Monitoring gas flow speed in mine ventilation systems - using acoustic source and receiver in flow and having whistle or microphone placed in duct

摘要

The gas flow speed monitoring device is esp. for monitoring underground mine ventilation systems is simply produced and installed and ensures positive reliable monitoring. It eliminates the disadvantage of membrane switches that are easily influenced by external sources and can fail to indicate flow speeds below the minimum permissible for safety. It avoids the contamination and overheating problems of semiconducting thermoresistance types. An acoustic transmitter (1) is placed in a ventilation duct (2). An associated acoustic receiver drives an evaluation circuit (5) whose pulse output is dependent on the flow speed reaching one or one of several defined values. The acoustic source (1) may consist of a whistle or microphone placed in a duct carrying the monitored flow. An amplifier may be placed between the receiver and evaluation circuits.