Expenditure Flowmeter is a typical differential pressure flowmeter. Industrial production is used to measure gas, liquid and steam flow of the most commonly used as a flow meter. According to the survey statistics, in the steel plant, oil refineries and other industrial production system used by a flow meter (70-80) percent of the expenditure flowmeter. In the entire industrial production in the area of New flowmeter flow meter also account for more than half of the total. Therefore, cutting expenditure flowmeter be so widely used, mainly because it has two very prominent advantages:

structure is simple, easy to install, reliable, low cost, but also has a certain accuracy. Can meet the needs of measurement.

have a long history of use, rich and reliable experimental data, design and processing have been standardized. As long as the standard design and processing of cutting expenditure flowmeter, which does not require the actual demarcation, also known in the uncertainty within the flow

Measurement

In particular, is the second advantage, making expenditure flowmeter in the manufacture and use are very convenient. Because of a flow meter, in particular the large flow measurement with the juice flows in the test will be encountered all sorts of difficulties.

Flowmeter usually by cutting expenditure can be fluid flow into the differential signal differential pressure measuring device and cutting expenditure and show the flow of differential composition. The installation of pipelines in the flow of savings device also called "a device", which includes cutting expenditure items, and take pressure before and after the installation of the straight. Display devices also called "secondary device", which includes differential signal line profits in the measurement instruments.

Many countries have done a lot of cutting expenditure on installation work. AGA (American Gas Association) and ASME (American Society of Mechanical Engineers) from the beginning of this century began cutting expenditure on the experimental device, the results were in 1969 and 1971 released in the report. DIN (German industry standard), have had to cut expenditure devices, to 1969 has been amended six times the international standard of difficult Organization (ISO) in a summary of the countries on the basis of research results, in 1967 and 1968 published ISO/R541 and ISO/R781, as a device to cut expenditure of international standards. 1980 also on the front of the two documents were revised and published in the appropriate orifice, and cultural Venturi nozzle of the international standards ISO 5167. China is also in 1981 published a flow measurement device to cut expenditure national standards GB 2624, the diagonal access pressure, flange pressure from the standard orifice and Kok access standard nozzle pressure to specific provisions.

The use of standard equipment to cut expenditure, and the fluid nature of the state must meet the following conditions:

must be filled with fluid channels, and cutting expenditure devices, and continuously flows through the pipeline.

fluid must be Newtonian, that is, in physics and thermodynamics is uniform, single-phase, or can be considered the single-phase, including mixed gases, solvents and dispersion of particles smaller than o. 1 m of colloid. In the gas in not more than two percent (the quality of ingredients) evenly dispersed particles of solid, liquid or in not more than 5% (volume elements) evenly distributed bubbles can also be considered to be single-phase fluid. However, its density should take the average density.

fluid flows through the expenditure of time is not in the intersection.

fluid flow does not change over time or change very slowly.

fluid flowing through cutting expenditure in the previous cases, the flow is parallel to the beam axis of the pipeline without swirl.

Standard installation does not apply to move to cut expenditure and the critical flow of the stream flow measurement.