1、Manual of Petroleum Measurement StandardsChapter 5MeteringSection 3Measurement of Liquid Hydrocarbons by Turbine MetersFIFTH EDITION, SEPTEMBER 2005ADDENDUM 1, JULY 2009Manual of Petroleum Measurement StandardsChapter 5MeteringSection 3Measurement of Liquid Hydrocarbons by Turbine MetersMeasurement
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11、an Petroleum InstituteFOREWORDChapter 5 of the API Manual of Petroleum Measurement Standards (API MPMS) pro-vides recommendations, based on best industry practice, for the custody transfer metering of liquid hydrocarbons. The various sections of this Chapter are intended to be used in conjunc-tion w
12、ith API MPMS Chapter 6 to provide design criteria for custody transfer metering encountered in most aircraft, marine, pipeline, and terminal applications. The information contained in this chapter may also be applied to non-custody transfer metering.The chapter deals with the principal types of mete
13、rs currently in use: displacement meters, turbine meters and Coriolis meters. If other types of meters gain wide acceptance for the measurement of liquid hydrocarbon custody transfers, they will be included in subsequent sections of this chapter.Nothing contained in any API publication is to be cons
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19、tandardsapi.org.iiiCONTENTSPage5.3.1 INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.3.2 SCOPE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.3.3
20、FIELD OF APPLICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25.3.4 REFERENCED PUBLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25.3.5 FLOW CONDITIONING. . . . . . . . . . . . . . . . . . . . . . . . . . .
21、. . . . . . . . . . . . . . . . . . . . .25.3.6 MINIMUM BACK PRESSURE TO PREVENT CAVITATION . . . . . . . . . . . . . . . .25.3.7 METER PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35.3.7.1 Meter Factor . . . . . . . . . . . . . . . . . . . .
22、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35.3.7.2 Causes of Variations in Meter Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4APPENDIX A FLOW CONDITIONING TECHNOLOGY WITHOUT STRAIGHTENING ELEMENTS . . . . . . . . . . . . . . . . . . . . . . . . .
23、 . . . . . . .7APPENDIX B SIGNAL GENERATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11APPENDIX C RECOMMENDED PRACTICE FOR PROVING TURBINE METERS AT MANUFACTURERS FACILITIES. . . . . . . . . . . . . . . . .13Figures1 Names of Typical Turbine Meter Parts. . . . . . .
24、. . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Example of Flow Conditioning Assembly with Tube Type Straightening Element. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 Effects of Cavitation on Rotor Speed . . . . . . . . . . . . . . .
25、 . . . . . . . . . . . . . . . . . . . . . .44 Turbine Meter Performance Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5A-1 Piping Configuration in Which a Concentric Reducer Precedes the Meter Run (Ks= 0.75). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26、. . . . . . . . . . . . . . . .7A-2 Piping Configuration in Which a Sweeping Elbow Precedes the Meter Run (Ks= 1.0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8A-3 Piping Configuration in Which Two Sweeping Elbows Precede the Meter Run (Ks= 1.25
27、). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8A-4 Piping Configuration in Which Two Sweeping Elbows at Right Angles Precede the Meter Run (Ks= unknown). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9A-5 Piping Configuration i
28、n Which a Valve Precedes the Meter Run (Ks= 2.50). . . . . .9TableA-1 Values for L and L/D for Figures A-1 Through A-5 . . . . . . . . . . . . . . . . . . . . . . . . .8v1Chapter 5MeteringSection 3Measurement of Liquid Hydrocarbons by Turbine Meters5.3.1 IntroductionAPI MPMS Chapter 5.3, together wi
29、th general consider-ations for measurement by meters in API MPMS Chapter 5.1, is intended to describe methods of obtaining accurate quan-tity measurements with turbine meters in liquid hydrocarbon service.A turbine meter is a flow-measuring device with a rotor that senses the velocity of flowing liq
30、uid in a closed conduit (see Figure 1). The flowing liquid causes the rotor to move with a tangential velocity proportional to the average stream velocity (which is true if the drag on the rotormechanical and viscousis negligible). The average stream velocity is assumed to be proportional to the vol
31、umetric flow rate (which is true if the cross-sectional flow area through the rotor remains constant). The movement of the rotor can be detected mechanically, optically, or electrically and is registered. The volume that passes through the meter is determined by prov-ing against a known volume, as d
32、iscussed in API MPMSChapter 4.It is recognized that meters other than the types described in Chapter 5.3 are used to meter liquid hydrocarbons. This publication does not endorse or advocate the preferential use of turbine meters, nor does it intend to restrict the develop-ment of other types of mete
33、rs. Those who use other types of meters may find sections of this chapter useful.5.3.2 ScopeThis section of API MPMS Chapter 5 covers the unique installation requirements and performance characteristics of turbine meters in liquid-hydrocarbon service.Figure 1Names of Typical Turbine Meter Parts)ORZ
34、)ORZ however, the observed shifts were significantly greater in magnitude with the 20 diameter straight pipe flow conditioner. It is unknown how far upstream of the turbine meter run the strainer needs to be located to minimize or eliminate this problem. Thus, it is preferable to use a flow conditio
35、ning element, rather than just straight pipe, for more effective turbine meter flow conditioning.d. Furthermore, this limited research testing found that, unless a positive strainer basket positioning and locking mechanism is utilized, changing the amount and location of debris on the strainer baske
36、t screen caused significant meter factor shifts, when using a tube bundle type or high perfor-mance plate type flow conditioning element. 5.3.5.4 A straightening element or swirl-breaker type of flow conditioner usually consists of a cluster of tubes, vanes, or equivalent devices that are inserted l
37、ongitudinally in a sec-tion of straight pipe (e.g. Figure 2). Straightening elements effectively assist flow conditioning by eliminating swirl. Straightening elements may also consist of perforated plates or vortex generating devices, but these forms may cause a larger pressure drop than do tubes or
38、 vanes.5.3.5.5 Proper design and construction of the straightening element is important to ensure that swirl is not generated by the straightening element since swirl negates the function of the flow conditioner. The following guidelines are recom-mended to avoid the generation of swirl:a. the cross
39、-section should be as uniform and symmetrical as possible,b. the design and construction should be rugged enough to resist distortion or movement at high flow rates,c. the general internal construction should be clean and free from welding protrusions and other obstructions.5.3.5.6 Isolating or high
40、 performance type flow condition-ers, which theoretically produce a swirl-free, uniform veloc-ity profile, independent of upstream piping configurations, may provide a performance advantage and should be consid-ered. 5.3.5.7 Flanges and gaskets shall be internally aligned, and gaskets shall not prot
41、rude into the liquid stream. Meters and the adjoining straightening section shall be concentrically aligned. SECTION 3MEASUREMENT OF LIQUID HYDROCARBONS BY TURBINE METERS 35.3.6 Minimum Back Pressure to Prevent CavitationIn the absence of a manufacturers recommendation, the numerical value of the mi
42、nimum back pressure at the outlet of the meter to prevent cavitation (see Figure 3) may be cal-culated with the following expression, which has been com-monly used. The calculated back pressure has proven to be adequate in most applications, and it may be conservative for some situations.wherePb= mi
43、nimum back pressure, pounds per square inch gauge (psig),p = pressure drop through the meter at the maxi-mum operating flow rate for the liquid being measured, pounds per square inch (psi),pe= equilibrium vapor pressure of the liquid at the operating temperature, pounds per square inch absolute (psi
44、a), (gauge pressure plus atmo-spheric pressure).For higher vapor pressure liquids, it may be possible to reduce the coefficient of 1.25 to some other practical and operable margin. The recommendations of the meter manu-facturer should be considered. 5.3.7 Meter PerformanceMeter performance is define
45、d by how well a metering sys-tem produces, or can be made to produce, accurate quantity measurement. See API MPMS Chapter 5.1.9 for additional details.5.3.7.1 METER FACTORMeter factors shall be determined by proving the meter under conditions of rate, viscosity, temperature, density, and pressure si
46、milar to those that exist during intended operation.Meter performance curves can be developed from a set of proving results. The curve in Figure 4 is called a meter linear-ity curve.The following conditions may affect the meter perfor-mance:a. Flow rate.b. Viscosity of the liquid.c. Temperature of t
47、he liquid.d. Density of the liquid.e. Pressure of the flowing liquid.f. Cleanliness and lubricating qualities of the liquid.g. Foreign material lodged in the meter or flow-conditioning element.h. Changes in mechanical clearances or blade geometry due to wear or damage.i. Changes in piping, valves, o
48、r valve positions that affect fluid profile or swirl.j. Conditions of the prover (see API MPMS Chapter 4).Figure 2Example of Flow Conditioning Assembly with Tube Type Straightening ElementGQ/$ % these factors must be overcome by properly designing and operating the meter system.Conventional multi-bl
49、aded turbine meters perform in their most linear range when operated at Reynolds numbers (Re) above 30,000. Two-bladed helical turbine meters perform in their most linear range when operated well within the turbu-lent flow regime (i.e., above 10,000 Re). Each turbine meter usually has a “universal performance curve”, which is a plot of k-factor or meter factor versus Re. See Figure 4. Re is basi-cally proportional to flow rate divided by kinematic viscosity for a given size meter. Therefore, if both the flow rate and the viscosity a
