Metals are destroyed by chemical, physical and biological factors in seawater. As a result of corrosion of the metal structure, the material becomes thinner and the strength is getting weak. Sometimes local perforation or fracture occurs, and even the structure is destroyed. According to the statistics, about one-tenth of the steel products produced in the world each year are scrapped due to corrosion. The economic losses caused by corrosion in industrially developed countries each year account for about 2% to 4% of the total national economic output value.
Duplex ball valve, Super Duplex ball valve and 254 SMO ball valve become solution for the plant dealing with sea water, specially the desalination skid or plant.
For past few years, nearly 80% of the special alloy ball valve received by Zipson required CD3MN (2205 Duplex, 4A), CE3MN (2507 Super Duplex, 5A) or CK3MCuN (254 SMO) material as the best choice for valve for sea water.
In our experiences, these materials are mainly used in seawater desalination skid/ container/ plant or offshore facilities/ pumps which ask for a better anti-corrosion ability against the Chlorine (Cl) element in seawater. Super Duplex ball valve 5A (CE3MN) is the most common and popular option, 254 SMO （CK3MCuN) is evem higher grade solution for better and long term operation. Duplex 4A (CD3MN) valve is suggest to be used in lower pressure working condition with seawater. There materials offer better combination of material properties for these applications. It combines with nearly twice the strength of common stainless steel.
Pitting resistance equivalent number (PREN) is a predictive measurement of a metal’s resistance to localized pitting corrosion based on its chemical composition. In general: the higher PREN-value, the more resistant is the metal to localized pitting corrosion by chloride.
There are several PREN formulas. The most common is PREN = 1 x %Cr+ 3.3 x %Mo + 16 x %N
PREN is frequently specified when metal will be exposed to seawater or other high chloride solutions. In some metals with PREN-values > 32 may provide useful resistance to pitting corrosion in seawater, but is dependent on optimal conditions. However, crevice corrosion is also a significant possibility and a PREN > 40 is typically specified for seawater service such as Super Duplex ball valve.
Among all kind of special alloys, the materials we provide most often are Duplex, Super Duplex and 254 SMO. And, we do stock for these 2 materials mainly over flange ball valves (207F type) and 3-pc ball valves (305D & 302F type).
Except different end connections (thread/ SW/ BW/ flange), for specially alloy ball valve, we also offer metal seat for critical application, such as high temperature or media with particle.