The IPS2050-20 OS-20L is Benchmark Industrial's 20-liter capacity overhead stirrer — a high-torque, microprocessor-controlled mixing instrument for low and medium viscosity samples in vessels up to 24 inches tall. Where magnetic stirrers cap out at small-vessel low-viscosity mixing, overhead stirrers handle the workflow that mid-scale industrial, pharmaceutical, food-science, and process-development labs need: direct mechanical agitation via a propeller or paddle on a feed-through chuck, with torque sufficient to keep liquid moving even as viscosity rises through the mix cycle. The OS-20L ships with complete stand assembly + mounting hardware plus a 4-arm stainless steel propeller (IPS2050-P-S4) — unlike most overhead-stirrer SKUs from competing brands, this is a complete operating setup out of the box, not a head-only purchase requiring separate stand procurement.
Voltage options: This unit can be ordered with European voltage requirements (230V/50Hz). Contact us to order.
Key Specifications
| Mixing capacity (water-equivalent) | 20 L |
| Maximum viscosity | 10,000 mPa·s |
| Maximum torque | 40 Ncm |
| Speed range | 30 – 2,200 rpm |
| Motor type | DC Brushless |
| Input power | 60 W |
| Output power | 50 W |
| Net weight (mixer head) | 2.6 kg |
| Maximum vessel height | 24 inches |
| Voltage | 100 to 240 V (universal); 50/60 Hz |
| Display | LCD control panel; speed and run time set + monitored |
| Included | OS-20L mixer head + complete stand assembly + mounting hardware + 4-arm stainless steel propeller (IPS2050-P-S4) |
Application Profile
Pharmaceutical formulation pilot lines. Aqueous and aqueous-organic suspension mixing for formulation-development and small-batch pilot work — the 20 L capacity and 10,000 mPa·s viscosity ceiling cover most semi-solid and emulsion formulations.
Food-science and beverage development. Solution preparation, suspension, and re-suspension at the 5–20 L scale typical of beverage R&D and food-formulation labs.
Cosmetic and personal-care formulation. Cream, lotion, gel, and surfactant-system mixing in development-scale batches; the choice of propeller (4-arm or paddle, stainless or Teflon) covers the chemical-compatibility range typical of personal-care formulations.
Industrial-process suspension prep. Pre-mix preparation for process feed streams where the operator needs to suspend particulates in a carrier fluid before downstream pumping or processing.
Aqueous reaction agitation. Lab-scale chemistry reactions in 5–20 L vessels where uniform agitation throughout the reaction time is required — the high-torque DC brushless motor maintains set speed even as reaction viscosity changes.
Brewing / fermentation pilot work. Wort mixing, fermentation prep, and ingredient-suspension steps at the pilot-batch scale before scale-up to production fermenters.
Design Architecture
DC brushless motor at 60 W input / 50 W output. No brush wear; designed for daily institutional duty. The DC brushless architecture provides smooth speed control across the 30–2,200 rpm range without the cogging or speed-drop-under-load that brushed-motor mixers exhibit.
40 Ncm maximum torque. Sufficient for the 10,000 mPa·s maximum viscosity spec — meaningfully higher than typical magnetic-stirrer torque, lower than the 60 Ncm of the larger OS-40L (IPS2050-40). For viscosities above 10,000 mPa·s, step up to the OS-40L.
Microprocessor-controlled speed regulation. Speed and run time set + monitored via the LCD; the microprocessor maintains set speed under variable load (rising viscosity, vessel-shape variation, propeller-depth changes during the mix cycle).
Sensor-based shutdown protection. The mixer monitors load; if the propeller hits a high-viscosity blockage or mechanical obstruction, the drive shuts down before motor damage. Splash cover protects the connection mechanism from corrosion.
Feed-through chuck for accessory shafts. Tool-less tightening and loosening — the chuck holds the propeller / paddle shaft firmly without requiring a wrench, supporting fast accessory swaps between protocols.
Complete stand assembly included. The mixer ships with a support stand and mounting hardware that securely attaches the head to the stand for compatibility with vessels up to 24 inches tall. Most competing overhead-stirrer SKUs require separate stand procurement — Benchmark Industrial bundles it.
LCD control panel. Speed, run time, and operating mode displayed; programming via panel buttons.
Compact and quiet operation. Designed for shared lab use; lower noise than competing overhead-stirrer brands at equivalent torque rating.
Frequently Asked Questions
What viscosity and capacity does the OS-20L handle? Up to 10,000 mPa·s in a 20 L water-equivalent vessel, covering most semi-solid and emulsion formulations.
What is the maximum torque and speed range? 40 Ncm maximum torque across a 30–2,200 rpm speed range, from a 60 W-input / 50 W-output DC brushless motor.
Does it include a stand? Yes. Unlike most competing head-only SKUs, the OS-20L ships as a complete operating setup with a stand assembly, mounting hardware, and a 4-arm stainless steel propeller (IPS2050-P-S4).
When should I step up to the OS-40L instead? For viscosities above 10,000 mPa·s or vessels above 20 L water-equivalent, the OS-40L (60 Ncm torque, 120 W input) is the right spec.
What size vessel does it accommodate? Vessels up to 24 inches tall.
Ordering & Configuration
Standard configuration. This is a complete operating setup out of the box: the OS-20L mixer head (60 W DC brushless, 40 Ncm torque, 30–2,200 rpm), a complete stand assembly with mounting hardware, a 4-arm stainless steel propeller (IPS2050-P-S4, also sold separately), an LCD control panel, a 100–240 V US power cord, and the operator's manual.
Optional propellers and paddles (sold separately):
- IPS2050-P-S1 / -S2 / -S3 / -S4 — Stainless steel propellers (4 styles for varying mixing-pattern needs; -S4 is the included default)
- IPS2050-P-T1 / -T2 / -T3 / -T4 — Teflon propellers (chemical-resistance for aggressive solvents; -T2 is centrifugal impeller, -T1 is one-line, -T3 is paddle with flat holes, -T4 is 4-arm)
Voltage variants. This SKU is the US-plug configuration; 115 V or 230 V is available by special order.
Family alternative. The IPS2050-40 OS-40L (40 L capacity, 50,000 mPa·s viscosity ceiling, 60 Ncm torque, 120 W input) is the right pick for higher-viscosity or larger-volume work.
Use the quote request to specify: voltage and plug type, propeller / paddle accessory selection per intended sample chemistry (Teflon for aggressive solvents, stainless for general-purpose), training, and lead time.
Warranty: Manufacturer's standard Benchmark Industrial warranty applies.
OS-20L vs OS-40L selection: the OS-20L (this product) covers 20 L water-equivalent at 10,000 mPa·s viscosity ceiling. The OS-40L covers 40 L at 50,000 mPa·s viscosity ceiling — meaningful step-up for viscous formulations or larger vessel sizes. For occasional small-vessel low-viscosity mixing, a magnetic stirrer (e.g., the IPS7101 series) at lower price point may be sufficient.
