Home › Forums › Coking › Safety › Safety Interlocks, Automation, Fire Suppression › Safety Interlocks › Proximity Switches for Manual Switch Valve and Drum Isolation Valves › RE: Proximity Switches for Manual Switch Valve and Drum Isolation Valves
The Coker I worked at evolved from the old Wilson/Snyder valves to the ball valve with proximity switches. Back in 67 the blowdown valves and warm up valves also had proximity switches which were later discontinued when the vibration and heat and crusty environment caused wiring to fail and valves would open or close causing some major upsets. We went to Operator Training and physical use of chains and padlocks with a well written set of procedures with keys left in the control room and only the correct keys for the operation at hand was allowed to accompany the operator to the structure during that particular procedure. Over time, operators would carry all keys to the structure and being human and tired (as we never convinced management that naps on the midnight shift might me beneficial to fewer mistakes being made by tired humans) mistakes were being made. The joining of companies, new engineers, new money of the nineties brought back the proximity switches and ball valves to avoid operator error mistakes. We’re talking about 30 to 35 years later than the original stuff, so over those years better wiring, better switches, smarter operators came into play. The ball valves, proximity switches of today work well and avoid many mistakes. That having been said, we still had the locks and chains on the blowdown and warmup valves and upstairs on the vent valves, only the switching valves were upgraded to the proximity switches. They were combined with software that the TDC or rather GUS operator had to “OK” the outside structure operators moves in order that the outside man could move the valves needed to make the switches. Me coming out of the old era of nothing locked and not many, but some, mistakes made to using the new stuff with not many but some mistakes being made, well IMHO it was a waste of a lot of hard earned cash. But engineers are paid to think and think they will. Refiners of the future will need to rely on everybodies input in the design and planning stages if they want to avoid mistakes totally and design a fool proof system that works. Will there be money for this? Hopefully so.