SD Type SS316L Mixing Element
SD type SS316L dual-helical mixing element for high-viscosity laminar flow mixing. DN15-DN300, handles up to 100,000 cP, ideal for polymer compounding, adhesive blending, and heavy-oil service.
Product Overview
The SD type SS316L mixing element is the dual-helical replacement cartridge used in the SD family of high-viscosity laminar-flow static mixers. The element consists of two concentric helical blade stacks — an outer helix rotated 180° to an inner helix — that together create a continuous flow-diverting geometry. This is the only ywmixing element geometry that operates effectively in the fully laminar regime (Re < 100), where the standard SK and SX elements see their mixing efficiency collapse. The SD element is the workhorse for polymer compounding, adhesive blending, and heavy-oil service.
Material Properties
SS316L for the SD element is the same UNS S31603 specification as the other stainless elements, but the blade thickness is increased to 1.5-3.0 mm (vs. 1.2-2.0 mm for the SK element) to handle the higher torque loads generated by viscous flow. The blade edges are deburred and stress-relieved at 1050°C for 30 minutes after forming, to prevent fatigue cracking at the helix roots. Surface finish is 2B as standard, with optional electropolish to Ra ≤ 0.8 μm for pharmaceutical service.
Compatible Housings
The SS316L SD element fits the ywmixing SD type housing in DN15-DN300, with flanged (ANSI B16.5 Class 150, DIN PN16) or weld-neck end connections. The housing interior is bored to a tighter tolerance than the SK housing (±0.1 mm rather than ±0.2 mm) to maintain the concentric alignment of the inner and outer helices. End retention is by a key-lock retainer at each end. The element is supplied as a single welded cartridge in all sizes.
Installation & Replacement Guide
The SD element is heavier than the equivalent SK element and requires two people to lift in sizes above DN200. Depressurize, drain, and remove the end retainer using the supplied key. Pull the element out axially with steady hand pressure, taking care not to bend the outer helix. Inspect the housing interior for fouling and clean if needed. Fit new EPDM or FKM gaskets, slide the new element in (orientation marks face inlet), and refit the retainer. Total replacement time is 30-45 minutes in the field, including the alignment check.
Technical Specifications
| Parameter | Value |
|---|---|
| Material | SS316L (UNS S31603) sheet and bar, 2B finish, optional electropolish Ra ≤ 0.8 μm |
| Element Geometry | Dual concentric helices, 180° twist each, 4-8 blade pairs |
| Blade Thickness | 1.5 mm (DN15-DN50); 2.0 mm (DN65-DN100); 2.5 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 |
| Viscosity Range | 100 cP to 100,000 cP (laminar regime) |
| Reynolds Number Range | Re = 0.1-100 (laminar) |
| Pressure Drop | ΔP = 3-8 × empty-pipe ΔP at Re = 1-100 |
| Mixing Precision | Coefficient of variation σX ≤ 5% at L/D = 10, 6 blade pairs |
| Connection Types | Flange, weld-neck, tri-clamp |
| Mass (DN100, L/D=10) | 3.5 kg per element |
Applications
The SS316L SD element is the standard replacement for high-viscosity laminar-flow service. Polymer compounding lines use the element in DN50-DN200 melt-blending reactors (polyethylene, polypropylene, polystyrene at melt temperatures 200-280°C and viscosities 1,000-50,000 cP). Adhesive manufacturers use the element in hot-melt adhesive lines (EVA, polyamide at 150-180°C and 5,000-30,000 cP). Heavy-oil service includes bitumen blending (10,000-100,000 cP at 150°C) in refinery residue upgrading. Other typical services include chocolate conching, cosmetic cream homogenization, pharmaceutical ointment blending, and food-grade fat crystallization.