Variable area flowmeters, also known as rotameters, offers visual flow indication through a transparent tube with a linear scale. It consists of a float that moves through the tube as the liquid or gas passes through. When liquid or gas passes through the tube, the float begins to elevate up to the top of the tube.
Rotameters are versatile and simple to use flow device that does not requires power to operate. It measures the volumetric flow rate of clean, loaded and viscous liquids as well as clean gases. However, it is not suitable for liquids with suspended solid particles.
Medium Compatibility
Plastic rotameters are best suited for applications such as ionized water or corrosive medium.
Glass tube rotameters are highly sensitive with a wide measuring range and low-pressure drop. They are suitable to measure low-pressure medium without particles.
Vertical Mounting
Rotameters must be mounted vertically, with the flow flowing from bottom to the top. The flow rate inside the rotameter is measured using a float that is lifted by the fluid flow based on the buoyancy and velocity of the fluid opposing gravity pulling the float down.
Pipe Alignment
Rotameter is placed in between two sections of process piping by fittings. To prevent mechanical stress in the connecting pipes, the rotameter must be aligned in parallel and axial direction with the connecting pipe.
Straight piping sections requirement for the inlet is 5DN and 10DN for the outlet of the rotameter.
Fittings and Connections
Use an appropriate amount of Teflon tape on threaded connections before making connections to prevent leaking. Over-tightening will damage the fittings, while under-tightening will also cause leakage.
Valves should be closed before installation, and opened gradually when it is ready for testing or operation. It is highly recommended to conduct a leak test especially when the measuring liquid or gas is hazardous.
Grounding Connection
Grounding connection helps eliminate electrical noise or interference that affects the measurement accuracy of the flow meter.
Establishing a process ground is one of the most important installation details. Proper process grounding ensures that the sensor and medium are at the same potential so that only the induced flow signal is measured.
Float Movement
Before installation, place the rotameter horizontally on a flat surface, and incline the rotameter slowly to check if the float can move freely. Foreign particles may prevent the continuous motion of the float.
