Positive displacement flow meters are mechanical instruments that measure the volumetric flow rate of a fluid. The main advantage of these types of flow meters is their ability to handle high viscous and corrosive fluid, and they typically do not require filtration prior to processing. Here is a guide to positive displacement flow meters which includes an overview of the basic design, operation and benefits of this type of mechanical flow meter.
General Components and Operation
Though the details of each design vary, positive displacement flow meters all contain these major components:
- Inlet and outlet ports
- Measuring chamber
- One or more rotors
Fluid enters the measuring chamber through the inlet port and imparts energy on the rotor. The rotation of the rotor corresponds to the volume of fluid entering the chamber, and a signal is collected by the connected flow meter transmitter. The fluid then exits the chamber through the outlet port.
Two gears are commonly used as rotors for this type of flow meter. The gears can be aligned vertically or horizontally, and they can either be circular or oval shaped. In either case, the purpose of having two gears is to create a seal within the measuring chamber so that all fluid is measured before passing through. Other positive displacement flow meter designs may utilize two helical or screw-shaped gears, while some use one or more pistons or diaphragms to physically push fluid through the chamber.
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