A new client, a hydraulic repairer, consulted me about the failure of one of their piston pump rebuilds. The pump was not installed by them, but when the failed unit came back for inspection, it was obvious the drive coupling had been hammered onto the pump's drive shaft.
For the uninitiated, this is a really dumb thing to do. If you ever come across a drive coupling that is tight on its shaft, do NOT reach for a hammer; reach for the emery paper and get busy with it. And this applies to any piece of rotating equipment, not just a hydraulic pump or motor.
Of course, my client was interested to know what influence the battering of the pump's drive shaft may have had on its failure. And that's a rather long story for another time. But I mention it here because, separately, another client contacted me about getting a commissioning procedure or checklist they can hand out to their customers with every hydraulic component they rebuild.
This is something all hydraulic repairers should do to avoid unnecessary 'infant mortalities' and the warranty claims that usually result from them. It's also something I instigated at the hydraulic repair shop I was managing 15 years ago. And the use of checklists is something I advocate all hydraulic equipment users adopt in Insider Secrets to Hydraulics.
Checklists are a great tool for eliminating human error and have application in any situation where the cost of mistake or omission is significant. But there are a couple of important points with checklists when it comes to their effectiveness. The first, as I explained to my client who want's to include one with each hydraulic component they rebuild, is to be most effective they need to be machine specific. The pre-flight checklist for a Boeing 747 is no use to the pilot of an Airbus A340.
Sure, you can cover the steps common to all situations, such as, in the case of a piston pump: "fill the case with clean hydraulic oil through the uppermost drain port". But beyond that, there are so many different variants of pump installation, it's difficult - and potentially confusing, to try and cover all necessary steps, in a single, generic procedure.
The other point is, the very best checklists are dynamic; they're a work in progress. A friend of mine, who is ex-military, uses a checklist before embarking on a camping trip with his family. Obviously, he does this so he doesn't leave any essential equipment at home. But he takes this one step further. When he returns from each trip, he updates his checklist - no only does he add to his list things he should have taken, he also removes from his list, things he did take but did not need.
The point about this is, when you sit down to right a check list, it is difficult to foresee every eventually. Not only the things that should be done; but also the things that should not be done. My previous, pre-start checklists haven't included the instruction: "Do NOT force the drive coupling onto the pump or motor shaft!" But they will now. And so should yours.
Bottom line: not using a checklist when starting or restarting a hydraulic system after maintenance work has been carried out can turn out to be an expensive mistake. 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.