A municipal water plant in the southeast United States treats and supplies potable water to a large metropolitan area. Part of the process requires accurate flow measurement of the water from individual pumps to the main distribution system. The flow meters provide information of the current output of the individual pumps. The customer also requires a device that can signal a reverse (negative) flow in the event a pump had stopped. This is so they would know if water was being forced back through the pump. If water flows back through the pump in a reverse direction and an attempt is made to start the pump during this reverse flow, it could cause severe damage to the pump and motor.    
The customer had been using insertiontype, hot-tap magnetic flowmeters from another manufacturer. Due to the placement of the insertion meters (at least one in a downward flow condition), the meters were only lasting from 8 to 12 months and then required replacement at approximately $5000 each.  

The local Siemens representative suggested the customer try the SITRANS FS230 ultrasonic clamp-on meter, mounting it on the pipe being monitored before or after the pump, depend-ing on space and piping configurations. These are 20 to 36 inch pipes, ductile, and cast iron, and some are up to 60 years old.