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The INCREMENT EXTRACTION ERROR
at the plant
The INCREMENT EXTRACTION ERROR
at the plant
Like the INCREMENT DELIMITATION ERROR, the INCREMENT
EXTRACTION ERRORIEE introduces the largest biasesencountered in sampling
The Rule of the Center of Gravity must be respected
All !ragments ha"ing their center o! gra"it# inside the model
e$tended increment belong to the model e$tracted increment
M u s t f a l l o n e i t h e r
s i d e
a t r a n d o m
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Conditions of e!traction correctness
relative to the cutter characteristics
Conditions of e!traction correctness
relative to the cutter characteristics
Conditions li"ely to play an important role
% &traightness o! the cutteredges
' Thickness o! the cutteredges
( &hape o! the cutteredges
) Length o! the cutteropening
* Inclination o! the cutteropening
+ Cutter idth
- Cutter speed
. Depth, capacit# and general design o! the cutter
/ &tream turbulences and stream "elocit#
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#trai$htness of the Cutter Ed$es
#trai$htness of the Cutter Ed$es
C o r r e c t
I n c o r r e c t
0e assume that both cutter edges are
straight and perpendicular to the cutter
tra1ector#
The main condition to !ul!ill is to ensure
that the trailing edge is per!ectl#superposable to the leading edge,
% 2# a translation for strai$ht path
cutters, or
' 2# a rotation for circular path
cutters
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Thic"ness of the Cutter Ed$es
Thic"ness of the Cutter Ed$es
L e a d i n ge d g e
T r a i l i n ge d g e
I n n e r w a l l s
G a i n e df r a g m e n t
L o s tf r a g m e n t
C u t t e r d i r e c t i o n
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#hape of the Cutter Ed$es
#hape of the Cutter Ed$es
I n n e r w a l l s
F r a g m e n t g a i n e d w i t h
d i f f i c u l t y
a s i l y l o s tf r a g m e n t
C u t t e r d i r e c t i o n
T r a i l i n ge d g e
L e a d i n ge d g e
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Ad%ustable cutter ed$es
They may ruin the correctness of thesamplin$ system&
Ad%ustable cutter ed$es
They may ruin the correctness of thesamplin$ system&
C u t t e rt r a " e c t o r y
#ccumulatedmaterial
The leading edge o! a rotating cutter ma# ala#s be dirt#, hile
the trailing edge sta#s clean
Also, ad1ustable plates are rarel# kept per!ectl# s#mmetrical
#d"usta$le%late
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'esi$n of the Cutter Ed$es'esi$n of the Cutter Ed$es
' a d ( e s i g n s
G o o d ( e s i g n
& ) o*
+
+ >
*
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(en$th of the Cutter Openin$(en$th of the Cutter Openin$
- t r e a mI n c r e m e n t
- t r e a m
I n c r e m e n t
L o s t f r a g m e n t
. e c o / e r e d f r a g m e n t
0 r o n g e t r a c t i o n
C o r r e c t e t r a c t i o n
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The secondary stream must be
represented in the sample&
The secondary stream must be
represented in the sample&
- t r e a mI n c r e m e n t
12
1 M a i n s t r e a m2 - e c o n d a r y s t r e a m
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Inclination of the Cutter Openin$
Inclination of the Cutter Openin$
I n c r e m e n t
- t r e a m
- t r e a m
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Cutters should not be vertical&
Cutters should not be vertical&
I n c r e m e n t - t r e a m
- t r e a m
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The cutter should not overflo)&
The cutter should not overflo)&
I n c r e m e n t - t r e a m
- t r e a m
olume of material %resent inside the cutter
Time
Maimum acce%ta$le /olume in cutter
-tream cutting time (ischarge time
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Many cutters are poorly desi$ned&
Many cutters are poorly desi$ned&
I n c r e m e n t - t r e a m
- t r e a m
?
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The cutter must cross a *uiet stream&
The cutter must cross a *uiet stream&
e e d l e
t a n 6
0 o r 6 i n g% l a t f o r m
D i v e r g i n g
c h u t e
3or e$traction correctness to take place, the stream should not
tra"el !aster than + meters,second
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A cross-stream buc"et cutter should not
$et more than .,/ full&
A cross-stream buc"et cutter should not
$et more than .,/ full&
C o r r e c t I n c o r r e c t
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Recommended cutter desi$n for
samplin$ stic"y material
Recommended cutter desi$n for
samplin$ stic"y material
+
*
Y X
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Recommended cutter desi$n
Recommended cutter desi$n
0
4
5
6
7 ' 8
9 e r # h a r d s t e e l ,p e r ! e c t l # s # m m e t r i c a l
c u t t e r b l a d e s
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E!tremely narro) cutter openin$s cannot
)or" properly&
E!tremely narro) cutter openin$s cannot
)or" properly&
A mo"ing cutter opening cannot be smaller than . centimeter
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Cutter )idth re*uirements for e!traction
correctness
Cutter )idth re*uirements for e!traction
correctness
The !olloing rules are based on e$perience and are notuni"ersal
#olids lar$er than 0&/ centimeter
dWW 3) =
W 0
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Cutter )idth re*uirements for very lar$e
flo) rates in floatation plants
Cutter )idth re*uirements for very lar$e
flo) rates in floatation plants
)
1 ) ) )
2 ) ) )
3 ) ) )
4 ) ) )
5 ) ) )
! ) ) )
& ) ) )
, ) ) )
) ) )
1 ) ) ) )
) 1 2 3 4 5 ! & , 1 )
. e c o m m e n d e d c u t t e r o % e n i n g 0 ) i nc e n t i m e t e r
- l u r r y s t r e a m f l o w r a t e
i n m 3 7 h o u r
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Cutter speed re*uirements for the
e!traction correctness of rotatin$samplers
Cutter speed re*uirements for the
e!traction correctness of rotatin$samplers
V 0
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E!traction correctness of riffle splittersE!traction correctness of riffle splitters
Do not !eed ri!!le splitters too !ast
C o r r e c t I n c o r r e c t
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Riffle splitters are easily misused&Riffle splitters are easily misused&