SAFETY ALERT FOR FLETCHER CANOPIES
A close-call incident involving the drill station canopy on a Fletcher roof bolting machine occurred recently in a District 3 underground mine. A roof bolter operator was nearly struck in the head by the canopy as it suddenly fell after being momentarily stuck in the raised position. Fortunately, the operator was not injured.
The Fletcher drill station canopy support assembly consists of three nested square tubes raised up and down by a hydraulic cylinder. The incident apparently occurred because the bolt attaching the canopy and the square tubing to the hydraulic cylinder became loose. Without this bolt connecting the tubing and cylinder, when the bolter operator activated the lever to lower the canopy, only the hydraulic cylinder retracted. The square tubing and canopy remained in the raised position for a few seconds and then suddenly dropped and nearly struck the operator. The investigation revealed this warning in the Fletcher service manual:
(See example of service manual page.)
Although the recent accident occurred as a result of a 3-inch-long bolt backing out of the cylinder rod, a similar scenario could result on the "older" style tubing/ cylinder attachment. Prior to 1992 the top of the cylinder rod was threaded and the tubing assembly attached with a nut. It is even more important that older machines with this design be checked due to a shorter thread engagement length at the connection point.