Why Was the Presence of Flammable Gas Not Detected

The geometry of the piping layout trapped the lighter-than-air flammable gas. The coupling was 42 inches in diameter and there was a concentric reducer to 36 inches. This was 

Investigators used an adjacent pump of the same detail and size to inspect for methane accumulation. A small flow of well water was routed to the gland on an idle sister pump for more than a day. The explosion meter tests performed after a day revealed that there was sufficient accumulation of methane to be troublesome. 

Why was this different from all the other times The river water pump gland was originally lubricated with grease. About 15 years earlier, in an effort to reduce potential environmental situations, such as an occasional sheen on the river water discharge, the grease lubrication was replaced with environmentally friendly well water. Furthermore, it is believed that when a river water pump was shut down for scheduled maintenance, the motor was shut off and the well water was turned off immediately. Despite the fact that this area handled only water, we must be concerned about the impurities that can be dissolved in the water. [3] 

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