Selecting the Right Glass Rotameter—Part 1

With the many glass rotameter available today, choosing the most appropriate one for a given application can be difficult. This article discusses sixteen popular glass rotameter technologies,  and gives several suggestion correspondingly.

1.Operating principle

The glass rotameter is a variable area flowmeter consisting of a bottom-up vertical glass cone and a float that can move up and down with the flow. When the fluid flows cone from the bottom to top, The lift in the float generated by the fluid kinetic energy and fluid buoyancy make the float up.

As the annular flow area between the inner wall of the cone and the float increases, the lift of the fluid kinetic energy in the float decreases. When the sum of lift and buoyancy is equal to the gravity of the float itself, the float is in equilibrium and stabilized at a certain height, which represents the flow rate flowing through the flowmeter. Since the flow rate flowing through the flow meter is proportional to the flow area of the flowmeter, the height position of the float can be used as the flow rate.