How Many Microns Filter For Steering Hydraulics?

[Shanaly]

Hi I have a hand pump hydraulic steering system, the Nulon 46 oil is structurally good but has a dark colour, probably very fine alloy dust.

I would like to drain and filter it - would an engine oil filter or fuel filter do? or a special filter sock? most importantly, how many microns? 0.5 - 25 has been suggested!

thanks

John

[Acushla]

The valving on hydraulic steering systems have tight tolerances and need well filtered oils. Suggest that a 3 micron abs filter is required.

Cheers
Jim

[CaptainRoss76]

From an experienced marine engineer and delivery captain;

Rig a engine (not pre-filter) fuel filter to filter the oil if you think you need to.
I've never had to do that in twenty years as marine engineer. If there is enough metallic dust that on a black cloth you can see shiney particles you should think about full overhaul or replacement..
Would recommend changing the oil if you know its old though...
Dark hydraulic fluid is normally hose degradation contaminants - in the long term plan to change the pipes and oil...
Hope this helps