Alert 10 – 06 Near Misses Involving Rig Braking Systems
WHAT HAPPENED:
Recently a company has experienced several serious incidents that are of a kind you can describe as a “Driller’s worst nightmare”.
1. One driller had miscommunication with a crewman who, instead of opening the valves to fill the trip tank, disengaged the auxiliary brake handle. Because the electric auxiliary brake was not engaged, the drawworks brakes overheated resulting in the driller not being able to stop the blocks, which ran into the top drive rail stops.
2. On another rig the driller turned the hydromatic brake water valve the wrong direction. This resulted in shutting off the water supply to the auxiliary hydromatic brake which caused the drawworks brakes to overheat. He was unable to stop the descent of the blocks and the elevators which struck the rotary table, bending the joint of pipe in the elevators.
No injuries resulted from these incidents and each could have been far worse.