Cameron International Corporation the second-largest United States maker of oilfield equipment,provided the blowout preventer for the Transocean Ltd. rig in the Gulf of Mexico that caught fire and sank last week.

Cameron’s gear has been used on the Deepwater Horizon rig, which was built in 2001 to operate in seas as deep as 8,000 feet, since the vessel was commissioned, company spokesman Scott Amann said today. The rig caught fire after an April 20, 2010 explosion that may have been caused by a blowout, an unexpected surge in pressure that ejected petroleum at the top of the well, Transocean said.

Eleven crew members were killed, making the blast the most deadly offshore rig explosion since 1968.  BP Plc, the London- based oil producer that leased the Deepwater Horizon from Transocean, is spending $6 million a day trying to clean up an oil spill from the well and stop a leak that is gushing crude from the seabed at a rate of about 1,000 barrels a day. The cause of the offshore oil rig explosion remains under investigation.

Amann declined to comment on Houston-based Cameron’s potential liability, saying the company will wait to learn what might have caused the blast. “We are not going to speculate on what the causes might have been,” he said.

Cameron makes a hydraulically operated system of safety valves that prevent increases in pressure from causing blowouts. The preventers used on the Deepwater Horizon are designed to withstand 15,000 pounds of pressure per square inch, according to Transocean’s Web site. That’s enough pressure to crush a pickup truck.

Oil and natural-gas producers are accelerating exploration in waters deeper than 1,000 feet to tap new sources of reserves. The threat of pressure surges, or blowouts, that can smash steel equipment and create gushing columns of fire increases as drillers probe deeper.