Alloy 20 Flanged Gate Valve Manufacturer and Supplier in Africa

Isolation valves used in sulphuric acid service must resist corrosion without adding unnecessary restriction to the pipeline. An Alloy 20 flanged gate valve provides a straight flow passage when fully open and a bolted flange connection that can be removed during maintenance. Its nickel-chromium-molybdenum-copper construction is used where carbon steel or common stainless grades have insufficient chemical resistance. African Valve is a top Alloy 20 Flanged Gate Valve Manufacturer and Supplier in Africa, supplying Nigeria, Egypt, South Africa, Kenya and Ghana and supporting exports to the Middle East, Europe and international industrial projects.

Why Is a Gate Valve Used on Acid Lines?

A gate valve is selected primarily for isolation. As the gate rises, it moves completely away from the bore, leaving a flow path with little internal obstruction. This makes the design appropriate for lines that remain open for long operating periods and where pressure loss needs to be limited.It should not be used as a routine throttling valve. A partly open gate is exposed to high local velocity, uneven loading and vibration. Over time, this can damage the seating surfaces and the lower edge of the wedge.

Wedge Movement and Seat Contact

Handwheel or actuator movement rotates the stem nut and moves the stem vertically. The attached wedge enters the body seat area during closure. In a flexible-wedge design, a machined groove allows limited movement between the two seating faces. This helps the wedge accommodate small dimensional changes caused by temperature or pipeline stress.A rising stem provides a direct visual indication of position. When the valve opens, the stem extends above the handwheel or gearbox. The external stem threads are also separated from the process fluid, which simplifies lubrication and inspection.

Why Does Flange Design Matter?

Flanged ends allow the valve to be installed without field welding. Raised-face flanges are common in moderate pressure classes, while ring-type-joint connections may be specified for higher pressure or critical chemical duties.

Flange drilling, facing finish and face-to-face dimensions must match the piping specification. ASME B16.5 governs many flange dimensions, while ASME B16.10 is normally referenced for valve installation length.

Alloy 20 Pressure Parts

Cast bodies and bonnets are generally manufactured from ASTM A351 CN7M. Internal or forged components may use ASTM A182 F20. The alloy contains copper along with nickel, chromium and molybdenum, giving it better behaviour in sulphuric acid than many standard austenitic stainless steels.

Trim materials, packing and gaskets should be evaluated separately. Graphite packing may suit elevated temperatures, while PTFE-based packing is used in compatible lower-temperature chemical service.

Technical Specifications

Size Range: DN15 to DN900
Pressure Ratings: Class 150 to Class 600; PN10 to PN100
Design Standards: API 600 and ASME B16.34
Testing Standard: API 598
End Connections: Flanged RF, RTJ or project-specific facing
Operation: Handwheel, gearbox, electric, pneumatic or hydraulic actuator

Product Features

• Full opening produces limited pressure loss.

• Flanged ends permit removal without cutting the pipeline.

• Rising stem construction shows the valve position externally.

• Flexible wedges accommodate limited seat movement.

• Alloy 20 resists many sulphuric acid and chloride-bearing environments.

• Manual and actuated versions can be supplied.

Suitable Applications

The valve is used in sulphuric acid production, fertilizer plants, acid storage terminals, chemical transfer lines, pickling units and solvent-processing systems. It is best suited to services requiring infrequent but positive isolation.

Manufacturing and Inspection

Seat alignment, stem straightness, wedge contact and flange dimensions are checked during assembly. Shell pressure testing confirms the body and bonnet joint, followed by closure testing across both seats. PMI and NDT may be included where specified.

Each valve can be supplied with MTCs, hydrostatic test reports and dimensional inspection records.