One Part Of A Hydraulic System You Should Never Paint

Painted-hydraulic-tank In chapter 13 of The Hydraulic Maintenance Handbook, I discuss the principle of engineering out issues that have the potential to cause recurring maintenance problems. Since maintenance occurs after the event, that is, after the machine is designed and built, this strategy is very much a retrospective one. Which means it’s desirable and preferable not to engineer in such potential problems in the first place.

And I was reminded of this recently. While conducting failure analysis for a client, small flakes of paint were found to be present on and in parts of the failed piston pump’s rotating group. Uh oh. Better lift the tank lid. And what we found is shown on the inset photo.

As you can see, the inside of the tank has been painted and the coating is flaking off. This tank is narrow and deep, so getting rid of the rest of the flaking paint proved to be a real challenge. Suffice to say, this maintenance disaster was totally unnecessary. If the inside of a hydraulic tank is not painted, there’s no paint to come off. End of story.

Hydraulic oil contains rust inhibitors. And if any settled water is drained off periodically, the inside of the tank cannot rust below oil level. Yes, condensation can cause the tank to rust in the air space above oil level, but this can be minimized by keeping the tank topped off and installing a hygroscopic breather. Or if you really must, mask off and paint above maximum oil level.

It is possible to paint the inside of a hydraulic tank and have it stick. I know Hagglunds used to paint the inside of the hydraulic tank on their power packs. And I’ve seen the inside of some of them when decommissioned after many years in service–still immaculate. Suffice to say the coating used on the inside is necessarily very different from that used on the outside.

But the bottom line is, when the case for painting the inside of the hydraulic tank is not at all compelling, why would you take a ticket in what is essentially a chemical compatibility lottery? As this example shows, painting the inside of a hydraulic tank can be a very costly 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.




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