Orifice Meter

Construction:
An Orifice Meter is a device used to measure the flow rate of a fluid in a pipe. It consists of the following components:

1. Orifice Plate: A thin plate with a precisely sized hole (orifice) in the center, which is installed perpendicular to the flow direction of the fluid. The orifice plate is typically made of stainless steel or other durable materials to resist wear and corrosion.
2. Flanges: These are used to mount the orifice plate within the pipe, forming a secure seal around the edges of the orifice plate. The flanges also allow for pressure taps (inlet and outlet) to be connected to a differential pressure gauge.
3. Pressure Taps: Located at the upstream and downstream of the orifice plate. These taps measure the pressure difference across the orifice, which is related to the flow rate.
4. Differential Pressure Transmitter/Gauge: A device that measures the pressure difference between the two pressure taps. The pressure drop across the orifice is proportional to the flow rate.

Working:
When a fluid flows through the pipe, it is forced through the small hole in the orifice plate. According to Bernoulli’s principle, the velocity of the fluid increases as it passes through the orifice, causing a drop in pressure. This pressure drop can be measured by the differential pressure gauge. The relationship between the flow rate and the pressure drop is given by the continuity equation and Bernoulli’s equation

Venturi Meter

Construction:
A Venturi Meter is another device used for measuring fluid flow, but it operates on the principle of gradual changes in pipe diameter. Its key components include:

1. Converging Section: This is the section of the pipe where the diameter gradually decreases. As the fluid enters this section, its velocity increases and pressure decreases.
2. Throat: The narrowest part of the Venturi meter, where the fluid velocity reaches its maximum and the pressure is at its minimum.
3. Diverging Section: After the throat, the pipe diameter increases again, causing the fluid’s velocity to decrease and its pressure to recover.
4. Pressure Taps: Located at the inlet (upstream of the converging section) and at the throat (the narrowest part of the Venturi). These taps measure the pressure at these two locations.
5. Differential Pressure Gauge: Measures the pressure difference between the inlet and the throat. The difference in pressure is used to determine the flow rate.

Working:
The fluid flows into the converging section of the Venturi meter, where its velocity increases and pressure decreases due to the reduced cross-sectional area. At the throat, the velocity is at a maximum, and pressure is at a minimum. As the fluid exits the throat into the diverging section, the velocity decreases and pressure increases.

The flow rate is determined by measuring the pressure difference between the inlet and the throat.