hydraulic filtration/strainer questions

[territorialmillworks]

I've spent several hours of unproductive time concerning pros/cons of suction strainers, suction filters and return filters. Seems that knowledgeable people in this field have firmly held differences of opinions.  So what works in the real world of shop built forging presses used by blacksmiths.  Thanks for all advise...Keith 

[Frosty]

A lot depends on the system what are you using hydraulics for? WE had strainers on the pickups in the tanks on the drills but they see really rough service in the field so keeping the fluid clean can be hard. Hydraulic presses are much lower stress, almost the only moving part that sees wear is the pump itself and any debris will be caught in the filter so placing the pickup off the bottom of the tank is usually plenty for a press.

That is a VERY basic run down and I don't have near enough info to give you the  most superficial guesstimate of what YOU might need.

Frosty The Lucky.

[TJ Smith]

After looking at maybe a kazillion different set ups I placed my filter on the return line. After all it is a closed system.Maybe between the tank and the pump would be better.

I'll rethink that for a bit(2-3 years) before I move IT

Check out several working presses and build one.

Take Care

TJ Smith

[Frosty]

NOT between the tank and pump it would be depending on vacuum not pressure to flow. Put it on the return line and catch any debris before it gets to the tank. Then if you have a high enough flow rate to generate currents in the tank you'll want baffles so anything the filter misses settles out. At any rate put the pickup a few inches off the bottom of the tank at the far end from the return.

This is a press, yes? If so it's a low flow rate and isn't going to generate currents to speak of so just putting a diffuser plate under the return to break up the stream will more than start settlement of crud.

Don't over think this, it's a really straight forward hydraulic system and easy to keep clean. Too many filters or in the wrong place can starve the pump for fluid and that WILL damage it.

Frosty The Lucky.

[j.w.s.]

My large hydraulic tank has an automotive type filter on the return and a magnet that is suspended on a rod connected to the cap in the tank through the fill port. Both seem to catch any unwanted particles in the tank. My valve only bypasses the flow so any time it's running idle the oil circulates through the tank about once every 2 minutes or so. Yes, its a closed system, but things can still get in there, just dont ask me how.

J

[notownkid]

When we built wood splitters we put a screw on auto type filter(filter and base came from NAPA) between the pump and piston.  Thoughts were it was easy to get stuff in the tank when checking or adding fluid esp.. in the woods, and it would stop particles which might break away from the pumps internals from getting into the piston and scoring it.  Nothing says you can't put on both lines for extra safety.  Filters are cheap compared to hard parts.   We did the same thing when installing truck dump bodies but did use three there.  The two on the pressure side were two different Microns and the return usually matched the less fine pressure one. 

Different theories on a subject is what makes the world go round.  

   

[Frosty]

My, "NO NOT THERE!" For a filter is on the pickup side of the pump, I don't know of an oil filter system that depends on vacuum to circulate oil through the filter. Put enough draw on it and get cavitation would be a B-A-D thing.

A magnet in the tank is a good thing. If you put it in a plastic bag that won't dissolve in the oil it makes cleaning the crud off easy just turn the bag inside out and take it off. It's how I collect black sand without having to work hard cleaning it off the magnet.

Frosty The Lucky.

[Charles R. Stevens]

I wouldn't have thought that oil filters would be rated for that kind if PSI, have to pick dad's brain, he as I only have the most cursery experiance with hydraulics. 

[Frosty]

We didn't use engine oil filters but I suppose a log splitter doesn't develop a whole lot of psi. but I've never put a gauge on one.

Frosty The Lucky.

[j.w.s.]

My, "NO NOT THERE!" For a filter is on the pickup side of the pump, I don't know of an oil filter system that depends on vacuum to circulate oil through the filter. Put enough draw on it and get cavitation would be a B-A-D thing.

A magnet in the tank is a good thing. If you put it in a plastic bag that won't dissolve in the oil it makes cleaning the crud off easy just turn the bag inside out and take it off. It's how I collect black sand without having to work hard cleaning it off the magnet.

Frosty The Lucky.

​I'm not sure the mechanics of my tank, it's professionally built by a hydraulics company so I'll assume they did their homework.

J

[Frosty]

I stand corrected. It may have been the systems we used or the filters or who knows what "might ifs" might apply. If I'm wrong I'm wrong or at best no longer current.

Frosty The Lucky.

[Charles R. Stevens]

Oh, your "wrong" alright, Master Frost, lol. But your in goog company

[Frosty]

Mother told me for years not to hang out with the wrong types but she never mentioned Goog company even once. <snicker>

Frosty The Lucky.

[j.w.s.]

I stand corrected. It may have been the systems we used or the filters or who knows what "might ifs" might apply. If I'm wrong I'm wrong or at best no longer current.

Frosty The Lucky.

​I'd tear it apart tomorrow and tell you how it "actually" works, because now you've made me really want to know, but I kinda need the pump to be in working condition for the next 4 weeks, now in july I have 2 weeks of down time scheduled -- so maybe.. lol

J

[Charles R. Stevens]

Lmaby thats grog? Lol

[ptree]

Built industrial systems for years and even went to a filtration school:) Here are the tidbits I can offer.

1. Every hydraulic system that has a cylinder that is NOT a double rod, that is has a rod only on one side of the cylinder, breaths air in and out every stroke. The rod displaces oil so it takes more oil on the side of the piston without the rod to fill and this pulls oil out of the system. When the cylinder is retracted this extra oil return to the tanks displacing the air. Sooo... you are making the tank breath every stroke. The air you move in and out carries water vapor that condenses and dirt.

2. The stuff that kills hydraulic components is too small to see. Clearances in normal spool valves is on the the order of 6-10 micro meters. In a simple gear pump about 10-15 micrometers. In a high tech variable volume axial piston pump about 2-6 micrometers. A micrometer is a millionth of a meter. A red blood cell in our blood is about 4 x 6 micrometers in size. The average human with good eyesight, looking at a black spec on a white background can see a 70 micrometer particle. The air is full of those hydraulic killer particles. Everywhere, in every state and nation. The air is full of dirt, you just can't see it.

3. We also do stuff like pouring oil that is full of these tiny particles into our tanks. We use old used buckets coffee cups dirty funnels etc. Remember that wiping that stuff with a rag gets the stuff you can see, not the stuff that kills you system.

4. Want to know how the air gets in and out? look at the filler cap. Has a Breather built in. The breather usually looks like the oil breather off a 63 Chevy. Has some mesh inside to keep out dead rats cigarette buts and gravel, not dust you can't see. Want to improve? get a new spin on oil filter that will screw onto a pipe nipple. make a flange to fit where that 63 Chevy breather goes and weld the nipple to it. Install and screw on the filter. Now you have a cheap filter to catch the dust in the air.

5. Add you oil by pumping through a filter. rig up a cheap spin-on oil filter to a pump and use that to pull the oil from your bucket and to then run into your tank. Now you have clean oil in a tank that breaths cleanly.

6. A magnet suspended is cheap insurance.

7. if building your tank, take guidance from industrial practice. use a rectangular layout. use a baffle down the long axis that is open at one end. put your return at one of the blind corners. put your suction at the other blind corner. This forces the oil to take a path twice the length of the tank to go from the return to the suction. this allows it to cool, settle out debris, and the entrained air to float out the top.

8. A suction filter is usually bad practice as they must have a bypass to avoid cavitation when it clogs. They are usually too course to actually protect the pump. But if you use clean oil and a breather that filters then a Return filter is a good thing. And since it is not inside the tank it is easy to change.

9. I like on bigger, more expensive systems to use a "Kidney loop" filtration system. That is a small gear pump usually mounted on a "Thru shafted main pump" that runs when the system is on. I use a 50 gallon a minute spin-on filter, with a 5 micrometer beta rating of 20. that picks up the hottest, dirtiest oil at the return, filters it, runs though a cooler, and returns between the return and the suction for the main pump.

10. Beta rating you ask? Beta rating is the simple rating that tells you how many particles make it through the filter on each pass as in "number upstream/number down stream. Most regular filters like a cheap spin-on are Beta +2 so if you have 100 upstream you have 50 downstream. THAT MEANS HALF ARE GETTING THROUGH!!! Beta 20 is near absolute and is as close to 100% capture as technology will allow. You know those big Lubrafiner filters you see on the side of Semi-trucks? that is  Beta 20. If you can fine a housing the filters are pretty cheap:)

11. So we have not discussed the water vapor. It will get in the oil. Period. So hydraulic oil has an additive that deals with that. when that additive is consumed then you start to form carboxylic acid. That is what gives you that classic Burnt smell. If your oil is milky, then you have gross water, not carboxylic acid. Either is a replace the oil NOW. Milky means gross water from say a roof leak or similar is getting in the tank.

12. With the exception of flammability regular old ATF oil is usually one of the best choices in hydraulic oils for home built equipment. It has the best pour point of any easily available oil meaning it does not jell up at very low temps. It has an excellent viscosity index meaning it maintains its viscosity at elevated temps. It has an excellent additive package for extreme pressure, and antiwear as well as a very good anti-oxidation additive. Anti-oxidation additive is the one that deals with water.

I offer these thoughts for free and like many opinions they are worth exactly what you paid for them:)

[Frosty]

Thank you, that's as good a rundown of basics as I've ever heard. This a perfect example of what I love about IFI while questions get a raft of answers from the opinions of folk with little knowledge to opinions of guys with working field experience like mine to the opinions of folk with serious professional experience like yours.

This is a put it in the bank post, thanks again.

Frosty The Lucky.

[ptree]

Anytime Frosty:)

I used to put up all sorts of things to not do in forge presses but was trolled away. But then I worked in forge shops with hydraulic presses from 1981 till 2005. Seen the failures and the fires and injuries. But trolls are trolls.

I do not now hve a press in my shop, but may. Have a nice big 14" bore and the 32 GPM pump. Now just figuring the prime mover and it will be after the toy helve hammer now in works and after the 200# guided helve hammer that is behind that. So many projects so little time.