本标准规定了孔板、喷嘴和文丘里管插入满管导管时的几何形状和使用方法（安装和流动条件），以确定流体流动速率。它还提供了计算流量及其相关不确定性的必要信息。它仅适用于差压装置，在该装置中，整个测量段内的流动保持湍流和亚音速，是稳定的，或仅随时间缓慢变化，且流体被视为单相流体。此外，在规定的管道尺寸和雷诺数限制范围内，本标准的适当章节中给出了这些装置的不确定性。 它涉及已进行充分校准的设备，以便能够规范一致的应用系统，并能够在某些可预测的不确定度范围内进行计算。引入管道的设备称为主要设备。术语一次设备还包括测压口和相关的上游和下游管道。测量或传输差压所需的所有其他仪器或装置称为二次元件，组合称为二次装置。本标准涵盖主要设备；次要设备只会偶尔提及。本标准涵盖以下主要设备: （a） 孔板，可与以下测压口布置一起使用:（1）法兰测压口，（2）D和D/2测压口，（3）拐角测压口。（b） 喷嘴:（1）ASME长半径喷嘴。（c） 文丘里管:（1）经典文丘里管。本标准不适用于尺寸小于50 mm{2 in.}的管道或导管名义上的本标准不适用于ASME性能试验规范测量。本标准适用于测量任何流体（液体、蒸汽或气体）的流量。

This Standard specifies the geometry and method of use (installation and flowing conditions) for orifice plates, nozzles, and Venturi tubes when they are inserted in a conduit running full, to determine the rate of the fluid flowing. It also gives necessary information for calculating flow rate and its associated uncertainty. It applies only to pressure difference devices in which the flow remains turbulent and subsonic throughout the measuring section is steady or varies only slowly with time and the fluid is considered single-phased. 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. It deals with 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; secondary devices will be mentioned only occasionally. The following primary devices are covered in this Standard: (a) orifice plates, which can be used with the following arrangements of pressure taps: (1) flange pressure taps, (2) D and D/2 pressure taps, (3) corner pressure taps. (b) nozzles: (1) ASME long radius nozzles. (c) Venturi tubes: (1) classical Venturi tubes. This Standard does not pipe or conduit sizes under 50 mm {2 in.} nominal. This Standard does not apply to ASME Performance Test Code measurements. The Standard is applicable to measurement of flow of any fluid, (liquid, vapor, or gas).