Transparent SK Type Mixer

Product Overview

The ywmixing transparent SK type mixer is a sight-glass version of our standard SK helical-element mixer. The housing is a transparent polymer tube (PMMA, PC, or PSU) and the internal elements are 180° or 270° left-right twisted rods of PP or PVDF. The mixer is designed specifically for teaching, R&D, and process-development applications where the operator needs to see the actual mixing front as it develops through the housing — a capability that no opaque mixer (metallic or polymer) can offer.

The transparent SK is the workhorse of chemical-engineering teaching laboratories worldwide. It is used in undergraduate unit-operations courses to demonstrate residence-time distribution, in graduate reaction-engineering courses to study reactor inlet conditions, and in research labs to validate computational fluid dynamics (CFD) models of static mixers. The clear housing lets students see the color front develop element by element, which is the most intuitive way to teach the concept of mixing progression and the relationship between L/D ratio and coefficient of variation.

The mixer is supplied as a complete assembly with the transparent housing, the internal elements, and the end connections. Standard end connections include flanged (ANSI 150, DIN PN10, JIS 10K), threaded (NPT or BSP, DN15-DN50 only), and Tri-Clamp (ISO 2852, DIN 32676). For teaching applications, the mixer is typically supplied with a mounting frame that holds the mixer vertically or horizontally and integrates a tracer-injection port and a downstream sampling port.

Three housing polymers are available — cast PMMA (acrylic) for general-purpose laboratory service, polycarbonate (PC) for higher impact resistance and higher temperature, and polysulfone (PSU) for chemical resistance. All three materials exceed 90% light transmission (PSU is amber-tinted, so light transmission is 70-75%) so the operator can see the flow clearly under normal laboratory lighting. Internal elements are PP (default) or PVDF (for higher-temperature or more aggressive service).

Material Properties

The housing polymer is the defining selection parameter. Cast PMMA (acrylic) is the default for general-purpose teaching and R&D service. Its light transmission is 92% (highest of the three), its density is 1.18 g/cm³, and its tensile strength is 70 MPa. It is rated for continuous service from -10°C to +60°C, with a Vicat softening point of 105°C. PMMA is the lowest-cost option and is widely used in undergraduate teaching labs. The principal limitation is chemical resistance: PMMA is attacked by acetone, MEK, esters, aromatic and chlorinated hydrocarbons, and concentrated mineral acids above 30%.

Polycarbonate (PC) offers roughly 250× the impact strength of PMMA and a higher service temperature ceiling of 80°C continuous, 100°C short-term. Light transmission is 88-90%, slightly lower than PMMA but still excellent for visual work. PC is the standard selection for graduate research labs and industrial R&D where the mixer will see more demanding service (hot water, dilute cleaning solutions, occasional bumps). Chemical resistance is similar to PMMA against polar solvents; PC is also attacked by ketones, esters, and chlorinated solvents.

Polysulfone (PSU) is the chemically resistant option. PSU resists dilute mineral acids (HCl up to 10%, H₂SO₄ up to 20%, HNO₃ up to 10%), most bases, surfactants, and hot water/steam up to 100°C continuous (150°C short-term). It is amber-tinted, so light transmission drops to about 70-75% — still adequate for visual observation. PSU is the standard selection for pharmaceutical API process development where the mixer must tolerate the cleaning solutions used between batches. PSU is also USP Class VI compliant, which is required for pharmaceutical and biomedical applications.

The internal mixing elements are molded from PP (default) or PVDF (for higher-temperature or more aggressive service). PP is rated to 90°C continuous, has good resistance to acids, alkalis, and salts, and is FDA-compliant for food contact. PVDF extends the service envelope to 140°C and adds resistance to halogens, strong acids, and most organic solvents except ketones and strong bases. Element count is 4 to 8, with element twist angle selectable at 180° (default) or 270° (for higher-viscosity media or tighter coefficient of variation).

The end-cap material is matched to the housing polymer: PMMA end caps for PMMA housing, PSU end caps for PSU housing. For higher-pressure service (above 4 bar), the end caps are upgraded to PVDF or 316L stainless to carry the mechanical load while the transparent section remains in hoop stress only. The transparent section is mechanically clamped between the two end caps and can be replaced in under 10 minutes if it is scratched or chemically attacked.

Construction Design

The transparent SK is built around a one-piece or flanged transparent housing. For DN15-DN50, the housing is a single extruded tube with bonded end caps; for DN65-DN100, the housing is a flanged assembly with a transparent central section bolted between two flanged end fittings. The end fittings are typically PVDF for chemical service or 316L stainless for higher-pressure service, and they carry the pressure load while the transparent section remains in pure hoop stress.

The internal element set is the standard SK helical geometry: 4-8 elements of 180° (default) or 270° (option) twist, alternating left-right. Element rod diameter is typically 0.10-0.15 × DN, and the L/D ratio of the housing is 6-10 depending on the target σX. Elements are mechanically fastened to the housing at each end by element holders that are bonded (PMMA, PSU) or welded (PP, PVDF elements) to the housing wall.

End connections are available in three styles. Flanged (ANSI 150, DIN PN10, JIS 10K) is the most common for laboratory service. Flanges are polymer (PP, PVDF) or 316L stainless with PTFE-encapsulated O-rings. Threaded (NPT or BSP) is available for DN15-DN50 in PP or PVDF for instrument-air and low-pressure water service. Tri-clamp (ISO 2852, DIN 32676) is the standard for pharmaceutical and food-service installations, with sanitary ferrules machined from PP or PVDF.

The O-ring groove is machined into each end cap, and the standard elastomer is EPDM (water, dilute bases), with FKM and FFKM (Kalrez) available for solvent and high-temperature service. The O-ring is the only consumable in the mixer and is specified for 50,000 cycle operation at the rated temperature. Each mixer ships with a test certificate documenting hydrostatic test (1.5× design pressure held for 30 minutes) and a clarity inspection report.

For teaching applications, the mixer is typically supplied with an optional mounting frame. The frame is a powder-coated steel structure that holds the mixer vertically or horizontally, integrates a tracer-injection port upstream and a conductivity probe port downstream, and provides a backlight mounting point for high-speed video recording of the mixing front. The frame is optional and can be supplied as a separate item.

Technical Specifications

Parameter	Value
Housing Material Options	Cast PMMA (acrylic), Polycarbonate (PC), Polysulfone (PSU)
Internal Element Material	PP (standard) or PVDF (chemical / high-temp upgrade)
Light Transmission	92% (PMMA) / 88-90% (PC) / 70-75% (PSU)
Internal Structure	SK helical elements — 180° / 270° left-right twist (4-8 elements)
Mixing Precision	Coefficient of variation σX ≤ 3-5% (Re > 10,000)
Operating Temperature	-10°C to +60°C (PMMA) / -20°C to +80°C (PC) / -40°C to +100°C (PSU)
Design Pressure	6 bar at 23°C (PMMA, PC) / 6 bar at 100°C (PSU)
Test Pressure	9 bar (1.5× design) held 30 minutes
Connection Types	Flange (ANSI 150, DIN PN10, JIS 10K), NPT/BSP thread, Tri-Clamp
Pipe Diameter Range	DN15 to DN100
Flow Rate Range	0.05 to 30 m³/h
Viscosity Range	≤ 1,000 cP
End-Cap Material	PMMA, PSU (matched to housing), PVDF or 316L stainless (high-pressure upgrade)
O-Ring Material	EPDM (standard), FKM, FFKM (Kalrez)
USP Class VI	Available for PSU housing + PVDF elements

Applications

Chemical-engineering teaching laboratories. The transparent SK is the workhorse of chemical-engineering teaching worldwide. It is used in undergraduate unit-operations laboratories to demonstrate residence-time distribution, in graduate reaction-engineering courses to study reactor inlet conditions, and in research labs to validate computational fluid dynamics (CFD) models of static mixers. The clear housing lets students see the color front develop element by element, which is the most intuitive way to teach the concept of mixing progression and the relationship between L/D ratio and coefficient of variation.

Pharmaceutical process development and R&D. The transparent SK is used in pre-clinical API manufacture to validate mixing uniformity and CIP/SIP effectiveness. Operators can confirm visually that the cleaning solution reaches every internal surface, eliminating the sampling-based verification required with opaque metallic mixers. PSU housing with PVDF elements is the standard selection for API service because it tolerates the solvent and acid cleaning cycles used between batches and is USP Class VI compliant.

Food and beverage process development. New flavor, color, and ingredient systems are developed using transparent SK mixers so that the formulator can observe dispersion behavior, color saturation, and any phase separation. The FDA-compliant PP elements and PSU housing combination is the standard selection for food contact. The visual observation eliminates the trial-and-error approach of opaque-mixer development.

CFD model validation and benchmarking. The transparent SK is used as a benchmark for computational fluid dynamics (CFD) models of static mixers. The visual observation of the mixing front provides a direct comparison with the CFD-predicted concentration field, and the residence-time distribution measured by step-input tracer injection provides a quantitative benchmark for the model. This application is most common in academic research groups and in the R&D departments of mixer manufacturers.

Trade-show and demonstration equipment. The transparent SK is widely used in trade-show displays and customer-demonstration equipment because the visual mixing front is highly engaging and immediately communicates the value of static mixing. OEM skid builders and process-equipment manufacturers include a transparent SK on their demonstration skids for this reason.

Quality control and failure diagnosis. When a full-scale metallic mixer in the field is suspected of under-performing, a transparent SK of the same DN and element count can be installed in a parallel test rig to reproduce the problem visually. This is a common diagnostic technique during root-cause failure analysis in food, pharmaceutical, and chemical plants.

Residence-time distribution measurement. The transparent SK, combined with a step-input tracer injection (typically NaCl or food coloring) and a downstream conductivity probe, is the standard laboratory apparatus for measuring residence-time distribution (RTD). The measured RTD curve can be analyzed using the tanks-in-series model to determine the equivalent number of stirred tanks, which is then used to predict the mixer's performance on the full-scale process.

Frequently Asked Questions

Related Products