A Block and Bleed Valve System is a combination of one or more block/isolation valves, usually ball valves, and one or more bleed/vent valves, usually ball or needle valves. The purpose of the block and bleed valve system is to isolate or block the flow of fluid in the system so the fluid from upstream does not reach other components of the system that are downstream. This enables the engineers to bleed off or vent or drain the remaining fluid from the system on the downstream side in order to execute some kind of work (maintenance/ repair/ replacement), sampling, flow diversion, chemical injections, integrity check for leakage etc.
