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low price Trunnion Mounted Ball Valve How Does a Double Block and Bleed Ball Valve Work? Double block and bleed valves are used for isolation in critical applications. They also prevent product contamination and maintain system integrity. DBB valves make it easy to remove machinery for cleaning, repair, and maintenance. Before DBB valves were used, isolating pipelines and machinery was a difficult process. You had to install two individual isolation valves, a spool piece, and a bleed valve to maintain system integrity. The machines were expensive and heavy. There was an increased risk of emission since multiple machines had to be installed. It was also difficult to operate the system since the technician had to check three valves at the same time. API 6D defines a double block and bleed valve as a "single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve with a means of vending/bleeding the cavity between the seating surfaces." There are a couple different styles of double block and bleed valves. One style has two independently seating valves inside, with a bleed or drain valve. This configuration is referred to as a double isolation and bleed (DIB). The DIB valve can isolate either side of the valve (bi-directionally) to vent or bleed the cavity and isolate piping. Which applications require a double bock and bleed valve? Double block and bleed valves are most commonly used in the oil and gas industry, but can also be helpful in many other industries. It's typically used where bleeding the valve cavity is required, where piping needs isolation for maintenance, or for any of these other scenarios: Prevent product contamination Remove eq