A quotation is only as specific as the brief behind it. When a request arrives as "quote a 500 L mixer for our powder", the honest answer is a catalogue page — because 500 L means nothing without knowing whether the powder weighs 0.3 or 1.8 kg/L, or whether it clumps. Five items fix that entirely.
The five essentials
| Item | Unit | What it changes on the machine |
|---|---|---|
| Loose bulk density | kg/L | Working volume, impeller diameter, motor power, discharge type |
| Moisture content | % | Whether you need breaking action (plough) or only circulating action |
| Batch weight | kg per batch | Working volume once density is applied, and the fill level it implies |
| Required uniformity | e.g. CV% or blend time | Impeller form, speed and whether a pre-mix or grind is needed |
| Cleaning standard | text | Steel grade, shaft sealing, surface finish, discharge containment |
Two useful additions if you have them: target cycle time and pack format. Neither is essential to select the mixer, but both affect the discharge and the downstream specification, and having them saves a round of clarification.
If you do not know the bulk density
This is the item we most often have to chase, and it is genuinely easy to measure on site in about ten minutes.
- Take a container of known volume — a calibrated one-litre measuring jug is ideal.
- Fill it level from the middle of the batch, not scooped from the top of a heap. Sampling from the top of a heap is the most common error and gives a materially wrong figure.
- Tap the container lightly on a bench to settle the powder and remove trapped air.
- Weigh the filled container and subtract the empty container weight.
- Divide mass in kg by volume in litres. That is your loose bulk density in kg/L.
- Repeat twice with fresh samples.
Loose versus tapped density
Loose and lightly tapped density can differ by ten percent or more, particularly for fluffy powders. State clearly which one you measured and whether it was tapped. We will size against the figure you give, so labelling it honestly is more useful than guessing.
Describing the uniformity you need
"Good mixing" is not a specification. Three practical levels are enough to work from, and you may already have a figure in your own quality documentation.
- General blend — visually even, no specification limit. Suitable for feed, agricultural or construction powders where appearance rather than assay governs.
- Specification blend — a defined assay or active-content tolerance per batch. This drives impeller selection and often cycle time validation, and it is the usual requirement for food, chemical and battery applications.
- Low-microvariation blend — a tight coefficient of variation, typically for pharmaceutical or high-value active materials. Usually demands a gentler, higher-turnover geometry rather than a more aggressive one.
If you have a target figure already, use it. If not, tell us the application and we will tell you what is normally achievable rather than leaving you to find out later.
Naming the cleaning standard
Cleaning standard is the item most often omitted, and it is the one that cannot be added after delivery without rebuilding the machine. Four levels are common in our work:
| Standard | What it requires | Typical use |
|---|---|---|
| Industrial clean-down | Sealed bearings, smooth contact surfaces, accessible vessel | Construction, minerals, general chemical |
| Wash-down / hygienic design | Food-grade stainless, polished surfaces, full disassembly, CIP-capable piping | Food, beverage, nutrition, cosmetics |
| Pharmaceutical / GMP | Documented surface finish, validated disassembly, controlled cleaning regime | APIs, pharmaceutical intermediates |
| Contained / dust-tight | Sealed discharge, dust collection at outlet, closed transfer path | Dyes, pigments, fine chemicals, battery materials |
These pull in different directions
A hygienic design and a contained design are not the same machine in different finishes. Hygienic specification prioritises cleanability of wetted surfaces; containment prioritises keeping powder inside. If your application needs both, say so at the specification stage — it is achievable, but it has to be designed in.
Hazardous materials and safety data
For flammable, corrosive, toxic or otherwise hazardous powders, include the safety data sheet. It determines material of construction, seal specification and whether any explosion-protection requirement applies — all of which affect the machine fundamentally rather than decoratively.
For ordinary food, feed or mineral powders the data sheet is not needed for a quotation, though it is useful if you are specifying food-grade construction and want to confirm the powder's classification.
A brief you can copy
Minimum viable brief
Material: ______
Loose bulk density: ______ kg/L (loose / tapped)
Moisture content: ______ %
Batch weight: ______ kg
Required uniformity: ______
Cleaning standard: ______
Target cycle time: ______
Pack format: ______
Current process and what is failing: ______
That last line is worth including even when you are buying a new machine rather than replacing a failing one. Knowing what the existing process does badly is often the most informative part of the brief, and it frequently changes what we propose.
Brief questions
What information does a mixer supplier actually need to quote accurately?
Five things: loose bulk density in kg/L, moisture content percentage, batch weight, the blend uniformity you need to hold, and the cleaning standard. Target cycle time and pack format are helpful additions. With the five essentials we can specify a machine type and working volume rather than send a catalogue page.
How do I measure bulk density if I do not have the figure?
Take a calibrated container of known volume, fill it level from the middle of the batch rather than from the top of a heap, tap it lightly to settle the powder and weigh it. Divide the mass in kilograms by the volume in litres. Repeat twice with fresh samples, as loose and lightly tapped density can differ by ten percent or more.
Do I need to provide the material safety data sheet?
For flammable, corrosive, toxic or otherwise hazardous powders, yes — the data sheet determines material of construction, sealing and any explosion-protection requirements. For ordinary food, feed or mineral powders it is not needed for a quotation, though it is useful if the application is food grade.
Send the brief
Fill in the five essentials and we will come back with a specific machine type, working volume and motor sizing — not a catalogue page.