The DBB (Double Block and Bleed) double ball valve is a safety control device specifically designed for medium and high pressure (2.5MPa to 100MPa) and hazardous/valuable media (oil and gas, chemical reagents, liquefied hydrocarbons, high-purity gases, etc.) scenarios. It is suitable for temperatures from -60℃ to 450℃ and is widely used in petrochemical main pipelines, LNG/CNG storage and transportation systems, pharmaceutical high-pressure reaction pipelines, nuclear power auxiliary circuits, and other fields.
Based on the integrated double ball valve series structure, independent discharge channel, and forging of corrosion-resistant and temperature-resistant alloys (A105, 316L, F11), and manufactured according to API 6D and ASME B16.34 standards, it achieves the function of "double sealing shut-off + intermediate chamber pressure relief discharge". It is suitable for nominal diameters of DN6-DN150 and can be driven manually, pneumatically, and electrically. It is a core safety component for high-pressure pipeline maintenance isolation and media leakage prevention.
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The core function of the DBB ball valve is "double block + double bleed":
- Double Block: When the valve is closed, the sealing surfaces on both sides of the valve body can simultaneously and independently block the flow of the medium, forming a double sealing barrier to prevent medium leakage or cross-flow.
- Double Bleed: The valve has a bleed port in the middle to discharge residual medium or pressure from the valve cavity, preventing the medium from accumulating in the valve cavity and causing corrosion or safety hazards.
Double Block and Bleed Ball Valve Working Principle:
The core design logic of the DBB ball valve is "double shut-off + bleed," achieving safe isolation of the medium through two independent sealing surfaces and a bleed device:
Double Shut-off Function
When the valve is closed, two independent balls (or the double sealing surfaces of a single ball) simultaneously shut off the upstream and downstream medium flow. The valve seat and ball form a high-precision seal through precision grinding technology (such as Ball/Seat Lapping), ensuring zero leakage. For example, in LNG cryogenic conditions, the duplex steel material + self-tightening metal seal design can withstand extreme temperatures from -196℃ to +600℃, preventing cryogenic embrittlement.
Bleed Function
After the valve is closed, the bleed port integrated on the valve body can drain residual medium or pressure from the cavity, forming a safe isolation space. The bleed process supports manual or automatic operation, and the cavity pressure can be monitored by a pressure gauge to ensure complete depressurization. For example, in aviation kerosene pipelines, the bleed function can prevent abnormal pressure rise in the valve cavity and avoid the risk of medium backflow.
Double Block and Bleed Ball Valve Structural Features
Three-section valve body:
Comprising two valve seats and an intermediate valve chamber, with a ball joint between the seats for sealing.
The intermediate valve chamber is typically designed as an independent cavity for easy installation of a drain port and pressure test interface.
Sealing Design:
Utilizing a bidirectional sealing structure, a double sealing surface is formed between the valve seat and the ball, ensuring that the media on both sides do not interfere with each other.
Some models are equipped with a combination of soft seals (such as PTFE) and hard seals (such as metal) to adapt to different media and temperature requirements.
Drainage System:
The drain port can be connected to pipelines or instruments for pressure relief, sampling, or testing of the medium state within the valve chamber.
The drain port is typically equipped with a stop valve or needle valve for easy operation and control.
Double Block and Bleed Ball Valve Application
DBB ball valves are widely used in industrial fields requiring high safety and reliability:
Oil & Gas Industry:
Used in pipeline shut-off, wellhead control, separators, and other equipment to prevent media leakage or cross-contamination.
In subsea pipelines, DBB ball valves ensure that no residual media remains in the valve cavity after closure, preventing corrosion.
Chemical Industry:
Suitable for pipeline systems containing toxic, flammable, or corrosive media, such as chlor-alkali production and oil refining units.
The state of the media in the valve cavity can be periodically monitored through the discharge port to ensure safe operation.
Power Industry:
Used in steam pipelines, boiler feedwater systems, etc., to prevent media backflow or leakage.
Water Treatment Industry:
In wastewater treatment, seawater desalination, and other scenarios, DBB ball valves prevent media contamination or cross-mixing.
Double Block and Bleed Ball Valve factory
