Thread: Hydraulic question.

All hydraulic systems develop pressure due to the microscopic air bubbles in the oil. Oil itself doesn't compress so cannot produce pressure only flow. The oil is the lubricant, cooling mechanism and the solid that causes movement - you don't need any oil to actually cause movement, any gas can do that. Cavitation can occur in pumps, motors, valves, cylinders, sharp bends, etc, etc, when the microscopic air bubbles expand due to low pressure i.e. motor over running, hence anti-cav valves fitted to motors.

Aeration is introduced air in a system on the suction side of a pump, motor (suction side on over run), valves on the low pressure side, leaking cylinder seals, etc, etc. Dieseling is when the enlarged air bubbles from cavitation are suddenly compressed again and explode - diesel. Aeration usually causes wear (lack of lubrication and cooling), can cause dieseling - on the pressure side of a pump or cylinder. Erosion is caused by dirt, metal, cavitation and dieseling.

and the thousand other causes and scenarios of problems in hydraulic systems. Generally you need positive pressure to the pump and no air in a hydraulic system and as already stated, the return line must be below the lowest oil level in the tank.

and jplambs, you will 100% guaranteed fail components early in your hydraulic system with the setup you have. How early is in length of string territory.

Rick

Hi Rick, thanks for that, what exactly is going to cause the failure in the system, do you still believe that it will fail if the oil return is below the oil level and a filter is installed inline?

Cheers JP

all hydraulic systems fail, eventually... I've currently got 2 failed $100K+ pressure rigs at work at the moment....

the more overkill you build into them the longer and crappier they will continue to run.

Originally Posted by jplambs

Hi Rick, thanks for that, what exactly is going to cause the failure in the system, do you still believe that it will fail if the oil return is below the oil level and a filter is installed inline?

Cheers JP

JP

Hydraulic pumps don't like a suction head so every time the tank is below the pump you risk damage and as already stated return oil in to the top of a tank will aerate the oil and possibly cause damage to any part of your system.

How long will it last.............................................. ................................ who knows, but a well set up system running at the same speed, volume, pressure etc as yours will last longer.

Bottom line, if you can raise the tank so the oil level will never be lower than the pump inlet and put the return in the lower part of the tank or as already said, extend a tube to the bottom of the tank, you will go a long way to improving reliability.

Oh... and definitely fit a return filter or if you insist a high pressure filter as well after the pump - but get advice on what to use before doing this.

Plenty of good advise on here. Just set it up well, keep the oil clean and cool and you won't have a problem.


Rick

If you run into trouble, give me screw dia, auger length, numbers on motor and pump i can double check it.



Yeah, return should be below oil level. Prevents airating the oil and problems stated above.

Filter in the pressure line is good, IF its a high pressure filter (expensive). If its a spin on canister, it will be a return filter and should be in the return line between spool valve and tank. High pressure will make short work of a spin on element.

Suction strainer is good, but must be of an decent size and you must be able to get access to it to replace it. This can sometimes be hard in a smallish tank like yours.

Keep an eye on the oil temp when using it, if you can hold your hand on the tank, its generally ok.

If it was me, i wouldn't be running it till there is a filter in place. A lot of contaminats in a hydraulic system are put there bolting it all together and the filter removes a lot of this. Do a filter change shortly after putting the auger into use, sorta 1st service kinda thing. Filler/breather cap on the tank is a service item too, and should be replaced when you do the oil/filter.

I know that you proberly coppied a factory built auger, but most of the the manufactures designs are 99% cost motivated and the quality of a lot of the crap sold to farmers amazes me.

Hi Rick, Rick and Dave,

I confirmed the order of the filter this morning - it's one for the return side - there is a drain plug on the bottom of the tank that utilises a bsp thread so I should be able to plumb the oil return in there. It is at the opposite end of the tank to the suction as I was mindful to ensure that I allowed for some cooling in the system.

Regarding the oil height issue I have discovered that when I raise the auger to what I would consider to be its lowest working height the oil tank - or at least a third of it - is above the pump.

What I'm thinking of doing at this stage is changing a couple of fittings around this week so I can hydraulically drive it from the tractor for harvest next week - this should allow the screw to bed in to the barrel - and then try to get the engine sorted when I don't have to rush.

Rick the motor is a MR 125 C004 and the pump is a 20C22X016G (the 016 used to be ?77 - it has been stamped over) the petrol is a 16HP Briggs Vanguard 303447 1302-E1 and the Auger is 40' and 8" diameter.

The Auger is a copy of a F.A. Miller and Sons auger in terms of the scissor lift however there are a couple of differences, FAMSON used 1"1/4 pipe for the carriage I've used 2"x3" 2.5mm RHS. They used a hydraulic cylinder for lift and lower and I've used a braked winch (the cylinder was $1600). The reason for the auger build was that my old one was completely destroyed when a neighbour borrowed it and the motor broke away from the front linkage arm, swung up and smashed the barrel as he was going up his driveway. It wasn't his fault as it could have happened to anyone. The motor wasn't damaged during the incident (it was the platform it was on that caused the damage to the barrel) so that is the motor that is being reused for this project. I wasn't too worried about it initially as another neighbour has a similar auger, albeit 34 or 36 feet and a 9 inch barrel and he is powering that hydraulically with a 13 HP Briggs. Not only that he often has it working at 45 Deg angles.

Cheers again,

Jonathan.

Ok, the pumps appears to be 22cc so at 3600rpm (i take thats its a direct drive engine, no reduction) you should be getting around 20GPM (US). The motor is 125cc so auger speed @3600 engine rpm will be around the 600rpm mark and deliver about 78t/hour. 8" screw @ 600rpm takes .42hp/foot @ 45', so 16.8hp to drive auger. With a 125cc motor, the line pressure would have to be around 1450 psi. To drive a pump with an output of 20gpm @ 1450psi would take 20.3hp..............basicaly a 24hp petrol engine. Even running the auger vertical (lest hp required and lest grain shifted) would take 9.2hp at the auger.

With oil flow like this, you would also need 3/4" hoses for the pressure and work lines, 1 1/2" for the suction and 1" for the return.

If it was me, i would be dropping that pump size to something in the 11-13cc range, dropping your oil flow to around 10-12gpm and auger speed closer to 350rpm.

Returning the oil straight into the bottom is ok, but you will need some type of baffle in/over the port to stop the oil pushing straight up through the tank, basically airaiting it from the other side from where it is now. Weld/silver solder a drop tube into the existing fitting to drop the return point under oil level would be easier.

Nice looking unit there.

A suggestion for you. Seeing that you are using a braked winch for the raise/lower you could drive it with a small hydraulic motor instead of the handle and make it quicker to raise. Can you easily add another spool? My auger runs like that and works really well.

Cheers,
Nova