How must tube- and ball-type flowmeters be mounted?

• A. Horizontally
• B. Vertically
• C. Between 5 ft and 5.5 ft above the floor
• D. On a solid surface

Answer: (B)

Tube- and ball-type flowmeters (rotameters) work by letting a float rise inside a tapered tube as gas flow increases. The float position is what indicates the flow rate, and it is stabilized by gravity as the gas pushes the float upward. Because the float relies on this vertical balance to settle at a precise height, the meter must be mounted vertically with the flow moving upward. Mounting it horizontally would let gravity pull the float to the side or bottom, causing unstable or inaccurate readings and possible sticking. So the correct mounting is vertical to ensure accurate measurement and easy reading.