Super Duplex Gate Valve Manufacturer in Africa 

Chloride-bearing pipelines need an isolation valve that can remain fully open with little flow restriction and still resist attack around the wedge, stem and seat pockets. Super Duplex stainless steel provides the strength and corrosion margin needed for many seawater and offshore duties. African Valve is a prominent Super Duplex Gate Valve Manufacturer in Africa, supplying South Africa, Nigeria, Egypt, Angola, other African countries and export markets.

Gate Movement and Flow Passage

The wedge travels vertically between two seats. When fully raised, it clears the bore and leaves a nearly straight flow path. This makes the valve suitable for full-open or full-closed isolation where pressure loss must remain low.
The valve should not be held partly open for control duty. A partially exposed wedge can vibrate, erode at the seat edges and suffer uneven loading. Solid or flexible wedges may be used according to size, pressure class and temperature.

Material Selection

Cast bodies may use ASTM A995 Grade 5A, while forged bodies or trim may use ASTM A182 F53 or F55. The bonnet, wedge, stem and seat rings should use compatible Super Duplex material or another approved corrosion-resistant alloy.
The alloy provides high strength and strong resistance to pitting, crevice corrosion and chloride stress-corrosion cracking. Correct heat treatment, ferrite balance, surface condition and welding remain essential. Warm seawater and stagnant crevices should be reviewed separately from the main flowing condition.

Bonnet, Stem and Seating

A rising-stem outside-screw-and-yoke arrangement keeps the stem threads outside the main pressure boundary and gives visible valve position. Bolted bonnets allow access during maintenance. Welded or pressure-seal bonnets may be selected for compact or higher-pressure service.
Seat rings may be integral or renewable. Hard-facing can reduce galling and erosion where the valve cycles frequently or closes against high differential pressure. Flexible graphite packing may be used for elevated temperature, while low-emission arrangements can be included when specified.