The Justice Department is clamping down on the Crane Co., a Stamford-based manufacturer of valves and marine components. In a $7.5 million settlement, the company agreed to pay fines to resolve False Claims Act allegations, in which the company did not follow Defense Department regulations when bidding on government contracts. Crane is also allegedly in violation of the Berry Amendment and the Buy America Act, after providing valves that were not domestically produced to Navy vessels.