Applications for Duplex Stainless Steel Split-Case Pumps

I. Application Scenarios

Duplex stainless steel, with its unique austenitic-ferritic microstructure, combines the excellent toughness and corrosion resistance of austenitic stainless steel with the high strength and resistance to chloride stress corrosion cracking of ferritic stainless steel. This makes split-case pumps constructed from this material particularly suitable for the following industries:

1,Oil, Gas, and Offshore Platforms

Applications: Seawater lift, firewater systems, water injection, oil/gas pipeline boosting, ballast water systems, desalination systems.

Advantages: Superior resistance to corrosion from seawater, chloride-containing media, and oilfield brines; high strength and reliability.

2,Chemical and Petrochemical Industries

Applications: Handling various highly corrosive media such as sulfuric acid, phosphoric acid, nitric acid, salts, organic acids, and alkaline solutions.

Advantages: Exceptional resistance to localized corrosion (pitting, crevice corrosion) and stress corrosion cracking (SCC); ideal for complex chemical fluids.

3,Energy and Power Generation

Applications: Slurry circulation pumps in flue gas desulfurization (FGD) systems, seawater cooling pumps, boiler feedwater systems.

Advantages: Excellent performance in chloride-containing and weakly acidic environments; resistant to erosion-corrosion; long service life.

4,Seawater Desalination and Utilization

Applications: High-pressure pumps for reverse osmosis (RO) systems, seawater intake pumps, brine discharge pumps.

Advantages: This is a premier application area. Duplex stainless steel offers outstanding resistance to general and pitting corrosion in seawater.

5,Pulp and Paper Industry

Applications: Transferring pulping liquors (e.g., black liquor, white liquor), bleaching chemicals, process water.

Advantages: Resists corrosion from chlorides and chemicals, meeting the demands of harsh processing environments.

6,Environmental Protection and Wastewater Treatment

Applications: Effluent discharge pumps, treatment of industrial wastewater containing corrosive components, landfill leachate handling.

Advantages: Capable of handling complex wastewater containing chlorides and sulfides; resistant to erosion-corrosion.

II. Key Considerations

Despite its superior properties, the following critical points must be observed during selection, installation, and operation to prevent loss of performance or premature failure:

1,Precise Material Selection:

Duplex stainless steel is a family of grades. Common ones include 2205 (S32205/S31803), 2507 (S32750), and S32760.

2205 is suitable for most seawater and moderately corrosive environments.

Super Duplex grades (e.g., 2507) are used for more severe conditions (high chloride concentration, elevated temperatures, high acidity).

It is essential to consult with professional engineers or materials specialists for selection based on specific parameters: medium composition, concentration, temperature, pH, and chloride content.

2,Stringent Welding Requirements:

Welding is a critical process for duplex stainless steel. Improper welding can disrupt the austenite-ferrite phase balance, leading to excessive ferrite content in the weld and heat-affected zone (HAZ), which severely reduces corrosion resistance and toughness.

It is mandatory to use correct welding consumables (electrodes, wires) and strict procedures (controlling heat input, interpass temperature, shielding gas), performed by qualified welders. Post-weld solution annealing (if required) and phase balance inspection are recommended.

3,Installation and Operation:

Avoid Stress Concentration: Ensure proper pipeline alignment during installation to avoid imposing extra mechanical or thermal stress on the pump casing, which could increase the risk of SCC.

Cathodic Protection: Pay attention to galvanic corrosion when connecting to metals with lower electrochemical potential (e.g., carbon steel). Proper insulation or cathodic protection measures should be applied.

Standstill Protection: For long-term pump shutdown, especially in corrosive environments, drain, flush, and dry the internal parts to prevent aggravated localized corrosion from stagnant fluid.

III.Conclusion

Duplex stainless steel split-case pumps are powerful tools for solving challenging industrial fluid transfer problems involving high corrosion, high chloride content, and demanding requirements. The key to successful application lies in "selecting the right grade, executing proper welding, avoiding critical temperatures, and ensuring correct operation." When used in the right applications and operated according to specifications, they provide unparalleled reliability and cost-effectiveness.