Field tests undertaken by MSHA at two underground coal mines proved the flashing headlight warning circuit’s mine worthiness, in addition to its acceptability as a warning device to the miners operating the diesel powered equipment.
The electrical control circuit flashes the headlights of permissible diesel powered equipment when the water in the wet exhaust conditioner system is nearly depleted.
The flashing headlights will warn the machine operator that the system water is low and will allow adequate time for the operator to tram to a water source and replenish the water before the machine's safety system shuts down the diesel engine.
The permissible electric flashing headlight control circuit was designed for easy retrofit into the existing machine lighting circuit.
The device was designed in response to the increased chance of filter fires caused by the installation of paper filters (combustible type) in the exhaust systems of diesel equipment. MSHA said filter fires can even occur on permissible equipment where exhaust temperatures are controlled.
Such fires can be attributed to the lack of water in the exhaust system's wet scrubber and the failure of the safety system shutdown float. Adequate levels of water must be maintained in the wet scrubber to prevent filter fires and maintain the permissibility characteristics of the diesel equipment.
MSHA said the majority of permissible diesel powered machines in the U.S. don't have an indicator for a low water condition in the wet scrubber. Only operator experience or a sudden shut down of the machine indicates this low water condition.
