Double block and blade is a single set of two internal block valves and one blade valve. The three-valve task is performed separately by this set while saving large space, installation time, weight and cost. The main purpose of using a double block and blade system, however, is to ensure that the liquid does not reach the other components of the system from upstream and downstream. Therefore, engineers can easily remove or drain the remaining fluid from the middle and perform repair, repair or replacement work. In a double block and blade system, the separation is achieved from both upstream or downstream current or pressure. The drain valve is used to drain the cavity created between two block valves.
A 4.3-inch or 1-inch NPS blade valve is installed between two valve blocks for drainage as shown in Figure 1.
How Black Double Valve and Blade Valve work
Operation of two valves and a bleeding valve
The two block valves separate the upstream and downstream streams. A set of gate valves, ball valves, needle valves or globes are commonly used as block valves in a row. In the central part of the block valves is the third valve known as the blade valves.
Figure 2: Double block and blade valve
Using three separate valves, the same arrangement and double block can be obtained. But the double block and blade single valve saves space, weight, installation time and a lot of cost. Also, in terms of performance and maintenance, double-block and single-valve valves are better than single-unit because potential leakage pathways are significantly reduced per unit. The pressure drop is also minimized.
The main function of the blade
- For the vent created in the hole between the two separating valves.
- Current deviation
- Sampling and connection of injection point
- Check connection integrity or maintenance for leak monitoring
The valve blade can be moved directly into the atmosphere or a pipe / hose piping system can be used for a closed disposal system.
Codes and standards are double blocked even valve
Double block and blade valve or DBBV is designed and manufactured according to each of the governing rules
BS6755- Part 2
BS EN ISO 17292
The benefits of double block and blade valve
The benefits of double block and blade valve can be summarized as follows:
- Compact design
- Provides sealing against pressure from both upstream and downstream ends.
- Ability to drain by tapping between two block valves.
- About 60% weight savings and 70% installation time savings.
- Highly reduce leakage paths, ensuring low risk. More safety at work.
- Large space savings compared to conventional makeup using separate valves.
- Can be used as chemical injections and sampling points.
- Prevent product contamination
- Take equipment out of service for cleaning or repair
- Reduce stress and vibration stresses
- Uninterrupted flow for slight pressure drop
Use double block and blade valve
Double Block and Bleed Valve or DBB is widely used in systems that require critical separation. The most important uses of DBB valves are:
- Oil and gas, chemical and petrochemical industries
- LNG and natural gas industrial processes
- Separate instruments such as level measurement, pressure indicator and so on
- Pipelines and manifolds.
- Prevent product contamination
- Transfer and storage, transmission lines of refined products.
- Chemical injection and sampling.
- Liquid services near waterways or municipalities.
- Tool drain connections.
- Take equipment out of service for repair or cleaning.
Factors influencing the choice of double block and blade valve (DBB)
The parameters influencing the selection of double block and blade are:
- Media process and application
- Temperature and pressure
- Toxicity and work environment
- Material of valve parts
Different types of DBB Valve configuration are available in the market depending on the needs. In general, there are three types of double block and blade valves available.
- Single unit DBB
- Cartridge Type Standard Length DBB
- Three Piece Non-Standard Length DBB
DBB vs. DIB
Double Insulation & Build or DIB is a single valve with two seating levels. In the closed state, each of these living surfaces creates a positive seal against the pressure of a single source. There is a device for venting / draining the valve between the living surfaces. Therefore, DIB looks almost like DBB and is quite confusing to many. The main differences between DBB and DIB valves are listed below:
- The DBB valve seals against the pressure on both sides of the valve. **** DIB creates an additional seal against the pressure on either side of the valve.
- The DBB valve has two self-contained one-way sets that are independent of the external pressure relief mechanism. **** DIB uses one or two two-way sets that are not self-soothing and require an external pressure relief mechanism.
- In DBB, if the first seal leaks, the second seal does not leak in the same direction. **** DIB provides the extra pressure barrier from the main pressure barrier.
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