Positive displacement meter (PD) or Quantity meters

These flow meters are volumetric flow measuring instruments that measure flow by passing a discrete volume of fluid.

1. Positive Displacement Meters Quantity Meters Presented by Dr.T.Mrunalini

2. Positive Displacement (PD) Flow meters are volumetric flow measurement instruments that measure flow by passing a precise volume of fluid with each revolution The meter can measure intermittent flows, very low flow rates, and liquids of almost any viscosity The PD meter instantly moves when there is fluid motion, and instantly stops when the fluid motion stops This type of measurement is not affected by the liquid’s viscosity, density or the turbulence in the pipe All incompressible fluids will occupy the same volume and there is no need to correct the meter’s output to compensate for these factors It is a type of flow meter that requires fluid to mechanically displace components in the meter in order for flow measurement

3. B asic analogy: Volume displaced per unit of time H olding a bucket below a tap, filling it to a set level, then quickly replacing it with another bucket and timing the rate at which the buckets are filled (or the total number of buckets for the “totalized” flow). With appropriate pressure and temperature compensation, the mass flow rate can be accurately determined.

4. It consist of a chamber(s) that obstructs the media flow and a rotating or reciprocating mechanism that allows the passage of fixed-volume amounts The number of parcels that pass through the chamber determines the media volume Types of Positive Displacement Flow Meters: Nutating disk Type Reciprocating Piston Type Oval Gear Type Helix Type

5. Low to medium viscous fluids

6. Fixed volume per revolution – High viscous fluids

7. Factors to be considered while selecting PD

8. Positive Displacement Flowmeters: A Comprehensive Exploration (youtube.com)