Gas and Liquid Metering

Why Metering?

• Measuring flow rate and cumulative volume

• Selling• System Control• Losses detection• Reservoir outlets• Pumping stations

Accuracy

• Accuracy of meters depends on:

Linearity: percentage of true reading over a stated flow

Repeatability: ability to indicate the same reading each

time the same flow condition

Pressure loss

Resolution

Rangeability

Mechanism of Meters

• All meters are consisted of two parts:

The primary element, which is in contact with

the fluid, resulting in some form of interaction.

The second or secondary element translates

the interaction between fluid and primary

element into a signal.

Different Types of Meters

• Positive displacement meter

• Turbine meter

• Orifice meter

• Magnetic meter

• Coriolis meter

Affecting Factors

• Fluid properties Viscosity

Specific gravity

• Conditions Temperature

Pressure

• Flow pattern

Positive Displacement

• Positive displacement meters measure the volume flow rate directly by repeatedly trapping a sample of the fluid.

• Positive displacement meters can be less accurate than other meters because of leakage past the internal sealing surfaces.

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Turbine Meter

• A turbine meter uses a multi-bladed rotor. • The turbine rotation is proportional to the

fluid velocity• A magnetic coil outside the meter

produces an alternating voltage. The voltage is then related to the flow rate.

• They have fast response.

Orifice Meter

• A concentric orifice plate

• The pressure between both sides of plate

is related to the flow rate using Bernoulli's

equation.

Orifice Meter (cont.)

• The simplest and least expensive

• Produces a relatively high pressure drop.

Magnetic Meter

• Insensitivity to specific gravity

Viscosity

Pressure

Temperature

• Sensitive to magnetic properties of the liquid.

Coriolis Meter

• The Coriolis meter uses a U- tube sensor • Applies Newton’s Second Law• Fluid momentum changes natural vibration

of the U-tube and twists it.• Two sensors detect vibrating velocity of

the U-tube at each side and relate it to mass flow.