Turbine Flow Meters

Question 1

Explain the principle of operation of a turbine meter

Answer 1

Turbine flow meters measure flow by measuring the velocity of spinning turbine blades. Volume flow rate (turbine rotations) is proportional to velocity.

Question 2

How is the k-factor determined for a turbine flow meter?

Answer 2

K factor is number of pulses per unit volume. K-factor is determined by proving the meter through a certain fluid.

Question 3

Explain the two magnetic methods of pulse detection.

Answer 3

1) Reluctance: a permanent magnet is in the sensor of the meter. once a blade passes a magnetic signal is generated.

2) Inductance: a permanent magnet is in the rotor and generates a magnetic pulse per one rotation of the turbine.

Question 4

Explain the effect that flow rate has on the k-factor of a turbine meter.

Answer 4

The k-factor is constant only for a certain range of flow and a specific liquid.

Question 5

How can the turndown ratio of a turbine meter be improved?

Answer 5

If the meter has a specific k-factor for a flow, as that flow changes so will the k-factor.

Question 6

What process condition has the most effect on the performance of a liquid turbine flow
meter? Explain three ways to compensate for this and which is the best method.

Answer 6

Viscosity of the process.
To compensate for this:
1) Use supplied graphs that show % deviation in the k-factor versus flow rates for a specific viscosity
2) Calibrate the meter with a prover for a certain flow and viscosity
3) Use a characterized k-factor

Question 7

Explain the basic differences between turbine meters used on liquids and those used for gas
flow measurement.

Answer 7

Turbine meters used on gasses are equipped with hubs to reduce the area around the turbine which increases the kinetic energy of the flow.

Question 8

What is a spin test and what it is used for?

Answer 8

An equipment check method. If a jet of air spins the turbine and the turbine stops at consistent times between tests the K-factor is assumed to be correct as the bearings are not worn out.

Question 9

List the typical applications for turbine meters.

Answer 9

1) Custody transfer
2) Inventory control (bi directional)
3) Dirty flows with entrained particles
4) Blending and batch processes where accuracy is key

Question 10

What turbine meter component can be checked for by performing a spin test?

Answer 10

Turbine bearings