Testing of Generic Differential Pressure Cone Meters to API 22.2 Test Protocol Part 1.0 (Water).

Philip A Lawrence. Cameron Valve and Measurement, USA.

Dr. N.W Sung. Flow Calibration Centre Ltd, South Korea.

Abstract

During 2003 a standard was developed by the American Petroleum Institute (API) Manual of Petroleum Measurement Standards (MPMS) Chapter 5.7 Working Group, entitled “Differential Pressure Flow Measurement Devices.”

It was subsequently moved and changed to Chapter 22, Section 2, and is now called API chapter 22.2 the differential test protocol.

This paper details the work done on various sizes of differential pressure cone meters at the FCC Ltd Independent water test laboratory near to Seoul in South Korea.

The paper will detail the results for baseline and perturbation testing performed at the laboratory using their gravimetric system traceable to Korean National Standards through KOLAS and KRIS.

The demonstration of the laboratories alignment to the RG (Reader-Harris-Gallagher) equation will be shown and also results from a recently available technique called “PIV” particle image velocimetry which is a laser optical method used to obtain instantaneous velocity measurements and related properties in fluids.

This technique was used to determine that the velocity profile in the pipe was fully developed thus enabling the RG equation to be validated effectively in the calibration system. Figure-1a

The line velocity profile effects where shown by using a computer generated nomogram - Figure 1b

The system was also used during the test to view the fluid flow dynamics through a cone meter that was installed in a clear view flexi-glass pipe.

Fig 1a Fig 1b

Dmm 

Introduction

The NuFlo™ D.P. Cone Meter fabricated by Hitrol Ltd of South Korea Cameron Measurement Systems sub-contractor was tested in accordance with the American Petroleum Institute Manual of Petroleum Measurement Standards, Chapter 22 – “Testing Protocol,” Section 2 – “Differential Pressure Flow Measurement Devices” (API MPMS 22.2), First Edition, August 2005. The testing was performed in the test facility of Flow Calibration Center (F.C.C.) Co., Ltd In South KOREA traceable to Korean National Standards via KOLAS and certified to ISO 17025.

The cone flow meters for the test had 2-inch and 6-inch as a nominal diameter and for each line size two different area ratio, 0.45 and 0.75 were selected. Orifice plates for the test facilities verification had same nominal diameters. But covering the test range of flow rate for NuFlo ™ cone meters the area ratio of orifice plates were selected as 0.3 or 0.5 and 0.7 in same line size with the cone flow meters.

Description of the Liquid Test Laboratory System

Cold water testing was performed using a water gravimetric system having the ISO 17025 certification. The best measurement uncertainty capability (BMCs) of the system for the liquid flow rate are 0.42% in the range of from 2.9 to 50 cubic meters per hour and 0.2% in the range of 50~425 cubic meters per hour.

Acceptability of Test System

According to API MPMS 22.2, the test set-up must be confirmed using the standard orifice plates and alignment with the Reader Harris- Gallagher equation. The orifice plates (O.P.)of 2-inch and 6-inch were installed in straight line, which contains over 36D of each upstream pipe. 19D straight pipe was used for the downstream from flow meters. 2-inch and 6-inch flange tapped orifice flow meters were tested in each line prior to the cone test. The beta ratio was decided considering the upper and lower limits of the cone flow meter testing range.

The result of orifice test was compared with the results of Reader-Harris Gallagher equation for test verification. The 2-inch orifice plate was tested from 17,700 to 152,000 Reynolds number and the 6-inch meter was from 32,200 to 745,000.

Flow condition of test apparatus was investigated using the particle image velocimetry (PIV) method as shown in Figure 1 and Figure 2. With image processing results of the non-invasive instrumentation, acceptability of flow profiles for flow meter test can be detected clearly; Figure 2.0

The main devices of a PIV system are high speed CCD camera and LASER source & PC. The specifications of those devices are listed in Table 1 and Table 2 each. According to MPMS 22.2,a fully-developed flow condition must be obtained upstream of the O.P, for good uncertainty determination of the rig. The flow velocity profile was established and investigated and confirmed as being in a fully developed regime by use of the PIV method.

Figure 1c Flow condition test - PIV instrumentation in 6-inch line  

Figure 2 Test specimen for PIV test in 6-inch line  

Table 1 Specification of high speed CCD camera Max resolution 1280 x 1024

Max frame rate 2200 fts

Pixel size 12 x 12μm

Shutter 2 μsec to 20 msec

Sensor 10 bit mono / 24 bit color

Trigger source Standard TTL / Image cued

Lens mount C mount

Digital output Trigger / Strobe

Interface TCP/IP

Software Video record and playback

Table 2 Specification of laser Model VA-II-N-532

Wavelength (nm) 532

Output power (mW) 2000

Working mode CW

Beam mode Transverse TEM00,TEM01

Longitude Multi-longitude

Spectral line width (nm) <0.1

Polarization Line polarization

Polarization ratio >100:1

Beam quality (M2 factor) <1.2

Beam divergence (full angle, mrad) 1.2~2.0

Beam diameter at aperture (mm) 2.0~3.0

Beam roundness >90%

Power stability(RMS) <5% @8hours

Aperture position (mm) 20

Dimensions of Laser head (L×W×H, mm) 180 x 62 x 62.5

Integrated driver model VD-III Series

External modulation 5V TTL / 5V Analogue

Modulating frequency 30KHz TTL / 10KHz Analogue

Cooling system TEC

Warm-up time (minutes) <15

Operation temperature (℃) 18~30

Expected lifetime (hours) >10000

Standard Test

Standard testing was performed to establish the reference coefficient of discharge (C.d.) curve for each of the cone flow meters in enough straight upstream and downstream piping conditions without any flow disturbance. The 2-inch cone flow meter was tested from 18,000 to 152,000 Reynolds number and the 6-inch meter was from 61,800 to 715,000.

Non-Standard Test : Out of Plane ninety degree elbows (O.P.)

As shown in Figure 3 and Figure 4, to generate asymmetric swirl, three elbows in different planes were used. Elbow sets were symmetrically installed upstream and downstream of the cone flow meter. Testing was performed in the each case of line size and beta ratio of the cone flow meters. Because the elbow sets were symmetric for the cone flow meter, the distance between upstream elbow set and the cone and the distance between downstream elbow set and the NuFlo™ cone were same. The maximum flow rate of 2-inch and 6-inch cone flow meters were 148,000 and 556,000 Reynolds number each.

Figure 3 Out of plane elbows piping.

Non-Standard Test : Half-Moon Orifice Plate Disturbance

To generate a strong asymmetric axial velocity profile (50% closed valves), half-moon orifice plates were installed at each test line.

The distances between the half-moon orifice plate and the cone flow meter and the upstream piping were 3D and 5D, and a downstream distance was same in the case of the pressure recovery test. The case of placing the half moon plates at 0D (direct piping of half-moon orifice plate and the cone flow meter) was not considered because this installation condition is not recommended.

The maximum ReD flow rate of 2-inch and 6-inch NuFlo ™ Cone flow meters were 148,000 and 556,000 Reynolds number each. Half-moon orifice plates used were shown in Figure 5

Figure 4 - Out of plane elbows piping. Figure 5 - ½ moon orifice plate -

flanged pipes.

Flow Coefficient Determination

The flow coefficient or discharge coefficient, dC for each meter tested was determined using the following

equation.

ρβ/2

1 4

PAQ

QQC

o

v

ltheoretica

actuald Δ

−==

where, vQ is the actual volumetric flow rate in cubic meter per second, oA is the area of the annular

meter ring within the cone flow meter in square meter, PΔ is the differential pressure generating across the restriction device in Pascals, and ρ is the fluid density. The cone beta ratio, β is defined as the ratio of the equivalent diameter of the annular meter ring to the inlet pipe diameter.

The Reader-Harris Gallagher equation was used to determine the reference discharge coefficient for 2-inch and 6-inch orifice flow meters, because the equation is well known in standards, it is not shown in this paper.

As can be seen from the results in figures; 7-26 the meter deviations varied according to the beta ratio and the disturbance type the 50% ½ moon plate being the worst case for any DP meter to operate with some semblance of accuracy. The out of plane elbow test proves that this type of meter can resist the effect of swirl., Besides the frictional forces that act on the fluid across the upstream cone frustum, there is an effect cause by the flowing mass of the gas (moment of inertia) being forced to the pipe wall by cone interaction, this is why the meter is less sensitive to swirl.

In a future paper entitled “The API 22.2 Testing of DP Cone Meters Part II Gases”, the effect of swirl and the effect on the meters recovery region by partial blockage will be shown.

The following hypothesis is shown to inform the reader regarding the swirl effect passing through a cone meter and its comparison with a similar orifice equivalent area ratio. A CFD simulation is shown below indicating the fluid velocity pathway through the meter. The wake can be circulatory in two ways either split or circulatory - Figure 6

FLOW

The following hypothesis is based on a theoretical approach in regards to swirl effects.

Figure 6

Flow velocity profiles in a pipe after an elbow or out of plane elbow become distorted or become asymmetric. It must be noted that surface roughness and friction can slightly affect the fluid distortion also Figure 6

Cone Wake Region

 High Velocity Region 

High Velocity Region 

Cantilever Wake Region

Distortion

Flow Velocity through a Cone and Orifice Plate ; (Figure 6a below)

FLOW

Cone Meter: Simple Swirl Component Orifice Plate : Simple Swirl Component ( being forced to expand by the cone) (being forced to contract by the orifice)

Effect of Swirl Angle on the C.d of an Orifice Plate (Figure 6b)

Mathematical Proof Swirl ; Orifice Plate (Excluding Friction)

   

 

Mathematical Proof Swirl : Cone Meter (Figure 6b below )

Basic Conclusion (Excluding Frictional Forces)

The swirl is effectively halved using a cone meter and either increased 4 or 16X depending on the beta ratio of the O.P.

Results of the water testing

The test data chart present a summary of acquired data for each tests above mentioned through Figure 7 to Figure 25. For a given Reynolds number, three individual test runs provided and plotted. At the end of results section, the comparison of standard test results and non-standard test results is presented.

Figure 7 Standard test results of cone flow meter (2-inch, 0.45 beta)

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000

Reynolds number, Re

Dis

charg

e c

oeff

icie

nt,

Cd

Figure 8 Out of plane elbows set test results of cone flow meter (2-inch, 0.45 beta).

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

Reynolds number, Re

Dis

charg

e c

oeff

icie

nt,

Cd

Figure 9 Half-moon test results of cone flow meter (2-inch, 0.45 beta, 3D)  

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

Reynolds number, Re

Dis

charg

e c

oeff

icie

nt,

Cd

Figure 10 Half-moon test results of cone flow meter (2-inch, 0.45 beta, 5D)

Figure 11 Standard test results of cone flow meter (2-inch, 0.75 beta)

Figure 12 Out of plane elbows set test results of cone flow meter (2-inch, 0.75 beta)  

 

Figure 13 Half-moon test results of cone flow meter (2-inch, 0.75 beta, 3D)

Figure 14 Half-moon test results of cone flow meter (2-inch, 0.75 beta,5D)

Figure 15 Standard test results of cone flow meter (6-inch, 0.45 beta)

Figure 16 Out of plane elbows set test results of cone flow meter (6-inch, 0.45 beta).  

 

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 100,000 200,000 300,000 400,000 500,000 600,000 700,000

Reynolds number, Re

Dis

charg

e c

oeff

icie

nt,

Cd

Figure 17 Half-moon test results of cone flow meter (6-inch, 0.45 beta, 3D).    

 

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 100,000 200,000 300,000 400,000 500,000 600,000

Reynolds number, Re

Dis

charg

e c

oeff

icie

nt,

Cd

Figure 18 Half-moon test results of cone flow meter (6-inch, 0.45 beta, 5D)

Figure 19 Standard test results of cone flow meter (6-inch, 0.75 beta)

Figure 20 Out of plane elbows set test results of cone flow meter (6-inch, 0.75 beta)

Figure 21 Half-moon test results of cone flow meter (6-inch, 0.75 beta, 3D)

Figure 22 Half-moon test results of cone flow meter (6-inch, 0.75 beta,5D)

Figure 23 Comparison of 2-inch cone flow meter performance (0.45 beta)

Figure 24 Comparison of 2-inch cone flow meter performance (0.75 beta)

Figure 25 Comparison of 6-inch cone flow meter performance (0.45 beta)

Figure 26 Comparison of 6-inch cone flow meter performance (0.75 beta)

Conclusion

The API standard allows by virtue of the 22.2 protocol for “level playing field testing” to be performed that can be applied and accepted by end users to allow the use of Dp metering devices in a Custody / Fiscal environment.

The testing shown in this paper in indicates the good linearity and performance that can be achieved by these genre of meters.

The data indicates a good response to disturbed velocity profile or perturbation effects on the meter with small changes on C.d. compared with other D.p. metering devices.

It is anticipated that the results from the current ongoing gas fluids testing at the CEESI laboratory in Nunn C.O. will be just as fruitful !

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