ASME MFC-12M pdf download

ASME MFC-12M pdf download.Measurement of Fluid Flow in Closed Conduits Using Multiport Averaging Pitot Primary Elements.
ASME MFC-12M, provides information on the use of multiport averaging Pitot head-type devices used to measure liquids and gases. The Standard applies when the conduits are full and the flow
(a) has a fully developed profile
(b) remains subsonic throughout the measurement section
(c) is steady or varies only slowly with time
(ci) is considered single-phase
A differential pressure transmitter or other pressure measuring device, known as a secondary element, must be used with a multiport averaging Pitot primary element to produce a flow rate measurement.
Although multiport averaging Pitot primary elements are sometimes used in noncircular conduits, such applications are beyond the scope of this Standard.
2 TERMS AND DEFINITIONS
The terminology and symbols (Table 1) used in this Standard are in accordance with ASME MFC-IM. Some items from ASME MFC-IM are listed in para. 2.2.1 for easier reference.
Terminology not defined in ASME MFC-1M, but used in this Standard, are defined in para. 2.2.2.
2.1 Symbols
See Table 1.
2,2 Definitions
2.2.1 Definitions Found in ASME MFC-1M
cavitation: the implosion of vapor bubbles formed after flashing when the local pressure rises above the vapor pressure of the liquid. See also flashing.
differential pressure device: device inserted in a pipe to create a pressure differential whose measurement, together with a knowledge of the fluid conditions and of the geometry of the device and the pipe, enables the flow rate to be calculated.
7.1 Velocity Profile
Manufacturers define the performance of their APT for reference profile conditions with specific upstream and downstream lengths of straight pipe. These lengths are chosen to ensure the performance of the APT. Under nonreference conditions, upstream velocity profiles may affect the velocity profile at the flow measurement point and influence the performance. The manufacturer should be consulted for the sensitivity of the AFT to nonreference flow conditions. In some cases, the use of a flow conditioner may restore the velocity profile to the reference profile.
7.2 Upstream and Downstream Pipe Length Requirements
The minimum upstream and downstream straight lengths of pipe required to meet the performance specification of the APT should be stated by the manufacturer. The minimum lengths required downstream of different pipe fittings may vary for each APT and piping configuration.
When the flow measurement application or installation configuration does not match one of the manufacturer’s listed applications and installations, the flowmeter manufacturer should be consulted. If the manufacturer cannot provide sufficient guidance, in-situ calibration may be considered.
In-situ calibration establishes the flow coefficient of the APT and uncertainty under actual operating conditions. If in-situ calibration is performed, the calibration should be done in accordance with acceptable standards as listed in section 3. If in-situ calibration is not possible, the effect of installation can be reduced by performing a flow laboratory calibration of the meter replicating the actual upstream and downstream piping installations.
7.3 Alignment and Orientation
7.3.1 Alignment. The manufacturer shall specify the limits of the allowable angular tolerances for the installation of the APT. Deviation of the APT primary element in any angular alignment from the allowable limits can result in erroneous flow measurement.
7.3.2 Orientation. Manufacturers shall specify preferred APT locations and orientations with respect to the horizontal or vertical axis of the flow conduit. These preferred orientations may depend on the fluid being measured.
7.4 Conduit Internal Surface Condition
Surface roughness of the flow conduit can affect the velocity distribution at the metering location. The manufacturer should advise the user on the effects of internal pipe surfaces. In some cases, buildup of mineral or other deposits on the internal wall of the conduit may alter the velocity distribution or obscure the APT sensing ports.