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Precis File
SHIP NAME: San Jacinto KEY: NUM. ENTRIES: 2
source USCG
type L
volume Y
material G
dead 1
link http://www.uscg.mil/hq/cg5/docs/boards/sanjacinto.pdf

This ship was the ex-Fort Mercer (see 19520218_002), a T2 which broke in two off Cape Cod. Everything forward of frame 59 was new, and she ended up with an extra row of tanks, and a grt of 11252.

The ship was in ballast from Portland Maine to a drydocking in Jacksonville. They were tank cleaning for the docking putting the slops into 8C. The previous cargo was a mixture of gasoline, kerosene, and fuel oil.

At about 1930, the crew stopped work for the day. At 2315, there was an explosion in way of the 8's. But the fire immediately went out. The explosion clobbered the deck and side shell but the two halves were held together by the bottom. The crew ballasted some tanks to reduce hog and a port list but at 0345, the two sections split apart.

Winds were SW 12 to 13 knots, visibility 7-8 miles. The sea was moderate with a SW swell. Air temp was 49F, water temp 42F.

The crew forward launched the starboard lifeboat but the steward had a fatal heart attack while attempting to trip the releasing gear. This was the only casualty. The port forward lifeboat could not be launched due to the damage.

Both sections were towed to Newport News and inspected by the USCG in drydock. They found considerable wastage but that was not deemed causal. Nor was the fact that there were known cracks and faulty welds in way of No 8 tanks. Nor was the fact that there was known leaks between 8 wings and 9 wings in the top section of the 8/9 transverse bulkhead. And there were leaks between 8C and 8S. To quote the report "While these cracks and leaks had been known for some time, they were considered as routine in tanker service and were not considered important". The USCG found no evidence in the ruptured steel that a structural failure had preceded the explosion.

3, 5, 8 across and 9 port and stbd were used as ballast tanks and fitted with magnesium anodes. The USCG found these anodes badly wasted, and several remnants of anodes on deck. The crew had removed these during the tank cleaning. The crew had a policy of removing anodes that looks like they were about to fall, but only the ones they could get to easily. Finding fallen anodes was not uncommon.

Magnesium anodes can easily generate a spark when they hit steel. The USCG concluded that by far the most likely cause of the explosion was that one of the anodes in 8C, not gas free and being used for slops, had fallen, and ignited vapors in the tank.

As a result of this casualty, the USCG banned magnesium anodes, a ban that was eventually extended to the whole tanker fleet.


source CTX
type C
volume -1
material
dead 1
link

The CTX guesses the USCG is probably right on this one. But the cavalier treatment of the wasted steel is disappointing. As is the apparent failure to do any strength calculations. In order to aid in the tank cleaning, the master had ballasted tha 166 m long ship with lots of trim, 3.51 m forward and 6.55 m aft, using 3's across, 5's across, 8 P and S, and 9 P and S. All the other tanks were empty. The ship was probably hogged with large vertical shear forces at the 7/8 bulkhead. But since the report does not give us quantative data on the loading pattern, no real calcualtions can be done.

There is no mention of inerting anywhere in the report. Yet if the USCG is correct, inerting would have prevented this casualty. Enforcing inerting would have been far more effective than banning magnesium anodes. This regulatory trend ended up banning internal impressed current which combined with inerting could have been a far more effective means of corrosion control than we currently have.

The ship was re-jumboized, put back together, and became the Pasadena. She traded until age 38, when she was broken up in 1983. The Fort Mercer had a long but hardly trouble-free life.