“Experience: that most brutal of teachers. But you learn, my God do you learn.” — C.S.Lewis
We all learn from experience. When it comes to brutal lessons, though, it is better to learn from someone else’s experience. In the course of our work, clients have shared some experiences with us that everyone can learn from. Fortunately, while each experience had the potential to end in disaster, each experience ended as a near miss.
Electrified Filing Cabinets
An office worker felt a sharp twinge when he opened a filing cabinet drawer. He was surprised and immediately sat down, attributing it to a spasm from overexertion. As he sat there, a second worker opened a drawer in an adjacent filing cabinet and was also jolted. Painfully. At that point, they agreed there was an electrical problem. A maintenance tech came, not believing that anyone could be shocked by a filing cabinet, and to humor them, put a voltmeter to the filing cabinet. It read 114 volts.
The tech went and flipped the breaker to the office and after making sure the filing cabinet was no longer live, pulled it out to discover an outlet behind the cabinets. The electric pencil sharpener sitting on top of the filing cabinet was plugged into it. Right where the cord was attached to the plug, the cabinet had worn through the insulation. The abrasion caused by opening and closing file drawers had been enough not only to wear through the insulation but to wear through the paint on the file cabinet. A circuit was completed and filing cabinets were electrified.
Asphyxiation Potential in an MCC Room
At a different plant, there was a problem in the motor control center room for a unit that was being upgraded. Several people who worked in the room were complaining of flu-like symptoms: headache, fatigue, nausea, and dizziness. The plant engineer went to check progress in the MCC room and while down on his hands and knees there, felt the same symptoms. When he stepped outside, however, he noticed that the symptoms cleared. On a hunch, he took a gas meter they used for confined space entry and checked the MCC room. The LEL monitor indicated that there was no flammable gas, but the oxygen monitor showed that the oxygen concentration in the room was less than 15%, a third less than normal oxygen levels.
They immediately evacuated the room.
With doors open and fans ventilating the room, they set about looking for the asphyxiant. It wasn’t refrigerant from the air handling unit on the roof. It wasn’t carbon dioxide from the fire suppression equipment. There weren’t any compressed gases stored in the MCC room. However, the unit was being upgraded to a new hazard classification: Class 1, Division 1, Group B. The pump motors had been equipped with nitrogen purges. Seals had not been poured in all of the conduits, and they discovered that nitrogen purge gas was blowing down the conduits into the MCC room.
At a third plant, a toll facility, an interlock failed to trip when it should have. The maintenance tech had simulated a trip condition and the feed valves should have closed. They didn’t. He checked the valves, which worked. He checked the calibration of the sensor and the wiring to the sensor and they were correct. He then he went to the electrical cabinet to check the safety relay. There, he found a corroded set of alligator clips jumpering around the relay.
An interesting discussion followed over the course of the next few days. Plant personnel were finally able to pin down the instance when the alligator clips had been applied. A few years earlier there had been a lot of pressure to finish a campaign for a new customer and the interlock had kept tripping. Someone in the C-suite had declared that the issue needed to be resolved, “Whatever it takes.” The young engineer responsible for the unit (who had since moved onto to a new job at a different company) had taken care of it and they were able to finish the last few batches without any more problems. Since then, there had been no problems with interlock—that is, there hadn’t been a single spurious trip.
Awareness as Defense Against Danger
Extension cords should be used only as temporary wiring, which is an OSHA requirement for all workplaces. So, there should be ample opportunity to examine cords periodically, at the time they are unplugged and put away. But other electrical cords also need to be examined. While the reason to not run cords under rugs may seem obvious, given the abrasion from walking on them, cords tucked behind desks and other office furniture need periodic attention as well. Don’t wait for an electrical shock as a prompt.
Inert gas purges on electrical equipment are not typical, even for equipment in areas with a hazard classification. Nonetheless, inert purge gas is a valid way to address electrical hazards in hazardous areas and is sometimes used. The important thing to keep in mind is that inert gases, even non-toxic gases like nitrogen and argon, pose their own hazards as simple asphyxiants. Most discussions of hazardous area wiring discuss pouring seals on conduits exclusively in terms of the role that the seal has to play in preventing flammable gas from migrating down the conduit to an ignition source. This suggests that seals are not necessary until just before the flammable gas is introduced to the process. In the case of inerted equipment, however, we should not lose sight of the role that conduit sealing plays in preventing inert gas from travelling down the conduit to an occupied, enclosed space.
Regarding temporary fixes, make sure they are temporary. The young engineer that jumpered around the safety relay was not chastised for his action at the time he “fixed” the problem. He wasn’t questioned at all. He did whatever it took and was congratulated for saving the account. Had the process been covered under the Process Safety Management standard, plant personnel insist that the temporary bypass would have been handled under their management of change procedure. Perhaps. However, there is a lesson there for all of us regarding temporary fixes, particularly as they relate to safety equipment.
The best way to defend against hazards is awareness. We hope these examples help with your awareness. If you have your own examples, please share them with us so we can share them with others. Experience is the best teacher, although it can be a brutal teacher. Let’s spare our colleagues some of that brutality and allow them to learn from our experiences. While we are at it, let’s all avoid some of that brutality and learn from the experiences of others.
This blog is based on an earlier version, “Experiences to Learn From”, posted on 21-Jul-2017 by Elsevier in Chemicals & Materials Now!