Method for generating a diagnostic from a deviation of a flow meter parameter

1. A method for detecting a deviation in a flow meter parameter, comprising the steps of:

measuring a differential pressure across at least a portion of the flow meter;

calculating a friction factor based on a measured flow rate and the measured differential pressure; and

comparing the calculated friction factor to an expected friction factor based on the measured flow rate and detecting a deviation in the flow meter parameter if the difference between the calculated friction factor and the expected friction factor exceeds a threshold limit.

2. The method of claim 1 , wherein the step of calculating a friction factor comprises using the equation:

f

=

D

⁢

⁢

Δ

⁢

⁢

P

2

⁢

V

_

2

⁢

ρ

⁢

⁢

L

;

where:

ΔP=Differential pressure;

L=length of tube between pressure taps;

f=friction factor;

V =average fluid velocity;

ρ=fluid density; and

D=tube diameter.

3. The method of claim 1 , wherein the expected friction factor is obtained from a previous measurement.

4. The method of claim 1 , wherein the differential pressure is measured across the entire flow meter.

5. The method of claim 1 , wherein the expected friction factor is calculated based on a Reynold's number for the measured flow rate.

6. The method of claim 1 , further comprising the step of storing the expected friction factor in meter electronics.

7. The method of claim 1 , wherein the flow meter comprises a Coriolis flow meter.

8. The method of claim 1 , wherein the deviation in the flow meter parameter indicates the presence of a coating in the flow meter.