1. Comminution Equipment and
Selection Techniques
Lawrence Novotny
Midwest AOAC
June 6, 2018

2. Hand Tools
mainly used to cut material to be fed into equipment
scissors
clippers
pruning shears
knives
paper cutter
saws
salad choppers

3. Selection Techniques
Selection process is the physical selection of a smaller mass from a larger mass to obtain a subsample or a test portion.
Mass Reduction – selection of a smaller mass from a larger mass
Splitting – division of a mass into 2 or more equal portions

4. (grouping & segregation error)2 = distributional heterogeneity
Selection Techniques
(grouping & segregation error)2 = distributional heterogeneity
number of increments
Technique No. of increments RSD Est max error, %
coning and quartering
should never be used
stationary splitting –
rotary splitting >

5. Stationary or riffle splitting
Selection Techniques
for Flowable Solids
dry ground feeds and forages, grains, oilseeds, mineral mixes, solid fertilizers and dry soils
Rotary splitting
Fractional shoveling
Stationary or riffle splitting

6. Criteria for Selecting Splitters
chute width be 2X the diameter of the largest particle + 5 mm
constructed of inert material
easy to clean
fine powders may have a tendency to stick

7. Rotary Splitter

8. Rotary Splitter

9. Fractional Shoveling

10. Fractional Shoveling Advantages used in lab or field
bo extra equipment
minimal clean-up and decontamination
any number of splits can be generated
Critical
mass of each increment must be consistent
same number of increments in each split

11. Stationary or Riffle Splitters

12. Stationary or Riffle Splitters
operator dependent and must be used properly
gated rifflers are preferable
material must be distributed and fed evenly across the chutes
material is to be fed perpendicularly to the longitudinal axis of the chutes
do not feed to fast to avoid overflowing and clogging of chutes

13. for Nonflowable Solids
Selection Techniques
for Nonflowable Solids
wet soils, semi-moist fertilizers, solid manures meat and food products, slurries
can also be used for flowable solids
1-dimensional slab cake
2-dimensional slab cake

14. 1-dimensional slab cake
create elongated pile as entire sample is poured from container
can be poured in single pass or in back & forth motion
each increment is taken by removing a slice across the entire width & depth of the pile
each increment must be of uniform mass or volume
slab cake can be reformed perpendicular to original slab cake to collect additional increments

15. 1-dimensional slab cake

16. 2-dimensional slab cake
formed by flattening entire sample using a straight edged tool
final shape not critical
uniform depth is critical, < 1 cm
formed with minimal manipulation to avoid segregation of fines
select increments of equal mass from random locations across entire surface of slab cake
try to remove a perfectly vertical column in each increment

17. 2-dimensional slab cake

18. Sampling Tools flat blade spatula rounded scoopula square scoop
bias small particles bias large particles no bias

19. pour out test portion needed or remove single increment by pipet
Selection Techniques for
Single-Phase Liquids without Solids
water, oil, molasses, liquid fertilizer
pour out test portion needed or
remove single increment by pipet

20. Selection Techniques for Multi-Phase Liquids without Solids
whole milk, salad dressing
oil contaminated water
some cases, do thorough mixing, provided phases do not immediately separate (milk)
complete separation of phases; sample each phase as single phase liquid
selection of cylindrical core through entire depth of all phases

21. Selection Techniques for Multi-Phase Liquids without Solids

22. Selection Techniques for Liquids with Solids
water containing sediment, liquid manure
juices containing pulp
mixing does not work since segregation immediately starts when mixing stops
separate solids from liquid (centrifuging or filtering), analyze separately, and combine results mathematically
lab churn

23. Lab Churn

24. Achieve Sample Correctness
Conclusion
Achieve Sample Correctness
reducing particle size thru comminution
selecting numerous increments
using the correct techniques and tools

25. Laboratory Sampling Resources
Questions?