Double Block & Bleed Valves
The purpose of Double Block & Bleed is isolation. Double Block & Bleeds valves are utilized in the petroleum and natural gas industries where every seal is critical.
API 6D defines a double-block-and-bleed valve (DBB) as a “single valve 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 TWIN SEAL VALVE replaces the antiquated two-valve system with one double seated, bubble-tight valve.
Outmoded Double Block & Bleed Method:
2 Gate Valve
Operator would close one valve, close the second valve, open the bleed, once all product was bled out, you knew you had a positive shut off in both directions.
The inherent flaws with the outmoded design:
Significant space and weight required
Any issues with the valves and the entire valve would need to come out of the pipeline.
With most gate valves, the seats are ground or wedged against metal every time the valve cycles. Any foreign matter lodged between the seats or gate will score the seating surfaces. Once the seating segment is scored, product loss and contamination result.
The General Twin Seal Valve accomplishes this positive shut off in one valve (saving critical space and weight). The upstream and downstream seals provide the same function as the two block valves. The body (serving as a spool piece) bleed verifies seal integrity. The Twin Seal Valve is mechanically torque seated. Any repairs needed can be done in-line without removing the valve.
Double Block and Bleed Valves
Double block and bleed valves are a dual isolation solution mechanism that reduces the need for expensive multi-valve systems. It combines all block and bleed components into one unit, thus the valve minimize the risk of possible leak while providing weight savings. The Double block and bleed valves design is a one-piece assembly used for the primary isolation of pressure take-off and process flow.
Double Block & Bleed Valves are designed for the pipeline, liquid bulk terminals, aviation fueling, refining, oil/gas production and transfer for the petroleum and oil and gas industries. It is an ideal design for the isolation chemical injection, gauge isolation, oil and gas production, and direct or remote mounting of instruments.