More than 20,000 individuals who have asbestos-related tort claims pending against the Robert A. Keasbey Co. scored a major victory Tuesday, as Manhattan Supreme Court Justice Richard Braun ruled that the defunct insulation giant’s insurers may be liable for hundreds of millions of dollars in coverage.

The ruling came in an unusual defendant class action — in which the class constitutes a defendant, not the plaintiff — initiated by the Keasbey Co.’s primary insurers, plaintiffs Continental Casualty Coverage and American Casualty Co. of Reading, Pa.