Double Block and Bleed Ball Valve: Definition, Principle, Parameters & Features

1. Definition of Double Block and Bleed Ball Valve

The Double Block and Bleed Ball Valve is a type of ball valve equipped with two balls in one valve body. It can be opened/closed simultaneously or with one ball open and the other closed, realizing the double block and bleed function.

It is divided into two major series: fixed ball and floating ball, and features double blocking and bleeding capabilities. One valve body contains two balls, and the valve cavity between the two balls is equipped with an external bleed valve (needle globe valve). With reliable sealing performance, it is suitable for occasions where multiple valves are connected in series and strict sealing requirements are required.

2. Working Principle of Double Block and Bleed Ball Valve

The operating states of the Double Block and Bleed Ball Valve include two scenarios: both balls opening simultaneously and both closing simultaneously. When the through-hole in the ball aligns with the valve body passage, the valve is in the open state. According to installation requirements, the medium can enter from either end of the valve to achieve the purpose of connecting the fluid in the pipeline.

When the actuator drives the valve stem to rotate 90° clockwise and the valve is in the closed position, the two sealing pairs can simultaneously seal the pressure from the ends, and the medium in the cavity between the two sealing pairs can be vented or drained completely. This product replaces the complex configuration of multiple ball valves connected in series in traditional pipelines, reduces leakage points in the pipeline system, realizes rapid bleeding and closing functions, and has excellent sealing performance.

3. Technical Parameters of Double Block and Bleed Ball Valve

• Size: NPS 3 - NPS 24

• Pressure Class: Class 150 - Class 1500

3.1 Available Materials

A105, LF2, F304, F316, F51, F53, F55, Alloy 20, Monel, Inconel, Hastelloy

3.2 Design Features

• Full port or reduced port

• RF (Raised Face), RTJ (Ring Type Joint), or BW (Butt Weld) connections

• Bolted bonnet

• Replaceable valve seats

• Metal seats or soft seats

4. Structural Features of Double Block and Bleed Ball Valve

• During the opening and closing process of the valve, there is no contact between the valve body sealing surface and the sliding plate sealing surface. Therefore, there is no friction or wear on the sealing surfaces, ensuring a long service life of the valve and low operating torque.

• During maintenance, there is no need to remove the valve from the pipeline. It is only necessary to disassemble the valve bottom cover and replace a pair of sliding plates, making maintenance very convenient.

• The valve body and plug are of reduced port design, which can reduce costs.

• The inner cavity of the valve body is hard chrome-plated, making the sealing area hard and smooth.