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The world's worst air disaster occurred in 1977 on the Spanish Island of Tenerife. The accident which claimed the lives of 583 people onboard two Boeing 747s was attributed to a series of unfortunate coincidences and mistakes, the most heinous being the decision by one of the pilots to initiate an unauthorized takeoff on a runway where the second plane was taxiing. As a result of this accident, new rules were established for cockpit communication between pilot and first officer, which until 1977, allowed for a dogmatic style of command where the second officer was not permitted to challenge or second-guess any pilot decision. This, along with other changes, was immediately implemented in an attempt to prevent a similar catastrophe from recurring.
Like most accidents involving commercial transportation, as soon as the route causes have been determined, regulatory bodies such as the National Transportation Safety Board (NTSB) and Federal Aviation Administration (FAA) typically recommend changes to procedures, or where component failure is found to be the problem, to the design of the system. This process is often referred to as error-proofing and is around us on a daily basis. Consider the left-handed thread on your barbecue grill's propane tank, designed to prevent the attachment of an oxygen pressure regulator, which could result in an explosion when an oxidizing agent is mixed with a flammable gas such as propane. Or the catch on the lid of a medicine bottle, designed to prevent children from opening the bottle. In each case, we don't necessarily think about why these household items are designed as they are, we simply trust that they do the job as intended.
The same holds true for basic maintenance tasks such as lubrication. Too many organizations try to train human error out of the mix; this is a mistake. Think back to the unfortunate incident in Tenerife. It's fairly certain that one of the first rules the pilot learned in flight school is do not attempt a takeoff unless authorized to do so by air traffic control. Yet he elected to do so, despite the fact that he was a senior captain in charge of safety for his airline. Though the consequences were fatal, this act simply falls into the category of "mistakes happen" - a fact of life when any human process is involved, whether it is flying a plane or lubricating a bearing. Rather than teaching technicians that adding the wrong oil to a machine is bad - most already know this - we need to develop a system to error-proof our lubrication practices.
So how can we error-proof against lubrication mistakes? One obvious way is through tagging: applying color- and shape-coded tags to machines, transfer devices and storage tanks to ensure that the wrong oil or grease is not accidentally added. But even with tagging, mistakes can still happen. So maybe you want to go one stage further by using different fittings - just like the propane tank. For example, I often advise clients in food processing to use different styles of grease fittings - a standard zerk fitting for nonfood grade applications and a button-head fitting for food-grade greases. Again, this doesn't guarantee mistakes won't happen, but with such a setup, it would require someone removing the grease fitting and replacing it with a different style of fitting - far less likely than simply picking up a different grease gun with the correct connector.
Figure 1. Lubricant Identification
In error-proofing, we should aim for the second principle of mistake minimization which is Keep It Super Simple, or KISS. You see, we're all creatures of habit. Mistakes happen when we're either performing a task so common and routine that we "zone out" or lose focus, or when we try to cut corners. Cutting corners can be a major source of mistakes, but this can be minimized by making the simplest way, the right way.
Take for example the act of changing oil in a gearbox. When changing oil, it's important to remove as much of the old oil as possible to prevent contamination of the new oil with particles, water or degraded fluid. Depending on gearbox design, this can be a tricky proposition, particularly if the gearbox is cool, meaning the oil is fairly viscous. In an attempt to save time (cut corners), we might be tempted to not wait for the last drop of oil to drain from the box under gravity, instead electing to get the job done as quickly as possible. But by adding a quick-connect to the drain, it allows a filter cart to be used to drain the oil (with the cart in bypass mode) which takes a fraction of the time, and allows for flushing in the event that heavy contamination has built up in the box. Similarly, the same cart can be used to add oil using the filter - again the right way (prefiltering new oil) is far easier than hand-cranking an unfiltered drum pump. This is a prime example of the KISS principle: make the right way the easiest way and nine times out of 10, the job will get done correctly.
I'm a firm believer that few people wake up each morning, intent on doing a "bad job". Clearly the pilot of the 747 who initiated the unauthorized takeoff had no intention of causing such a tragic accident - but mistakes can and do happen. So when trying to prevent error in maintenance and lubrication, remember to error-proof as much as possible, and keep it simple!