BI-DIRECTIONAL FLOW PROVERS TRUTH IN MEASUREMENT WITH DIRECT TRACEABILITY TO INTERNATIONALLY ACCEPTED STANDARDS

WHAT IS A PROVER? An open or closed vessel of known volume that is used as a volumetric reference standard for the calibration of meters in liquid petroleum service.

– API Chapter 4 Section 1

WHAT IS ITS PURPOSE? In order to eliminate bias, the calibrated volume of a prover is used to determine a meter factor.

WHAT IS METER FACTOR? A meter factor is the ratio obtained by dividing the actual volume proven by the indicated volume registered by the meter. – API Chapter 4 Note: Factors that can influence the meter’s meter factor are flow rate, temperature, viscosity, wear, and contamination. Proving conditions should match operating conditions in order to maintain the most accurate results possible.

Meter Factor = Prover Volume Meter’s Indicated Volume _________________

BI-DIRECTIONAL PROVER

Launch Chamber Sphere Displacer

Detector Switch

Four-Way Valve

Valve Actuator

Detector Switch Receiving Chamber

PROVER DESIGN REQUIREMENTS • Pipe Size, Schedule & Flange Rating • Sphere Displacer Velocity

• Volume Between Detector Switches

• Four-Way Valve Sizing

• Four-Way Valve Actuator • Pre-Run Length

SPHERE DISPLACER VELOCITY

Note: Minimum Velocity to be no less than 0.5 fps

Max. V = BPH x 0.286 (I.D. [in])

___________ 2 < 5.0 fps _ =

Example: Max. Flow Rate = 3,960 BPH Pipe Diameter = 16”

Max. V = 3,960 x 0.286 (16) 2 = 4.42 fps

PROVER VOLUME • Pre-run length • Distance (volume) between detector switches

Pre-Run Length

Distance between Detector Switches

LENGTH BETWEEN DETECTORS •  In order to maintain an

uncertainty of +0.01%, at least 10,000 meter pulses should be collected between detector switches.

Distance between Detector Switches

Example: Meter K-Factor = 2,000 pulses/bbl Min. volume to achieve 10,000 pulses (VBS) = 210 gallons Measuring section pipe inside diameter = 16” Pipe cross sectional area (A) = 1.396 ft Distance between detector switches (VBS/A) = 20.11 ft.

2

FOUR-WAY VALVE SIZING

FOUR-WAY VALVE SIZING

Example: Max. Flow Rate = 3,960 BPH Pipe Diameter = 10”

Max. V = BPH x 0.286 (I.D. [in]) 2 < 15.0 fps _ =

Max. V = 3,960 x 0.286 (16) 2 = 11.33 fps

FOUR-WAY VALVE ACTUATOR • Mechanical • Electrical • Hydraulic Note: The actuator is sized to maintain a reasonable Four-way valve cycle time, or Closed to Closed time (T c-c). This will be used to determine the required prover pre-run length.

LENGTH OF PRE-RUN (RP)

T C-­‐C  ( ) RP= ___ 2 + 2

1 SEC x Max V __

Pre-Run Length

LENGTH OF PRE-RUN (RP)

T C-­‐C  ( ) RP= ___

Example: Actuator Speed (T c-c) = 4.9 Seconds Sphere Velocity (Max V) = 4.42 fps

2 + 2 1 SEC x Max V

RP= ( ) + 2 __ SEC x 4.42 1 4.9

2 ___ = 13.03 ft

__

LENGTH OF PRE-RUN (RP)

RP=

Pre-Run Length

13.03 ft