SK Type Hastelloy Mixing Element
SK type Hastelloy C-276 mixing element for hot concentrated acids, wet chlorine, and seawater. DN15-DN250, 1040°C melting point, PREN 65. Used in HCl absorbers, bleach plants, and FGD.
Product Overview
The SK type Hastelloy C-276 mixing element is the premium high-nickel-alloy replacement cartridge for service environments where neither SS316L nor PTFE is adequate. Hastelloy C-276 (UNS N10276) is a Ni-Mo-Cr alloy with 57% Ni, 16% Mo, 15.5% Cr, 5.5% Fe, and 4% W — a composition that delivers exceptional resistance to pitting, crevice corrosion, and stress-corrosion cracking in chloride-rich and reducing-acid environments. The element is machined from solid bar stock rather than stamped from sheet, which is why it carries a price premium but can be supplied in geometries that are impossible to achieve with rolled stainless.
Material Properties
Hastelloy C-276 has a density of 8.89 g/cm³, a melting range of 1325-1370°C, and a PREN (pitting resistance equivalent number) of 65 — roughly 2.5× the value for SS316L. The alloy resists all concentrations of HCl up to 65°C, all concentrations of H₂SO₄ below 90°C, wet chlorine gas, hypochlorite solutions, ferric and cupric chloride, and seawater at any temperature. It also handles oxidizing contaminants in acid streams (Fe³⁺, Cu²⁺, dissolved O₂) that would normally attack the lower-molybdenum stainless grades. Mechanical strength is excellent: tensile strength 690 MPa minimum, yield 280 MPa, and useful ductility down to -196°C. The alloy is supplied in the solution-annealed condition (1150°C water quench) and is fully stabilized against grain-boundary carbide precipitation, which means welded elements require no post-weld heat treatment.
Compatible Housings
The Hastelloy element fits the ywmixing SK type housing in DN15-DN250. The housing is supplied either in solid Hastelloy C-276 (for the most aggressive services) or as a carbon-steel shell with a loose Hastelloy liner (for pressure containment at lower cost). Flange classes are limited to PN16/ANSI 150 because higher classes would require Hastelloy forgings, which are not cost-effective. End retention is by a Hastelloy spring-clip retainer identical in geometry to the SS316L version.
Installation & Replacement Guide
Replacement procedure is identical to the SS316L element, with two additional precautions. First, never use carbon-steel tools in contact with the Hastelloy surface — iron contamination will cause rust-staining and create a galvanic cell that initiates pitting in chloride service. Use only stainless or Hastelloy tools. Second, when fitting the element, ensure that the O-ring is made of FKM, EPDM, or PTFE only — never natural rubber or nitrile, which the alloy will degrade. After re-assembly, the housing should be flushed with deionized water and passivated with 20% HNO₃ for 30 minutes before being returned to service.
Technical Specifications
| Parameter | Value |
|---|---|
| Material | Hastelloy C-276 (UNS N10276), solution-annealed, ASTM B574 / B575 |
| Element Geometry | 180° or 270° helical twist, 2-6 elements, 90° cross-rotation |
| Twist Length (L) | 45 mm per 180° twist (DN15-DN50); 90 mm per 180° twist (DN65-DN150); 135 mm per 180° twist (DN200-DN250) |
| Blade Thickness | 1.5 mm (DN15-DN50); 2.0 mm (DN65-DN100); 2.5 mm (DN125-DN200); 3.0 mm (DN250) |
| Pipe Diameter Range | DN15 to DN250 |
| Pressure Rating | PN16 standard; PN25 available |
| Temperature Range | -196°C to +400°C continuous; up to 1040°C melting point |
| Viscosity Range | 1 cP to 1,000,000 cP |
| Pressure Drop | ΔP = 1.2-2.5 × empty-pipe ΔP at Re = 1,000-10,000 |
| Mixing Precision | Coefficient of variation σX ≤ 5% at L/D = 7, 4 elements |
| Connection Types | Flange (ANSI B16.5 Class 150, DIN PN16), weld-neck |
| Mass (DN100, L/D=7) | 2.0 kg per element |
Applications
The Hastelloy C-276 SK element is specified for the most demanding service in chlor-alkali, flue-gas desulfurization, and pharmaceutical fine-chemical plants. In HCl absorbers, the element handles 30-36% HCl at 60-80°C in DN80-DN200 absorbers where SS316L would fail within 6 months. In flue-gas desulfurization (FGD) absorbers, the element operates in 10-20% H₂SO₄ slurry at 60-70°C with chloride concentrations up to 50,000 ppm. Other typical services include wet chlorine gas cooling in bleach plants, hypochlorite storage circulation, hydrogen chloride synthesis gas quench lines, vinyl chloride monomer (VCM) reactor feed, and isocyanate intermediate production where the chemistry combines HCl, Cl₂, and organic solvents in a single stream.