HOW-TO
How to Prepare a PAM Solution: Concentration, Mixing and the Mistakes That Cost You
More PAM is wasted in the make-down tank than at the dosing point. A polymer chain that is never fully unwound, or that gets shredded by a too-fast mixer, cannot flocculate no matter how much you dose. Here is the routine we teach every customer.
Target concentration: 0.1 – 0.3%
Prepare the stock solution at 0.1-0.3% by weight (1-3 kg PAM per cubic metre of water). Below 0.05% you are hauling water; above 0.5% the solution becomes so viscous that it pumps poorly and the polymer chains can degrade under transfer shear. For emulsion products, 0.3-0.5% is workable because they disperse faster.
The make-down routine, step by step
- Fill the tank with clean water first. Avoid water with high iron or high hardness if you can - multivalent cations slightly reduce achievable viscosity.
- Start the agitator. Aim for a gentle vortex: 200-400 rpm on a small tank, tip speed under about 3 m/s. A violently splashing mixer destroys polymer.
- Sprinkle the powder slowly and evenly onto the vortex - never dump a bag in. Each grain must wet individually.
- Keep gentle mixing for 40-60 minutes. The solution thickens noticeably as the chains unwind.
- Let it age 30-60 minutes more before first use. Aging is when full viscosity develops; dosing early wastes polymer.
- Transfer with a low-shear pump (progressive cavity or diaphragm). Centrifugal pumps at full speed will shear the solution; if a centrifugal pump is all you have, throttle it and accept the loss.
Secondary dilution at the dosing point
Before PAM meets your stream, dilute the stock down to about 0.05-0.1% inline. Dilute polymer spreads through the flow faster and forms more even flocs. A simple static mixer or an eductor on the carrier water line does the job.
The six classic failures
| Symptom | Likely cause | Fix |
|---|---|---|
| White gel blobs ("fisheyes") in the tank | Powder added too fast or dumped in | Slower addition onto a proper vortex; stir until dissolved |
| Solution never thickens | Mixing time or aging too short | Extend to full 40-60 min plus 30-60 min aging |
| Performance drops after transfer | High-shear pump destroyed the chains | Switch to progressive cavity or diaphragm pump |
| Viscosity varies day to day | Inconsistent make-down concentration | Weigh both polymer and water; keep a log |
| Tank walls slimy, dose creeping up | Dead zones where powder settles | Check agitator position and baffles |
| Anionic and cationic both dosing today | Shared tank or funnel | Two complete, separate make-down systems |
Storage of the prepared solution
Use prepared stock within 1-2 days for best results; viscosity and performance slowly decline as the solution sits, especially in warm rooms. Keep the tank covered to exclude dust and evaporation, and never let prepared PAM freeze.
Frequently asked questions
Can I prepare PAM with warm water to speed it up?
Moderately warm water (20-30 °C) helps dissolution. Do not exceed about 50 °C - high temperature accelerates chain degradation, and hot water can also gel some grades on contact.
How do I know my solution reached full viscosity?
It should feel uniformly slippery, pour in a continuous rope, and show no separate grains. For a 0.2% anionic solution, expect a viscosity of several hundred centipoise at room temperature. If your lab has a viscometer, record day-one values as your benchmark.
Can the same tank serve anionic and cationic products?
Not safely. Traces of one charge react with the other and gel immediately - one uncleaned tank can waste a whole batch. Run two separate make-down systems, or at minimum wash the tank, agitator and pump thoroughly with the change documented.