What is a Double Block and Bleed Valve?

What is a Double Block and Bleed Valve?

Double block and bleed always sounded like a move out of the Cobra Kai karate dojo. However, a double block and bleed valve has nothing to do with karate; it is more about controlling process flow to facilitate maintenance, sampling, and flow diversion. This post describes the attributes, functions, and applications of a double block and bleed valve.

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Definition of a Double Block and Bleed Valve

A double block and bleed valve is essentially three valves combined into one unit. According to API 6D, a double block and bleed valve is defined as “a single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends, with a means of venting or bleeding the cavity between the seating surfaces.”

Two common styles of double block and bleed valves exist. One style features two independently seating valves inside, along with a bleed or drain valve. This configuration is known as double isolation and bleed (DIB). The DIB valve can isolate either side of the valve (bi-directionally) to vent or bleed the cavity and isolate piping.

This trunnion style ball valve from Val-Matic delivers double block and bleed functionality in a single valve. This design allows for piping isolation on both sides of the valve (uni-directionally) while venting or bleeding the valve cavity between the seats.

Utilizing a single double block and bleed valve system instead of three separate valves can save installation time, reduce weight on the piping system, and require less space. Additionally, it decreases the number of leak paths to the atmosphere, lowering the risk of hazards when transporting harmful liquids.

Applications of Double Block and Bleed Valves

Double block and bleed valves are primarily used in the oil and gas industry, but they are also beneficial in various other sectors.

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Common applications requiring a double block and bleed valve include:

• Preventing product contamination
• Removing equipment from service for cleaning or repair
• Meter calibration
• Liquid service near waterways or municipalities
• Transmission and storage
• Chemical injection and sampling
• Isolating instrumentation such as pressure indicators and lever gauges
• Primary process steam management

Choosing the Right Double Block and Bleed Valve

When selecting a double block and bleed valve, it is essential to consider factors such as fluid properties, pressure, and temperature. However, the most crucial aspect is understanding how the valve will be used. Given the variety of available configurations, assess which will best meet your specific process and requirements.

If you are uncertain about which double block and bleed valve is suitable for your process, consult an engineer who can assist in identifying the best option to achieve your objectives.

Need assistance with selecting a double block and bleed valve? Contact us! We are pleased to offer technical support to businesses in Wisconsin, Minnesota, Iowa, and Upper Michigan.

Double Block & Bleed Valves - DDB Valves

Bonney Forge manufactures Double Block and Bleed Valves (DDB valves) in a wide range of designs, materials, sizes, pressure classes, and end connections. These designs adhere to ASME B16.34 and, when applicable, API 6D or BS EN ISO standards. Our valves are fire-safe test approved and include features to ensure electrical continuity between the ball, stem, and body. Cryogenic and high-temperature metal-seated configurations are also available. All designs are forged for enhanced mechanical properties, pressure retention, and overall quality.

The primary uses for Double Block and Bleed Valves include:

Interested in learning more about Cryogenic Ball Valves? Contact us today to secure an expert consultation!