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1. What kind of instrument does an orifice flowmeter belong to?
An orifice flowmeter belongs to a differential pressure flow instrument.
1. Instrument classification attributes: 1 The measurement principle is based on the pressure difference generated upstream and downstream when the fluid flows through the throttling element (orifice plate), and the flow rate is calculated by measuring the differential pressure value, which conforms to the Bernoulli equation and continuity equation principles. According to the national standard classification based on GB/T 2624-2006 "Measurement of full pipe fluid flow using differential pressure devices installed in circular cross-section pipelines for seepage control", the orifice plate flowmeter is clearly classified as a differential pressure ridge flow detection instrument.
2. Core Features 1 Structural composition • Throttling device: standard orifice plate (with circular hole thin plate) • Pressure sensing device: corner joint pressure sensing/flange pressure sensing • Differential pressure transmitter: measures pressure difference and outputs signal • Flow meter: converts flow rate based on differential pressure value 2 Technical parameters (data source: Metrology Technical Specifications released by the State Administration for Market Regulation in 2023) • Accuracy level: ± 1.0%~± 2.5% • Reynolds number range: 5 × 10 ³~1 × 10 ⁷ • Diameter range: DN50~DN1000 • Applicable media: gas, liquid, steam
III. Application restrictions • Large permanent pressure loss (about 50%~90% differential pressure value) • Strict requirements for straight pipe sections (above 10D and 5D) • Not suitable for viscous and solid particle media • Range ratio usually not excee
2. Working principle of orifice flowmeter
An orifice flowmeter is a device that calculates gas flow by measuring pressure difference. Its core principle is based on energy conservation and flow continuity in fluid mechanics.
. Here is a detailed explanation:1. Working principle: When gas flows through an orifice plate, due to the sudden reduction in the cross-sectional area of the orifice plate, the gas flow velocity increases significantly at the orifice, while the pressure decreases. According to the Bernoulli equation, the kinetic energy and static pressure energy of a fluid are converted into each other, and an increase in flow velocity leads to a decrease in static pressure, thereby forming a pressure difference (Δ P) between the upstream (high-pressure side) and downstream (low-pressure side) of the orifice plate. The relationship between flow rate and pressure difference: Under stable flow conditions, the gas flow rate (qv) is proportional to the square root of the pressure difference (Δ P), that is: qv: gas volume flow rate (m3/min) K: orifice plate coefficient (determined by orifice plate geometry, gas properties, etc., calibrated at the factory) Δ h: water column pressure difference measured by U-tube (mm), multiplied by density ratio 13.6 if using mercury column. By measuring the pressure difference Δ h and combining it with the known K value, the gas flow rate can be calculated.
2. Structure Composition: The orifice flowmeter consists of the following core components: orifice plate: a circular thin plate with a precisely sized c