It is really usually used wherever bleeding the valve cavity is needed, the place piping requires isolation for upkeep, or for virtually any of these other situations: This kind of Double Block and Bleed Valves (DBB Valves) feature the normal sort of flange-by-flange variety valve and is offered with ANSI http://doubleblockandbleedvalve76420.total-blog.com/double-block-and-bleed-valve-an-overview-19146274