Double Block and Bleed Plug Valve Manufacturers

ZZJG is the professional double block and bleed plug valve manufacturers with over 40 years of production experience. As a world-renowned double block and bleed plug valve manufacturer, its double block and bleed plug valves(DBB plug valves) are used in a variety of harsh working conditions, such as in the chemical, oil and gas, and nuclear power industries. The double block and bleed plug valves of ZZJG have exported to countries including Saudi Arabia, the United States, the United Arab Emirates, Chile, Iraq, Russia, Mexico and etc.

Double block and bleed plug valves can be divided into full-bore and reduced-bore types based on their diameter. Full-bore double block and bleed plug valves have a channel diameter roughly equal to the nominal diameter of the pipeline. They offer low flow resistance, smooth media flow, and facilitate pigging and the passage of larger solid particles. Reduced-bore double block and bleed plug valves have a channel diameter smaller than the nominal diameter of the pipeline. They are more compact, lighter, and have lower manufacturing costs, but they also offer relatively higher flow resistance.

ZZJG full-bore double block and bleed plug valve and reduced-bore double block and bleed plug valve have the following functional features:

1. Dual Block and Bleed Functions

A double-block, double-break valve only requires one valve. The valve has a drain port at the bottom, which can be removed when the valve is closed. If leakage occurs on one side of the valve, the leaked medium is discharged through the screw plug hole, preventing the two media from mixing. When the conveying medium is contaminated, sediment can be regularly drained through the drain plug. When the pipeline requires inspection, the residual medium can be removed through the drain port.

2. Fire Prevention and Sealing

The media used in oil and gas storage and transportation systems are flammable and explosive. Fire prevention is a key consideration in the design and selection of oil and gas storage and transportation equipment. The equipment must not only have excellent sealing properties but also maintain adequate sealing performance in the event of a fire.

Double-block valves utilize a combination of soft and hard seals, including the valve disc, end cap, and chassis. Soft seals ensure zero leakage during normal operation. However, in the event of a fire, the soft seals could be damaged. In this situation, the hard seals take over as the primary seal, preventing significant leakage. In comparison, gate valves use hard seals, which offer better fire protection, but their sealing performance is less reliable and cannot guarantee zero leakage over long periods of use. Ball valves use soft seals, which offer a longer service life but lack fire protection.

3. Provide a center cavity pressure relief function

The AP16D specification stipulates that "all double-seal valves must have a pressure differential relief function when used with liquid media." This pressure differential is generated by changes in ambient temperature. In the normally closed position, the center cavity pressure of a double-seal valve can rapidly increase due to rising temperatures. If this pressure is not relieved promptly, it can seriously affect valve operation. Manually operated double-block/double-break valves typically have the following two pressure relief systems:

4. Internal Leakage Detection

While it is difficult to verify the sealing effectiveness of ordinary valves when they are closed, double-block/double-break valves are easily inspected. Simply open the needle valve connecting the pressure relief system to the end cap while the valve is closed. If the valve slips, the medium will flow out through the needle valve.

5. Unique Pipeline Pressure Relief

Pipeline pressure relief is a key consideration in tank manifold design. Even after the tank valves are closed, the pipeline network remains filled with medium. As the ambient temperature rises, the medium pressure in the pipeline network rapidly increases. When the temperature differential fluctuates significantly, the increased pressure can exceed the pipeline's tolerance, easily causing pipeline leaks.

6. Online Maintenance

If the soft seal on the valve disc is damaged for some reason, causing internal leakage, or if the operator (actuator) malfunctions, replacement or repair can be performed without removing the valve from the pipeline. Operator maintenance can also be performed while the pipeline is still pressurized. When the sealing part of a gate valve or ball valve is damaged, the valve must be removed from the pipeline for repair or replacement, or even directly scrapped.

ZZJG Valve provides the above information on double block and bleed plug valve manufacturers. If you want to know more about the famous double block and bleed plug valve manufacturers, please contact us via WhatsApp or email.

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