Yokogawa RotaMASS 3-Series - Manual (Page 61)

5. BASIC OpErATINg prOCEdUrES
5-9
IM 01R04B04-00E-E 8th edition March 01, 2011 -00 All Rights Reserved. Copyright © 2003, Rota Yokogawa
After the flow meter is installed into the process pipe work, set up the parameter corresponding to calibration
certificate (generally set up in the factory) and perform the pre-operation zero adjustment.
Zero adjustment is required before beginning operation in order to obtain the output signals are accurately
proportional to the flow.
Zero adjustment is performed to set the instrument to 0% when the flow rate is 0.
- Stop flow before starting autozero (valve on outputs).
- During autozero time
- Flow is fixed to zero
- Totalizer stops counting.
- Display switches do not work.
Following procedure should be executed after installation but before starting measurement to get
best measuring results:
- Flush the meter with the fluid under process conditions. Flush the meter with the fluid under process conditions.
- Stop flow, the best way is closing valves upstream and downstream. Stop flow, the best way is closing valves upstream and downstream.
- Wait 2 minutes in which density, temperature and pressure should stabilize. Wait 2 minutes in which density, temperature and pressure should stabilize.
- Density check:
• for measurement of liquids control via expected medium density reading that the measuring for measurement of liquids control via expected medium density reading that the measuring
tubes are gas free (density not lower than expected. Do not forget to insert the process pressure
and pressure unit for the pressure compensation via Detailed Setup / Config Fld vars / Dens).
• for measurement of gases there is no possibility to check the density reading as the density for measurement of gases there is no possibility to check the density reading as the density
value of gases is lower than 0.3 kg/l and the ROTAMASS switches automatically to 0 kg/l, see
chapter 7.7.
- Perform Autozero. Perform Autozero.
- Store the Autozero value in Autozero History if required. (Only if you enter the date the values will Store the Autozero value in Autozero History if required. (Only if you enter the date the values will
be stored).
- Flow measurement can start. Flow measurement can start.
For setting a proper Autozero the conditions have to be well defined. Under certain circumstances it is
recommended not to perform Autozero but use the Autozero value set during flow calibration in the factory:
- zero flow condition cannot be guarantied while valves may be not tight
- two or multi phase medium whether the phases separates under no flow condition
- two phase medium whether there is gas contained in the fluid phase or liquid particles in the gas phase
ROTAMASS incorporates two measuring tubes which vibrates at a resonance frequency between 100 Hz
and 200 Hz. Under certain circumstances there is a similar resonance frequency in the pipe work or fixture
which might be excited. In this case high zero fluctuation may occur and Autozero value can’t be executed
properly. Changes in the mechanical support of the detector should be done to decouple the detector from
the vibrating structures.
5.6 Zero adjustment (Autozero)
IMPORTANT
IMPORTANT
CAUTION
WARNING