The Danger Of What You Don’t Know You Don’t Know

Posted by Bruce Brandt on September 4, 2012 @ 12:50 pm

Engineering disciplines, just like may other disciplines, have become very narrowly focused. At some level this is a necessary trend, since to be expert in every aspect of a field has become something that is almost impossible to accomplish. Very few mechanical engineers are experts in metallurgy, hydraulics, machine design, HVAC design, thermodynamics, mechanics of materials, strength of materials, metal cutting operations, metal forming operations, and, well, the list goes on. An engineering student attempting to delve deeply enough in every aspect of his or her chosen discipline to be an “expert” would never finish college.

What’s more, most colleges don’t even attempt to expose a student to all the aspects of a discipline, but expect specialization early on in the undergraduate program. If you’re an electrical engineer, you may have to choose between electronics and power.

The result is many engineers don’t even know what they don’t know about what their jobs require after they graduate. Take working in the field of process control as an example. Many of the controls engineers I’ve encountered have no innate knowledge of what’s connected to their control system and how that might affect their control design.

When asked what they are controlling, they can usually tell you if it is a level or flow or temperature or whatever, and they can usually tell you they are operating a valve to do so, but when asked what kind of valve, they may or may not know if it’s a globe or ball or butterfly, what size it is, what the characteristics of the trim are, or what the impact of all these details might have on the control design. Therefore, they also won’t know what the impact of the control design might be on the valve. Are they forcing the valve to operate in a range where it will cause cavitation or cause the fluid to flash? Are there operating conditions where the valve will wire draw its seat? Can the valve respond as fast as the control loop needs to control the process properly? Similar questions can be asked about the sensors.

Most of the time the answer to all these questions is, “It doesn’t really matter.” Most of the time the loop can be tuned to accommodate the requirements of the system. However, sometimes that isn’t enough, and changes to the code are required.

The danger lies in those times when it does matter and often it’s only revealed when the disaster happens. I once watched a six inch schedule 80 pipe whip like a rope because a piping designer didn’t know about water hammer. As a result, two men ended up in the hospital with broken bones and were lucky that’s all that happened to them. If any of the pipe welds had failed, people would probably have died.

So, if you don’t know that you don’t know something that you need to know, how do you find out?

If you’re new to a job, keep your eyes and ears open. When you see or hear something you don’t know about, ask. Fortunately, most engineers are more than happy to expound on their knowledge. Those of us who have been doing the job for a long time have been in your position at one time or another, so while we might get a laugh out of your question, we’ll respect you for asking it. Also keep in mind that an engineering degree doesn’t teach you everything, it just gives you the tools to learn.

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