Set the purchase boundary
A DAF offer should be evaluated for flotation duty, not accepted solely because the polymer settles solids well. The feed chemistry, bubble-contact stage and float removal conditions belong in the purchase specification.
Identify the proposed commercial grade and the operating condition that must be demonstrated before an order is released.
Identify the chemical role
Document coagulant, pH adjustment, feed variability and the proposed polymer addition point. Establish whether the purchase replaces the flocculant only or changes a wider treatment program. The clarification and DAF guide distinguishes the separator endpoints.
Avoid comparing a candidate under one coagulant sequence with an incumbent under another unless the intended decision explicitly includes that process change.
Use a relevant screen
Prepare the emulsion consistently and use a flotation test that reflects the decision where available. Record outlet turbidity or suspended solids, float formation, stability and handling. A settling jar can narrow chemistry questions but cannot by itself demonstrate DAF attachment and skimming performance.
Keep the dose basis and elapsed times visible. If only a settling screen is available, mark production flotation acceptance as outstanding.
Approve under stable plant conditions
Bracket active dose after stabilization while recording hydraulic loading, recycle operation, feed and skimming. Verify actual activation and injection before blaming an apparent chemistry failure. Link the accepted result to the product code, preparation and commercial consumption.
Include float removal and downstream handling in the decision; meeting outlet quality for a brief period while accumulating an unmanageable float is not complete acceptance.
Check the difficult case
If a candidate produces rapid settling in a jar but weak or unstable float in the DAF, the earlier result has not been disproved; it answered a different separator question. Keep those two evidence sets separate when deciding whether to purchase.
Keep unresolved limitations in the qualification record instead of presenting a proposed benefit as an established operating result.
Record the acceptance evidence
| Check | Evidence | Decision |
|---|---|---|
| Sequence | Coagulant and addition record | Comparable chemical role |
| Flotation | Float and outlet measurements | DAF-specific evidence |
| Operation | Stable loading and removal | Accepted result sustainable |
Retain the sample code, lot, preparation method and measured feed with the purchasing decision. Compare subsequent deliveries with that record, using the same test conditions wherever practicable.
Request a scoped offer
Send feed and upstream chemistry, DAF configuration, current polymer, preparation system, trial capability and target outlet measurement. State float-handling constraints and expected monthly use before requesting a grade and delivered offer.
Send the evidence through the sample and quotation form. Review packaging and lot controls with Gongyi Xinqi Polymer Co., Ltd., and confirm grade availability and order terms before committing.