hydraulic breaker repair

PaoloB · Apr 10, 2025

I'm repairing a hydraulic breaker, upon stripping found light scratches in the piston rod and housing (sleeve).
Planning to repair the rod by machining the scratches and have it hard chromed.
Is there any info regarding the allowable clearance between the rod and sleeve?
I'm just worried the new clearance due to machining might affect the performance of the breaker when oil heats up.

FluidPowerUser · Apr 10, 2025

Aim for 0.008mm radial clearance.

Equation for leakage is

Q = [πR (R-r₀)³/ (6 µ L )] (1+ 3/2ε²) ∆p
where ε =e/ (R-r₀)

R is bore radius
r_ois spool radius
μ is oil viscosity
L is sealing length
Δp is pressure drop
e is eccentricity

PaoloB · Apr 12, 2025

FluidPowerUser said:
Aim for 0.008mm radial clearance.

Equation for leakage is

Q = [πR (R-r₀)³/ (6 µ L )] (1+ 3/2ε²) ∆p
where ε =e/ (R-r₀)

R is bore radius
r_ois spool radius
μ is oil viscosity
L is sealing length
Δp is pressure drop
e is eccentricity

Thank you very much.
I wonder, is above equation can be found in the CFD subjects?

FluidPowerUser · Apr 12, 2025

Possibly
A derivative can be found on Wikipedia.

I’ve used it in 1D simulations like Amesim and Matlab.

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hydraulic breaker repair

PaoloB

Mechanical

FluidPowerUser

Mechanical

PaoloB

Mechanical

FluidPowerUser

Mechanical

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