Pump Output Monitored by Flow Meter Provides Direct GPM Readout
Flow meters provide an alternative means of monitoring pump output to hose lines by providing a direct gpm readout.
The newest flow meter to be offered to the fire service is the Eagle Eye System manufactured by Dieterich Standard Corporation of Boulder, Colo. The heart of this system is a flow sensor. As water is pumped through a hose outlet, a small tube, or annubar, spans the inside diameter at a 90-degree angle to the flow. This tube has four holes facing upstream which sense the flow pressures in each area of the flow profile.
Another tube, inside the annubar, averages the four velocity pressures and sends an average pressure through an instrument line to a flow meter. Static or residual pressure is measured by a probe located downstream from the annubar. This line pressure is also transmitted to the flow meter through an adjacent instrument line.
Inside the flow meter, velocity pressure of the water is applied to one side of a cavity, while the static pressure is applied to the other side of the same cavity.
A diaphragm is between the two sides. As flow increases, a differential pressure causes the diaphragm to move. This movement is picked up by a set of permanent magnets and is transmitted to a motion multiplier—or the needle on the flow meter dial. This arrangement translates differential pressure into a gallons-per-minute reading.
This system requires no electronics. The flow meter uses the water being pumped to power the system and it provides a gpm readout only when there is flow through the system.
Flow meters also come in portable, detachable units that can be used for pump tests and hydraulic training.
