DBB ball valve (Double Block and Bleed Ball Valve), that is, Double Block and Bleed Ball Valve is a kind of high-performance industrial valves through double sealing structure to achieve the pipeline medium two-way cut off, and can safely release the pressure of the valve cavity. The following is its core features and technical analysis:
1. The core structure and working principle
Double sealing sub-design
Equipped with two independent SPE (single piston effect) valve seat, are unidirectional sealing structure, respectively, blocking the upstream and downstream media when closed;
Seats rely on media pressure to enhance sealing (pressure-excited sealing.)
Drain function
The valve cavity is equipped with a relief port, which can manually/automatically discharge the medium trapped between the two seats or abnormal pressure rise (e.g. liquefied gas vaporisation pressure);
The relief operation achieves 'zero pressure build-up' and avoids the risk of overpressurisation of the valve cavity.
Driving method
Mostly fixed ball valves (trunnion support ball), suitable for high-pressure conditions;
The operating mode includes manual, pneumatic or electric actuators.
2. Core functional advantages
| Functionality | Realisation mechanism | technical value |
|---|---|---|
| Double blocking | Two SPE seats act independently to cut off media flow in both directions. | Provides redundant sealing assurance with leakage rates ≤ 10-⁶ m³/s |
| Release | Relief valve to discharge residual media or pressure in the valve cavity (e.g. after pipe cleaning operations) | Eliminate safety hazards and support online maintenance |
| Integration | Single valve replaces the traditional tandem structure of double valve + discharge valve | Reduced leakage points, saving more than 40 per cent of installation space |
3. Typical Application Scenarios
Oil and gas transmission: emergency cut-off of long-distance pipelines, resistant to Class600 high pressure (≥10MPa);
Chemical safety: maintenance isolation of toxic/flammable media (such as liquefied natural gas);
Energy system: power station boiler steam pipeline, hydraulic control system;
Pipe cleaning operations: pipeline cleaning to achieve double blocking of media and residual liquid release.
4. Key Differences with DIB Ball Valves
| Features | DBB ball valve | DIB ball valve |
|---|---|---|
| Valve Seat Type | Double SPE Check Valve Seat | DIB-1: Dual DPE bi-directional seat; DIB-2: SPE+DPE hybrid seat |
| Pressure relief mechanism | Dependent on active venting of valve cavity relief ports | DIB-2 automatically relieves pressure upstream (no additional operation required) |
| Security level | Basic Double Isolation | Higher level of isolation (especially DIB-2 bi-directional sealing) |
