API MPMS 5.7 2003 pdf download.Manual of Petroleum Measurement Standards Chapter 5—Metering Section 7—Testing Protocol for Differential Pressure Flow Measurement Devices.
1.1 SCOPE The protocols are limited to single-phase Newtonian fluid flow, and no consideration is given to pulsation effects. Fur- ther revisions of this document may include the testing of such meters in wet gas or multi-phase service and the effects of pulsation. This standard does not address testing protocols of those devices that operate on the principle of critical or choked flow condition of fluids. The testing protocol covers any flow meter operating on the principle of a local change in flow velocity, caused by the meter geometry, giving a corresponding change of pressure between two set locations. There are several types of differen- tial pressure meters available to industry. It is the purpose of this standard to illustrate the range of applications of each meter and not to endorse any specific meter. The basic princi- ple of operation of the flow measuring devices follows the physical laws relating to the conservation of energy and mass for the fluid flows through the device. Any existing or later developed API MPMS document addressing a specific type or design of differential pressure flow measuring device will supersede the requirements of this document. Example of one such existing standard is API Manual Petroleum Measurement Standards Chapter 14.3— “Concentric, Square-Edged Orifice Meters.” 1.2 DIFFERENTIAL PRESSURE OR HEAD-TYPE FLOW METERS The operating principle of a differential pressure flow meter is based on two physical laws—the conservation of energy and conservation of mass, where changes in flow cross-sectional area and/or flow path produce a differential pressure, which is a function of the flow velocity, fluid path, and fluid properties. The following diagrams are presented as examples of the some of the possible differential pressure devices. Other variations of meter designs are available and possible.
2 Terminology and Definitions The definitions are given to emphasize and clarify the par- ticular meaning of terms as used in this document. 2.1 METER A meter is the assembly of a primary element , a differential producer holder with the upstream and downstream meter tubes that will generate a differential pressure when placed in a flow stream. The differential pressure is monitored by sec- ondary device (s) to derive the flow rate. 2.2 PRIMARY ELEMENT OR DIFFERENTIAL PRODUCER The primary element is defined as the differential producer when placed in a flowing stream. 2.3 DIFFERENTIAL PRODUCER HOLDER The differential producer holder is defined as a pressure- containing piping element used to contain and position the differential producer and its associated differential pressure sensing taps in the piping system. An orifice fitting would be an example of such a device. 2.4 METER TUBE The meter tube is defined as the straight sections of pipe, including all segments that are integral to the differential pro- ducer holder, upstream and downstream of the differential producer and the flow conditioner, if required. 2.5 METER TUBE INTERNAL DIAMETER, D , D i , D m , or D r In this document it has been assumed that the meter tube is circular. If the meter is used in a non-circular cross-sectional flow line or a non-circular device is installed in a circular flow line, the manufacturer of the device must explain how the critical dimensions of the primary element would be defined and calculated. In addition, other necessary or critical upstream and downstream flow conduit geometry and dimen- sions for the non-circular differential pressure producing flow measuring device must be defined by the manufacturer. The published meter tube internal diameter ( D i ) is the inside diameter as published in standard piping handbooks.
2.6.1 Pressure Measurement The static pressure and differential pressure are measured using either a digital or an analog transmitter. Static pressure transmitters measure either the absolute or gage pressure of the fluid. Differential pressure transmitters measure the dif- ferential pressure developed between two points of measure- ment, caused by the primary element. A multivariable transmitter measures both static and differential pressure and may also accept a temperature sensor input. Analog transmit- ters provide an analog output proportional to the measured variable. The output of digital transmitters can be either ana- log and/or digital. 2.6.2 Static and Differential Pressure Measurement, P 1 , P 2 , and ∆ ∆ ∆ P The static pressure of the process is usually measured upstream of the differential producer by a tap normal to the flow velocity. The static pressure can be used (in conjunction with the temperature and composition) to determine the den- sity of the flowing fluid.