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Presentation TitleSeptember 23, 2016
Table of Contents
2
• Intro• Machine mantainance• Blow bar design and alloy
selection• Machine design• Operation of machine
3
Breakage
• Customer says defective bar
• Manufacturer says steel must have gone through the machine
What else can happen?
• Foreign objects enter the machine (steel bucket teeth, etc)
• Voids occur in castings when produced, etc.
• Wrong alloy selected for feed size,material or machine design
• Poor fit of blow bar to rotor due to design of bar or rotor
• Rotor in need of repair not supporting blow bar properly
• Etc.
INTRO
Here are a series of questionsto evaluate the conditions of wear or breakage.
Blow bar breakage & poor
performance
A rotor in poor condition A rotor in poor condition
This rotor in good condition This rotor in good condition
4
Machine & Site Conditions
• Is machine set level on the ground?
• Are there excess vibrations?
• Is there water logged or rotten cribbing, etc.
Balance of Rotor
• Are bars all the same weight and alloy? (different alloys wear at
different rates, so bars that start at same weights can become
mis-matched after use)
• Poor hard facing application adds weight unevenly
• Are bars of similar weight opposite each other on a 4 bar rotor?
Let rotor roll to find heaviest station, then install lightest blow
bar (if available) at that station
• What is the condition of the shaft, is it cracked or bent (check for
runout or bad bearings)
MACHINE MAINTENENCE
Worn out wedges being improperly secured
Nuts were being driven under wedges
5
MACHINE MAINTENENCE
Wedges (Lack of proper blow bar
support)
• Are wedges tightened properly, what is the
condition of the wedges?
• Are they being checked periodically for tightness,
especially after initial installation?
Image 1 & 2
Here is an example of wedges not being used
properly; user was forcing old nuts/bolts under
wedges to push them up instead of jacking bolts/ set
screws. These wedges need to be replaced with new
ones !
Image 3
Another example of breakage due to insufficient
support of the blow bar. Notice how the wedge &
rotor is worn down so it only contacts the bar
properly at the bottom.
1
2 3
6
MACHINE MAINTENENCE
Question #1
Has the customer or previous machine owner
modified the machine at all, especially to how the bars
fit?
Question #2
After a rotor rebuild, make sure dimensions of built up
partds are correct (CRD exp.)
Question #3
Sometimes customers take a rotor from one machine
and install it on a chassis from a different machine,
what was intended purpose of the rotor?
Question #4
Are they running the rotor at proper speeds? See rotor
penetration.
Question #5
Are the locking rods worn or have they been replaced with
improper parts?
Machine modifications for
a better world.
Machine Modifications
7
MACHINE MAINTENENCE
Bar with excellent machining No machining
Fact #1
Poor alloy selection (Example: Medium chrome used to crush
everything)
Fact #2
Review Amcast alloy selection chart and understand the A, B &C
ratings
A. = EXCELLENT 4” or thicker blow bar with no or shallow grooves
in the bar to locate blow bar. Ideally with a nose to locate the
blow bar
B. = AVERAGE 4” blow bar with minimal groove to locate blow bar
C. = POOR less than 4” thick blow bar, or multiple grooves to locate
the blow bar
Fact #3Work to be done (Pietro Fines/brick/canyon effect)
Fact #4Geometry of blow bar (see images next page)
Fact #5Thickness of blow bar
Fact #6Shape of blow bar (are there deep pocket in the bars ?)
Fact #7Poor fit of blow bars to the machine, are the bars machined where
they touch rotor?
Image #1
An image of well machined blow bars from Am Cast.
Image #2
A competitors blow bar, notice there is little or no machining left
and right of the ridge. In most cases, blow bars should be machined
where they contact rotor (or should at least be flat and straight).
Notice the gaps under the straight edge showing light.
This does not support the blow bar properly and can lead to
breakage!
Blow Bar Design & Alloy
Selection
1 2
8
“C” poor shape (Average 4” thickness
blow bar with 3 deep grooves)
“C” poor shape (Less that average thickness blow bar 3.4” with a
single deep groove)
“C” poor shape (Less that average thickness blow bar 3.4” with
a single deep groove)
MACHINE MAINTENENCEBlow Bar Design & Alloy
Selection
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Rotor Penetration
• Too much can cause breakage, Also causes rotor to wear.
• Too much can cause more face impact on blow bar
• Too little can cause material rejection (material coming back out
of feed opening)
• Penetration can sometimes be adjusted on the machine, if not
then changes to feed should be considered.
2 bars vs. 4 bars
Running two new bars with two “dummy” bars allows more rotor
penetration allowing more face impact. Since the distance between
bars is greater, more material can be feed into machine before next
blow bar can make an impact. Running 2 bars instead of 4 bars can
cause excessive rotor penetration, which leads to more impact on
the blow bars and possible rotor wear & breakage. Rotor speed is
important when going 4-2 or 2-4
Expectation of Machine
Is the machine being used it the way it was designed for, or being
expected to accomplish tasks it is not meant to handle?
• Example: Secondary Crusher used as a Primary
• Example: is crusher being used to take large material down to
small finished product in one pass? Consider other options to get
your final product. size the material so the crusher can work
efficiently.
• Example: Trying to get more production out of a machine than
it was designed for can cause breakage issues along with wear
issues (recirculation of oversize material)
• (To get out 100 tons it needs to process 150 tons for example)
Image #2This is a picture of an excellent machine for secondary crushing
applications, but it is not adequate enough to handle tough primary
applications. Even with the use of proper blow bar alloys, this machine
would never properly support a bar for primary applications. (Note the
thickness of rotor wings
MACHINE DESIGN
1 2
10
Fact #1
Due to rotor only having 3 “wings” & the center one
being offset, the blow bar does not get enough
support. A blow bar of this length normally has 4-5
heavier rotor wings.
Fact #2
Bar also has a lifting hole in the center, (that can be
filled in with pattern change to increase strength) This
is a secondary type rotor, so we cannot apply alloy
selection just based on material being crushed, we
have to take the machine’s design into consideration.
Fact #3
We cannot use our normal application of alloys in this
case, we must use alloys that are tougher rather than
applying alloys that last longer.
Fact #4
We cannot use our normal application of alloys in this
case, we must use alloys that are tougher rather than
applying alloys that last longer.
Fact #5
We should move away from F60WRI and try F60
,F6045HRC, manganese instead for recycling
Fact #6
For the Secondary application, where we would normally
offer FX25WRI, instead we should try FX25 or F60WRI. In
other words we need to move “down” the alloy
application chart.
MACHINE DESIGN
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Preparation of material to be crushed
• Is steel being removed?
• A jaw crusher is better in some applications
• Is a pulverizer being used first?
• What is the material size and hardness ?
Apron settings
a good starting point is OEM A,B,C & D settings see
below (better image neede) Choking the impactor
with tight settings can cause breakage and excessive
wear.
OPERATION OF A CRUSHER
Material Input
• What is the feed size of the material being fed?
• Feed rate of material (is the customer pushing the
machine limits to get higher output values)?
• Is recirculation of oversize being fed to one side of
rotor causing cupping then breakage? Solution
could be to introduce the recirculation further back
in the feed so it can mix in better
• Manufactures manuals may provide guidelines for
feed size and production that are for “perfect
scenarios,” which do not apply to your specific
application.
• Talk to people in region with similar applications,
and/or with the same machine & material
12
Question #1
• Are there a lot of fines or moisture mixed in with
the material being crushed?
Question #2
• Is the customer using the proper alloy selection?
Question #3
• Are the grizzly bars clogged or has the customer
covered them over with steel plate?
Question #4
• Are the worn out side liners protecting the sides of
bars
Question #5
• Are the aprons worn? Or unevenly worn? This may
cause material to spend excessive time in the
crushing chamber or cause it to be re-circulated
because of its oversize.
POOR WEAR PERFORMANCE
Question #6
• Is there clearance between the blow bars and
aprons in the apron adjustment settings?
Question #7
• Hat is the material input?
Question #8
• What is the feed size of the material being fed?
Question #9
• Feed rate of material (is the customer pushing the
machine limits to get higher output values)?
Question #10
• Is recirculation of oversize being fed to one side of
rotor causing cupping then breakage? Solution
could be to introduce the recirculation further back
in the feed so it can mix in better.
Question #11
• Does your specific application apply to the
guidelines for feed size and production that are for
“perfect scenarios,” in the manufactures manuals?
Question #12
• Talk to people in region with similar applications,
and/or with the same machine & material?
13
DELIVERY OF MATERIAL TO ROTOR
• Feed opening design is very important in the
delivery of material towards the rotor.
Variations in the angles and distances between
blow bars and feed chute from machine to
machine causes machine specific results and
consequences.
• Some machines allow adjustment of feed angle
to change to the way material approaches the
blow bars. (rotor penetration)
Is material being delivered above, below or at the
rotor center line, this varies from machine to
machine, but has a big impact on the machines
performance
1
2
OPERATIONOF A CRUSHER
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OPERATIONOF A CRUSHER
Photos A and B
show a modified hopper; covering the grizzly bars is a
common practice, not allowing fines to drop out, fines
instead going to crushing chamber. Clearly this
hopper floor needs maintenance; a neglected hopper
floor leads to poor and uneven wear of blow bars.
A B
Photo C
Below is an example of wear in middle of the bar that
was eventually corrected by repairing the feed chute.
(Feed chute was worn in middle, so most of the
material was dropping down on the center of the bars
first).
C
15
Image #1
This is another example of how wet material can create a sludge
buildup of fines in the corners of the feeder floor and chute liners,
which can lead to uneven wear on the blow bars.
Image #2
The sludge buildup shown in the right corner of the hopper
continues down the feeder chute and is the cause of uneven wear
focused on the right side of all 4 blow bars (bottom right). This
photo also demonstrates a machine that is out of balance.
OPERATIONOF A CRUSHERPoor Wear Performance Caused by Wet
Slurry Buildup
Generally, if there is “Odd” wear
on all bars in a rotor, it is a FEED
ISSUE.
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34 Aero Road, Bohemia New York 11716Toll Free: 888-993-2772Local: 631-750-1644Fax: 631-750-1646
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