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A block and bleed manifold is a hydraulic manifold that combines one or more block/isolate valves, usually ball valves, and one or more bleed/vent valves, usually ball or needle valves, into one component, for interface with other components (pressure measurement transmitters, gauges, switches, etc.) of a hydraulic (fluid) system. The purpose of the block and bleed manifold is to isolate or block the flow of fluid in the system, so the fluid from upstream of the manifold does not reach other components of the system that are downstream, then bleed off or vent the remaining fluid from the system on the downstream side of the manifold. For example, a block and bleed manifold would be used to stop the flow of fluids to some component, then vent the fluid from that component’s side of the manifold, in order to effect some kind of work (maintenance/repair/replacement) on that component. A block and bleed manifold with one block valve and one bleed valve is also known as an isolation valve or block and bleed valve; a block and bleed manifold with multiple valves is also known as an isolation manifold. Also used in combustionable gas trains in many industrial applications. Double Block and Bleed Valves replace existing traditional techniques employed by pipeline engineers to generate a double block and bleed configuration in the pipeline. Cartridge Type Standard Length Double Block and Bleed Valves have a patented design which incorporates two ball valves and a bleed valve into one compact cartridge type unit with ANSI B16.5 tapped flanged connections. The major benefit of this design configuration is that the valve has the same face-to-face dimension as a single block ball valve (as specified in API 6D and ANSI B16.10), which means the valve can easily be installed into an existing pipeline without the need for any pipeline re-working. Three Piece Non Standard Length Double Block and Bleed Valves (DBB Valves) feature the traditional style of flange-by-flange type valve and is available with ANSI B16.5 flanges, hub connections and welded ends to suit the pipeline system it is to be installed in. It features all the benefits of the single unit DBB valve, with the added benefit of a bespoke face-to-face dimension if required. The single unit DBB design also has operational advantages, there are significantly fewer potential leak paths within the double block and bleed section of the pipeline. Because the valves are full bore with an uninterrupted flow orifice they have got a negligible pressure drop across the unit. The pipelines where these valves are installed can also be pigged without any problems. There are several advantages in using a Double Block and Bleed Valve. Significantly, because all the valve components are housed in a single unit, the space required for the installation is dramatically reduced thus freeing up room for other pieces of essential equipment. Considering the operations and procedures executed before an operator can intervene, the Double Block and Bleed manifold offers further advantages over the traditional hook up. Due to the volume of the cavity between the two balls being so small, the operator is afforded the opportunity to evacuate this space efficiently thereby quickly establishing a safe working environment. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Block and bleed manifold」の詳細全文を読む スポンサード リンク
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