ASME MFC-12M-2006 pdf free download.Measurement of Fluid Flow in Closed Conduits Using Multiport Averaging Pitot Primary Elements.
The equations developed in Nonmandatory Appendix B and used in this section are for fluid flow in a horizontal pipe. Multiport averaging Pilot primary elements can be used in horizontal and vertical installations. In vertical installations the pressure head difference is zeroed out during installation and startup.
For incompressible fluids the expansibility (expansion factor), a, has a value 011.0.
The value of the flow coefficient, K. or an expression for its computation for a given APT primary element design is specified by the manufacturer.
6 UNIT CONSTRUCTION CONSIDERATiONS
The construction of an All’ primary element must he suitable in design and material to operate tinder the conditions to which the meter will be exposed, including temperature. pressure. flow rate, and corrosion. It is the responsibility of the manufacturer to clearly identify to the user the safe limits of pressure, temperature. and flow rate. Th user should deline the operating and maximum pressure, temperature, and flow rate ranges, as well as the flowing fluid and environmental constraints.
6.1 Sensor Construction
Since the primary element is installed within the fluid stream, it must he designed to withstand the loads imposed due to piping pressure and the dynamics of the flow stream. Some of the multiport averaging l’itot type pr mary elements that are commerually available are shown in NorLmandatory Appendix A. The compatibility of an application or process condition for a particular primary element design should be determined individually.
6.2 Pressure Containment Elements
In all systems, a portion of the device is exposed to the system pressure. The components shall be designed and/or specified in accordance with applicable standards. The pressure containment portion of the APT primary flow element, regardless of design, shall be leak free in its construction.
6.3 Mounting Methods and Hardware
A wide variety of mounting techniques and hardware are used depending on the design of the unil Mounting hardware must be constructed so that all elements or components of the unit are constrained by proper design. This Is particularly true in hot/wet tap units where there is a provision for insertion or removal of the sensor from the system under pressure. For safety reasons, the manufacturer must supply pressure and temperature limits for each niounting configuration.
6.4 Hot Taps
When considering hot/wet tap Lklments. the manu• facturer shall perform the structural calculations and provide flow rates or signal limits for the following two conditions:
(ai when the sensor is not in contact with the opposite side of the pipe
(b) when the sensor is not in contact with the opposite side of the pipe, while being inserted or retracted from the closed conduit
6.5 MateriaLs
In addition to the requirement that the materials of construction are compatible with the system process fluid. they must be compatible with the method of construction When dissimibr metals are used, selection should be such that galvanic corrosion is not induced to the extent that the performance and life of the device is impaired. Selection of the materials of construction must also consider atmosphenc cormmon when hostile atmospheres are present
6.6 Structural Consideration
The system must provide structural integrity with respect to pnure, temperature, induced bending due to fluid drag, expansion due to thermal effects, and any other impressed loads. In addition, fluid mechanical forces caused by the fluid flowing past the sensing element may cause the sensor to vibrate. This vibration can affect the performance of the meter and could result in fatigue failure of the sensor. Consult the manufacturer for appropriate flow rate or signal limits for the specified sensor size, design, and pipe size.
7 INSTALLATiON EFFECTS
The primary element performance can be affected by installation and velocity profile. [)eviations in the velocitv profile can be caused by in-line equipment. the piping configuration, and disturbances upstream and downstream of the primary element.
The manufacturer’s performance specifications should include a statement of the reference conditions under which the flow coefficient and uncertainties were determined.