Crusher drum bits

The Challenge

When mining coal underground, the severe environment takes a brutal toll on the crusher drum bits. In operation, it is an extremely violent application with high rpm’s and constant pounding as the bits cuts into coal and rock. In some instances, the bits break off the drum completely, reducing its efficiency. For this reason, crusher drum bits need repaired or changed often and to save time and money, the bits are changed underground.

Accessibility is difficult and limited. Sometimes workers only have four feet of vertical space to operate in. Additionally, the bits are located around the crusher drum, making some spots extremely difficult to do maintenance work. Many different methods have been used to torque the bolts, without much success.

The Solution

This crusher has (12) bits spread around the entire circumference of the drum. Superbolt designed an M36 x 4 pitch bolt-style multi-jackbolt tensioner (MJT) assembly to provide 102,960 lbs. of clamping force. This force was generated by applying only 43 lb•ft of torque on the jackbolts (the equivalent torque on the standard bolt is 2,150 lb•ft).

The use of a small 3/8” drive hand held torque wrench was much safer and more accurate than previous bolting methods. Most importantly, space restrictions are less of a concern because only small hand tools are needed to install and remove the MJTs. This makes the whole process easier and faster.

Superbolt MJTs have significantly more holding power than the standard bolting methods used in the past. The machines stay in operation longer, making them more profitable because of less downtime.

More insights and references

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