Boiler Reheater Block Valve

The boiler reheater block valve is a key device in boiler systems used for hydraulic test isolation and pipeline function conversion. It is especially suitable for high-temperature and high-pressure environments of 25MW to 1000MW units. During a boiler pipe hydraulic test, the block valve can effectively isolate the test section, ensuring the test’s safety and accuracy. By replacing components (such as the valve disc and flow guide sleeve), the block valve can be converted into a regular pipeline after the hydraulic test, enabling multi-purpose use.

Technical Features of Boiler Reheater Block Valve

• Pressure self-tightening sealing structure:

  • Principle: Utilizes media pressure to push the valve disc tightly against the valve seat. The higher the pressure, the greater the sealing force, creating a self-reinforcing sealing effect.

  • Advantages: No additional pre-tightening force is required, reducing the risk of bolt loosening ; adapts to high-temperature and high-pressure conditions (e.g., reheater steam pressure can reach 6-10MPa, and temperatures can be 540-600°C) ; sealing performance remains stable after long-term operation, avoiding leakage caused by thermal expansion in traditional bolted valves.

• Two-pipe weld connection:

  • Design: The block valve and the reheater pipe are connected via a full-penetration weld structure, eliminating potential leakage points that can exist with flange connections.

  • Applicability: Suitable for large-diameter pipes (e.g., DN200-DN600), reducing on-site installation work ; the weld joint has high strength and can withstand stresses from pipe thermal expansion, avoiding stress concentration that could lead to cracks.

Operation Modes of Boiler Reheater Block Valve

• Hydraulic Test Phase:

  • Assembly process: Install the valve disc and “O” ring; close the block valve and fill the reheater system with water, pressurizing it to 1.25 times the design pressure (e.g., for a 6MPa system, pressurize to 7.5MPa) ; maintain the pressure for 5 minutes and check if the leakage rate meets the standard.

  • Function: Isolates the reheater from the main steam pipeline to prevent the hydraulic test from damaging equipment like the steam turbine.

• Function Conversion for Operation Phase:

  • Flow guide sleeve replacement: After the hydraulic test, remove the valve disc and “O” ring, and install the flow guide sleeve (usually with a streamlined design, with a surface roughness Ra≤3.2μm) ; the gap between the flow guide sleeve and the valve body is controlled at 0.5-1mm to reduce the pressure drop caused by steam turbulence (pressure drop loss ≤0.5%).

  • Pipeline operation: The block valve is converted into an unobstructed flow channel, reducing system resistance ; it avoids energy loss caused by throttling in traditional valves (e.g., a throttling valve can have a pressure drop of 1-2MPa).