Howard County-based Colfax Corp., an industrial pumps manufacturer founded by Washington billionaires Mitchell and Steven Rales, announced Monday a $2.4 billion cash-and-stock offer to buy Charter International.

Colfax had sales of $533 million last year, compared with Charter’s $2.7 billion.

The Rales brothers in 1984 founded Danaher Corp., a District-based industrial conglomerate with a market cap of $30 billion. Colfax shares closed down 8.59 percent Monday.