When installing a metal tube rotameter (a variable area flow meter) in a vertical orientation, there are several important considerations to ensure accurate measurement and long-term reliability. Below is a detailed guide on what to watch for during vertical installation:

1. Flow Direction

• Vertical Position Only: Metal tube rotameters are typically designed to be installed vertically, with fluid flowing from bottom to top. Ensure that the flow direction matches the design of the rotameter.
• Arrow Indication: Most rotameters have a flow direction arrow on the body. Make sure the installation follows this direction to avoid measurement errors.

2. Straight Pipe Length

• Upstream and Downstream Straight Runs: To ensure accurate measurement, the rotameter should be installed with adequate straight pipe lengths:
  • Upstream: Typically, at least 5 pipe diameters of straight pipe before the meter is required.
  • Downstream: 3 pipe diameters of straight pipe after the meter is usually sufficient.
• These straight sections help stabilize the flow and minimize turbulence, improving measurement accuracy.

3. Avoid Flow Disturbances

• No Obstructions Near the Meter: Avoid installing the rotameter near bends, valves, or fittings that can cause flow disturbances like turbulence or swirl.
• Installation After Valves or Pumps: If installed after control valves or pumps, ensure sufficient straight pipe length to avoid distorted flow patterns.

4. Stable Mounting

• Rigid Support: The rotameter should be mounted securely to prevent vibration or movement. Any instability can interfere with the float’s movement inside the tube, causing inaccurate readings.
• Avoid Vibrations: External vibrations from nearby equipment should be minimized as they can affect the float’s stability and lead to incorrect readings.