Filter location

[Ivan49]

I am planning out a project and I have been looking for info on where to put the hyd filter into the system. I looked at many different pieces of equitment and find that some ave it on the inlet line to the tank and many have it on the outlet line. Which way is correct? I am putting togather a hyd system for a wood processor that I am planning on building

 

[J_J]

Put it on the return side.

 

[oldnslo]

Unless you have a very sensitive device in your system like a proportional or servo valve the return line filter is the most cost effective filter location. Pump inlet filters are screens that only catch large particles and do very little for protecting components.

 

[J_J]

Roy,

I don't know about all hydrostatic tractors, but the fluid should be extra clean. I don't think I would rely on the fluid from the tank to be that clean.

In a wood processing or log splitter setup, the hyd filter is always on the return line usually at the tank.

All of our Power-Tracs have a 10 micron input filter to the variable pump as it needs very clean fluid.

Our hyd system is also a closed loop hydro system, with the charge pump feeding fresh fluid to replenish lost fluid and to flush out the VSP pump.

They do warn about the input filter change out time, as the blockage would severely hurt the pump.

 

[Ivan49]

Thanks for the info guys. I was leaning toward putting it on the return line but wanted to make sure

 

[IceStationZebra]

"I don't think I would rely on the fluid from the tank to be that clean."
I definitely filter any oil I get out of a barrel. It is not clean enough for anything but the crudest systems from 60 years ago. All the vendors know this, one local to me actually will filter their oil prior to delivery for a fee.

Inlet filters are only to keep the big junk out of the pump. A typicall 100 mesh will only filter to 150 micron. Any finer than that and you risk pump cavitation.

Return filters are the most economical, and therefore the most commonly used. Ideally it should be large enough to not bypass when it is cold, otherwise it could pass filtered debris into the tank. The filtration level is dependant on the components is the system and how many hours you need it to run. (example: piston pumps need cleaner oil than gear pumps)

On highly sensitive systems it is very common to put high pressure filters after the pump. That way if the pump goes south it doesn't comtaminate anything down stream. Some systems will also have a separate filter/cooling loop that always runs. This is the most efficient and the only guarenteed way to keep servos happy.

ISZ

 

[oldnslo]

Roy,

I don't know about all hydrostatic tractors, but the fluid should be extra clean. I don't think I would rely on the fluid from the tank to be that clean.

In a wood processing or log splitter setup, the hyd filter is always on the return line usually at the tank.

All of our Power-Tracs have a 10 micron input filter to the variable pump as it needs very clean fluid.

Our hyd system is also a closed loop hydro system, with the charge pump feeding fresh fluid to replenish lost fluid and to flush out the VSP pump.

They do warn about the input filter change out time, as the blockage would severely hurt the pump.

JJ,
You are correct in stating that hydrostatics need to be kept clean. Some companies use inlet filters on the charge pump and others use a pressure filter between the charge pump and main HST pump. In either case if the filter plugs their is potential for HST damage.