Back in January I mentioned getting into a rut when trying to trim a long technical paper meant for engineers down to a 10 to 12 minute speech for a nontechnical audience of 15 people at a Toastmasters club meeting. The topic was failure analysis of fire sprinkler heads. I already had a long, detailed PowerPoint presentation and was stuck trying to cut it down.
What I needed was a simple way to explain two different designs used for closing the water nozzle end of a sprinkler head. The old, reliable way is to put a metal cap (like a soda or beer bottle cap) over the end. The newer and much less reliable way is to stick a plug inside (similar to the cork for a wine bottle). The plug was brass, and it had a groove which held a rubber donut (called an O-ring) to do the sealing. I could have added two more images of a soda bottle and a wine bottle to show both designs.
While microwaving a bowl of oatmeal for breakfast I got another inspiration for “show and tell”. I noticed that the 5” diameter cylindrical container for the oatmeal already had a plastic lid similar to a soda bottle cap. The container got emptied and covered with a sheet of colored paper, as shown below.
In the garage I found a leftover chunk of spongy blue packaging foam. It was easily cut to make a plug for the interior. There are gaps on both edges for my thumb and fingers to grab and pull out the plug. So, now I had a working model to show the two different seal designs, as shown below.
The O-ring seal design got used in two different models of fire sprinkler heads from the Central Sprinkler Company. Unfortunately the “cork” tended to get stuck in the “bottle”. The Consumer Product Safety Commission made them recall 8 million Omega sprinkler heads and 35 million GB sprinkler heads. When the dust settled after that mess, Underwriters Laboratories changed their product standard to NOT allow ANY more sliding O-ring seals to be used in fire sprinkler heads.
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