Advantages of Lobed Impeller Flowmeter | disadvantages of Lobed Impeller Flowmeter

This page covers advantages and disadvantages of Lobed Impeller Flowmeter. It mentions Lobed Impeller Flowmeter advantages or benefits and Lobed Impeller Flowmeter disadvantages or drawbacks.

What is Lobed Impeller Flowmeter?

Introduction:
• This meter uses two lobed impellers, which are geared and meshed to rotate at opposite directions within the enclosure. This is shown in the figure-1.
• It is one of the positive displacement meter types. Other meter types include Nutating disk, Oscillating piston, Rotating vane, Oval gear, Reciprocating piston etc.
• Positive Displacement Flow meter directly measures volume of the fluid or gas passing through the meter.

• It uses two rotating impellers which are arranged in figure of eight as cross section. They rotate in opposite directions due to forces exerted by gas flow being measured.
• A known volume of fluid is transferred for each revolution.
• The number of revolutions or rotations is proportional to flow.

Benefits or advantages of Lobed Impeller Flowmeter

Following are the benefits or advantages of Lobed Impeller Flowmeter:
➨It provides excellent accuracy during gas measurement. Typical accuracy values range from +/- 0.1 % to +/- 0.5 % .
➨Inlet and outlet sections are not required.
➨It does not require external power supply.
➨It operates upto high operating pressures of 8 MPa.
➨It operates upto high temperatures of 200 ^oC.
➨Lobed impeller flowmeters are susceptible to contamination. This contamination affects the pressure drop.
➨Due to contamination, meter should be cleaned at regular intervals.

Drawbacks or disadvantages of Lobed Impeller Flowmeter

Following are the drawbacks or disadvantages of Lobed Impeller Flowmeter:
➨It is used for gases only.
➨It has moving parts which get wore down.
➨The flow gets blocked at zero flow due to solid impurities.
➨The measurements are affected due to quick changes at high differential pressure.
➨Monitoring is difficult task.
➨It has poor accuracy at low flow rates.
➨It is bulky and heavy.
➨It is expensive.

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