wide open) causing a sudden drop. I doubt that matters here, as the lifter is probably already down as the spool passed through full speed down on it’s way into float. You could remove the detent balls, put shims in there, tap a setscrew into the cap, anything that limits spool travel so it can’t go to float. Personally, I’d just use it as is.

One thing you don’t want is to reverse the hoses and have ‘float’ past the ‘up’ direction. If you went past ‘up’ into float, it would suddenly drop like a rock as A & B are connected to tank.k

Kevin,
This is one of those 11 GPM, 2 stage Barnes pumps hitched to a 5hp motor and, according to the tech I consulted, the Dinoil valve will not restrict the flow to the splitter valve. Since he seems to have been right about everything else he told me, I'm inclined to take his word for this as well. At this point I'm not sure if the float position on this valve lies beyond the retract or the extend position. I was under the impression it was beyond the extend (up), but its being beyond the retract makes more sense. I know which working port is extend and which retract, but I'm not certain about their operation sequence. If I don't figure it out before, I'll find out for sure after I have it all together and fired up for its first trial run, and switch the hoses around accordingly, if needed. Thanks for the heads up.

I truly appreciate your taking the time to put all this info together and feel much more confident I'll get this project done successfully, now that I actually understand what I'm doing.

Bob S.

 

[kevin j]

most valves there isn't really an extend or retract port, just A & B that can go either way.

Single acting cylinder valves do have assigned ports for extend or retract. (Single hose SA cylinder valves just have one port. Dual hose SA cylinder circuits use the second hose for venting oil back and forth but it isn't powered.)

Some valves have port reliefs, checks, pressure reducers on one port or the other, but I am guessing yours is simply a symmetrical run of the mill spool that send pressure to A or B and connects the other to tank. You can push soem air, or crank the pump over and see which port is oil coming out. Or try it and switch hoses. On a splitter, the consequences of backwards hoses are not severe on startup as long as you are careful. No big deal. It will work out.

k

 

[triptester]

If the the valve has a detent than the port controlled by the detent would be the retract port. Some log splitter valves have relief valves on extend port only.