How to Quickly Replace Mill Liner Bolts

When liner bolts in a tube mill break and fall off, dust leakage occurs—a common problem for mills that have been in operation for a long time. In such cases, the only conventional solution is to stop the mill and have personnel enter the mill to replace the bolts and tighten them. In practice, however, some plants have developed a “fishing method” that allows bolt replacement without anyone entering the mill, and it requires only 10–20 minutes of downtime—a time‑saving and labour‑saving approach.

The procedure is as follows:

(1) Rotate the mill so that the bolt to be replaced is brought to the topmost position.

(2) Remove the leaking nut, or use an oxy‑fuel torch to cut off the bolt that is spinning with the nut.

(3) Insert a long iron wire through the bolt hole, with the wire length exceeding the length of the mill compartment. From the mill inlet ventilation opening, use a long rod with a hook to pull the wire out from inside the mill.

(4) Weld a nut (with a diameter smaller than the bolt) securely onto the threaded end of the new bolt to be installed. Tie the pulled‑out end of the iron wire to this nut.

(5) Pull the inserted iron wire back out through the bolt hole on top of the mill shell. The new bolt will be carried by the wire through the bolt hole and emerge from the hole. At this point, you can put on and tighten the nut from the outside on top of the mill.