Is a filter absolutely necessary for hydraulics?

[chad22]

In summation, NO you don't NEED a filter but.... In my opinion you would be foolish to invest several hundred dollars in pump, valves, cylinders, etc and not add a decent $100 filter.

Roy

That's true. After having around $1,000.00 invested in this homemade backhoe. I would be a fool to not spend at least $100.00 more on a filter assembly and filter.

I don't want to damage an investment like that. And I'd like to have the backhoe last a long time. So I will buy a filter and put it on.

Thanks Everyone

Chad

 

[oldnslo]

What filtration factors are different in this case, Roy? I assume that by
servo-valve you mean a valve that is electrically controlled, with some
kind of feedback, and not just a solenoid-controlled valve.

Servo valves:
Yes they are precision Electrohydraulic valves with closed loop feed back. Their design is such that they have small metering lands and or orifices that are very susceptible to dirt.

One common use would befor injection molding machines or Die Cast. They can control pressure, flow, and oil direction (directional valve).

If you interested Welcome to Moog's Servovalve Home Page is the website for Moog Servo valves.

Roy

 

[Rocwin]

You don't need to spend anywhere close to $100 for an effective return line filter. You can buy the head for under $15 and the element for ~$8 (depending on how much flow you have.)

Expensive elements and head assemblies come into play when you are operating more expensive valves, as already mentioned, like porportional and servo valves which require absolute rating micron filters. Standard (paper) elements are nominal rating and allow larger particles than what is rated through all the time.

 

[dfkrug]

Their design is such that they have small metering lands and or orifices that are very susceptible to dirt.

Thx, Roy. Interesting site.

From a practical perspective, one can see that those $15-20 spin-on
hyd filters (Prince, Donaldson, Wix, etc) are intended for low pressure
applications. Something that size that could handle even 2000psi would
have to be made much much thicker and stronger, and cost heaps more.

 

[IceStationZebra]

A general note - if you are using oil from a 55 gallon barrel or a large tote you are already starting with dirty oil. On numerous occasions and from several different suppliers I have found alarming amounts of particles in the bottom of freshly opened and emptied barrels and totes.

Most of the places I have worked at use a simple filter cart to both lift the oil out of the barrel and filter it at the same time. A good filter cart set-up would have a trash screen, then a 30-40 micron filter, and finally a 3 to 20 micron filter depending on the use. Some people also put water absorbing filters on them.

A simple alternative would be to use elevated reservoirs with an oversized filter on the gravity feed outlet. Flow will be somewhat restricted but very reasonable cost.

ISZ

 

[wdchyd]

A general note - if you are using oil from a 55 gallon barrel or a large tote you are already starting with dirty oil. On numerous occasions and from several different suppliers I have found alarming amounts of particles in the bottom of freshly opened and emptied barrels and totes.

Most of the places I have worked at use a simple filter cart to both lift the oil out of the barrel and filter it at the same time. A good filter cart set-up would have a trash screen, then a 30-40 micron filter, and finally a 3 to 20 micron filter depending on the use. Some people also put water absorbing filters on them.

A simple alternative would be to use elevated reservoirs with an oversized filter on the gravity feed outlet. Flow will be somewhat restricted but very reasonable cost.

ISZ

Ahhh, There's a guy that knows the right way..!!....:thumbsup:

 

[IceStationZebra]

Ahhh, There's a guy that knows the right way..!!....:thumbsup:

Thanks. I have worked for several off-road OEM's as a test engineer putting prototypes through their paces. And the last thing you want is some dirt causing a malfuction or fouling up test results. I also worked with Moog/MTS servo valves for several years. ISZ

 

[wdchyd]

When you say "working with Moog/MTS servos" did you rebuild/test them or use them in installation/designing......

I need to get some training on these buggers.....I've sent them out for repair but never had the gumption/test stand to go any further.....

 

[955Lincoln]

Brings back memories of 2 Moog Hydra Point milling machines (Converted Bridgeports) from the 60's I bought surplus to convert to current day CNC. All of the axes were moved by large hydraulic cylinders with position accuracy of .001. My jaw remained on the ground while disassembling the feedback portion of the machine. Cams, binary air valves, hydraulic gizmos, orifices, so many complex parts and all ground to incredible tolerances controlled by a paper tape and relays. It must have cost a fortune to design and build these machines.

 

[IceStationZebra]

When you say "working with Moog/MTS servos" did you rebuild/test them or use them in installation/designing......

I need to get some training on these buggers.....I've sent them out for repair but never had the gumption/test stand to go any further.....

I created and ran a structural test lab for several years. Basically take high-end hydraulic cylinders controlled with Moog/MTS servos and flex parts of off-road equipment until something broke. Mostly skid steers and some telehandlers.

As far as testing them yourself, not sure what you want to do but I don't think there is much the average person can do to them besides clean out the filters (if equipped) and adjust the neutral position. I don't know if you can even buy the parts separately since everything has such a high precision.

ISZ