Generally in pipelines pumps , piping bends, vibrations, control valves will generate swirl. Any swirl present in the fluid which enters into turbine meter can change the effective angle of engagement and hence deviation in the reading will take place and false reading will be take place. so it is required to install flow straightener before turbine meter to minimize liquid rotation , the swirl effect of the fluid

After passing through the turbine meter the fluid enters into the downstream of the flow meter which is 5D flow straightener which controls any swirl existence on the rotor.

It is good practice to keep minimum straight run of pipe 10 times diameter of pipeline at upstream of turbine meter and 5 times diameter of pipeline at downstream of turbine meter.