Metal-Tube Rotameter Selection Guide

Ideal applications

• Purge and seal air, sampling and analyzer feed lines
• High pressure and temperature duties where glass would fail
• Small-bore lines from DN15 to DN100 with modest accuracy needs

Three sizing rules

1. Keep the operating float position in the middle third of the tube for best readability.
2. Confirm the fluid's density and viscosity at operating conditions — a rotameter is density-sensitive.
3. For gas meters, verify the maximum flow at working pressure is within range.

Where rotameters fail

• Pulsating flow from reciprocating pumps causes float bouncing
• Solids or dirty media clog the annular gap
• Dusty gas may coat the tube and make the scale unreadable

Options that add value

• Magnetic or reed switch alarm contacts for low/high flow trips
• 4–20 mA output with alarm for remote control rooms
• PTFE-lined versions or Hastelloy floats for corrosive chemicals
• Fall-safe variants for loss of flow detection on seal lines

Ask for our sizing sheet — send fluid, pressure, temperature and the flow range and we reply with a model and price within a day.