Vital warning systems on the Deepwater Horizon oil rig were switched off at the time of the explosion in order to spare workers being woken by false alarms, a federal investigation has heard.
With the number of alarms on a deepwater oil rig, it’s common practice to inhibit alarms and shutdown systems… not just for waking people up but also to prevent unwanted consequences.
For example, on one rig we have a button mounted at all the lifeboats that shuts down ALL power systems… a great feature to have if you have a gas blowout that hasn’t yet ignited but what if someone pressed it in heavy seas? The rig would loose propulsion and, naturally, her heading would fall off until she was perpendicular to the forces. Not a problem in 5 foot seas but what if someone pressed it in 50 foot seas? … you would have real difficulty launching the boats.
[QUOTE=john;40304]With the number of alarms on a deepwater oil rig, it’s common practice to inhibit alarms and shutdown systems… not just for waking people up but also to prevent unwanted consequences.
For example, on one rig we have a button mounted at all the lifeboats that shuts down ALL power systems… a great feature to have if you have a gas blowout that hasn’t yet ignited but what if someone pressed it in heavy seas? The rig would loose propulsion and, naturally, her heading would fall off until she was perpendicular to the forces. Not a problem in 5 foot seas but what if someone pressed it in 50 foot seas? … you would have real difficulty launching the boats.[/QUOTE]
Sounds like a perfect example of something designed for sailors by a desk driver.
They weren’t bi-passed or disabled. Unless they changed common practice after I left in December, the general alarm itself was usually inhibited. That’s only one “effect” of a very large and overly complex “cause and effect” matrix. The causes, the detectors themselves (smoke, gas, H2S, heat, manual call station, or IR), would still have been active and would have alarmed on the Bridge, Dog House, and ECR.
The cause and effect matrix was a book of spreadsheets an inch thick and listed every sensor and effect. Effects were grouped together as an ESD. Certain conditions such as two smoke detectors in one zone, or an H2S sensor reaching 10ppm would trip an ESD. Again, the only thing that was normally inhibited was the general alarm. Ventilation fans would shut off, fire doors would close, dampers would close, and machinery would shut off depending where it was (the heli-fuel pump for example.) With some sensors, the general alarm would be delayed and would only go off if not acknowledged in 2 minutes such as an H2S sensor reaching 5ppm.
Putting a specific detector in inhibit would stop it from triggering an ESD, but it would still alarm on the Bridge. You would do this for a troublesome detector until repaired or if the welder was working in that area. Putting the the sensor in “passive” would stop it from alarming altogether, but that was only done when it was being worked on. You could also inhibit a whole ESD, and that was only done while maintenance was going on.
With the general alarm “inhibited”, the Bridge still monitored the whole system. If a sensor alarmed, the watchstanders would immediately take necessary action, including if necessary, sounding the general, gas, or H2S alarm. If the general alarm was not inhibited, then the whole crew would have awoken several times daily to a false alarm. That could be dust in the sack room, the heat detectors in the engine rooms during the summer, dust in the elevator shaft (which doubled as a ventilation duct for the columns), burning popcorn in the microwave, folks showering with the door open letting the steam trip the smoke detector, or a roughneck washing down in the mud pumproom hitting the detector with the pressure washer. We even had a third party hand use a manual call box, thinking it was the start for the central high pressure washdown pump. When you ran the riser skate in and out of the floor it would set off the H2S or gas sensor below it (by the intakes for engines 3 and 4.)
The ESD would still trip in those cases. They were wrong in the hearing today to suggest that the engine room ESD would not trip because the general alarm was inhibited. The ESD’s worked, I tripped them myself many times working on the sprinkler system or testing the foam pump.
They mentioned the Deepwater Millennium today too which I also sailed on. Her system was no where near as complicated. It wasn’t hooked to the Kongsberg SVC. I remember we always had two minutes to acknowledge the alarm before the general alarm went off so there was usually no reason to inhibit anything. There was only one override for the whole ship and false alarms were rare.
The other thing they got wrong was the incident involving the doors getting ripped off the hinges. That was in 2004 or 05. It wasn’t while testing an ESD and it wasn’t Tommy Daniels that did it. The ET that did cause it was doing a PM to reboot the two fire and gas computers. He didn’t wait for the first to reboot before rebooting the second. I was at the DP console. The result was all the dampers closing in the engine rooms. With three engines running, it created a vacuum back there. One engine fell off line, but there was enough extra power available to pick up the load.
I hope the Board has access to the Cause and Effect Matrix and the Marine Operations Manual. That’s where all the answers are.
… also the 2002 Second Deck Fire and Safety plan the Board posted on their web site is old. See http://www.piersystem.com/posted/3043/086_ABS_Safety_and_Fire_Control_Plan.820871.pdf . It was redone in 2007 or 2008, with ABS approval that took forever. Not at lot of changes on the second deck except a few extinguishers. The biggest change was the added fixed CO2 in the crane pedestals on the main deck.
Is Transocean giving them this old stuff?
[QUOTE=Orniphobe;40315]They weren’t bi-passed or disabled[/QUOTE]
The Treanocean lawyers should then have said so. These lawyers are clowns and clearly concentrate on the wrong stuff. Why is the Rig Mananger not in the room and tells them these sorts of things?