Impact Crusher Blow Bars
A comprehensive blow bar selection guide to maximize your crushing profits!
Impact crusher blow bars (also called hammers) are the main wear item of horizontal shaft impact crushers and a major cost driver. The purpose of blow bars is to strike material entering the crushing chamber and throwing it against the impact wall causing the material to fracture into smaller particles (see also: how does an impact crusher work). In the process of striking the material blow bars wear out and need to be replaced. They are made out of cast steel with various metallurgical ingrediants optimized for a specific applications. Selecting blow bars that match your application is crucial for achieving a long wear life.
Blow bars are manufactured in foundries- where they are cast to the manufactureres shape and metallugical specifications. While the crusher hammer shape can be easily copied the metallurgical composition is the actual secret ingredient.
Cast iron martensic hammers with ceramic inlays. While the martensitic alloy provides impact resistance the ceramic inlays improve abrasion resistance. This combination makes them ideal for concrete recycling and primary crushing applications.
High chrome blow bars are used for abrasive applications such as asphalt crushing or natural rock. They tend to be more brittal than martensitic ceramic hammers and thus could crack when impacting uncrushable contaminants (e.g. milling teeth, drilling bits, rebar, tramp iron, aso). This could also mean to maintain a smaller feed size to reduce the risk of breakage.
Similar to the high chrome hammers these feature a longer wear life because of the ceramic inlays. As with any chrome bar, they do no perform well in applications with tramp metal or large feed sizes, but they are effective in highly abrasive applications. For this reason, chrome ceramic blow bars are often used in secondary and tertiary crushing including asphalt crushing applications.
Your blow bar wear life depends on the feed material chracteristics, crusher settings, and your overall crusher operation.
|Rotor speed||Wear||Fines||Oversize material|
|Low||less wear||less fines||more oversize|
|High||more wear||more fines||less oversize|
The way how you run your impact crusher affects your wear life greatly.
A rotor has either 3 or 4 blow bars. In case of a 4-bar rotor you can either run 4 tall hammers, or 2 tall and 2 short. Generally speaking, 4 tall hammers work best in a tertiary crushing application with a homogenous small infeed material. In all other applications, 2 tall and 2 short hammers work best. The short hammers (also dummy hammers) have no function other than protecting the rotor body from damage. They also don't wear as fast as its long counterparts.