dirty hydraulics? 1

[subsearobot]

We are comissioning a mobile hydraulic system, ~65 hp. We have an onboard pump with 6 micron filter on the pressure sied, and 12 on the return. Most of the plumbing is seamless 316. some hose is used too. we are independantly driving up to 7 hydraulic motors using pressure control valves(with no load in testing and flushing).

we also have driven the vehicle's system with a new "bench top" HPU. this unit has the same filtering as the vehicle, with the addition of a 5 micron and water filter, and a 3 (not sure it's absolute though) micron spin-on.

We not loaded the system. we have flushed, changed fluid, and tuned valves a bit - a few hours total.

So, I pulled off a manifold cover that had pockets facing up. the pockets served like setting ponds in the bottom of your resivoir. there was a film of shiny metal "dust" covering the surfaces. they sort of looked like silt or even clay sized particles. We checked varoius points in the system (including filter resivoirs) and found this pixie dust in the oil everywhere. the strange part is that this stuff is not magnetic.

Two questions:
1. do we need to worry? have we endangered our valves?
considering we have so much filtration, this stuff must be smaller than our filtration goal (10 micron abs).
2. where did this glitter come from?

 

[hydtools]

A component of the oil you are using? What is the oil your are using?

Did you filter the new oil as you filled the system?

Copper from motor bushing and/or pump bushing wear-in.

Why do you have a pressure side filter? If your reservoir is clean and your return line filter is effective and you filtered the new oil as it was added to the system, you will only capture pump-generated particles which should be nil unless you have a bad or dirty pump. Otherwise, all system generated particles will be captured by the return filter keeping the reservoir and system clean.

Do the filters have bypass valves which open when the system is cold and pressure drop across the filter pushes the bypass valve open bypassing the filter element allowing particles to pass the filter for a short time until the system warms up?

Ted

 

[subsearobot]

Ted,
We are using Tellus 32 at present. We fill our "resivoir" (it's a closed system on the vehicle, with a 15psi pressurized res) with our deck HPU, which is filtered on the pressure side twice at 6 micron.

copper sounds plausible!

we use a pressure side filter to protect expensive valving and motors in the event of problems with the onboard pump. this is an expensive system, which will operate quite remotely.

the filters do not have a bypass, just gauge taps. dP across the gauges is quite low on all filters.

 

[budt]

What is the Name and model number of your pump?


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[subsearobot]

on the vehicle, oilgear pvm-065 and pvm-014 operating off the same motor, independant hydraulic systems.

i'm not sure of the customer supplied external HPU. my guess is it's a gear pump, but have not been able to get the documentation.

 

[budt]

These are Axial Piston Pumps.

One important BEFORE PUMP START question, Did you fill the Pump Case with new oil?

It sounds like you have worn the pump's piston shoes due to lack of lubrication. At least that would be a reason for the fine particles you see.

If so the pumpm is in bad need of repair.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING