SH Type Dual-Channel Static Mixer

Product Overview

The SH type dual-channel static mixer addresses a specific class of process problems that sit awkwardly between the SK and the SX. The fluids in question are highly viscous — often 50,000 to 500,000 cP — but the mixing requirement is not so much "blend two streams together" as "guarantee that the concentration at every point across the pipe cross-section is within a defined tolerance." Color masterbatch dosing into polymer melt, pigment dispersion in synthetic fiber spinning solution, and active-ingredient incorporation into pharmaceutical ointment all share this profile. The dual-channel geometry of the SH, with its internal helical vanes and redistribution chambers between elements, is purpose-built for it.

Where the SK uses a single twisted blade that occupies the full pipe cross-section, the SH divides the flow into two parallel channels. Each channel contains its own helical vane, and the two channels rotate the fluid in opposite directions. At the end of each element, the two channels are recombined in a redistribution chamber, then split again into the next pair of channels — but rotated 90° relative to the first pair. This is what gives the SH its defining characteristic: a very narrow, very predictable residence time distribution, even at viscosities where the SK and SX would produce broader distributions because of their less-constrained geometries.

The SH is a small-flow, small-diameter model. It is manufactured from DN15 to DN200, which corresponds to flow rates of roughly 0.01 to 50 m³/h. This size limitation is deliberate — at larger diameters, the redistribution chambers become too large for the channel-equalization effect to work, and the SK becomes the more appropriate choice. The SH is also restricted to clean media. The dual channels have a narrower free cross-section than the SK blade, and any particulate above 0.5 mm will accumulate in the redistribution chambers over time, unbalancing the two channels and degrading the mixing performance.

Working Principle

An SH element consists of two parallel semicircular channels formed by a divider plate running along the pipe axis, with a helical vane fitted inside each channel. The vane pitch is typically 30-50 mm, and the channel width is 40-50% of the pipe diameter. The element length is 1.5-2.0D — longer than the SK's 1.0-1.5D because the dual-channel geometry requires more axial distance to produce the same number of theoretical mixing stages.

Fluid entering the SH is split immediately into the two channels. Within each channel, the helical vane induces a swirl component, but unlike the SK's 180° twist, the swirl in each SH channel is only 60-90° over the element length. The two channels are designed to swirl in opposite directions, so when the fluid reaches the end of the element, the two streams have similar but counter-rotating velocity profiles. The redistribution chamber then merges them. Because the two streams have been processed identically (just in mirror-image channels), their composition profiles are matched — and the merged stream has a much more uniform cross-sectional composition than either stream would have alone.

The next element is rotated 90° from the first, so the two channels now point "up" and "down" instead of "left" and "right." The fluid is split again, and the same helical induction occurs. Over 4-6 elements, the fluid has been processed 4-6 times by the matched-channel system, and the residence time distribution narrows to within σX ≤ 1-5%. The 1-2 mm dispersion precision quoted in our specifications refers to the spatial scale of concentration fluctuations in the mixed stream — not to droplet size, since the SH is typically used for miscible-liquid blending rather than emulsification.

The redistribution chambers are the key design feature that distinguishes the SH from a simple "two parallel SK elements" configuration. Without the chambers, the two channels would slowly develop different pressure drops (because of slight manufacturing asymmetries and because the fluid properties are not perfectly matched), and one channel would end up carrying most of the flow. The chambers equalize the pressure between elements, ensuring that both channels continue to operate near their design flow split throughout the life of the mixer.

Technical Specifications

Parameter	Value
Internal Structure	Dual parallel channels with internal helical vanes; adjacent units offset 90°; redistribution chambers between elements
Dispersion Precision	1-2 mm spatial scale of concentration variation (not droplet size)
Viscosity Range	100 cP to 1,000,000 cP (clean, high-viscosity media)
Pressure Drop	Moderate; 3-6 velocity heads per element + chamber losses
Non-Uniformity Coefficient	σX ≤ 1-5% with 4-6 elements (depending on viscosity and L/D)
Material Options	SS304, SS316L, Carbon Steel, PVC, PP, Hastelloy C-276
Connection Types	Flange (ANSI / DIN / JIS), Threaded (NPT / BSP), Welded, Tri-Clamp
Temperature Range	-50°C to +300°C (metallic) / -10°C to +80°C (PVC/PP)
Pipe Diameter Range	DN15 to DN200 (small-flow model by design)
Flow Rate Range	0.01 to 50 m³/h (model and pipe-size dependent)
Clogging Risk	Moderate — restricted to clean media; particles < 0.5 mm

Material Options

The dual-channel divider plate and helical vanes of the SH are fabricated by welding or investment casting, depending on size and material. For SS316L (the default material in pharmaceutical and high-purity chemical service), the divider plate is machined from plate stock and the vanes are formed by stamping; the assembly is then TIG-welded and passivated. The L-grade carbon content prevents sensitization at the welds, which is critical because the SH's narrow channels leave very little wall thickness for corrosion allowance.

SS304 is used in the food and color-masterbatch industries for non-corrosive service. The slightly higher carbon content of standard 304 (vs 316L) is acceptable here because the operating temperatures are typically below 100°C and sensitization is not a concern. Carbon steel is rarely used in the SH because the model's primary applications (color, pharmaceutical, fine chemicals) are not compatible with iron contamination. When carbon steel is specified, it is usually because the SH is being used in a polymer or adhesive application where trace iron is acceptable — the divider plate is then 6-10 mm thick carbon steel with the vanes welded in place.

PVC and PP SH mixers are produced in sizes DN15 to DN100 and used in low-temperature chemical service (electroplating baths, photographic chemicals, and certain water-treatment reagents). The dual-channel divider and vanes are machined from solid plastic stock and solvent-welded together. Hastelloy C-276 is reserved for hot concentrated acids — typically DN25-DN100 sizes for analytical reagent production and specialty catalyst manufacture, where the contamination tolerance is measured in parts per billion.

Installation Methods

The four standard connection types apply to the SH, with the smaller end of the size range (DN15-DN50) dominated by threaded and tri-clamp connections, and the larger sizes (DN65-DN200) dominated by flanged and welded connections. Flanged connections (ANSI B16.5 Class 150, DIN PN16) are standard for DN65 and above, and the flange faces are raised-face (RF) for the standard range and tongue-and-groove (T&G) for sanitary service.

Threaded connections (NPT or BSP) are used for DN15-DN50 mixers in laboratory and pilot-plant service. The threaded end is NPT per ASME B1.20.1 or BSP per ISO 228, and the mixer housing is supplied with a hex nut for installation in confined spaces. Welded connections are used for permanent installations in polymer and adhesive service, where the process temperature is too high for a gasketed joint. The weld is typically a socket-weld or butt-weld depending on the pipe schedule, and post-weld heat treatment is applied when the wall thickness exceeds 6 mm.

Tri-clamp connections (ISO 2852 or DIN 32676) are mandatory for pharmaceutical, biotech, and food SH installations. The sanitary design specifies Ra ≤ 0.8 μm surface finish, fully drainable geometry, and CIP/SIP capability. The clamp ferrules are 1.5" or 2" for the DN15-DN50 sizes and 3" or 4" for the DN65-DN100 sizes. Tri-clamp connections also make the SH mixer easy to remove for inspection of the dual channels — an important consideration in color-matching service, where any buildup of pigment on the channel walls will shift the apparent color of subsequent batches.

For all installation types, the SH requires a minimum straight-pipe run of 3D upstream and 3D downstream. The 3D figure is higher than for the SK or SX because the dual-channel geometry is less forgiving of inlet velocity-profile distortion — if the inlet flow is not symmetric, one channel will see more flow than the other and the mixing performance will be degraded.

Typical Applications

Precision color matching for injection molding. Color masterbatch (typically 2-5% concentration in a polymer carrier) is dosed into natural polymer (PP, PE, ABS, PA) just before the injection-molding machine's plasticizing screw. Color consistency is the key quality metric — a ΔE of 0.5 or less is usually required for automotive interior parts and consumer electronics housings. The SH mixer, installed in the melt line between the masterbatch dosing unit and the machine, achieves ΔE < 0.3 in a single pass for viscosities up to 100,000 cP. The dual-channel design provides the predictable residence time distribution that the statistical process control charts demand.

Synthetic fiber spinning solution preparation. Polyacrylonitrile (PAN) and polyester spinning solutions have viscosities of 50,000-500,000 cP at the spinning temperature (80-150°C). Pigments, delustrants (TiO₂), and UV stabilizers must be uniformly dispersed at the parts-per-million level before the solution is extruded through the spinneret. The SH mixer provides the required uniformity in a 1-2 second residence time, eliminating the hold-up tanks that older dissolving processes required.

Fine chemical processing. Specialty chemicals — pharmaceutical intermediates, agrochemical active ingredients, dye intermediates — often involve the last-step blending of an active ingredient into a carrier or solvent at 5-30% concentration. The SH is used to homogenize the active into the carrier at viscosities of 1,000-50,000 cP, where the SK would over-sheAR the product and the SX would produce a broader residence time distribution than the active's stability window allows.

Small-flow high-precision blending. Many pilot plants and kilo-labs operate at flow rates below 1 m³/h, where the SH is the only model in our line that can deliver the required mixing precision. Typical applications include active pharmaceutical ingredient (API) crystallization feeds, catalyst preparation, and the production of reference standards for analytical chemistry. The small size of the SH (DN15-DN25 typical for kilo-lab service) fits into the existing piping without requiring oversized process connections.

Pharmaceutical ointment mixing. Topical ointments and transdermal gels have viscosities of 50,000-500,000 cP at 25°C. The active ingredient (typically 0.1-5% concentration) must be uniformly distributed throughout the base, and the United States Pharmacopeia (USP) content uniformity test requires that the variation between sampled points be below 6%. The sanitary SH in SS316L with Ra ≤ 0.8 μm finish delivers this uniformity in a single pass at 5-15 m³/h, replacing the planetary mixers and three-roll mills that traditional ointment manufacture requires.

Model Comparison

Parameter	SH	SV	SK	SX	SL
Internal Structure	Dual-channel helical	Corrugated plates	Helical twist	Crossed bars	Single-X bars
Dispersion Precision	1-2 mm	1-2 μm	≤ 10 μm	2-5 μm	Medium
Max Viscosity (cP)	1,000,000	100	1,000,000	10,000	10 (or polymer)
Pipe Diameter	DN15-DN200	DN15-DN1000	DN15-DN500	DN25-DN800	DN15-DN600
Clogging Risk	Moderate	High	Lowest	Moderate	Low
Best For	High-viscosity clean	Fine dispersion	High-viscosity	Mid-range	Heat transfer

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