Acid and Alkali Resistant Pump

The Acid and Alkali Resistant Pump is purpose-engineered for the safe transfer of highly corrosive chemicals in industrial processes. Pumping aggressive acids such as sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), and hydrofluoric acid (HF) requires specialized materials that resist chemical attack. Similarly, strong alkalis such as sodium hydroxide (NaOH) and potassium hydroxide (KOH) demand corrosion-resistant construction. Our pumps employ two primary technologies for corrosion resistance: fluoropolymer-lined construction and high-performance alloys. Each approach has advantages depending on the chemical concentration, temperature, and pressure requirements of the application.

Fluoropolymer-lined pumps provide exceptional chemical resistance at a lower cost than high-performance alloys for many applications. The pump casing is constructed from carbon steel or ductile iron for structural strength. A liner of PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy), or PVDF (polyvinylidene fluoride) is molded inside the casing, creating a barrier between the metal structure and the corrosive fluid. PTFE is chemically inert to virtually all chemicals except molten alkali metals and fluorine gas. PFA offers similar chemical resistance with better high temperature performance (up to 180°C). PVDF provides excellent resistance to acids, alkalis, and solvents at a lower cost but with a lower temperature limit (120°C). The liner thickness is typically 3 to 5mm, providing a long service life even in aggressive service.

High-performance alloy pumps are specified when temperatures exceed the limits of fluoropolymer linings or when the fluid is not compatible with fluoropolymers. Alloy options include stainless steel (SS304, SS316, SS316L), duplex stainless steel (2205, 2507), Hastelloy (C276, B2, C22), titanium (Grade 2, Grade 7, Grade 12), and zirconium. Each alloy has specific corrosion resistance characteristics. SS316 provides good resistance to many acids and alkalis but is attacked by chlorides and reducing acids. Hastelloy C276 provides excellent resistance to wet chlorine, hypochlorite, and mixed acids. Titanium is outstanding for seawater and oxidizing acids. Our metallurgists assist in selecting the optimal alloy for your specific chemical concentration and temperature.

The pump hydraulic design is optimized for chemical service. For lined pumps, the impeller is of the semi-open or open type, as the thickness of the lining affects internal clearances. The impeller is manufactured from the same fluoropolymer material or from high-performance alloy. For alloy pumps, enclosed impellers with close-clearance wear rings provide maximum efficiency. The volute casing is designed with smooth transitions to minimize turbulence and erosion of the corrosion-resistant layer. For lined pumps, the casing includes a conductive carbon-filled PTFE layer to dissipate static electricity when pumping flammable solvents.

Material traceability is critical for chemical pumps. Every casting is accompanied by a material test certificate (EN 10204 3.1 or 3.2) documenting chemical composition and mechanical properties. Positive Material Identification (PMI) is performed on all alloy components to verify alloy grade. This is especially important when multiple alloys are used in the same facility, as visual inspection cannot distinguish between SS304 and SS316 or between SS316 and Hastelloy.

The shaft sealing system must prevent leakage of hazardous chemicals to the atmosphere. For most chemical applications, we offer double mechanical seals (API 682 Arrangement 2 or 3) with a pressurized barrier fluid. The barrier fluid is contained in a sealed reservoir, and any leakage is contained rather than released. For applications where absolutely zero leakage is mandatory, we offer magnetic drive (sealless) pumps. The magnetic drive eliminates the dynamic shaft seal entirely, with the impeller driven through a containment shell. This provides the highest level of containment for toxic, carcinogenic, or valuable chemicals.

The pump is available in end-suction, horizontal, or vertical configurations. End-suction pumps are the most common for chemical transfer applications. Horizontal split-case pumps are used for higher flow rates. Vertical in-line and vertical sump pumps are available for tank and sump applications. The configuration is selected based on the installation requirements and available NPSH.

In summary, the Acid and Alkali Resistant Pump delivers safe, reliable, long-lasting service in the most aggressive chemical environments.