What is an acceptable level of oil loss for a hydraulic machine:
a). Zero
b). 2%
c). 5% or more?

In a perfect world, the right answer would of course be zero. But in reality, the true answer is 5% or more–of tank oil volume per year. And the reason I can say this with confidence is because total hydraulic oil consumption is composed of losses from:
1. Slow leaks; weeps and drips.
2. Sudden and catastrophic conductor failure–usually hoses.
3. Opening of the system–usually for change-out of components.

When these three types of losses are considered together, it’s all too easy to get up to and beyond an oil consumption of 5% of tank oil volume per year. For example, consider a Komatsu PC1250-7 hydraulic excavator. This is quite a big digger: 100 ton operating weight. And it has a tank oil volume of 670 liters. So a 1% oil loss amounts to 6.7 litres. And a 5% loss equates to 33.5 liters. These are not huge volumes. And it’s possible, but not desirable, that a machine of this size, with its large number of conductors and connections could lose 5% or more of tank oil volume per year through slow leaks; weeps and drips.

But even if slow leaks were close to zero, a single hose failure could account for a 5% loss of tank oil volume. And since hydraulic hoses are typically a run-to-failure item, their contribution to total oil consumption (loss) over a multi-year run is mostly unavoidable.

A similar situation applies to losses arising from component change-outs. It’s conceivable that on an excavator of this size, the change-out of a boom cylinder could result in a loss of 5% or more of tank oil volume. You would not expect to change-out the boom cylinders every year, but just as with hoses, over a multi-year run there is a certain percentage of losses which are locked in as a result of the unavoidable change-out of components.

I always encourage hydraulic equipment users to measure and record all hydraulic oil top-offs. Because it’s the only way you can know for sure how much hydraulic oil each of your machines consumes in a year. And as you can see from the above discussion, this record keeping exercise can be made more qualitative by noting which top-off amounts were due to components change-outs or hose failures. Then, by elimination, the remainder can be approximated to slow leaks; weeps and drips.

So if you’re a hydraulic machine owner or responsible for the same, not recording all hydraulic oil top-offs is a mistake. And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get “Six Costly Mistakes Most Hydraulics Users Make… And How You Can Avoid Them!” available for FREE download here.