Is a filter absolutely necessary for hydraulics?

[AKKAMAAN]

The reason you need a suction strainer is because you do not use a strainer in the fill cap....If you start with a clean tank, use a return filter, fill cap strainer and an air breather filter....nothing can go wrong....more than water...
The very best is to have a recessed return filter into the top of tank, and have the fill cap into the filter.......no strainer at all needed...

 

[bakerg]

I sorry about that, should have stuck with what I thought and said return. I asked a Millwright on shift here at work and he said pressure side. What do I know, I am only a electrician, but I guess I was right afterall.

 

[tommu56]

manual online

http://www.metalwebnews.org/ftp/hydraulics.pdf

 

[J_J]

Yes, you do need to filter most fluids. The longevity of most products depends on it. Filters are cheap enough, so why not. Can you get by without a filter, certainly, but you have to accept the risk. Looking at all the millions of oil and hyd filters that are made, you should have answered your own question.

 

[beenthere]

Yes, you do need to filter most fluids. The longevity of most products depends on it. Filters are cheap enough, so why not. Can you get by without a filter, certainly, but you have to accept the risk. Looking at all the millions of oil and hyd filters that are made, you should have answered your own question.

That implies it was a dumb or needless question.
There are likely many readers who learned something from this short discussion as a result of the OP question.
I think increasing knowledge to members is the real worth and value of the TBN forum.

 

[oldnslo]

I'm building a backhoe and I was wondering if it was absolutely necessary for it to have a hydraulic filter hooked up to it?

Would anything bad happen if I just hooked the lines up and run it without a filter?

I don't want to ruin anything, if I run it without a filter.

Chad

Depending on the pressure you are going to be operating at at the type of components you are using will somewhat dictate where and what type of filter(s) you should use.

Gear pump, and manual valves at 500 PSi or less you could probably get several years of service with no filter as long as there is no ingression of dirt.

General rules of thumb:

Pressure filters: are a must for Servo valves and should be strongly considered for proportional valves. Normally around 3 micron is recommended.

Return Line filters: Used on most hydraulic systems. They are relatively inexpensive and help keep the reservoir clean. It is must easier and less costly to keep the reservoir clean vs trying to clean it up.

Inlet filters: Occasionally used on charge pumps in mobile equipment but GREAT care must be taken to prevent starving / cavitating the pump.

Inlet screens: Very common as noted above. Again care must be taken to prevent starving the pump.

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

 

[wdchyd]

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

Very well said Roy......:thumbsup:

 

[oldnslo]

Very well said Roy......:thumbsup:

thanks,
I suspect most of us have been guilty of the "Penny wise and pound foolish" syndrome.

 

[dfkrug]

General rules of thumb:

Pressure filters: are a must for Servo valves and should be strongly considered for proportional valves. Normally around 3 micron is recommended.

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.

As for the OP's original question, that term "absolutely" is overused, bigtime.
Drag racers may not use an AIR filter at the track, but for most of us,
going without a filter hardly makes sense.

 

[Mace Canute]

From http://www.metalwebnews.org/ftp/hydraulics.pdf:

a. Strainers. A strainer is the primary filtering system that removes large particles of foreign matter from a hydraulic liquid. Even though its screening action is not as good as a filter's, a strainer offer less resistance to flow. A strainer usually consists of a metal frame wrapped with a fine-mesh wire screen or a screening element made up of varying thickness of specially processed wire. Strainers are used to pump inlet lines (Figure 2-11, page 2-10) where pressure drop must be kept to a minimum.

Where does the author think those "large particles of foreign matter" are getting into the oil? Think about it. There's only two places. One is from the equipment itself and the other is through the filler and tank vent. If your equipment is wearing/grinding off particles inside the hydraulic motors or cylinders or valves or anywhere the hydraulic oil is to be found that are LARGE enough that a strainer will catch them, do you really think a strainer is going to do any good? What about all the particles that make it through the strainer? Does anyone think you will be able to run that piece of equipment for any length of time before it totally self destructs? Remember, you do have a filter in the return line to the tank (or you certainly should!). The other point of entry could be the tank vent but that should be a filter or a screened breather that stops all particles and not just a hole open to the atmosphere. That leaves the filler hole and that is where a strainer should be. Why would you want to have some foreign body make it into the tank when you could trap it right at the inlet where you can actually see it and clean it out? Another reason to have the strainer in the tank filler and not in the suction line is elimination of cavitation caused by a plugged strainer. Hydraulic oil thickened by low temperature can easily limit a strainer's flow which can cause cavitation and worse yet, you might not realize you have cavitation, it could be masked by other noises. Cavitation is much more of a worry than any particles that a strainer might catch.