Hydraulic system design exspert, question.

Adding oil capacity to tractor by mounting another reservoir above the existing one. Joining with a one inch line. Suction line to pump one inch size from near bottom of lower reservoir. . Lower reservoir sealed except for line from upper reservoir. Upper reservoir vented. Plan to return oil from open center valve bank to upper reservoir.
Is it better to return oil below or above the oil level in the reservoir? Also the upper reservoir has a suction screen that can be installed so the outlet line oil to the lower reservoir goes through it. Would this cause a problem? Fixed it so I can put a screen at the lower reservoir suction line and leave the other out if needed, but would have to purchase it and already have one for upper suction to lower tank.
Thanks for any thoughts or advice.

Can't answer all of your questions but you should return the oil below the oil level and as far from pump suction as possible. This will help to prevent fluid aeration and allow settling of trapped air and contaminants. Sam

The return to upper reservoir should be below the level of lowest activity if possible as this reduces air entrainment/foaming. A hydraulic specialist from IH medium duty truck division stated "All system filtration should be just at the suction input of the pump with an easily changed filter with high flow. He said preventing all filterable particles from being introduced into the active components was a primary objective of preventing system contamination. He also indicated that a screen in the high pressure output with proper flow would stop failed pump parts from contaminating down stream valving and regulators.
A reservoir should not have an outlet to suction or other reservoirs from its bottom. Allowing sediments and particles to settle out with less chance of being induced into the flow was his rationale.
I have found his advice to be operational, and reciently worked on a design for a hydraulic company, through graduate students sfforts, using these principles. We designed a check valve testing station with multiple analysis of the performance of the valve. 100% post6 production testing. We fabricated the reservoirs and built the rack systems and mounts for multiple parallel filtration (.5 micron). I hope this helps, Jim

I tried that and it didn't work. Return oil wanted to puke out the upper vent.

So, tied the return into a tee right at the suction sump feed. Thing just works great.

Allan

Posters, putting 2 pictures on. Fixing up a M for a user tractor out of parts I have. thought this would work but wondered if there would be a problem after getting into it. Don't have the hoses on yet, but you can see the openings. Planed to have the oil level 1/3 to 1/2 in the top tank. Mostly using it for expansion so the lower can be run full. Upper tank is from a 400 tractor turned backwards. Outlet is taped to the same passage as used on the 400 and plates on top sealing the regular outlet. Planed to return oil to the lower opening in front of top reservoir. Made a baffle droping down from plate on top of reservoir to the inside to baffle the return port. Vent port is on the other side of the reservoir and exstends to other side of the baffle near top center of the reservoir. Lower belley pump housing is just a empty housing now with all but top and bottom holes pluged and inside cleaned. I can put a screen in place of the bushing in lower reservoir, or use the 400 screen in the upper tank.

Another

Not saying I'm an expert, but... I did work in a hydraulics plant for 38 years with 25 of those in the engineering experimental lab, building and maintaining test machines, and modifying customer equipment to incorporate our hydraulics.
1. Return your open center valve to somewhere in the lower reservoir... not at the suction port to the pump... you will be recirculating the hottest oil.
2. No need for a screen between the two reservoirs... what good would it do there if your return is to the bottom one?
3. A screen in the suction line from the lower reservoir to the pump is a great idea... filter on the return line from your valve would also be good.

I take it you need the extra volume for displacement in a cylinder(s), so all it needs to do is raise and lower the level in the reservoirs, so you don't cavitate your pump. Pump cavitation under pressure can be as damaging as any other contaminant... the higher the pressure the worse it gets.

I would put a high capacity cartridge filter in the suction to the pump. The lower supply hose from the Liftall housing would be at the bottom of that res. A filter there would give me piece of mind. (a gate valve ahead of the filter would also allow filter changes W/O grief. Jim

Thanks for the input. Just to make sure were on the same page the suction to pump will be from the lower tank opening. I thought if I returned oil to the upper tank below its oil level the oil would have more time to cool before getting down to the suction. Suction will be to a live pump on the engine. I taped the 3/4 pipe thread hole in the top of the gutted belley pump to 1 inch. planed to go from the 1 inch 90 on the lower level of top tank to top 90 on lower tank to join tanks. Yes going to run a loader on front and 2 point on the rear. Useing the 9 speed for the faster reverse and other.

Best place for any filter is at output of valve body before it returns to tank. Some pressure is available to feed the filter and it won't increase cavitation in the pump due to supply restriction. Sure the old M isn't going to see a lot of hours so longevity isn't really a concern but cold oil problems go away, a smaller filter will work great, and your pump will thank you in the long run.

personally I want to filter what goes in not what comes out. down Stream Beer and all. Jim

(quoted from post at 19:40:22 01/19/11) personally I want to filter what goes in not what comes out. down Stream Beer and all. Jim

Click to expand...

If the system is clean to start with, a filter on the return is best just as M Diesel said. On our test machines and customer machines (tractors, skid steer, swathers, combines, etc.), we filtered the return with a finer mesh, in our case a 10 micron filter and customers sometimes used a 25 mic. On customer machines, there was typically just a screen on the suction, but on our test machines we installed a large 74 or 49 micron screen element. We also on test machines had a circulating system, which you will not have on a tractor or implement, that had a large capacity 10 mic filter as well as a cooling or temperature control system.
A couple of things to consider here.... 1. You can not use a very fine micron element in a suction line, because as the filter fills with contaminant, it will "choke off" really quickly, like a snowball effect. and 2. In cold weather conditions, or even just normal cold start conditions, the filter will not flow as easily. Like I said, we over-sized the flow capacity and used a 49 or more often, a 74 mic cleanable steel element.

I would just use the IH 400 hydraulic screen provided the Liftall reservoir can maintain the partial vacuum caused by the pump. Of course, it must be capable otherwise it would leak oil

Without going outside and trying to find a 400 reservoir in two feet of snow, I am guessing you will have to weld a pipe fitting to the steel exterior of the brass screened filter. I am sure that a homemade plate where the pipe manifold attaches to reservoir is in your plans. Or maybe you could just draw from the plate that would be threaded for a 1" NPT and forget modifying the filter.

Don't you love it when you can recycle an old IH part and put it to a new unintended use.

I suppose the F-400 reservoir is rotated 180 due to clearance problems with steering column. If you had a W-400 reservoir, that would not be necessary as there is a recess for the large steering gear housing.

<a href="http://s140.photobucket.com/albums/r16/Wardner/?action=view&current=W-400234.jpg" target="_blank"></a>

<a href="http://s140.photobucket.com/albums/r16/Wardner/?action=view&current=W-400275.jpg" target="_blank"></a>.

If you are adding the extra capacity and using it to the point where the top reservoir is empty and you are lowering the level in the LiftAll housing you are going to have problems just as Allan said if you return the oil to the top reservoir.

The reason is that once you empty the top and start to drawn down the oil level in the bottom the oil will be replaced with air. When you return the oil to the top reservoir you will continue to circulate oil through the system. The oil that is returning to the top it has to pass down the pipe between the two reservoirs as it circulates. With the oil going down the pipe the air can't get back out of the lower reservoir. It has the same effect as adding that much additional oil which will now be more than the system can hold so it will be forced out the breather.

Lots of good points, sounds like some rework. I would have to return oil at the suction opening, don't want that or at the one inch top line. would still be a problem if oil level droped to low I think. Do have a 3/4 inch opening pluged where the control lever went near the top of the liftall housing. Problem is I used a 11 inch clutch liftall with a 12 inch clutch. Don't know if you can see in the picture, made up 5/8 inch spacers to drop housing down to clear since I wasn't using the side openings. Would have to make hole in the center housing bigger to use the side opening or drop housing back out and rework. Already cleaned it after screwing fittings in to make sure no metal was dislodged before installing the cover plate. Oh well.
Another question on a 400 hydraulic system they returned oil above the fluid level. Only used them set to single acting with a small cylinder myself. Do they blow oil out the vent with bigger single acting cylinders?

I remember Dad had an "expansion tank" on a Farmall C with a loader, but all it did was cycle the level up and down in the upper tank, with the return to the factory internal tank.
You might trade the 90 elbow in the top of the lower reservoir for a tee, standing up so the port going to the upper reservoir is still plumbed like you show, and a return line filter and return flow go back in the top of the tee. This might gain you a little edge over returning to the top tank. Chances are, you will not be extending your cylinders all the way, all the time, so it might not be a serious problem.
A lot will depend on how fast your single acting cylinders retract and how large the diameter is. Large cylinders dropping fast will dump a lot of flow real fast back to the reservoir. If this happens, you may need to meter the return so it doesn't "overload" the 1" fittings and force a large portion of the oil into the top reservoir before filling the bottom one.