What makes the venturi a practical flow meter

The orifice plates are simple, cheap and can be delivered for almost any application in any material. Turndown Ratio : Turndown ratio can be expressed as:. Maximum and minimum flow is stated within a specified accuracy and repeatability for the device. Example — Turndown Ratio for an Orifice Meter. This is a typical turndown ratio for a orifice plate. In general a orifice plates has turndown ratio between and In the Venturi Tube the fluid flowrate is measured by reducing the cross sectional flow area in the flow path, generating a pressure difference.

The rotameter consists of a vertically oriented glass or plastic tube with a larger end at the top, and a metering float which is free to move within the tube. Fluid flow causes the float to rise in the tube as the upward pressure differential and buoyancy of the fluid overcome the effect of gravity.

The float rises until the annular area between the float and tube increases sufficiently to allow a state of dynamic equilibrium between the upward differential pressure and buoyancy factors, and downward gravity factors.

The rotameter meter typically have a TurnDown Ratio up to Fluid scouring and abrasion of the throat are severe. Long-term measurement accuracy cannot be guaranteed.

The length of the structure must be manufactured according to regulations. Otherwise, the required accuracy will not be achieved. Due to the strict structural regulations of the classic venturi, its flow measurement range is the largest and the minimum flow ratio is very small, generally between 3 and 5.

This makes it difficult for Venturi flowmeters to meet flow measurements with large flow changes. There is a pressure measuring ring at 0. In addition, in the center of the throat, there is also a multi-channel pressure measuring ring leading to the pressure gauge.

The pressure difference between the inlet section and the smallest section that is, the throat section can be measured through the scale of the pressure gauge or the automatic recorder. The main advantage of the venturi tube is its simplicity of installation.

Secondly, due to its diffusion section, the fluid gradually decelerates, reducing the turbulence see turbulence. According to the manufacturing process and use, the venturi is divided into standard venturi, general venturi, venturi flow tube, small diameter venturi, rectangular venturi, and other structures. The detailed structure is as follows:. The standard classic Venturi tube is composed of an inlet cylindrical section A, a conical contraction section B, a cylindrical throat C, and a conical diffusion section E.

The general-purpose venturi , like the standard venturi, is composed of an inlet cylindrical section A, a conical contraction section B, a cylindrical throat C, and a conical diffusion section E.

The general-purpose venturi adopts the method of changing the contraction angle of the standard venturi and the length of the diffusion section to make it have the advantages of venturi, greatly shortening the length of the body, and effectively reducing the pressure loss. The Venturi flow tube is also composed of an inlet cylindrical section A, a conical contraction section B, a cylindrical throat C, and a conical diffusion section E.

The Venturi flow tube adopts a special pressure method to make it widely used in the flow measurement of dirty media and mixed-phase flow. The small diameter venturi is composed of an inlet cylindrical section A, a conical contraction section B, a cylindrical throat C, and a conical diffusion section E. The small diameter venturi adopts an integrated mechanical processing method to measure the fluid flow of small diameters. At the same time, it can use a variety of materials to meet the requirements of the on-site working conditions and can meet various connection methods such as welding, flange connection, and threaded connection.

The rectangular venturi is composed of an inlet cylindrical section A, a conical contraction section B, a cylindrical throat C, and a conical diffusion section E.

Main technical parameters of rectangular venturi:. Rectangular venturi is mainly used in power plant air supply and suction, heating furnace air supply, and suction occasions. Since its development, venturi products have been successfully applied to the measurement of high-humidity natural gas, low-pressure dirty biogas, coke oven gas, gas, steam, hot water, high-temperature hot kerosene, etc.

Besides, the venturi tube has a unique measurement advantage, for measuring conditions such as long straight pipe installation conditions, special high temperature , high pressure, strong corrosive and dirty media, and non-single phase flow measurement.

Of course, in the sewage and wastewater treatment industry, in addition to venturi flowmeters, electromagnetic flowmeters are also the first consideration for many users. For example, if you need to measure the flow of wastewater in a 2-inch pipe. Then you can refer to Magnetic Flow Meters Guides. Sino-Inst offers over 50 flow meter products. A wide variety of Annubar flow meter options are available to you, such as free samples, paid samples. Sino-Inst is a globally recognized supplier and manufacturer of flow measurement instrumentation, located in China.

Sino-Inst sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. Your email address will not be published. What is a Venturi Tube?

Get a Quote. More Flowmeters. Table of Contents. Venturi Flow Meter. Advantages of Venturi flowmeter If it can be accurately manufactured in accordance with ASME standards, the measurement accuracy can also reach 0. Listed in Table 1 are the venturi dimensions.

Athroat is the cross-sectional area of the throat, where hthroat is measured; A1 is the area at the point where h1 is measured. Table 1: Venturi Data A1 d1 Athroat dthroat 0. This is converted to volumetric flow rate by multiplying the cross-sectional area. Procedure The venturi meter experiment is initiated by closing the valves on the hydraulic bench, turning on the pump, and slowly opening them to ensure that water is flowing. Place weight on the balance lever and begin timing and weighing.

When the balance tips, the time is recorded and used to calculate the actual mass flow rate. Mass flow rates are calculated five times for each adjustment in flow on the hydraulic bench. Five flow adjustments are to be made, with an average time calculated.

Additional mass may be added if the time is too short to accurately measure. The head loss between manometers A and D is also recorded for each flow rate. In order to determine a more realistic value, a coefficient determined either empirically or from charts of Reynolds Numbers and venturi materials must be used.

The coefficient will always be less than 1, as in the real world energy is always lost. This coefficient is multiplied Equation 3.