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Sub surfaces after oxygen generator fails

The failure of the oxygen generator aboard one of the Navy’s newest submarines is not a major casualty, according to the service.

“U.S. Navy submarines employ redundant systems that provide safe and operationally suitable environments for their crews,” Naval Sea Systems Command said in an emailed statement. “At no time was there any elevated risk for the crew of the submarine.”

The submarine New Hampshire, a Virginia-class attack boat that entered service in 2008, was approaching a floating ice station north of Prudhoe Bay, Alaska, on March 19, when its oxygen generator failed. The submarine switched to its backup system — oxygen-producing sodium chlorate “candles” — and continued operations, according to NAVSEA.

New Hampshire, along with the Seawolf-class submarine Connecticut, was taking part in Ice Exercise 2011, working with the Applied Physics Laboratory Ice Station built on an ice floe in the Beaufort Sea.

A sailor onboard New Hampshire was also suffering from appendicitis, and the submarine surfaced in shallow ice to evacuate him.

ICEX routinely attracts a stream of VIPs, and Navy Secretary Ray Mabus was on hand at the station to witness Connecticut surfacing through the ice cap. Mabus had been scheduled to visit New Hampshire, as well, but did not because the submarine surfaced earlier than planned and farther away from the scene, he did not.

New Hampshire also suffered from condensation that dripped water on sensitive equipment, Reuters reported. Plastic sheets were rigged over the equipment to protect it.

“The submarine incurred other minor habitability issues relating to temperature and humidity levels,” NAVSEA said March 24. “These issues have been addressed and also do not affect the safe operation of the submarine.”

The failed oxygen generator is known as an integrated low-pressure electrolyzer and is made by Hamilton Sunstrand. With the ship unable to fix the ILPE, technicians were dispatched from Hamilton’s base in Windsor Locks, Conn., according to company spokesman Dan Coulom.

The technicians arrived at Prudhoe Bay late March 24, according to Kevin Copeland, spokesman for Submarine Force Atlantic. They flew to the ICEX base March 25 and were to be taken by helicopter to the sub March 26.

The oxygen generator aboard Virginia-class submarines is a low-pressure system introduced with that class, according to the Navy. Earlier U.S. submarines use a high-pressure generator. The system is considered very reliable, according to a number of Navy and industry sources; this may be the first instance of a sustained failure of an ILPE.

The Navy took pains to point out that the oxygen-generating system onboard the submarine is different from that used onboard the British submarine Tireless during an earlier ICEX. Two Royal Navy sailors were killed March 21, 2007, by an explosion when similar candles were used on the ship. An investigation later revealed that the Self-Contained Oxygen Generators used on Tireless could have come from a batch once sent to a hazardous waste dump and then returned to the Royal Navy.

The British navy made several changes in its system as a result of the Tireless explosion. Although a sustained oxygen generator failure is not normal, use of the candles aboard a submarine is fairly routine, according to a number of Navy sources.

Generators are shut down for maintenance and sometimes for operational reasons, as well as for training, said one retired submarine commander.

“They do a great job putting out oxygen,” he said. “They work like a champ. They’re a good backup source for oxygen. Ships have been using them forever.”

The candles have been in use for about 50 years, according to NAVSEA, but the retired commander added that they produce a fine dust that has to be cleaned around the ship.

Submarines can operate for prolonged periods using the candles, the Navy said. New Hampshire is carrying enough candles to make it back to its base in Connecticut if need be, and if the submarine can surface or come up to periscope depth, the ship can be ventilated.