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Proline Prosonic Flow 91
"
Endress+Hauser
5.4
Application specific commissioning
5.4.1
Zero point adjustment
Consequently, zero point adjustment is generally not necessary.
Experience shows that the zero point adjustment is advisable only in special cases:
• To achieve highest measuring accuracy also with very small flow rates.
• Under extreme process or operating conditions (e.g. very high process temperatures or very high-
viscosity fluids).
Preconditions for a zero point adjustment
Note the following before performing a zero point adjustment:
• A zero point adjustment can be performed only with fluids that contain no gas or solid contents.
• Zero point adjustment is performed with the pipe completely filled and at zero flow
(v = 0 m/s). This can be achieved, for example, with shutoff valves upstream and/or downstream
of the measuring range or by using existing valves and gates ( å 38).
– Standard operation valves 1 and 2 open
– Zero point adjustment with pump pressure valve 1 open / valve 2 closed
– Zero point adjustment without pump pressure valve 1 closed / valve 2 open
Caution!
• If the fluid is very difficult to measure (e.g. containing entrained solids or gas) it may prove
impossible to obtain a stable zero point despite repeated zero point adjustments. In instances of
this nature, please contact your Endress+Hauser service center.
• You can view the currently valid zero point value using the "ZERO POINT" function ( ä 104).
Fig. 38:
Zero point adjustment and shutoff valves
Performing a zero point adjustment
1.
Operate the system until normal operating conditions resume.
2.
Stop the flow (v = 0 m/s).
3.
Check the shutoff valves for leaks.
4.
Check that operating pressure is correct.
2
1
Commissioning
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