Help with slowing down a hydraulic circuit

[VirginiaIron]

Greetings All,
Today I installed a 1/16" restrictor in the circuit of my log lift, located at the 1/4" fitting of the 2" cylinder. The restrictor has slowed the lift down about half (unloaded) and has increased the pressure to about 1200 psi; originally this circuit was running close to 500psi unloaded. My detent is not adjustable and will no longer return the table to the ground without holding the handle.

I would like to slow the circuit down even further, will I need to install a SMALLER restrictor prior to the valve?

Thanks for viewing and special thanks to all replies.

 

[VirginiaIron]

Well I removed the restrictor and decided it was considerably faster without the restrictor. Then I remembered those kind words from a long ago role model, "Boys and girls, can you say the word "Feather"? Someone here mentioned this a while back, thank you. Lol, well it looks like I need to practice feathering the lift. It's actually much easier feathering with the restrictor than not. I noticed the feathering with the restrictor limits my pressure to under 200 psi.

 

[kevin j]

You don't want an orifice before the control valve unless there is another relief valve nearer to the pump.

Since the pump is a constant flow device, when you move the valve fully shifted, the pump moves flow, but since it can't all go through the orifice the pressure rises until most goes across relief, and very little to the log lift. All the energy created in the pump is throttled across the relief valve and changed to heat.

if you 'feather' the valve, it does not fully close off the path in neutral to tank, You only create enough resistance (pressure) to move small amount through the orifice to the lift. The oil going through neutr4al to tank is at lower pressure, 200-400-800 or whatever, so cfreates much less heat.

Also, the fixed orifice restricts in both directions. Lifting is fine you want the restriction, But lowering it will restrict also, and depending on circuit can intensify and create higher pressure than the pump relief is set at. Do the math on that, or post a sketch with bore and rod and rv setting info.

There are several better choices than fixed orifice:
-Priority flow divider to send a couple gpm to the cylinder, and the rest is sent to tank, but at lower pressure than relief setting.
-Pressure compensagted flow control to the cylinder that adjust for load, but stillsends oil across relief and creates heat.
-Stop screws that limit the spool motion in the valve. Some valves have stop screws against the ends of the spool, but I doubt you have that. So, basically make a mechanical stop to prevent the handle from moving morfe than a certain distance. I have done this, and is what I would do here. Find a space around the lever where you can drill and tap, or weld a nut, and add a set screw or bolt. Adjust this so when you pull the lever hard against these stops, maybe it only moves 1/4 stroke in one direction, or 1/8 stroke in the other direction. You could also make a slotted bracket around the lever and bolt on some sort of plate that stops the lever travel.
Basically, you are creating a stop where the lever still 'feathers' (ie. meters) but doesn't depend on the operator to move the handle correctly.

I would do something just for safety reasons: Full travel of the lever launches the log lift way too fast. So either an orifice, or mechanical stop I would add something.

 

[VirginiaIron]

@kevinj- thanks for the wealth of information, I will need to digest this information some, and the lever stop sounds like the way to go. I did reinstall the restrictor so i feel more confident and safe operating the lift with it in.

 

[VirginiaIron]

I am going to go with the lever stop and remove the restrictor. I will post photos when I am finished and have it working, thanks.

 

[VirginiaIron]

After changing out the valve my lift is more controllable and easier to feather. I do not need the restrictor anymore.

 

[VirginiaIron]

Howdy folks. In the honor of not hijacking a currently running thread I would like to dispel a couple of often repeated talking points when it comes to hydraulics. Hopefully I can do it without causing more confusion.

First - can we all agree that fluid doesn't compress? At least no measurable amount to mere human types. Yes - good.

Second - can we agree that a positive displacement pump will put out its rated volume as long as there is no Incoming fluid restriction and it is operating properly (not wore, slipping the lovejoy, etc.) Basically, it has to unless you stall the engine or it hits bypass pressure at the valve. The exact reason a bypass is needed - so things don't break.

With these two factual statements I would like to clear up some common misconceptions about splitters.
Small ports or hoses do NOT reduce flow unless you create enough pressure to bypass the relief valve or in the case of a splitter pump, kick it into the low side. Pressure and flow have to be treated as two different things (cuz they are).

A flow restriction can do bad things if it is too out of balance (create heat, increase pressure, increase wear), but one thing it won't do is reduce speed. Again, at least not measurable to us human types.

I know there are at least a few out there that are thinking "oh yeah - well how does a restrictor valve slow down my log lift"? By decreasing flow, increasing pressure and bypassing the excess fluid (that is the short answer).

I believe that this confusion is just a terminology issue as much as it is a misunderstanding.

So - I am gonna put it right out there...
Using a 16 GPM pump (just an example) with half inch hoses or ports is NOT going to be SLOWER than using 3/4 inch hoses or ports unless you build enough pressure to bypass the relief valve or kick the pump into low gear (so to speak). Yes - you can increase heat, yes, you will increase pressure, but you ain't gonna slow down the flow. Remember - fluid doesn't compress.

A real life example was when I was building my small splitter - I used a 3.5" cylinder with 3/8 inch ports and a 16 GPM pump. Sucker is fast. At no load (moving the cylinder back and forth) the pressure gauge in line barely wiggled, It never even touched 100 PSI (very small amounts for a system designed for up to 3000). What does this mean? Even at 16 GPM the restriction to the flow barely took an increase of pressure to balance out. All 16 GPM was running through those small ports with just a minor increase of pressure to compensate.

This is a very basic explanation of fluid dynamics. Basic being the key word here. There are many things at play, but for a splitter hydraulic circuit I hope I have hit the high points. Sorry for the long post (No jokes FFJ )
I am hoping @kevinj will be a proof reader for factual accuracy for this post. If I am wrong in any way I seriously would like it corrected. My intent is not to mislead anyone.

Sounds reasonable to me. That explains the rise in my pressure and my thoughts that my log lift had slowed somewhat- it was still too fast (edit and the restrictor wasnt my answer) for me.

 

[Jags]

This thread is only one of many I have seen that prompted me to post that thread. I get this feeling that some folks try to use "flow" and "pressure" interchangeably. They are not the same thing, related, yes, but two different measurements not unlike horse power and torque.

My purpose was to hopefully clarify some often misunderstood characteristics of hydraulics.

 

[VirginiaIron]

Wince, lol, I didn't remember saying "oh yeah,..." so I figured it wasn't me and that was the case. Perhaps you should make that topic a sticky thread.

 

[Jags]

If it raises enough interest, that is a possibility. Of course it is always searchable.

 

[kevin j]

jags has it nailed and great explanation. I don't see that post in this thread but I would agree with everything.
I sort of grit my teeth when I hear the discussions about the "I went to bigger hoses on my splitter goes faster "

for small open center gear pumps:
-flow makes it go
-pressure is a result of load
-pressure is limited by the load or the relief valve setting whichever is less
-Engine must have enough torque to turn the pump

them is the basics

 

[redktmrider]

After changing out the valve my lift is more controllable and easier to feather. I do not need the restrictor anymore.

What did you change the valve to? I am thinking about making the log lift on my TW-P1 hydraulic.

 

[VirginiaIron]

What did you change the valve to? I am thinking about making the log lift on my TW-P1 hydraulic.

I used the Nortrac 2000 from Northern Tool. Apparently the first valve was leakingj and was difficult to feather. Imho Every splitter needs a lift.

 

[VirginiaIron]

I am going to go with the lever stop and remove the restrictor. I will post photos when I am finished and have it working, thanks.

I went with the lever stop. The lift operates real smoothly with a large and heavy round. The splitter doesnt torque now. Now if I mistakenly grab the wrong handle I won't throw my back out trying to get away or be scared into cardiac arrest.

 

[Jags]

Easy, functional and built to last. I like it.

 

[rox3406]

An adjustable flow control valve inline right at the cylinder would work just fine. And they are cheap