Alloy 20 Flanged Globe Valve Manufacturer in Africa

Chemical lines that require regular adjustment cannot always be handled effectively by a gate valve or standard on-off ball valve. An Alloy 20 flanged globe valve provides controlled stem travel, guided disc movement and a defined seating opening for regulating corrosive fluids. Alloy 20 also provides useful resistance to sulphuric acid and chloride-bearing chemicals. African Valve is a leading Alloy 20 Flanged Globe Valve Manufacturer and Supplier in Africa, supplying Nigeria, Egypt, South Africa, Kenya and Ghana, with export capability for the Middle East, Europe and other industrial regions.

Why Is the Flow Path Different?

Fluid entering a conventional globe valve changes direction as it passes through the seat opening. The disc moves toward or away from this opening in a straight line. Each change in stem position alters the available flow area, giving the operator more control than a gate valve can provide.The change in direction creates a higher pressure drop. For that reason, a globe valve should be selected only after checking the available system pressure and required flow rate. Where accurate automatic control is required, a purpose-built control valve with a characterised trim may be more appropriate.

Disc and Stem Arrangements

The handwheel or actuator moves the stem axially rather than rotating the disc against the seat. This limits rubbing during closure. Plug-shaped discs can provide progressive flow adjustment, while needle-type trims are used for smaller flows and finer regulation.The stem must remain straight and correctly guided. Side loading can cause packing wear, irregular seat contact and increased operating torque. Depending on the design, the seat ring may be renewable, allowing the sealing surface to be repaired without replacing the complete body.

Alloy 20 Material Selection

ASTM A351 CN7M is commonly used for cast bodies and bonnets. Forged pressure components may be supplied in ASTM A182 F20. Alloy 20 contains nickel, chromium, molybdenum and copper and is associated particularly with sulphuric acid service.

The disc and seat may also be Alloy 20, although harder compatible materials can be used where frequent operation may produce wear. PTFE-based packing is suitable for many lower-temperature chemical duties, while graphite packing is considered when temperature exceeds the practical range of fluoropolymer packing.

Flanged End Configuration

Raised-face flanges are widely used in Class 150 and Class 300 systems. RTJ ends may be specified for higher-pressure services or piping systems that already use metallic ring gaskets.

Flange facing, bolt-hole orientation and face-to-face length must match the connected piping. Incorrect installation can distort the body and prevent proper seat alignment.

Technical Specifications

Size Range: DN15 to DN600
Pressure Ratings: Class 150 to Class 600; PN10 to PN100
Design Standards: BS 1873 and ASME B16.34
Testing Standard: API 598
End Connections: Flanged RF, RTJ or project-specific facing
Operation: Handwheel, gearbox, electric or pneumatic actuator

Performance Benefits

• Linear disc travel allows controlled flow adjustment.

• The disc approaches the seat without rotational rubbing.

• Flanged construction simplifies valve removal.

• Alloy 20 pressure parts support aggressive chemical service.

• Replaceable seats may reduce long-term repair requirements.

• Actuation can be selected for remote or automatic operation.

Process Applications

Common uses include sulphuric acid metering, chemical dosing, acid recovery, fertilizer production, pickling systems and corrosive utility lines. The valve is suitable where the process requires more frequent operation than a gate valve would normally receive.

Inspection and Pressure Testing

Stem movement, disc guidance, seat contact and flange dimensions are checked before pressure testing. Hydrostatic testing verifies shell integrity, followed by seat leakage testing. PMI can be used to verify Alloy 20 parts, while MTC and test records support project traceability.