New loader valve not working properly

[Farmerford]

JD4310man:

I think the engine loading is caused by the flow divider. I assume priority flow is to the FEL valve. Assume your pump is producing 16 gpm and you have the flow divider set to provide an 8gpm priority flow to the loader valve. The flow divider sends the first 8gpm to the loader and the excess of 8gpm in this case to the other valve (you never said what that valve was, but I assume three point hitch; it doesn't really matter).

When the pump flow enters the flow divider it can take one of two paths: out the priority flow port or out the excess port. The flow divider works by forcing 8gpm to flow out of the priority flow port regardless of the pressure in that port; it does that by partially blocking the flow out of the excess port. If the FEL valve is in neutral there is very little pressure in the priority flow port because the only resistance to flow comes from losses inside the FEL valve, fittings, hoses, etc.; the spring loaded spool in the priority flow valve restricts the excess flow path only enough to cause 8gpm to flow through the priority port. But suppose you lift the FEL with a heavy load in the bucker that requires 500psig of pressure in the lift cylinders to move the load as fast as you want; that is the 8gpm of priority flow you want from the priority flow valve must over come 500psig of resistance in order to flow into the lift cylinder. The priority flow valve makes the 8gpm keep flowing out of the priority port, despite the fact that it now has to have at least 500psig of pressure, by restricting the flow in the excess port until it is also under 500psig of pressure. The spool in the priority flow valve shifts to partially block the excess flow port until the pressure in the excess flow port and priority flow port are the same; and the spring in the priority flow valve (that you adjusted) determines how much of the flow goes to the priority flow port when those pressures are equal.

Put simply, when you shift the loader valve to send fluid to the loader cylinders you increase the pressure in not only the loader circuit (the priority flow circuit), you also increase pressure to the same level in the excess flow circuit. In the above example, it is not only the 8gpm going to the FEL valve that requires 500psig pressure from the pump, it is also the 8gpm that is passing through the excess flow circuit. So, in your prior two pump set up you were only loading the FEL pump with 500psig when you worked the loader; now in effect you are loading "both" pumps.

Anything increasing the pressure in the priority flow circuit will aggravate the problem; fittings that are too small or with flow restrictors will increase the resistance in the FEL circuit and in turn increase the pressure in both the priority flow port and excess flow port.

The effect was most noticeable in regenerative mode on the bucket for two reasons. First, the nature of the regenerative circuit itself. The faster movement of the cylinder in regenerative comes from redirecting the exhaust flow from the cylinder from the tank to the other cylinder port. For example, if the cylinder to rod area ratio is such that the cylinder moves twice as fast, the cost is that it takes twice as much pump pressure to overcome resistance in the cylinder. Of course, when the bucket is being dumped and the load pulls it down rapidly, there is little if any resistance in the cylinder and and therefore little extra pressure on the pump. Second, your sticky cylinder increased the resistance even when dumping the cylinder to the point that the pump had to produce pressure to make it move. And it had to produce twice the normal pressure because of the regenerative feature. Of course, the effect of that increased pressured was reflected all the way back to the priority valve, which restricted the excess flow enough to raise the pressure on both the priority flow and excess flow enough to overcome the sticky cylinder.

You helped the problem when you turned down the priority flow because the reduced flow caused smaller pressure losses in the fittings, hoses, valve, etc. And I suspect you did not have a load in the bucket, so these flow losses were the primary source of pressure in the circuit; therefore even a small reduction in them would produce a noticeable result. If the bucket had a heavy load most of the pressure would have come from the load and any reduction in pressure due to lower flow would have been relatively very small and probably not noticeable.

The main effect (in addition to loading your engine more than necessary) is that the temperature of the hydraulic fluid will increase substantially during heavy work. The 8gpm flow through the priority curcuit is doing useful work by moving the cylinders. The additional 8gpm through the excess flow circuit is doing no useful work; it releases its energy by heating up the fluid as the pressure drops across the excess flow port. Temperature increases about 1 deg F for each 140psi of pressure drop. For example, suppose you have a heavy load in the loader that requires 2,000psig to lift. During that lift the priority flow valve, in order to keep the 8gpm you programmed (by adjusting the spring pressure) flowing through the priority flow circuit the priority valve spool shifts to block the excess flow just enough to keep the same 2,000psig pressure in the excess flow. But as soon as that excess flow leaves the priority valve its pressure drops to practically zero; thus that fluid has a 2,000psig pressure drop that does no useful work. The temperature of the fluid that flows through the excess circuit during the lift cycle increases by 1deg F for each 140psi of temperature drop. That means that fluid temperature increased by about 14deg F. To make the math easy, suppose the lift cycle lasted 7 seconds, which is about 1/8 minute; at 8gpm, one gallon of fluid passed through the excess flow circuit during the lift and its temperature was increased by 14 deg F.

The temperature increase in the hydraulic fluid volume as a whole will depend, of course, on the pressure drop which in turn depends on the load on the FEL, and on the length of time the loader works. We know nothing about the size of your hydraulic reservoir or any oil coolers you may have, so it is not possible to predict how much fluid heating may occur.

If it were me I would ignore the engine loading as a necessary by-product of shifting from two pumps to a single pump and keep an eye on hydraulic fluid temperatures. Even a valve body or pump too hot to touch does not indicate a problem. Quality hydraulic fluids will maintain adequate viscosity to protect moving parts and retain a reasonable service live at temperatures of at least 165deg F.

Please keep us posted on how things turn out.

 

[oldnslo]

Farmer ford,
excellent reply and I believe 100% correct.

JD4310:

To eliminate the engine loading at heat generation caused by the larger pump and priority flow control you could use a double pump system. Each pump would feed a function and only that function would be under pressure. This is what is commonly used on CUT's one pump for steering and cooling, the other for FEL & 3PH.

 

[J_J]

JD4310man:

I think the engine loading is caused by the flow divider. I assume priority flow is to the FEL valve. Assume your pump is producing 16 gpm and you have the flow divider set to provide an 8gpm priority flow to the loader valve. The flow divider sends the first 8gpm to the loader and the excess of 8gpm in this case to the other valve (you never said what that valve was, but I assume three point hitch; it doesn't really matter).

When the pump flow enters the flow divider it can take one of two paths: out the priority flow port or out the excess port. The flow divider works by forcing 8gpm to flow out of the priority flow port regardless of the pressure in that port; it does that by partially blocking the flow out of the excess port. If the FEL valve is in neutral there is very little pressure in the priority flow port because the only resistance to flow comes from losses inside the FEL valve, fittings, hoses, etc.; the spring loaded spool in the priority flow valve restricts the excess flow path only enough to cause 8gpm to flow through the priority port. But suppose you lift the FEL with a heavy load in the bucker that requires 500psig of pressure in the lift cylinders to move the load as fast as you want; that is the 8gpm of priority flow you want from the priority flow valve must over come 500psig of resistance in order to flow into the lift cylinder. The priority flow valve makes the 8gpm keep flowing out of the priority port, despite the fact that it now has to have at least 500psig of pressure, by restricting the flow in the excess port until it is also under 500psig of pressure. The spool in the priority flow valve shifts to partially block the excess flow port until the pressure in the excess flow port and priority flow port are the same; and the spring in the priority flow valve (that you adjusted) determines how much of the flow goes to the priority flow port when those pressures are equal.

Put simply, when you shift the loader valve to send fluid to the loader cylinders you increase the pressure in not only the loader circuit (the priority flow circuit), you also increase pressure to the same level in the excess flow circuit. In the above example, it is not only the 8gpm going to the FEL valve that requires 500psig pressure from the pump, it is also the 8gpm that is passing through the excess flow circuit. So, in your prior two pump set up you were only loading the FEL pump with 500psig when you worked the loader; now in effect you are loading "both" pumps.

Anything increasing the pressure in the priority flow circuit will aggravate the problem; fittings that are too small or with flow restrictors will increase the resistance in the FEL circuit and in turn increase the pressure in both the priority flow port and excess flow port.

The effect was most noticeable in regenerative mode on the bucket for two reasons. First, the nature of the regenerative circuit itself. The faster movement of the cylinder in regenerative comes from redirecting the exhaust flow from the cylinder from the tank to the other cylinder port. For example, if the cylinder to rod area ratio is such that the cylinder moves twice as fast, the cost is that it takes twice as much pump pressure to overcome resistance in the cylinder. Of course, when the bucket is being dumped and the load pulls it down rapidly, there is little if any resistance in the cylinder and and therefore little extra pressure on the pump. Second, your sticky cylinder increased the resistance even when dumping the cylinder to the point that the pump had to produce pressure to make it move. And it had to produce twice the normal pressure because of the regenerative feature. Of course, the effect of that increased pressured was reflected all the way back to the priority valve, which restricted the excess flow enough to raise the pressure on both the priority flow and excess flow enough to overcome the sticky cylinder.

You helped the problem when you turned down the priority flow because the reduced flow caused smaller pressure losses in the fittings, hoses, valve, etc. And I suspect you did not have a load in the bucket, so these flow losses were the primary source of pressure in the circuit; therefore even a small reduction in them would produce a noticeable result. If the bucket had a heavy load most of the pressure would have come from the load and any reduction in pressure due to lower flow would have been relatively very small and probably not noticeable.

The main effect (in addition to loading your engine more than necessary) is that the temperature of the hydraulic fluid will increase substantially during heavy work. The 8gpm flow through the priority curcuit is doing useful work by moving the cylinders. The additional 8gpm through the excess flow circuit is doing no useful work; it releases its energy by heating up the fluid as the pressure drops across the excess flow port. Temperature increases about 1 deg F for each 140psi of pressure drop. For example, suppose you have a heavy load in the loader that requires 2,000psig to lift. During that lift the priority flow valve, in order to keep the 8gpm you programmed (by adjusting the spring pressure) flowing through the priority flow circuit the priority valve spool shifts to block the excess flow just enough to keep the same 2,000psig pressure in the excess flow. But as soon as that excess flow leaves the priority valve its pressure drops to practically zero; thus that fluid has a 2,000psig pressure drop that does no useful work. The temperature of the fluid that flows through the excess circuit during the lift cycle increases by 1deg F for each 140psi of temperature drop. That means that fluid temperature increased by about 14deg F. To make the math easy, suppose the lift cycle lasted 7 seconds, which is about 1/8 minute; at 8gpm, one gallon of fluid passed through the excess flow circuit during the lift and its temperature was increased by 14 deg F.

The temperature increase in the hydraulic fluid volume as a whole will depend, of course, on the pressure drop which in turn depends on the load on the FEL, and on the length of time the loader works. We know nothing about the size of your hydraulic reservoir or any oil coolers you may have, so it is not possible to predict how much fluid heating may occur.

If it were me I would ignore the engine loading as a necessary by-product of shifting from two pumps to a single pump and keep an eye on hydraulic fluid temperatures. Even a valve body or pump too hot to touch does not indicate a problem. Quality hydraulic fluids will maintain adequate viscosity to protect moving parts and retain a reasonable service live at temperatures of at least 165deg F.

Please keep us posted on how things turn out.

I believe priority flow is always to the steering circuit for safety reasons.

If the priority flow is adjustable, then you set it to the response you want from the steering, be it fast or slow.

Just don't think it has anything to do with the loader valve, as a lot of other tractors have flow dividers, and not the loader problems.

If you have 10 GPM tractor flow, and you adjust the steering to 3 GPM's, then you have 7 GPM's for the attachments, and that circuit should operate independent of the other hyd circuit.

 

[jd4310man]

J_J, Im not sure how much flow is coming out of the flow divider as it is infinitely variable flow between 2 and 12 gpm. The Hatz is the 2G40 diesel engine. rated at 23 hp at 3000 rpm. I thought by using the flow divider that it would split the 21 gpm pump out put in to 14 and 7 gpm. So when im using the track drive at 14gpm it would have enough power. The hose on the left of the top valve is coming from the adjustable flow divider. The blue hose coming out of the right side of the top valve, is feeding the lower auxiliary valve. I have the Brand power beyond plug, it is not currently hooked up. Anyway The machine doesn't do too bad with this pump, its the loader function that is giving me the fit.

 

[jd4310man]

Farmerford: I went with a single pump system as I changed from the factory Kohler gas with two pump system to a Hatz diesel. The diesel is a larger engine and I didnt have a way or the space to power two pumps like the factory setup. So the solution to me was a larger single pump and the use of a flow divider. So far its working good, the track drive works well and the up and down function of the loader works well. I replaced seals on the one bucket cylinder and Had problems with the seals causing friction on the cylinder. I think that this is my cause of strain on the system. The 4800 Magnatrac model utilized a single pump system to run everything like im doing here. It only had a 12 gpm pump and resulted in very slow machine travel speed. However im sure that all 12 gpm was not being fed to the attachment valve. Is a flow divider a proper thing to use in this type of application?

 

[J_J]

How is the 7 GPM used? I assumed steering, but the track drive does the steering.

Are you using one or two hyd motors to drive the tracks?

Are you using the 14 GPM for the track drive and letting the 7 go to tank?

If you are using the 14 GPM at 2000 psi, that takes about 19 HP.

Why are you limiting the pressure to 2000 psi?

As I said before I don't believe you have enough HP to run the pump to max.

Logic says you should be using the PB to feed the next valve, and run all the OUT lines to tank.

What is the purpose of the SA circuit in the stacked valve?

 

[oldnslo]

21 GPM @ 1650 PSI = 23 HP This allowing for hydraulic system to 85% efficient


Like farmerford stated: ALL of the oil being pumped by a single pump will be at whatever the max load requirement is.

 

[jd4310man]

The 7 gpm is used to run the loader and attachments. The 14 gpm is used to run two gerotor motors that use a tandem chain reduction box. The motors are factory. Only the loader and stack valves are set at 2000 psi. I believe the drive motor circuit is set at 3000 psi. The (SA circuit) on the stack valve is used to rout implement hydraulic flow to the drive motor valve to act as an overdrive. It basically diverts all pump flow to the drive system. I am going to reinstall the power beyond equipment to system. I was only experamenting running without the PB plug and hose.

 

[Fedup]

Is this crazy or what? I do believe even our worthless U.S. Congress is better suited to solve problems than this crew. I know I'm opening myself up to a blast of vitriol here, but this sounds like a lot of bickering back and forth about pressures and flows, priorities and minorities, or what have you. Each voice trying to outsolve the others. I'm no engineer, but if I were designing something of this sort, I would have given ten minutes more thought to the expected flow requirements of each system and looked for a double or triple stack pump. Each section matched to requirements of one particular system without all the crossovers and priorities. Just my opinion, mind you. Now for the list of reasons why I'm wrong.....

 

[Farmerford]

JD4310man:

That's nice looking work you are doing on the Struck. Looks very clean and well laid out; mine often looks like a bed of snakes somehow connected with a variety of fittings and adapters I happened to find in the corner.

I would have done the new engine exactly like you did, given that the original tandem pumps could not be used. I have two Prince flow dividers on projects I have made. The only difference is that on one of them I used what is sometimes called a hydraulic motor speed control because the flow adjustment bolt is replaced by a short lever that can be moved by hand; it does the same thing as the priority flow valve because the flow is pressure compensated; when pressure increases in the priority flow circuit the spool shifts to further restrict the passage for excess flow and thereby equalize pressure in both circuits. With the lever I can adjust the priority on the go without wrenches.

You have encountered and handled properly in my opinion the main drawback to a fixed displacement pump and the open circuit valves that it necessitates; to divide the flow you have to put both streams under the same pressure. But in most cases the greatly reduced cost of a gear or vane type fixed displacement pump compared to a variable displacement pump and the associated automated displacement control hardware (and now software) is worth the disadvantage of the inefficient way you have to split the flow.

The mechanical flow divider uses two or more gear pumps/motors mechanically connected through their shafts and does not require pressurization of the other flow. If the motors have the same displacement, then when the single input stream from the pump reaches the "Y" at the motors , one half must flow through each motor because the mechanical connection of the motor shafts forces them to turn at the same speed. But these types of mechanical flow dividers are several times the cost of the spool type, substantially more bulky, and have the disadvantage that the pressure in one out circuit can be twice that in the pump circuit because of the mechanically connected motors, so relief valves are required in each out port.


Spool type directional control valves in an open center system, when the spool is only partially shifted or "feathered", are dividing the pump flow into two parts; the part doing work is directed to the hydraulic cylinder via the work ports and the part of the pump flow not directed to the cylinder flows through the valve body to the tank. But inside the valve body the part passing to the tank is under the same pressure as the part going to the cylinder; the tank flow undergoes the same kind of pressure drop in the valve as the excess flow experiences in the priority flow valve.

Please send us pictures of the whole machine.

 

[Farmerford]

Fedup:

You supplied more than enough vitriol for all the posters; so we can limit posts to our feeble attempts to be helpful.

Perhaps you should avoid reading TBN since it upsets you.

 

[jd4310man]

Fedup: I spent a lot of time racking my brains and researching all kinds of different hydraulic components and comparing original stock machine specs to make this thing work. I am only trying to figure out why my loader circuit is giving me a problem. The machine drives, steers and runs well. I was hoping to find intelligent posters like J_J and Farmerford and the like to chime in and give me there opinions. Im not trying to start an argument.
Farmerford: I will post some pics tomorrow of the whole unit with the loader on. I had an idea on how to rout hoses and mount components but it all fell in place as I went along. There was a lot of figuring out one piece at a time. There isn't much room in this thing to work with. lots of hoses to deal with, but im overall happy with the outcome. Thanks for all the input Guys. Hear is a before pic of the machine. Also a couple after the diesel installation without the loader installed (center pics).

 

[J_J]

After reading back through all the info, you say you are using the SA valve to add the 7 GPM to the 14 GPM flowing to the motor valve.

Are all the valves open center valves?

Does the motor spool valves have a relief valve?

Is it possible that the motor valve fluid is causing back pressure to the loader valve?

How are you feeding the 7 GPM into the IN circuit on the motor valve. Is there a tee in the IN circuit.

Do you lock the SA valve to provide continuous flow?

If it is, you should add a check valve on the 7 GPM line to the tee.

What is the relief pressure on the stacked valve.

 

[jd4310man]

All the valves are open center. All valves have there own relief. I dont think that the motor valve is back feeding to the loader circuit as the spool is spring centered. You have to hold the spool open in order to get overdrive. It was only intended for intermittent use. There is a tee that the flow from the stack valve goes into the drive motor circuit. The relief pressure is set at 2000 psi on both attachment valves. I got to run it a bit yesterday, and its driving good but when you go to fill the bucket, it bogs down a bit. I works better when the fluid gets up to temp. I need to divert more flow to the attachment valve as Im probably not getting the full 7gpm to the valve.

 

[J_J]

I am a little confused as to where you want the fluid to go.

The loader will work on just about any GPM, the more you provide, the faster it will operate.

The same with the fluid for the drive motors, the more you provide the faster the machine will run.

Since most of your parts have about a 3000 psi rating, why not boost the relief pressure to 2500 psi or higher.

The pressure is what provides the torque or power. More pressure more torque.

Something else comes to mind. Since you have 7 GPM for the attachments and not used all the time, that potential HP is being wasted until you add that flow to the drive circuits.

Here is how I envision how it might work.

Bump up the pressure.

The other change I might make is to feed the flow from the stacked valve through a PB port and feed a tee with check valve at the input to the motor valve.

Now, you have the 14 GPM flow and the 7 GPM flow from the pump gong to the drive circuit, and when you use the attachments, the flow is reduced for the time you are using the loader. As soon as you release the loader lever, you are back up to speed on the drive motors.

 

[oldnslo]

JJ,
With the single pump he can't bump up the pressure. He does not have the HP available.

JD4310,
Can you put a gauge in the pump pressure line and also in the FEL valve inlet. I would be curious to see how much difference in pressure you are seeing between these two points.

 

[J_J]

Somehow, I was thinking the engine was 32 HP instead of 23 HP, but you are right, he is starting to run out of HP, speed and power.

Is the speed of the dozer satisfactory. I would prefer slower and more power.

By the way, I have the Magnatrack 1800 with a 16 HP engine turning a 5 speed gear box. I have a 25 HP Kohler engine I am thinking of installing whenever.

 

[jd4310man]

Actually, the speed might be a little fast for the available power. I should of got a smaller pump. But im learning by trial and error. But I wont know that for sure until I get the loader to work properly. I still cant turn up the divider valve like I want to. There is something causing a strain on the dump function. I was looking at these Magnatracs for quite some time and always wanted one. I also dreamed of re powering it with a diesel and modifying it to my needs. I could never see spending what they want for a new one and I finally found one used in good shape and everything is working out well. Im no engineer just trying to make something work. How do like the 1800? At least theirs less hydraulics to worry about on that one. I agree, slower and more power. Here is a few current pics of the machine.

 

[J_J]

On the M-1800 there is no hyd, just belts and a gear transmission. You brake one side to turn.

For raising and lowering implements, there is an electric LINEAR ACTUATOR motor on the front and back.

Do you have a large return hose on the loader valve and is it going direct to tank.

So you have the motor spool out/return hoses connected to the same return hose as the loader valve.

Have you looked at the pressure on each valve while using each valve and using both valves together, otherwise driving and loading.

If you take some pressure, readings, let us know what you see.

The two hyd circuits should be independent of each other.

If you reduce the flow to the hyd circuits, you should be able to raise the relief pressure and still be with in the HP of the engine.

Your 23 HP engine can support 12 GPM's, and 2800 psi.

Would you happen to have a hyd schematic of the dozer?

 

[jd4310man]

The return hose is the same diameter as the high pressure line, 1/2". The motor circuit is separate from the loader circuit. They each have their own return to tank. I don't have a gauge yet on system. Will be installing one soon. The stock motor pump had a displacement of .730 CI. and the attachment pump was .509 CI. That was a combined displacement of 1.239 CI. It was run by a 20 hp gas engine. Is running two smaller pumps easier on the engine than running one larger pump? Im thinking if I reduce the size of my current pump it will work better. Like gearing it down. Attached Is the stock Hydraulic diagram.