Five Whys When Troubleshooting
/Photo courtesy of toyota
As a commissioning engineer I frequently find myself interacting with equipment or systems that don't want to function. A motor that won't start, a breaker that trips, or a chiller that faults, each situation requires a fundamental understanding of all externalities and internal mechanics. Often under the gun (will touch on optimistic scheduling at a later date), any tech/engineer is forced to assess the issue as quickly as possible.
Photo courtesy of toyota
A great tool for this application is "Five Whys". The provenance of the Five Whys is traced to Taiichi Ohno, pioneer of the Toyota Production System in the 1950s. Developed as a high level root cause analysis, Ohno encouraged his staff to address problems first-hand until the issue was found. "The root cause of any problem is the key to a lasting solution," Ohno used to say.
Let's work through an example:
1. Why did the chiller trip offline? Ans: It was determined that the chiller shutdown on low flow.
2. Why was there a low flow condition at the chiller? Ans: The low flow condition occurred when pump 2 was rotated onto pump 3.
3. Why was there a low flow condition during the rotation? Ans: The operator did not ramp pump 3 fully before shutting down pump 2. Pump 2's deceleration time was set to 2 seconds.
4. Why was the pump deceleration time set to 2 seconds? Ans: Pump deceleration time standard is 30 seconds. The 2 second timer was accidentally inputted by the startup technician and overlooked by the operator.
5. Why was the 2 second timer overlooked by the operator? Ans: Operators are handed equipment that are supposed to be fully vetted by contractors, vendors, and engineers. Operators are not trained or required to verify pump drive settings after a project is turned-over.
The end result of this exercise leaves us with likely root causes. Was there an uncomprehensive startup and testing process during construction? Or is their a gap in operator training and associated SOPs (if they are rotating pumps weekly, shouldn’t this flaw have been identified earlier)?
Intuitively, the Five Whys is qualitative and therefore imprecise. Like a decision tree, there are many iterations of possible root causes. However, this does help organize thoughts and provide insight as to what direction the forensic study needs to follow.