Problems with crusher foot bolts

This is an article on the fracture of anchor bolts and corresponding solutions; there are many such articles in journals, and you can ask friends who are able to download them for free to obtain some of them in order to solve the problem. http://www.infocement.com/jishu/Print.asp?ArticleID=3112

It is first necessary to determine the reason for the breakage of the anchor bolts – whether it is due to excessive load on the equipment. It is not a problem with the strength of the anchor bolts, but rather the equipment itself is not capable of withstanding such loads. In such cases, when large-sized foundation bolts are used, it is possible that the equipment base or foundation will be damaged again, resulting in even greater problems.

Our company uses two-stage crushing for calcium carbide crushing; there are two primary crushers of the PE600×900 model, and four secondary crushers of the PE250×1200 model. The corner bolts of the four secondary crushers are M30 in diameter. Since they were put into use, these bolts have broken on multiple occasions; the corner bolts of all four crushers have been remolded. The steel bases of units A and B were replaced, but bolt breaks still occur from time to time. Additionally, one of the corner bolts of the primary crusher, which is M48 in diameter, has also broken. Our analysis indicates that the cause of the breakage of the corner bolts is 1: insufficient strength of the corner bolts ； 2. When the bolts and nuts become loose, the amplitude of vibration of the machine increases; the excitation forces act repeatedly on the corner bolts, causing them to fatigue and break ； 3. An uneven foundation increases the vibration of the machine base ； To address the frequent breaking of the foundation bolts, it is recommended to recast all the foundation bolts of the secondary crusher, use bolts with a diameter of M40, level the area, and add supports (which are already in use for machines A and B). The primary crusher had its fractured corner bolts reforged, with bolts of M60 size being used instead.

Attention should also be paid to the issue of preventing the anchor bolts from loosening; any loosening of these bolts must be detected and addressed promptly.

What are the causes of foundation bolt failure?

Due to the operating conditions at the site, crushers experience significant vibration, and the rotor can also suffer wear, leading to imbalance of the rotor. 1. Increase the stiffness of the equipment unit and enhance damping (use rigid supports for the equipment, increase the strength of bolts, and repour the foundation). 2. During installation, ensure that the foundation is level and properly aligned, and that the rotor is balanced. 3. If bolts or the foundation become loose, it will amplify the vibration of the equipment, affecting its lifespan

I’m not sure if there are any colleagues in the calcium carbide crushing industry; we’re having a lot of trouble controlling the conditions related to calcium carbide crushing at our company. We’ve installed many dust collectors, but that hasn’t led to much improvement. As a result, inspections of the site aren’t carried out frequently enough, and when the bolts at the corners become loose, no one notices it in time to tighten them. By the time it’s noticed, the vibration has already become abnormal and the bolts at those corners have broken

It is mainly a vibration issue; measures can be taken to address it, such as increasing the diameter of the anchor bolts or finding solutions to prevent the nuts from loosening.

How is it secured? Is the preload sufficient?

Generally, crushers generate significant vibration, which requires a strong foundation. The horizontal accuracy of the shims in both the longitudinal and transverse directions must be within 0.1/1000. More padding is also needed. I’m not sure if your factory does this. Also, the strength of the foundation bolts should be chosen to be higher, with double bolts used for fastening.