Handbook for Methane Control in Mining - AMMSA

129Welding and cutting. To the extentpossible, welding and cutting should bedone on the surface. When welding andcutting in the shaft cannot be avoided,gas check procedures must be carefullyfollowed, and the number of people inthe shaft must be held to the minimumrequired to conduct the work and checkfor gas—usually two individuals.Water rings. A water ring cross-sectionis shown in Figure 9–3. Water rings arecircular spaces excavated from the rockin a shaft wall. They are used to providewater drainage from the exterior side ofthe concrete shaft lining and are oftenlocated to drain water from an adjacentaquifer. Methane gas may be drainedalong with the water, resulting in additionalhazard.Figure 9–2.—Ventilation airflow is restricted by workdeck. Therefore, methane must be monitored at regulardistances between the work deck and the muck pile.Water ring spaces in shaft walls are an example ofa so-called restricted space, where the ventilationand methane sampling require extra effort. 4Failure to monitor restricted spaces such as water rings can have disastrous consequences. Forexample, in January 2003, three miners were killed by a methane explosion during a shaftsinkingoperation in West Virginia [Mills 2003]. A water ring space had been excavated backinto the strata from the shaft wall. Before pouring the concrete shaft lining, the water ring spacewas sealed off with corrugated sheets of steel to prevent it from being filled with concrete. Afterthe concrete had set, the three workers were killed while in the process of opening an access doorwith an acetylene torch. The torch ignited methane that had accumulated in the water ring spaceafter it was sealed off.4 Sampling for methane in restricted spaces is described in more detail in the sampling chapter (Chapter 2).