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Presentation TitleSeptember 23, 2016

Table of Contents

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• Intro• Machine mantainance• Blow bar design and alloy

selection• Machine design• Operation of machine

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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

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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

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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.

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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

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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

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“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

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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

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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?

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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

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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

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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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Am Cast WestTim Conklin - Branch Manager2303 West Oxford Ave, Sheridan, Colorado 80110Telephone: 303-761-6333Fax: 303-762-6151

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