Manual or automatic polymer make-up?
Batch tanks, eductors and automatic three-chamber units compared, with the practices that keep solution consistent in either case.
Why make-up matters
A good grade can still perform badly if it is poorly dissolved. Lumps, "fish-eyes" and under-aged solution all waste polymer and give uneven flocs.
Manual batch tank
A tank with a slow stirrer, filled with water and dosed by hand. It costs little and suits small plants that use a few kilograms a day. Its weak points are operator variation and powder clumping when it is tipped in too fast.
Adding an eductor or wetting cone
A water-driven eductor or wetting cone wets each granule as it goes in, which almost removes lumps. It is an inexpensive upgrade for any manual tank.
Automatic make-up units
Three-chamber units dose powder and water automatically, then pass the solution through mixing, ageing and dosing compartments. They give steady strength around the clock and suit larger plants, dewatering lines and sites with little operator time.
Practices that apply to both
Make up at 0.1 to 0.5 percent, within the grade's maximum use concentration. Sprinkle granules into the vortex, never in a heap. Let the solution mix gently for 45 to 60 minutes before dosing. Use it within a day, and keep the stirrer slow to avoid shearing the chains.
Choosing
Below a few kilograms a day, a manual tank with an eductor is usually enough. For continuous use, round-the-clock dewatering or several dosing points, an automatic unit soon pays for itself in consistency.
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