Axial Flow Check valve

Axial flow check valve otherwise known as nozzle check valve which is a non-return valve that allows flow in one direction and prevents reverse flow by using a spring-loaded disc that moves axially (in line with the flow). It is specifically designed to minimize pressure drop and water hammer effects in pipelines.

The axial flow check valve is a high-performance, the valve with a spring-loaded disc aligned with the flow axis. It is designed per API/ASME standards, used in critical pipeline and process services where fast closing, low pressure drop, and water hammer protection are required.

1.Structure of Axial Flow Check valve

The main components include:
Body: Cylindrical streamlined body, often forged or cast steel, designed for minimal turbulence.
Disc / Poppet: Moves axially along the flow direction, guided precisely to avoid misalignment.
Spring: Ensures quick closing of the disc when forward flow reduces or stops.
Seat: Hard-faced sealing surface for tight shutoff.
Guide & Stem: Keeps disc aligned during operation.
Typical flow path is straight-through, ensuring low energy loss.

2. Standards of Axial Flow Check valve

Axial flow check valves are typically manufactured in compliance with:
Design & Testing: API 6D, API 594, ASME B16.34
Face-to-Face Dimensions: API 594, EN 558
Pressure Testing: API 598, ISO 5208
End Connections: ASME B16.5 (flanged), ASME B16.25 (butt-welded)
Materials: ASTM / ASME standards for carbon steel, stainless steel, alloy steels

3. Features of Axial Flow Check valve

Very low pressure drop due to streamlined flow path.
Non-slam closing action → minimizes water hammer.
Spring-assisted closure ensures fast response.
Can operate in horizontal and vertical pipelines.
Compact design compared to swing check valves.
Suitable for high-pressure and high-velocity applications.
Available in cryogenic, high-temperature, and corrosive service designs.

4. Applications of Axial Flow Check valve

Axial flow check valves are widely used in:
Oil & Gas pipelines (transmission, distribution, offshore).
Petrochemical & Refinery plants.
Power plants (steam, condensate, cooling water).
Water injection and pumping stations.
Compressor discharge lines (to prevent backflow).
High-pressure natural gas and liquid hydrocarbon services.

5. Operations of Axial Flow Check valve

Forward Flow: Fluid pressure pushes the disc downstream, compressing the spring, allowing flow.
Reverse Flow: As soon as flow reduces, the spring pushes the disc back against the seat, closing before reverse flow can occur → prevents water hammer.
Dynamic Performance: The spring ensures closure occurs in milliseconds, even before flow reversal.

6. Maintenance Manual (General Guidelines) of Axial Flow Check valve

Inspection & Maintenance Steps:
Regular Inspection: Check for body leaks, unusual vibrations, or pressure loss.
Seat & Disc Inspection: Periodically check sealing surfaces for wear, erosion, or pitting.
Spring Condition: Verify spring tension and replace if weakened or corroded.
Guides & Stem: Ensure smooth movement of disc without sticking.
Cleaning: Remove debris or sediment buildup that may block movement.
Lubrication: Some designs require stem/guide lubrication (check OEM manual).
Testing: Conduct hydrostatic or pressure tests per API 598.
Storage: Keep valves in clean, dry environment; protect sealing faces with covers.
Common Issues & Fixes:
Leakage at seat → regrind / replace disc and seat.
Slow closing → check spring, clean guide.
Vibration / chatter → verify flow conditions; valve may be oversized.