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The INCREMENT DELIMITATION ERROR at the plant

The INCREMENT DELIMITATION ERROR IDE introduces the largest biases encountered in sampling.

x

y

z

1. A sample must be equiprobabilistic.

2. A process stream is always segregated.

3. A process stream is 3-dimensional.

4. But, it is up to us to perform 3-dimensional, 2-dimensional, or 1-dimensional sampling.

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One-dimensional samplingOne-dimensional sampling

F lo w in gs tream

C o n s is ten t s l iceacro ss th e s tream

For accurate metallurgical accounting, it is a must to perform 1-dimensional sampling.

For effective process control, it is recommended to perform 1-dimensional sampling.

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Examples of 3-dimensional sampling

Case #1: Sampling of a railroad car

Examples of 3-dimensional sampling

Case #1: Sampling of a railroad car

Find at least 3 problems.

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Examples of 3-dimensional sampling

Case #2: Sampling a front-loader bucket

Examples of 3-dimensional sampling

Case #2: Sampling a front-loader bucket

Com posite sam ple

S tockp ile

G rab increm ent

Find at least 3 problems.

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Stream SamplingStream Sampling

The entire stream part of the time

Part of the stream all the time

Part of the stream part of the time

There are 3 choices, but only one can be performed correctly.

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Increment Delimitation Correctness:

It does not take fragments into account.

Increment Delimitation Correctness:

It does not take fragments into account.

F lo w in g s tre am

T he w id th of theincre m ent m ust re m ain

c on stan t all the w ayacross the stre am .

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Correct frame positioned on a

Stopped conveyor belt

Correct frame positioned on a

Stopped conveyor belt

S to p p edco n veyo r b e lt

h yd rau licp o sitio n in g

R e fere n c esam p le

This system can provide a good reference sample when performing a bias test.

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Straight-path

Cross-stream Sampler

Straight-path

Cross-stream Sampler

F a llin gs trea m

S a m p lein c rem e n t

S a m p lein c rem e n t

T o p v iew

S tream

C u tte rd ire c tio n

W id th o f c u tke p t c o n s tan t

The cutter must cross the

Stream at constant speed.

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The cutter may get damaged

over time.

The cutter may get damaged

over time.

F a llin gs tre am

S am p lein c rem en t

T o p v iew

S tream

C u tte rd ire c tio n

W id th o f cu tn ot co n s tan t

Careful, systematic maintenance

of the cutter edges is a must.

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The cutter and cutter edges

must be cleaned every working shift.

The cutter and cutter edges

must be cleaned every working shift.

F a llin gs tream

S am p lein c rem en t

T o p v iew

S tream

C u tte rd ire c tio n

W id th o f cu tn ot co n s tan t

The cutter edges must be carefully washed after each cut.

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The Drive System of the cutter

must not be under-designed.

The Drive System of the cutter

must not be under-designed.

S tream

C u tte r d irec tio n W id th o f c u tn o t c o n sta n t

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The Parking Position of the cutter

must be far away from the stream.

The Parking Position of the cutter

must be far away from the stream.

S tream

C u tte r d ire c tio n W id th o f c u tn o t c o n sta n t

The Drive System of the cutter must be electric.

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The Rotating Vezin Sampler The Rotating Vezin Sampler

u 3 d

S a m pleincrem en tS trea m

S trea m

T o p vie w

S tre am

C u tte r d ire c tio n W id th o f c u tk e pt c o n sta n t

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Correctness of a Vezin Sampler Correctness of a Vezin Sampler

C utte r o p ening W

C utte r o p ening w

C ircum ference c

C ircum ference C

ConstantRatio Sampling W

w

C

c

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A common, incorrect Vezin Sampler A common, incorrect Vezin Sampler

S a m pleincrem en tS trea m

T o p vie w

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If part of the stream is missed by the

sampler, a delimitation bias results.

If part of the stream is missed by the

sampler, a delimitation bias results.

F a llin gs tream

S am p lein c rem en t

T o p v iew

S tream

C u tte rd ire c tio n

P a rt o f th es tream is m is s in g

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The cutter must not collect any material

when stopped in a parked position.

The cutter must not collect any material

when stopped in a parked position.

S trea m

A re a a ffe c te d b y a d u s t p ro b le m

S tream

C u tte rd ire c tio n

C o n tam in a tio n

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If only one parked position is available,

the cutter must not return across

the stream too soon.

If only one parked position is available,

the cutter must not return across

the stream too soon.

O nly o ne p a rk ingp o s itio n

S tream

D uring the re turn traje ctory,the re is an are a w he re

noth ing can be take n by the cu tte r.

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Stationary in-stream probes Stationary in-stream probes

S tream

S am ple

S tream

S am ple

S tream

S am ple

The intolerable assumption:

“The stream is not segregated, therefore collecting any part of the stream is good enough.”

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Introduction of a stream turbulence

to minimize segregation across the stream

Introduction of a stream turbulence

to minimize segregation across the stream

S tream

S am ple

Moving from very bad to bad!

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Flushing the probe is a must,

prior to collecting the sample.

Flushing the probe is a must,

prior to collecting the sample.

S tream

S am ple

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Stationary by-stream gate Stationary by-stream gate

S treamS am p lin g p o in t

S am p lein crem en t

T h e fin e m ateria l m o vin g a t th e to p o f th e s tream is n ever sam p led .

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The Grouping and Segregation Error

to the rescue: An attractive alternative

The Grouping and Segregation Error

to the rescue: An attractive alternative

• Dimension X is sampled all the time.

• Dimension Y is completely represented.

• Dimension Z is represented by grouping several increments minimizing the effect of across-the-stream segregation.

Un d er f lo w in d u c in gtu rb u len ce

M ain s treamS am p le s tream go in gto a s im ila r , sm a lle r

sam p lin g s tage

F ive C u tte rs

S uggested sam p ling system fo r p ro cess co ntro l sam p ling o f slur r ie s:T herm o G am m a-M etr ics A nsta t S ystem .

X

YZ

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Across the stream sampling slot Across the stream sampling slot

Exercise: Find what is wrong with this sampling system.

S tream

S am p leinc rem ent

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Stabilizing the flow rate of the stream

Prior to the on-line analyzer

Stabilizing the flow rate of the stream

Prior to the on-line analyzer

O n -lin ea n a ly z e r

S tre a m

S tre a m

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Exercise:

What is basically wrong

with a flap sampler?

Exercise:

What is basically wrong

with a flap sampler?

S tre a m S a m p lein c re m e n t

1

2

C losed , id leposition

O pened, id leposition

F alling stre am

1 2

T h e w id th o f th e in c re m e n ta c ro ss th e s tre a m

is n ot k e p t c o n sta n t.

S tre a m

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Most stream diversion systems lead

to an increment delimitation bias.

Most stream diversion systems lead

to an increment delimitation bias.

S tre a m

S a m p lein c re m e n t

S tre a m

S a m p lein c re m e n t

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Exercise:

What is basically wrong

with this hose sampler?

Exercise:

What is basically wrong

with this hose sampler?

H o se tra je c to ry

F all in gs tream

1

2

S tre a m S am p lein c re m en t

1

2

T h e w id th o f th e in c re m e n ta c ro ss th e s tre a m

is n ot ke p t co n s tan t.

S tre a m

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Exercise:

Why is this hose sampler correct?

Exercise:

Why is this hose sampler correct?

H o se tra je c to ry

F allin gs tream

1

2

S tre a m

S am p lein c rem en t

1

2

T h e w id th o f th e in c re m e n ta c ro ss th e s tre a mis k ep t co n s tan t.

S tre a m

S id e view o f th e cu tte r T o p view o f th e cu tte r

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Exercise:

Is the shape of the stream relevant?

Exercise:

Is the shape of the stream relevant?