Friday, September 25, 2009

Engineering Disasters: The Demise of the Ocean Ranger

The Ocean Ranger was, in its day, the largest Mobile Offshore Drilling Unit in the world. One toolpusher called the rig "unsinkable" (note to anyone offshore- if it floats, it can sink). The loss of the Ocean Ranger was one of the biggest disasters in the history of the oil industry.

The Ocean Ranger, owned by ODECO out of New Orleans, was under contract by a Mobil subsidiary off the coast of Newfoundland. A ferocious storm came up. After bracing for the storm, the men aboard thought they were safe, but a rogue wave smashed a porthole and flooded the ballast control panel. Between an under-trained crew and a serious design defect, the platform capsized in heavy seas that it should have been able to handle.

Some of the crew was washed into the water. Some got into lifeboats that were ripped to shreds as they were lowered. One boat, however, with approximately 20 souls made it down safely. A crewboat on standby at a nearby rig made a heroic effort to save the men in the water, but the frigid waters incapacitated the men in the water in seconds. ODECO deemed it too expensive to equip the rig with survival suits. The men on the crewboat, despite their best efforts, had neither the equipment or the training to rescue unconscious men from the heavy seas.

The one intact lifeboat was found by the M/V Seaforth Highlander. The crewboat lashed lines from the lifeboat and the men on board were just a couple of feet from safety, however the lifeboat depended on the men on board staying strapped into their seats for ballast. The lifeboat slowly capsized. All the men were washed into the water. The captain of the Seaforth Highlander described it as "watching a slow motion movie." All the men in the lifeboat were quickly overcome by hypothermia and drowned.

Every single crewman aboard the Ocean Ranger died. Only couple of dozen bodies were ever recovered, despite extensive search efforts.

The USCG Board of Inquiry [PDF] describes the incident in much, much more detail. I highly recommend it.

The USCG report comes up with a number of findings. A few I'll mention briefly:
* Insufficient training. Ballast Control crewmen only had basic, on the job training. They had no classroom training and didn't understand the working principals of the pumps. The ballast system also went into a "safe" mode in case of failure whereby all ballast compartments are sealed. It appears that the crew misunderstood a bypass system and unintentionally worsened flooding.
* The crew of the Ocean Ranger didn't call for help until it was deep into the storm. Once they did abandon ship, the Ocean Ranger actually stayed afloat for at least another hour. The crew died while the rig was still afloat.
* There was a critical design flaw that was completely missed by the designers and regulatory bodies: the chain lockers, storing the anchor chain, were open to the sea and un-sounded. The crew had no way of knowing if the chain lockers, an enormous void that could cause the rig to list or capsize if filled, had water in them. They had a 5' hole at the top for the chain to enter that had no way of closing off or sealing from the weather.

Inviting Disaster (thanks for the rec, PE) has a chapter on the Ocean Ranger. It closes with one interesting observation. The Ocean Ranger had drilled in the Baltimore Canyon off the East Coast. It drilled off the coast of Ireland. It drilled offshore Alaska. It had just begun drilling off Newfoundland. The largest, most advanced drilling rig of its day never once struck oil.


Couple notes to tack on the end:

* Here's an archive of Canadian news broadcasts about the sinking.

* Ocean Ranger had a sister ship. It was originally named Ocean Ranger II, but was renamed Ocean Odyssey while still in the shipyard. It suffered a well blowout that ended its oil drilling days. It now serves as a satellite launch platform as a part of the Sea Launch system. It's still operational, despite one rocket that blew up on launch.


Peripatetic Engineer said...

I worked for ODECO back when the Ranger was built. I was in the shipyard in Japan and although was assigned to the Ocean Bounty, we knew the Ranger intimately. In fact, I was later a regular member of her crew during rig moves in Alaska. She had a unique chain/wire mooring system designed for what was then deep water and I was one of the few who knew how to operate it.

One question I have always had was about the machinery room access hatch. There was a 20' x 20' hatch in the main deck to lower large items to the machinery room. It was held down by about 100 clamps. Usually nobody bothered to secure them because of the time involved in removing them when they wanted to open the hatch. If that hatch was washed off, there was a straight path for downflooding down the elevator shaft for the forward starboard column.

You can trace several improvements in offshore safety to the Ranger disaster. A new method of launching lifeboats was one. Ballast control operator training was another. (usually, the ballast control operator was a roustabout that couldn't hack the work on deck)

I'm not sure ODEDO ever used the name OCean Ranger II. The Odyssey may have been based on the Ranger class, but even they were not stupid enough to use the name again.

Clay said...

Inviting Disaster hammers the operators and operator training as the prime cause. They even go so far as to say the rig probably would have survived despite the chain lockers, had they just left the ballast valves locked closed.

Unsecured hatches is supposed to be one of the prime causes of the sinking of the Edmund Fitzgerald, on the Great Lakes.

LOTS of things changed as a result of Ocean Ranger (like Piper Alpha). A biggie is a survival suit. Did you get one when you were stationed in Alaska?

Ocean Ranger II was the placeholder name while it was in the shipyard, according to most of the sources. It probably would have been renamed something else regardless of what happened on its predecessor.

Peripatetic Engineer said...

Don't forget the failure of the ballast valve control panel when it got wet after the porthole broke. There was a manual sea chest valve but it was a bitch to operate and although it was supposed to be greased and exercised monthly, I doubt that was done.

We wore survival suits on the choppers. The lifeboats were outfitted per SOLAS. They had wool sweaters that were supposed to be for the engine room crew who wore light clothing. SOLAS was not really written for drilling rigs back then.

Little known fact: the Ranger was supposed to be so stable that they had a pool table in the rec room.

Clay said...

A dinky little porthole was the proximate cause that doomed a huge platform.

I think Discovery is going to have a special that will discuss the Ocean Ranger Sunday (October 4th).

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