Installation
Proline t-mass 65 PROFIBUS DP
14
3.2.4
Inlet and outlet runs
The sensitivity of the thermal dispersion principle to low flow rates means the flowmeter can also
be sensitive to internal disturbances in the flowing gas stream (e.g. swirl), especially in the larger
pipe diameters
≥
DN 150 (
≥
6").
As a general rule, the installed thermal flow sensor should always be installed as far away as possible
from any flow disturbances (see ISO14511 for further information).
Process components or pipework configuration
When disturbances (e. g. pipe elbows, reducers, valves, T-pieces etc.) are located upstream of the
thermal meter, precautions must be taken to minimise any effects on the measuring performance.
The figure on the following page illustrates the minimum recommended inlet and outlet runs,
expressed in multibles of the pipe diameter. Longer lengths should always be used if they are
available.
Regardless of any other consideration, the minimum recommendations for inlet and outlet runs on
either side of the sensor are:
Inlet runs:
Minimum 15 x DN for the flanged version (65F)
Minimum 20 x DN for the insertion version (65I)
Outlet runs:
Minimum 2 x DN for the flanged version (65F)
Minimum 5 x DN for the insertion version (65I)
!
Note!
• These are minimum values, increasing these dimensions will often improve the flowmeter
perfomance.
• Where two or more disturbances are located upstream of the meter, the longest recommended
upstream pipe run is to be observed as an absolute minimum.
• It is always recomended to install control valves downstream of the flowmeter.
• For very light gases such as Helium and Hydrogen all upstream distances should be doubled.
