BP has agreed to pay a record $50.6 million fine to the federal government for safety violations found by regulators last year at its troubled refinery in Texas City, Tex., where 15 workers died in a 2005 explosion.

In addition, the oil giant has agreed to take immediate steps to protect those now working at the refinery and to spend at least $500 million on safety efforts there, according to the federal Occupational Safety and Health Administration.

The fine is unconnected to BP’s April 20 offshore drilling disaster that spilled millions of barrels of oil into the Gulf of Mexico. The company faces multiple civil and criminal investigations in that episode, and it has set aside more than $32 billion to pay claims and fines connected to it.

But the OSHA penalty does reflect what many critics have said is a corporate culture that has emphasized speed and profits over safety.