Hydraulic forensics 1

[MintJulep]

I just completed an investigation of a failed hydraulic system.

Prior to my involvement the client performed their own investigation, inclusive of tear downs.

In the course of their investigation they used Brake Clean to flush hoses, hard lines and internal passages to look for particulate contaminates.

Now, I very well might have done the same thing in their place, but it got me thinking.

In theory, Brake Clean will evaporate completely, leaving no residue. So presumably whatever is left after the solvent evaporates is what was in the system.

But what might it do to the hydraulic fluid?

Would clean hydraulic fluid have been a better choice for flushing?

 

[MikeHalloran]

If the system is ventilated for a while after the Brakleen(r) is drained, it should evaporate and not contaminate any new fluid introduced.

( Brakleen also works well for flushing refrigerant lines, evaporators, condensers, etc. )

I don't think hydraulic fluid, with its typically higher viscosity, will do as good a job of flushing, and it always leaves a film behind... so you can never get all of the old fluid out, you just dilute it a lot.

I'd only be concerned about Brakleen as a flush in a system that uses Skydrol.



Mike Halloran
Pembroke Pines, FL, USA

 

[Ron]

Hydraulic fluid is an aliphatic hydrocarbon. Brakleen contains both aromatic and aliphatic hydrocarbons, but predominately aromatic. In an aliphatic system, aromatics can cause issues with seals and with effects on hoses and other "soft goods" in the system.

From a forensic standpoint, the system should have been flushed with hydraulic fluid, even if several applications were necessary. To do otherwise changes the evaluation parameters and each anomaly encountered then has to be evaluated as to whether it was influenced by the flushing process or not.

 

[MintJulep]

Great answer Ron. That was exactly what I was wondering, how might
it affect the evaluation.

 

[swall]

I used to work in the automotive brake industry. We wanted to do a fluid fill to facilitate testing of the main solenoid body for an ABS system, then flush it so it could be shipped dry. We used flushing solvents compatible with DOT 3 brake fluid. We could never completely get rid of the residual solvent, despite cycling the solenoids while dry air was blown through, etc. Very frustrating. We finally decided just to drain the unit after test, and ship it with some residual brake fluid.