Reactor Overhead Stirrer with Sealed Drive

What is the Reactor Overhead Stirrer with Sealed Drive?

A reactor overhead stirrer with sealed drive pairs a high-torque motor with a hollow shaft or magnetic coupling so it can agitate closed glass or steel reactors under vacuum, pressure or inert atmosphere without leakage along the shaft.

Overview

Closed reactors need a stirrer interface that keeps the vessel sealed. Two solutions are common. A mechanical seal or PTFE bearing around a solid shaft passes rotation through the reactor lid, and a magnetic coupling transmits torque through the lid wall without penetrating it. The drive unit is usually a high-torque overhead motor with speeds from 20 to 1,500 rpm and torque of 50 to 300 N·cm, often with torque display. These drives are used on jacketed glass reactors of 1 to 100 L, pressure reactors and autoclaves, and handle vacuum to a few millibar or positive pressure up to several bar depending on the seal. Materials in contact with the process, such as shaft, impeller and seal, are chosen from PTFE, glass-coated steel or stainless steel 316L for corrosion resistance.

How does it work?

An overhead stirrer mounts on a laboratory stand or clamp above the vessel and transmits rotation through a chuck to a shaft with an impeller. The motor is usually brushless DC or brushed DC, sometimes with a planetary gearbox, and the controller regulates speed using a tachometer or Hall sensor. Because torque equals force times radius and power demand rises with viscosity, stirrer selection is based on torque (N·cm) and viscosity capacity rather than wattage. Many models measure motor current or use a torque sensor to show torque on the display, which helps monitor viscosity changes during reactions such as polymerization. Impeller geometry determines the flow pattern: propeller and pitched-blade impellers give axial flow, anchors and helical ribbons suit viscous media near the wall, and turbines or dissolver discs generate radial shear.

What are the key features?

• Hollow shaft or magnetic coupling for leak-tight agitation
• Suitable for vacuum, pressure and inert gas atmospheres
• High torque with low-speed stability for viscous reaction masses
• Shaft and impeller in PTFE, glass-coated or stainless steel 316L
• Torque display and overload cutoff for process safety
• Mounting flange compatible with standard reactor lids

What are the technical specifications?

A typical reactor overhead stirrer with sealed drive configuration offers speed range of 20–1,500 rpm, max torque of 50–300 N·cm, seal type of PTFE mechanical seal or magnetic coupling, vacuum capability of Down to 5–10 mbar abs, max working pressure of Up to 6 bar (seal dependent) and reactor volume range of 1–100 L. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Reactor Overhead Stirrer with Sealed Drive is used in jacketed glass reactor agitation, reactions under vacuum or inert gas, pressure reactor and autoclave stirring, distillation and crystallization pilot work and polymer synthesis in closed vessels. Across the wider Overhead Stirrers class, laboratories also deploy it for polymer synthesis and resin mixing, coatings and adhesive formulation and pharmaceutical suspension and ointment preparation.

Which standards and certifications apply?

Relevant standards and methods include IEC 61010-1, IEC 61326-1, GB 4793.1, ASTM D2196, ISO 2555 and ISO 9001. Certification candidates for this model are CE, PED for pressure parts and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Mount the stirrer on a rigid stand so the shaft runs concentric with the vessel, and clamp the vessel independently. Always increase speed gradually and use a stirring guard or splash shield. Inspect shafts for bending and wear of the chuck, since imbalance causes vibration and shaft whip. Keep the motor housing away from solvent vapors unless it is approved for the environment. Clean impellers promptly so dried residue does not cross-contaminate. Verify speed and, if fitted, the torque display at intervals using a reference tachometer or torque gauge. Confirm electrical safety to IEC 61010-1 and ensure that the emergency stop or overload cutoff operates correctly.

How do I select the right Reactor Overhead Stirrer with Sealed Drive?

Select a sealed-drive stirrer when the vessel must stay closed, for vacuum, pressure, inert gas or volatile reagents. Choose a magnetic coupling for highest leak-tightness and a mechanical seal for higher torque. State reactor size and type, pressure, vacuum level, temperature, media compatibility and torque need in the RFQ.

How does it compare with other Overhead Stirrers variants?

The decisive parameter is maximum torque at the working speed, together with the viscosity and volume of the fluid. As a rule of thumb, small units of 20 to 60 N·cm cover up to a few liters of medium viscosity, while 100 to 400 N·cm models handle tens of liters or pastes above 50,000 mPa·s. Choose the speed range to suit the impeller: low-speed high-torque for anchor and ribbon, high-speed for dispersion. Check whether the unit measures torque and offers a data interface if process monitoring is needed. For flammable atmospheres or reactor jackets, consider air motors or explosion-protected drives. Also verify chuck capacity, compatibility with stand and clamp, shaft sealing options for reactors, and that the controller protects against overload. Include viscosity range, vessel diameter and target rpm in the inquiry.