DBB Valves

Double block and bleed valves give you two independent sealing boundaries with a verified vent cavity between them. That sounds redundant until you've stood next to a pressure gauge on a 1500-psi hydrocarbon line and watched a single isolation seat weep process fluid toward the instrument connection. One seat can leak. One seat can fail. DBB eliminates that risk by requiring both an upstream and a downstream seat to hold simultaneously, with the bleed cavity between them vented to atmosphere or closed drain so you can visually confirm both seats are sealing before opening the instrument side. FLOWKS manufactures gauge block, flange, trunnion, and needle-type DBB configurations—from compact 1/2" instrument isolation valves through full-bore pipeline DBB units. Gauge block DBBs mount directly at instrument taps with nonoflange or flanged connections. Flange and trunnion DBBs isolate pipeline sections for maintenance, inspection, and pressure verification. Sampling DBB needle valves add a sample port between the two blocking seats, allowing fluid extraction without breaking isolation. Every DBB configuration shares the same functional principle: two seats, one bleed, verified zero-pressure proof that both boundaries hold before you proceed.

FLOWKS double block and bleed (DBB) valves provide verified dual isolation with a vented cavity between two independent seating boundaries. The upstream seat blocks process pressure; the downstream seat protects the instrument or downstream line; the bleed cavity between them vents to atmosphere or closed drain, giving visual confirmation that both seats are holding before any downstream work begins. Gauge block nonoflange DBB valves thread directly onto instrument taps—1/2" through 2", Class 150–1500, compact installation without flange bolting or gasket alignment. Gauge block SBB (single block and bleed) valves provide one blocking seat plus a bleed vent for applications where dual isolation isn't mandated. Flange DBB valves bolt into pipeline flanged connections for larger-diameter isolation. Trunnion DBB valves integrate the double block and bleed function into a trunnion-mounted ball valve body for full-bore pipeline service. Flange-to-screw needle-type DBB valves combine flanged process connections with threaded instrument connections, bridging between piping standards. Sampling DBB needle valves add a sample extraction port within the bleed cavity, allowing fluid collection without breaking either isolation boundary. FLOWKS DBB valves meet API 6D requirements for double isolation, with ISO 15848 fugitive emission certification available. Seat options include PTFE, PEEK, and metal-to-metal (Stellite 6) for chemical compatibility and temperature range matching.