When there are obstructions in a pipe, and there is an insufficient straight run to deliver a fully developed flow profile to the thermal flow meter, a flow conditioner can recreate an optimum profile.

Flow Profile and Flow Conditioner
A flow meter’s performance is dependent upon the flow profile of the media entering the instrument.

Flow Profile

A flow meter’s performance is dependent upon the flow profile of the media entering the instrument. The desired flow profile is referred to as a fully developed flow profile where the profile is symmetrical in the pipe, and the centerline velocity when in turbulent flow, is 1.2 times the average velocity. This flow profile will naturally develop with sufficient straight run; a distance of 15 to 25 pipe diameters downstream of a single elbow is typically sufficient.

Conditioning Plates
Flow Conditioning Plates

Flow Obstructions

Longer lengths of a straight run are recommended for various upstream flow obstructions. Table 1 gives the recommended amounts of a straight run for different flow obstructions commonly encountered. Downstream distances are not as critical as upstream distances; a distance of generally 5 pipe diameters is adequate for most piping configurations.

Disturbance Chart
Table 1

Flow Conditioner

In some installations, the pipe layout does not permit this amount of straight run. In these cases, the straight run recommendations can be reduced by using Sage’s flow conditioning plates or flow conditioner.

Built-in Flow Conditioning

In some designs, such as Sage’s in-line flow body, the flow conditioning is designed and built into the thermal mass flow meter. In these cases, the upstream distances ahead of the flow body shown in the table should be maintained.


flow conditioning assembly.
The upstream distance decreased to three pipe diameters when using a flow conditioning assembly.

These dimensional relationships are used in Sage Metering’s calibration facility. Installing the flowmeter utilizing these same dimensions will provide the expected and repeatable flow profile at the sensors.


This entry was posted in . Bookmark the permalink.