D3 Prep Water Meters PT2

New Meter Testing

Should be tested before installed, states allow a representative sample of new meters to be tested for accuracy, if the tested meters prove accurate, the rest of the lot is assumed to read accurately as well.

Testing Frequency

• Meters deteriorate/metering accuracy goes down.

• Older meters benefit the customers while water utility loses revenue.

• Meters should be tested & repaired or replaced as required.

• No national standard has been frequency

• Most states that have established frequencies require that larger meters are tested more frequently than smaller meter.

Testing Procedures

• Run several different flow rates over the meter’s operating range to determine meter efficiency

• A known volume of water is passed through the meter at different flow rate.

• Determining if the meter meets acceptable accuracy limits for use.

Testing processes

Three ranges of flow are typically tested

• Maximum

• Intermediate

• Minimum

• For larger current and compound meters, 4 or 5 flow rates are tested

• Large meters are typically tested in the field while small meters r removed and brought back to the meter shop for testing.

• Only the lower 5-10% of range is tested since this tends to be the range where accuracy falls off and the upper ranger requires large volumes of water which makes it difficult to perform.

Current Meters

Commonly called velocity meters, current meters are usually installed on water lines that are 3in or more in diameter

• Turbine, MultiJet & Propeller

Turbine Meters

The flow of water causes a rotor to rotate within a measuring chamber that is recorded on the meter’s register.

• There is nearly a directly proportional relationship between the number of revolutions of the rotor and the volume of water that passed through the meter.

• The turbine meter requires a minimum flow rate b4 the rotor will begin to rotate which means this meter is best suited for high flow applications.

• Very low friction loss, unless sediment accumulates on the blades then meter would under register

MultiJet Meter

• Has a multiblade rotor that is mounted on a spindle within the cylindrical measuring chamber