DBB Double Block and Bleed Ball Valve

The Double‑Block‑and‑Bleed (DBB) Ball Valve is a high‑performance ball valve integrating double‑block shut‑off and intermediate‑cavity bleed functions. It normally consists of two independent ball‑valve shut‑off units arranged in series or incorporated within a single valve body. When closed, the valve provides reliable isolation for both upstream and downstream media, while the intermediate‑cavity bleed system releases or verifies the trapped pressure between the two shut‑off units.

Compared with conventional single‑valve isolation solutions, the DBB ball valve achieves double‑block isolation plus cavity bleed within a compact footprint. It reduces the quantity of valves, joint connections and potential leakage points, so as to enhance the safety and reliability of piping systems.

This valve is widely applied in oil, natural gas, petrochemical, oil‑refining, LNG, chemical industries and high‑pressure transmission pipelines, where stringent sealing performance and operational‑safety requirements are demanded.

Working Principle of Double‑Block‑and‑Bleed (DBB) Ball Valve
When the DBB ball valve is fully open, the flow passages of the two internal balls are aligned with the pipeline, allowing smooth medium flow, and the intermediate cavity bleed port remains closed.

Upon closing, both balls are rotated 90° to their shut‑off positions. Two independent sealing barriers are formed to isolate upstream and downstream media respectively. After double‑block shut‑off, the bleed valve on the intermediate cavity can be opened to release trapped pressure between the two balls. Operators can check for seat leakage through the bleed port to confirm safe isolation for maintenance.

To resume pipeline operation, close the bleed port first, then rotate the two balls back to the fully‑open position.