Coriolis mass flow meter

·         The measuring principle is based on the controlled generation of coriolis forces. These forces are always present when both translational and rotational movements are superimposed.

·         The amplitude of coriolis force depends on the moving mass.

Notes:- The fluids fights against this rotation because it wants to keep traveling in the straight line. For any given rotational velocity, the amount of fight will be directly proportional to the product of the fluid velocity and fluid mass. This is the basis of a “coriolis mass flowmeter”. The magnitude of the coriolis force will be directly proportional to the fluids mass flow rate.

Measuring principle:

·         When the mass flows through a vibrating pipe coriolies forces exist which bend or twist the pipe.

·         These very small meter tube distortions are measured by optimally located sensors and evaluated electronically

·         This measuring principle is independent of pressure, temperature, density, viscosity and conductivity.

Tube designs:

·         The tube can be curved or straight form.

·         When the design consist of two parallel tubes, flow is divide into streams by a splitter near the meters inlet and outlet its recombined at the exit.

·         The single continuous tube design (or in two tubes joined in series), the flow is not split inside the meter.

·         In either case, drivers vibrate the tube, these drivers consist of a coil contacted to one tube and a magnet connected to the other. The transmitter applies an alternating current to the coil, which cause the magnet to be attracted and repelled by turns.

·         If the electromagnetic sensors are used, the magnet and coil in the sensor change their relative positions as the tube vibrate, causing change in the magnetic field at the coil.

·         The main difference between the force coil and the sensor coil is that the force coil is powered by an AC signal to impart a vibratory force to the tubes, where as the sensor coils are both unpowered so they can detect tube motion by generating AC voltages to be sensed by the electronics module.

·         When there is no flow in the two tubes, the vibration caused by the drive results in identical displacements at the two sensing points.

·         When the flow is present, coriolis force act to produce a secondary twisting vibration, resulting in a small phase difference in the relative motions. This is detected at the sensing points.

·         Meters are available in size from 6mm or less to 200mm or more and for flow ranges from 0-3kg/hr upto 0-680,000kg/hr.

·         Accurate measurement of both liquids & gases.

·         Ranges cover from less than 5g/m to more than 350 ton/hr.

·         Mass flow, density and temperature can be accessed from the one sensor.

·         Many models are affected by vibrations.

·         The upper pipe line diameter is 150mm