Full Description

This Standard Practice covers cast or fabricated, bonneted or bonnetless knife gate valves designed and manufactured to serve as a "Double Block and Bleed"(a) single valve system in pipelines. These valve types shall have flanged body designs compatible with ASME B16.5 flanges for NPS 2 (DN 50) through NPS 24 (DN 600), ASME B16.47 Series A flanges for NPS 26 (DN 650) through NPS 36 (DN 900), and ASME B16.42 for sizes greater than NPS 36 (DN 900).

NOTE: (a) For the purposes of this Standard Practice, "Double Block and Bleed" refers to a valve (or valve application) with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve with a means of venting/bleeding the cavity between the seating surfaces.

The valves identified in this Standard Practice are intended for use in applications where a "Double Block and Bleed" type of isolation is required, and where two (2) individual isolation valves with a removable or drain-containing spool piece between them is typically used.