Rotameter Working and its advantage /limitations

Rotameter is a device that is used for measuring flow rate of the fluid.

Principal of Rotameter: It works on the principle that force exerted by the float is equal to the weight of the liquid displaced by the float.

Working of Rotameter: It consists of the tapered metering glass tube, inside which float is placed. The tapering of the rotameter is depend upon the inlet and outlet connections. The float that is placed inside the rotameter has a higher density as compared to the fluid flowing in the rotameter.

When the flow rate is constant the float remains at a steady pace. But when the flow rate increase  or decrease the float move upwards or downwards respectively. The discharge equation for the flow rotameter is given by

Here Q = flow rate of the liquid

Cd = discharge coefficient

Vf = volume of float

ρf   =  Density of the float material









 f

ρ = Density of the fluid flowing

A = Annular area of float

Af   = cross-sectional Area of the Float


 
 

Advantage of Rotameter :

• It is easy to install, read and operate.
• cheap as compare to other methods to measure flow
• Can equip electronic devices to it . To measure flow rate , record the data with respect to time.
• Can handle corrosive fluids

Limitations of Rotameter :

• Glass tube can break as it become weak with time
• Can be used with small pipe size and capacities
• Accuracy is lower as compare to venturimeter and orifice meter
• Rotameter is need to mounted vertically and that is not possible in all cases