The FBI has recently opened a criminal investigation on the container ship that brought down Baltimore’s Francis Scott Key Bridge in March. For sure, more information will be made available to the public in the coming weeks or months regarding the root cause of the power failure. We will save the root cause for another blog. However, this time, I want to think about the layers of protection. I want to think about a bridge with the mindset of a poka yoke.
Building layers
Anyone who built Legos as a kid or continues to build them as an adult probably built a castle. If you were not the Lego type, you may have been the individual who built castles on a PC with Castles 1 or Castles 2. Not the Castle’s type on a PC? You may have been the individual who built castles on the beaches of the Atlantic or Gulf during summer vacations. Regardless of where you built castles, you understand the layers of protection to protect the heart of a castle. Therefore, you built high walls, moats, or ripraps to protect the critical infrastructure.
With the Francis Scott Key Bridge, there seems to be minimal protection on the column for the bridge. There were no assemblies or rocks intended to divert a runaway barge. I see no layered walls protecting the infrastructure critical for the bridge's intent. Instead, it was a design that accepted the risk and vulnerability of a direct impact. If we were building a bridge in Castle on the PC, we would know to design layers of protection because the cost of the layers of protection was cheap. The mechanism to eliminate a failure was affordable and simply made sense to a fourteen-year-old kid.
I have not found regulatory requirements that require a protective layer to prevent bridge impacts. However, I see provisions that encourage designing protection into bridges as part of bridge contract bids but are selected to install based on the availability of funds. I see bidding processes that require a certain lifespan or the ability to absorb the direct impact of a loose barge. But I am missing the poka yoke to prevent damage to the critical infrastructure and instead recommended solutions of thicker walls or more concrete.
Designing in a poka yoke
As design engineers, we remain challenged to design poka yoke into our systems due to the additional cost and the "what ifs" of a loose barge. One of the best I had ever seen at this was an engineer named Tom Bereznak, who engineered these solutions into the original design cost-effectively. Tom would look at a system, understand its criticality, and build poka yokes to protect the system's intent. He protected the capacity and capability to be refurbished quickly and minimize downtime. I saw him design pins into assets to rapidly remove and replace damaged equipment after being unintentionally struck. I saw him adamantly design barriers around hydraulics systems, anticipating an impact from surrounding heavy mobile equipment. Tom designed layers of protection from the onslaught of a mistake. They were poka yokes. They were Bereznak-proofed. He called it "operator proof."
On your next Gemba walk, housekeeping audit, or doing your daily shift checks, look for the scratches. Look for the unintended impacts on handrails, walls, and pieces of equipment to see your impact areas. Consider the layers of protection that exist and those that are vulnerable to one rogue ship. Consider how a few poka yokes could eliminate the potential for failure.