CHAPTER 14 - MEASUREMENTS IN PRESSURE CONDUITS

2. General Comments on Pipeline Flowmeters

In-line flowmeters are usually classified by basic types of operation. Some of these basic types are:

• Differential head meters
• Positive volume displacement summing meters   (generally municipal water)
• Calibrated velocity sensing meters
• Measured proportional or calibrated bypass meters
• Acoustic-type meters

Flowmeters can display or record total volume delivered or instantaneous discharge rates. Direct reading of totalized volume, rather than computing volume from instantaneous discharge readings, is especially convenient where water is sold on the volume basis. Many flowmeters are also equipped with auxiliary equipment to record and display the instantaneous flow discharge. This feature is of great advantage for irrigation when setting rates and controlling delivery.

Water measured in closed conduits with mechanical meters must be free of foreign matter. Meters should be inspected regularly (see chapter 5) to detect wear, corrosion, or other change that would tend to alter accuracy. Flowmeter use is limited by relatively high cost and short life in adverse operating environments.