Case Drain modification to older skidsteer

[conc2steel]

Has anyone done, or know how to, add a case drain hydraulic coupler to a 853 or similar skidsteer? I recently purchased a Bobcat Stumpgrinder and it requires a Case Drain... but my Skid Steer doesn't have one. Any advice

 

[Tazza]

Don't quote me, but you should be able to install a shuttle valve so the case drain oil goes back via the return line. If you can't do that, there really is no reason why you can't install a line that hooks into your case drain line where it connects to the bottom of your hydraulic reserve tank. This line will have little to no pressure so you would be able to get away with more flexible one wire hydraulic hose.

 

[Bandit1047]

Don't quote me, but you should be able to install a shuttle valve so the case drain oil goes back via the return line. If you can't do that, there really is no reason why you can't install a line that hooks into your case drain line where it connects to the bottom of your hydraulic reserve tank. This line will have little to no pressure so you would be able to get away with more flexible one wire hydraulic hose.

From what I understand, a case drain is normally used on High flow systems to return some portion of the oil back to the tank to allow it to mix with the cooler oil in the tank. High flow systems would boil the oil if it circulated from the implement back to the pump and back to the implement, not getting any opportunity to cool down. If you are running a high-flow implement on low flow hydraulics, the performance will be less than spectacular. To make a case drain you need to run a simple return line to the hydraulic tank. You may be able to run it into the filler tube or top of the tank. Joe

 

[TriHonu]

From what I understand, a case drain is normally used on High flow systems to return some portion of the oil back to the tank to allow it to mix with the cooler oil in the tank. High flow systems would boil the oil if it circulated from the implement back to the pump and back to the implement, not getting any opportunity to cool down. If you are running a high-flow implement on low flow hydraulics, the performance will be less than spectacular. To make a case drain you need to run a simple return line to the hydraulic tank. You may be able to run it into the filler tube or top of the tank. Joe

Case drains are used in pumps and motors to allow slippage and seepage oil to exit the case and keep the seals from blowing out. If the oil in the case behind the seals gets to as little as 15 psi it can blow the seals.
Case drains are designed to return oil directly to to the reservoir with minimum restriction and should not be combined with other return lines. They should be connected to the reservoir through dedicated penetrations. This penetration should be connected to a drop-pipe inside the reservoir that extends below minimum fluid level.
Bandit1047 hit the key point - If this stump grinder has a case drain it is most likely a high flow grinder. Running it on a low flow machine will result in the cutting wheel turning much slower than needed to cut efficiently. You will probably be able to get it to tear away some wood but it will operate less effectively than a grinder designed for low flow.

 

[Bandit1047]

Case drains are used in pumps and motors to allow slippage and seepage oil to exit the case and keep the seals from blowing out. If the oil in the case behind the seals gets to as little as 15 psi it can blow the seals.
Case drains are designed to return oil directly to to the reservoir with minimum restriction and should not be combined with other return lines. They should be connected to the reservoir through dedicated penetrations. This penetration should be connected to a drop-pipe inside the reservoir that extends below minimum fluid level.
Bandit1047 hit the key point - If this stump grinder has a case drain it is most likely a high flow grinder. Running it on a low flow machine will result in the cutting wheel turning much slower than needed to cut efficiently. You will probably be able to get it to tear away some wood but it will operate less effectively than a grinder designed for low flow.

Trihonu, can you explain your first paragraph in a little more detail. I always like to learn as much as possible, especially from someone who knows their stuff. Also, what does TriHonu mean or where does that name come from? (Inquisitive people need to know) Joe

 

[TriHonu]

Trihonu, can you explain your first paragraph in a little more detail. I always like to learn as much as possible, especially from someone who knows their stuff. Also, what does TriHonu mean or where does that name come from? (Inquisitive people need to know) Joe

High case pressures cause the oil to press on the backside of seals causing the lips to wear a groove in the shaft and eventually the seal to totally fail. This is pressure on the back side of the seal which is not designed to handle pressure. Case drains are designed into pumps and motors to route this slippage/seepage oil from the back side of seals and pistons and allow the oil to return to the reservoir under minimal pressure.
If you were to route this oil into the return line (which has some pressure in the line do to restrictions) you have now pressurized the back side of the seals. This would be much worse if you were to reverse the hydraulic flow (by accident of course

) since the return line is now the pressure line and you would now put over 3000 psi of pressure into the case drain pressurizing the back side of the seals with immediate seal blowout.
In piston pumps the individual piston shafts are a rod with a ball machined on the end. The ball is connected to a concave sleeve that fits over the ball with a disk on the top and is called the slipper pad. Tazza has a picture of them about half way down the page on This Thread (Piston from the Rotating Group). In these types of pumps there is a small amount of oil that seeps past the piston. It is routed to a case drain to allow it to leave the rotating group. If it were to be trapped in the pump it will put pressure on the back of the slipper pad and will begin to hammer the slipper pad as the group rotates and can cause the slipper pads to detach from the piston or deform causing the pump to fail.
Piston pumps are also sensitive to vacuum in the inlet side of the pump. This is why the hydrostatic pump uses a charge pump to insure the pistons have sufficient inlet oil. If there is a vacuum the slipper pad is in tension as it trys to pull oil into the pump which over time can also cause the slipper pad to detach from the piston. This is the reason Bobcat tells you to periodically replace the filter cap on hydraulic reservoir to make sure oil can flow freely to and from the tank. If the tank vent filter plugs you can create a vacuum in the tank causing a vacuum condition on the inlet oil.

TriHonu is derived from:
Tri = 3 key principals the Army taught me that I apply to my life and business
1. Be technically proficient.
2. Take responsibility for your actions.
3. Keep your customers and subordinates informed.

Honu is the Hawaiian name for turtle. (Turtles being natures original Hardhats and steady persistence wins the race.)
TriHonu Cooperative Services is my business name.

 

[Tazza]

High case pressures cause the oil to press on the backside of seals causing the lips to wear a groove in the shaft and eventually the seal to totally fail. This is pressure on the back side of the seal which is not designed to handle pressure. Case drains are designed into pumps and motors to route this slippage/seepage oil from the back side of seals and pistons and allow the oil to return to the reservoir under minimal pressure.
If you were to route this oil into the return line (which has some pressure in the line do to restrictions) you have now pressurized the back side of the seals. This would be much worse if you were to reverse the hydraulic flow (by accident of course ) since the return line is now the pressure line and you would now put over 3000 psi of pressure into the case drain pressurizing the back side of the seals with immediate seal blowout.
In piston pumps the individual piston shafts are a rod with a ball machined on the end. The ball is connected to a concave sleeve that fits over the ball with a disk on the top and is called the slipper pad. Tazza has a picture of them about half way down the page on This Thread (Piston from the Rotating Group). In these types of pumps there is a small amount of oil that seeps past the piston. It is routed to a case drain to allow it to leave the rotating group. If it were to be trapped in the pump it will put pressure on the back of the slipper pad and will begin to hammer the slipper pad as the group rotates and can cause the slipper pads to detach from the piston or deform causing the pump to fail.
Piston pumps are also sensitive to vacuum in the inlet side of the pump. This is why the hydrostatic pump uses a charge pump to insure the pistons have sufficient inlet oil. If there is a vacuum the slipper pad is in tension as it trys to pull oil into the pump which over time can also cause the slipper pad to detach from the piston. This is the reason Bobcat tells you to periodically replace the filter cap on hydraulic reservoir to make sure oil can flow freely to and from the tank. If the tank vent filter plugs you can create a vacuum in the tank causing a vacuum condition on the inlet oil.
TriHonu is derived from:
Tri = 3 key principals the Army taught me that I apply to my life and business
1. Be technically proficient.
2. Take responsibility for your actions.
3. Keep your customers and subordinates informed.

Honu is the Hawaiian name for turtle. (Turtles being natures original Hardhats and steady persistence wins the race.)
TriHonu Cooperative Services is my business name.

All good points. The case drain hose on my 751 connects to the bottom of the hydraulic tank, so there is no pressure here. With the use of a shuttle valve it can be hooked up so the high pressure side never touches the case drain, when you reverse flow the valve moves to divert the flow to the correct side. I don't know the pressure that is on the return line though, but i know there is a little bit there. As for needing the case drain for cooling, there is leakage in the system to allow for this, and the case drain lines *should* have a very low flow. If there is excessive flow, you have a problem.
I will need to look into this a bit more as i have a hydro motor i want to use for a concrete mixer. It has a case drain and i was hoping to use a shuttle valve to prevent me having to plumb in a case drain line......

 

[TriHonu]

All good points. The case drain hose on my 751 connects to the bottom of the hydraulic tank, so there is no pressure here. With the use of a shuttle valve it can be hooked up so the high pressure side never touches the case drain, when you reverse flow the valve moves to divert the flow to the correct side. I don't know the pressure that is on the return line though, but i know there is a little bit there. As for needing the case drain for cooling, there is leakage in the system to allow for this, and the case drain lines *should* have a very low flow. If there is excessive flow, you have a problem.
I will need to look into this a bit more as i have a hydro motor i want to use for a concrete mixer. It has a case drain and i was hoping to use a shuttle valve to prevent me having to plumb in a case drain line......

Tazza, you need to check the shuttle valve's Cracking Pressure and Internal Leakage Rate. The Cracking Pressure will equate to the pressure contained in the case and still needs to be kept below 10 psi.
The Internal Leakage Rate is also a concern since an ILR as low as 1 drop per minute could cause significant pressure in the case in a relatively short period of time.
In your application of a concrete mixer the motor should not be under much of a load and should not need to be reversed. I am assuming you will not be using it frequently or for long durations. I would think a Check Valve with 10 psi cracking pressure should work as long as the pressure in your return line is less than 10 psi. I would be leery of using a shuttle valve if you are reversing since a small amount of oil will move back in to the case as the valve shifts. Even a small amount of oil pushing back in to the case could cause significant pressure.
You could route the case drain to a small tank attached to the mixer. As long as the motor is in good shape I wouldn't think you will have much if any oil to catch in your application. You would be safe even if you reverse frequently.

 

[Tazza]

Tazza, you need to check the shuttle valve's Cracking Pressure and Internal Leakage Rate. The Cracking Pressure will equate to the pressure contained in the case and still needs to be kept below 10 psi.
The Internal Leakage Rate is also a concern since an ILR as low as 1 drop per minute could cause significant pressure in the case in a relatively short period of time.
In your application of a concrete mixer the motor should not be under much of a load and should not need to be reversed. I am assuming you will not be using it frequently or for long durations. I would think a Check Valve with 10 psi cracking pressure should work as long as the pressure in your return line is less than 10 psi. I would be leery of using a shuttle valve if you are reversing since a small amount of oil will move back in to the case as the valve shifts. Even a small amount of oil pushing back in to the case could cause significant pressure.
You could route the case drain to a small tank attached to the mixer. As long as the motor is in good shape I wouldn't think you will have much if any oil to catch in your application. You would be safe even if you reverse frequently.

hmmmm i do like the tank idea. I think that will be an option.

 

[skidsteer.ca]

hmmmm i do like the tank idea. I think that will be an option.

When I Hi flowed my LS 160 they provided a extra coupler, hose and the instructions were to tie it into an existing case drain line down by the hydro pumps.
They did not worry about twinning the lines together. I guess if you are concerned about the back pressure a small guage in the line would let you know. A tank would work, but to me, it would becaome a pita in a hurry too.
Ken

 

[thetool]

I have before plumbed a direct return line on such a machine. It was as simple as welding on an extra bracket on the end of the boom for the coupler, running the extra hose up the boom and finding a place to tee in before filter/cooler/tank, but after the valve, which was a return line to run a hand-held hydraulic breaker. The return line going through the valve resulted in back-pressure that stalled the breaker. Such a set-up would provide you with a case drain circuit, BUT......
As others said:
Your Bobcat stump grinder is a high-flow attachment, and needs I believe in the neighborhood of 30+ gpm or you won't be satisfied with the results. Whoever sold it to you should have verified your power unit. If your bobcat does not have that extra coupler, it is not a high-flow machine.
Good luck.

 

[Deleted User 1107]

I have before plumbed a direct return line on such a machine. It was as simple as welding on an extra bracket on the end of the boom for the coupler, running the extra hose up the boom and finding a place to tee in before filter/cooler/tank, but after the valve, which was a return line to run a hand-held hydraulic breaker. The return line going through the valve resulted in back-pressure that stalled the breaker. Such a set-up would provide you with a case drain circuit, BUT......
As others said:
Your Bobcat stump grinder is a high-flow attachment, and needs I believe in the neighborhood of 30+ gpm or you won't be satisfied with the results. Whoever sold it to you should have verified your power unit. If your bobcat does not have that extra coupler, it is not a high-flow machine.
Good luck.

Hah! I clicked on this thread thinking it would be about draining the *Chain Case* - which on my 843 is supposed to have the fluid changed every 1000 hours. The operator's manual tells you how to check that you've put enough in, but not how to get the old stuff out. Looking at the parts book, and hastily at the machine, there does not seem to be a drain. I suppose you're supposed to suck it out the fill inlet with a pump, which has got to be a pain. I thought about drilling and tapping for a pipe plug, but I can also see that such a plug would be vulnerable to damage if it projected from the underside of the chain case. Not to mention the problem of making this modification without introducing drill/tap chips into the oil. Mickey

 

[Tazza]

Hah! I clicked on this thread thinking it would be about draining the *Chain Case* - which on my 843 is supposed to have the fluid changed every 1000 hours. The operator's manual tells you how to check that you've put enough in, but not how to get the old stuff out. Looking at the parts book, and hastily at the machine, there does not seem to be a drain. I suppose you're supposed to suck it out the fill inlet with a pump, which has got to be a pain. I thought about drilling and tapping for a pipe plug, but I can also see that such a plug would be vulnerable to damage if it projected from the underside of the chain case. Not to mention the problem of making this modification without introducing drill/tap chips into the oil. Mickey

The way they want you to do it is remove the front inspection plate and pump the oil out. You then mop the inside out and re-fill.

 

[Deleted User 1107]

The way they want you to do it is remove the front inspection plate and pump the oil out. You then mop the inside out and re-fill.

Thanks, Tazza! - They don't mention this in the 'Operations and Maintenance Manual', but it does sound more effective than sticking a tube down the fill hole. Mickey