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Sep 16, 2021

Service Tip - Replacement of blow bars on a NP impact crusher

A blow bar replacement on a NP impact crusher needs to be executed in a correct way in order to avoid damages on your crusher. Here are few rules to ensure that your NP is running properly.

Wear limit for blow bar replacement


The blow bars on a NP impact crusher are reversible. When one side is worn out, the blow bar can be rotated so that the other side can be used.

To avoid any damage due to wear, the wear limit indicated by the letter D on below draft should be lower than the values shown in the table hereunder.



Be carefull with rotor balancing


During a blow bar replacement operation, it is important to maintain rotor balancing. The two heavier blow bars have to be assembled in opposition (180°).

Note that the weight is always indicated on the blow bars.

In case of doubt, blow bars have to be weighted. A 2% mass difference between opposed blow bars is acceptable. If this value is exceeded, vibrations can appear and damage the bearings or the structure on the long term.

Our + advice


When replacing blow bars, fixing wedges have to be cleaned and checked. If these are worn, a replacement is mandatory, as some gaps can appear with new blow bars which can create a blow bar breakage or crusher break down. Pretty sure these are things you want avoid!

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