ASME MFC-14M-2003 (R2018)

This Standard specifies the geometry and method of use (installation and flowing conditions) for orifice meters of 6 mm to 40 mm (1⁄4 in. to 1 1⁄2 in.) line size when they are inserted in a conduit running full. It also gives necessary information for calculating flow rate and its associated uncertainty.

It applies only to differential pressure devices in which the flow remains subsonic throughout the measuring section, flow is steady or varies only slowly with time, and the fluid is considered single-phase. In addition, the uncertainties are given in the appropriate sections of this Standard for each of these devices within the pipe size and Reynolds number limits, which are specified.

This Standard covers devices for which sufficient calibrations have been made to enable the specification of coherent systems of application and to enable calculations to be made with certain predictable limits of uncertainty.

The devices introduced into the pipe are called primary devices. The term primary device also includes the pressure taps and the associated upstream and downstream piping. All other instruments or devices required for the measurement or transmission of the differential pressures are known as secondary elements, and in combination are referred to as the secondary devices. This Standard covers the primary devices; the secondary devices will be mentioned only occasionally, as and when necessary for the proper operation of the primary device.

The different primary devices covered in this Standard are:

(a) orifice plates used with corner pressure taps;

(b) orifice plates used with flange pressure taps;

(c) specially designed orifice meters with integral fittings.