Flow metering is very critical as it enables the users to monitor and hence control the use of utilities like steam, water etc.
Differential pressure type flow meters are widely used for different flow metering applications.
Principle of Operation
In any fluid flow, the pressure drop taking place is directly proportional to the flow of the fluid. Thus, if we know the pressure drop taking place in a fluid flow, the flow can be calculated by taking the square root of pressure drop and multiplying it with certain constants.
Each differential type flow meter consists of two fundamental blocks. The first block causes the kinetic energy of the fluid to change which results in the pressure drop. The second element measures this pressure drop and calculated the actual amount of flow. Differential type flow meters can be further classified depending on the element used to bring about the pressure drop, most common being an orifice.
Orifice Type Flow Meter
In an orifice type flow meter, the element which produces the pressure difference is an orifice plate. An orifice plate is nothing but a metal plate with a hole of required diameter bored in it. When the fluid passes through the orifice, the pressure drops. This pressure drop is measured and the flow is calculated.
Other Types of Differential Type Flow Meters
In place of an orifice plate, different elements can be used to produce the pressure difference. The different elements used for pressure reduction can be venturi tubes, pitot tubes, flow nozzles etc. Each type of meter has its own advantage or disadvantage and hence is used for specific applications. For instance, using venture tube instead of orifice plate gives ability to handle high flows with relatively low pressure drops.