Equipment
How process equipment works, from the basics to plant-level detail. Tap a card to open it.
Instrumentation
Sensors, transmitters, valves and safety devices, shown using ISA 5.1-inspired instrumentation symbols and tag conventions.
How to read instrument symbols and tags (ISA 5.1-inspired)
The bubble tells you where the instrument is. The letters tell you what it measures and what it does. The number identifies the loop.
Tag decoder. Type a tag such as LIC-201, PDT-105 or TSHH-310:
Letter table (common letters)
Agitators
How each impeller moves liquid, which flow regime it works in, and how to choose one. Tap a card for details.
Impeller types
Which agitator for which job?
| Duty | Usual first choice | Notes |
|---|---|---|
| Blending thin liquids | Hydrofoil, pitched-blade turbine; propeller in small tanks | Axial flow gives the most turnover per kW. |
| Suspending solids | Pitched-blade turbine (down-pumping), hydrofoil | Low off-bottom clearance; check the just-suspended speed (Njs). |
| Dispersing gas | Rushton or concave-blade (Smith) turbine; gas-inducing impeller for dead-end hydrogenation | Check gassed power and flooding. |
| Liquid-liquid dispersion | Rushton or pitched-blade turbine; rotor-stator for fine emulsions | Droplet size depends on tip speed and power per volume. |
| Heat transfer in viscous batches | Anchor or gate, often with scrapers | Wall sweeping renews the film at the jacket. |
| Very viscous blending | Helical ribbon | Laminar flow; size the drive for high torque. |
| Powder wetting and dispersion | Sawtooth disperser, rotor-stator | Set by tip speed; add a slow agitator for bulk flow. |
| Shear-sensitive crystals or cells | Hydrofoil or pitched-blade at modest tip speed | Avoid high-shear impellers. |
| Filtering, washing and drying in one vessel | ANFD agitator (Nutsche blades) | Lower the blades in steps; the drive is sized on torque. |
| Glass-lined reactors | Retreat-curve impeller with its baffle | Glass-lined turbine and pitched-blade versions also exist. |
Agitation basics
Flow patterns
Radial impellers throw liquid out to the wall in two loops. Axial impellers pump along the shaft in one loop. Close-clearance agitators move liquid around the vessel near the wall.
Baffles
In thin liquids, four wall baffles of about one tenth to one twelfth of the tank diameter stop swirl and vortexing. Close-clearance agitators in viscous, laminar batches usually run without baffles. Glass-lined vessels use one or two finger or beavertail baffles.
Power
Turbulent, baffled: P = Np × ρ × N³ × D⁵. Laminar: P = Kp × μ × N² × D³. Doubling the speed in turbulent flow needs about eight times the power.
Scale-up
Keep power per volume constant for dispersion and mass transfer, tip speed for shear-sensitive products, and check the just-suspended speed for solids. Blend time usually gets longer at larger scale. Try the Mixing / Scale-up Calculator.
Clearance and liquid height
A single impeller often sits about one third of the tank diameter off the bottom. Tall batches (liquid height well above the tank diameter) usually need two or more impellers on the shaft.
Compare them live
See flow patterns, blending and solids suspension side by side in the Agitator Simulator.
Flow regime calculator
Enter the impeller, speed and liquid. The Reynolds number tells you whether the flow is laminar, transitional or turbulent.