12 Questions to Ask Before Buying an Industrial Mixer
Ribbon mixer quotations are hard to compare because most of them describe the same three numbers: volume, motor power and RPM — which happen to be the three numbers least predictive of blend quality. Two mixers of the same nominal volume can differ by a factor of three in blend time and by an order of magnitude in discharge segregation.
Put these twelve questions to every supplier on your list, side by side, and the differences become visible immediately. Our answers are printed here so you can hold us to them.
The Twelve Questions
| # | Ask Every Supplier | The QuantumX Answer |
|---|---|---|
| 01 | What is the flight width, as a fraction of agitator diameter? | Stated on the quotation, selected against your material. |
| 02 | What are the inner and outer pitches, and are the two mass flows balanced? | Both stated. Balanced by calculation, not by convention. |
| 03 | What is the radial clearance to the trough wall, and how is it verified? | 3–8 mm by size and particle; recorded at FAT. |
| 04 | What tip speed does the quoted RPM actually produce? | Calculated and printed in m/s, not left as RPM. |
| 05 | What CV will the machine reach on my material, and in how many minutes? | Measured in trial before quotation, written into the order. |
| 06 | How was that CV sampled — how many points, by what method? | Thief probe, 10 points per interval, full curve supplied. |
| 07 | At what fill ratio was that result obtained, and what is the valid window? | Stated at both bounds — 40/70% horizontal, 30/70% vertical. |
| 08 | What Froude number does the scale-up hold from pilot to production? | Fr held constant below 1.0; the basis is disclosed. |
| 09 | How much heat-transfer area per litre, and is it jacket only or shaft and ribbon too? | Quantified; hollow shaft and ribbon add up to 45%. |
| 10 | Is the control loop on jacket temperature or on product temperature? | Product RTDs in the bed; control on the product. |
| 11 | What residual heel remains in the vessel after discharge? | Measured at FAT, not asserted in the datasheet. |
| 12 | Will the production machine be tested against the same criteria as the trial? | Yes. Same tracer method, same acceptance criteria, before shipment. |
Why These Twelve
Questions 1–4: the geometry
Flight width, pitch, clearance and tip speed are the four numbers that set circulation rate, shear and attrition — the actual mixing performance. A supplier who can't state them didn't engineer the agitator to your product; they picked a stock weldment. (Background: how ribbon geometry works.)
Questions 5–8: the evidence
CV, sampling method, fill window and Froude-number scale-up separate measured performance from asserted performance. A trial-derived CV curve with a disclosed sampling method is evidence; "achieves excellent homogeneity" is copywriting. (Background: blend uniformity & CV.)
Questions 9–12: the accountability
Thermal area, product-based control, measured heel and FAT-against-trial-criteria determine whether the machine performs in your plant the way it performed in the lab — and who owns the gap if it doesn't.
A supplier who will commit to these twelve in writing is quoting a process outcome. A supplier who will only quote volume, motor and RPM is quoting a steel fabrication. Both arrive on a truck; only one of them is guaranteed to make your product.
How to Use This in Your RFQ
- Paste the twelve questions into your RFQ as a required response table.
- Score answers: stated with numbers (2), stated qualitatively (1), not answered / "proprietary" (0).
- Weight questions 5 and 12 double — they carry the performance guarantee.
- Disqualify nobody on price until the scores are in. The cheapest quote with a score of 4 is the most expensive machine you can buy.