As discussed in our article How Keestrack Impact Crushers Work, Blow Bars are responsible for approximately 75% of the crushing work done inside the Impactors crushing chamber. So, it’s important for operators to maximise their wear by using the right blow bars.
Common Blow Bar Wear Indicators
Over feeding of the impactor is evident by excessive wear on the outsides of the Blow Bars. Material tends to bank up along the edges causing more wear.
Under feeding will cause material to ‘trickle’ into the center of the Blow Bar causing excessive wear at the center of the Blow Bar.
Grinding, which is combination of over feeding and packing, will produce a sharp burr on the trailing edge of the Blow Bar.
How to spot Blow Bar wear problems
The answer to fixing improper wear from the above examples may seem obvious but requires a little patience and good observation skills. By observing how the impactor is performing, will give an insight into how the crushing chamber and blow bars are wearing.
|Blow Bar Improper Wear||Observable Performance Indicator|
|Over Feeding||Very high rotor loading which results in high engine load as indicated at the PLC.|
|Under Feeding||Patchy main conveyor output and low engine load with some peaks.|
|Grinding||Reduced production & a lot of movement in the apron relief due to material being trapped between the blow bar and apron plate. Engine load may also be high.|
Choosing the right Blow Bar
Martensitic + Ceramic Insert Blow Bars are designed primary crushing of feed materials 0- 500mm in size. Martensite is a hardened type of steel but compared to the other Blow Bars in this list is the softest, making it ideal as a primary crushing bar as it handles large impacts well and resists chipping or fractures.
Medium Chrome FX15 + Ceramic Insert Bow Bars, like all chrome bars is a chrome alloy of chrome carbide in a martensitic ‘matrix’. FX refers to the amount of chrome carbide, 15% for a FX15 bar. These bars are best used with feed sizes up to 250mm in secondary applications or crushing highly abrasive and/or fine materials like asphalt and lime.
High Chrome FX25 + Ceramic Insert Blow Bars feature a high chrome carbide content of 25% in martensite. These bars are best used with feed sizes up to 150mm in secondary applications or crushing highly abrasive and/or fine materials like asphalt and lime.
High Chrome CR26 Blow Bars feature a similar chrome content to FX25 bars but with no ceramic insert, allowing them to crush larger materials whilst still retaining high abrasion resistance. These bars are best used with feed sizes up to 250mm in secondary applications or crushing highly abrasive and/or fine materials like asphalt and lime.
Using the right Blow Bar for your feed results in increased capacity and a higher quality product, saving money on wear parts, and increasing revenue form production. This makes it worth the time to change Blow Bars and keep an eye on crushing performance.