Ignoramus16281 wrote:

On 2013-12-10, Pete C. wrote:

Ignoramus16281 wrote:

On 2013-12-10, Pete C. wrote:

Ignoramus27028 wrote:

I own a semi trailer with a hydraulic beavertail. It has several
hydraulic cylinders and a hydraulic winch.

We run it using a hydraulic unit that we made with a Honda engine that
replaced the electric motor that was on the unit originally.

It always worked great.

The oil has developed a "water in oil" condition, and with cold
weather the ice crystals blocked the inlet and everything stopped
working. I suspect that this is so because the trailer's hydraulics
was full of water from the beginning.

We drained the oil today and I have plenty of new oil to put
in. However, I want to drain the old bad oil from all cylinders.

My plan is to remove the hydraulic filter that is on the return line
to the tank, connect a pipe to it that would drain into a bucket. Then
we would put new oil in the tank, and operate all cylinders and motors
until only clear oil comes out of the return line.

Would that give me a decent enough purge?

Anything I am missing?

i

Open center or closed center hydraulics? I presume open center on a
small unit like that in which case you get return flow when the pump is
operating regardless of operating the cylinders, so you'll go through a
lot of fluid by the time you cycle all the cylinders.

Good question. I am not sure. But there is a number of valves that can
be actuated to operate this beavertail. I do not think that they would
work together if they were open center.

Together or one at a time? If your power unit is a little gas engine
and

one at a time, or together.

a basic gear pump it's most likely open center, more common and cheaper.
Closed center uses variable displacement pumps and is used on large
construction equipment allowing simultaneous operation of functions.

The pump is variablle displacement. It is an expensive pump. It is not
from some kind of a toy like log splitter.
i

Well, if it is a closed center system that will help by only having
return flow when you are actuating the cylinders and whatnot. Less fluid
needed and less contaminated fluid to dispose of.