API MPMS 5.3:2005 pdf download.Manual of Petroleum Measurement Standards Chapter 5–Metering Section 3- -Measurement of Liquid Hydrocarbons by Turbine Meters.
5.3.5.4 For severe swirl, such as generated by two close coupled elbows out-of-plane (i.e.. non-symmetrical swirl) or by a header (i.e.. dual symmetrical swirl), a straightening element (i.e., swirl breaker) type of flow conditioner is required. These types of swirl are slow to dissipate in straight pipe. often existing after lOW diameters of straight pipe.
5.3.5.5 A straightening element or swirl-breaker type of flow conditioner usually consists of a cluster of tubes, vanes. or equivalent devices that are inserted longitudinally in a section of straight pipe (see Figure 2). Straightening elements effectively assist flow conditioning by eliminating swirl. Straightening elements may also consist of a series of perforated plates or wire-mesh screens, but these forms normally cause a larger pressure drop thaii do tubes or vanes.
5.3.5.6 Proper design and construction of the straightening element is importani to ensure that swirl is not generated by the straightening element since swirl negates the function of the flow conditioner, The following guidelines are recommended to avoid the generation of swirl:
a. The cross-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.
5.3.5.7 Isolating type flow conditioners, which produce a swirl-free, uniform velocity profile, independent of upstream piping configurations. are typically more sophisticated. expensive and higher pressure drop than simple straightening element type flow conditioners. However, in certain installations, they provide a pcrformance advantage and should be considered.
5.3.5.8 Flanges and gaskets shall be internally aligned, and gaskets shall not protrude into the liquid stream. Meters and the adjoining straightening section shall be concentrically aligned.
5.3.6 Minimum Back Pressure to Prevent Cavitation
In the absence of a manutuacturer’s recommendation, the numerical value of the minimum back pressure at the outlet ot’thc meter may be calculated with the following expression. which has been commonly used. The calculated back pressure has proven to be adequate in most applications, and it may be conservative for some situations.
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 manufacturer should be considered.
5.3.7 Meter Performance
Meter perfonnance is defined by how well a metering system 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 FACTOR
Meter factors shall be determined by proving the meter under conditions of rate, viscosity, temperature, density, and pressure similar 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 linearity curve.
API MPMS 5.3:2005 pdf download
