SK Type SS316L Mixing Element
SK type SS316L helical mixing element for replacement in static mixers. 180°/270° twist geometry, DN15-DN300, handles up to 1,000,000 cP. Corrosion-resistant, CIP-cleanable, food-grade option.
Product Overview
The SK type SS316L mixing element is the standard replacement cartridge used in helical-element static mixers. It consists of two to six right-handed or left-handed twisted blades stacked inside a cylindrical shell, with each successive element rotated 90° to the next. This geometry creates the cross-channel mixing pattern that gives the SK type its reputation as the most versatile static mixing element — the same physical design that handles low-viscosity water injection at one extreme and high-viscosity polymer melts at the other.
Material Properties
SS316L (UNS S31603) is an austenitic chromium-nickel stainless steel with 16-18% Cr, 10-14% Ni, and 2-3% Mo. The 'L' grade specifies a maximum carbon content of 0.03%, which prevents chromium-carbide precipitation at grain boundaries during welding and eliminates the intergranular corrosion risk that affects standard SS304 and SS316 in the sensitized condition. The molybdenum addition improves pitting resistance to roughly PREN 25, which translates to continuous chloride exposure up to 1,000 ppm at room temperature. SS316L maintains useful mechanical strength from -196°C (LNG service) to 800°C, although the working envelope for static mixers is normally limited to 300°C by the gasket material. Tensile strength is 485 MPa minimum with 40% elongation. The grade is non-magnetic in the annealed condition, fully compatible with CIP/SIP cleaning protocols using 1-3% NaOH at 80°C followed by 1% HNO₃ rinse, and is approved for food contact under FDA 21 CFR 110 and EU 1935/2004 when supplied with the appropriate surface finish.
Compatible Housings
The SS316L SK element fits all ywmixing SK type housings in the DN15 to DN300 range, including both flanged (ANSI B16.5 Class 150, DIN PN16, JIS 10K) and tri-clamp (ISO 2852) shell designs. The element length is factory-matched to the housing's L/D ratio — typically 5D, 7D, or 10D — and the twist geometry (180°/270° per element, 4-6 elements total) is selected at order entry. The element can also be installed as a direct replacement in housings from other OEM brands provided the cartridge OD and length match within ±0.2 mm. End retention is by a single spring-clip or split-ring retainer at the inlet and outlet.
Installation & Replacement Guide
Replacing an SS316L SK element takes 15-30 minutes in the field. Isolate the mixer section, depressurize, and drain the housing. Remove the end retainer rings using the supplied hook spanner. The element is pulled out axially with steady hand pressure; do not use pipe wrenches on the blade edges. Inspect the housing O-ring grooves for scoring, clean with isopropyl alcohol, and fit new EPDM or FKM O-rings depending on the service. Slide the new element in, taking care to align the twist orientation marks (red stripe on element #1, blue on #2, green on #3) with the corresponding marks on the housing flange. Refit the retainer rings, re-pressurize to test, then re-torque the flange bolts to the rated gasket seating stress.
Technical Specifications
| Parameter | Value |
|---|---|
| Material | SS316L (UNS S31603), 2B finish, optional electropolish Ra ≤ 0.8 μm |
| 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-DN300) |
| Blade Thickness | 1.2 mm (DN15-DN50); 1.5 mm (DN65-DN100); 2.0 mm (DN125-DN200); 3.0 mm (DN250-DN300) |
| Pipe Diameter Range | DN15 to DN300 |
| Pressure Rating | PN16 standard; PN25 / PN40 available |
| Temperature Range | -50°C to +300°C (metallic); -10°C to +80°C (PP/PTFE liner) |
| 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, tri-clamp, threaded, weld-neck |
| Mass (DN100, L/D=7) | 1.8 kg per element |
Applications
The SS316L SK element is the workhorse replacement for the majority of chemical, water-treatment, and food-processing installations. Typical applications include pH adjustment and neutralization in wastewater (5-25% NaOH, 5-15% H₂SO₄ dosing at DN50-DN200), polymer dilution in flocculant make-up units, sodium hypochlorite injection in chlorination skids, CIP chemical blending in dairy and beverage plants (3-5% NaOH at 75°C, 1% HNO₃ rinse), and biodiesel transesterification mixing in DN80-DN150 reactors. The SS316L grade is also the standard for marine ballast-water treatment and offshore produced-water chemical injection where chloride-rich service rules out SS304.