Recommended Installation; Start Up; Installation With An Upstream Valve; Installation With Upstream And Downstream Valves - WDV Molline MZ Manual De Instrucciones

• (7) Pressure pulses must be avoided
during starting and operating to preserve
the turbine wheel. To prevent damage
during starting, increase the pressure
slowly at less than 0,3 bar per second.

3.2 Recommended installation

Turbine meters are flow meters therefore
their metrology can be affected by distur-
bances existing in the flow of gas.
The best accuracy is achieved by respect-
ing the following rules:
• Use preferably elbow pieces with large
radius (> 5 DN) to be installed at the
inlet of the meter.
• For diameter variations, use preferably
concentric convergent and divergent
pieces; sudden changes must be avoid-
ed.
• Obstacles such as thermowells must not
protrude in the pipe within 2 DN up-
stream of the meter. Gaskets should be
correctly centred between the flanges
and not protrude into the pipe.

3.3 Start up

3.3.1. Installation with an upstream
valve
Open the valve very slowly until the me-
ter starts to operate. Increase slowly the
pressure in the downstream pipe (max.
0,3 bar/second). When the downstream
pressure is stabilised, open the valve com-
pletely.
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3.3.2 Installation with upstream and
downstream valves
Close the downstream valve. Open slowly
the upstream valve (max. 0,3 bar/second).
When the pressure is stabilised in the me-
ter, open gently the downstream valve to
maintain the pressure in the meter and to
avoid overflow.

3.3.3 Installation with a by-pass

Close all valves. Slowly open the by-pass
and wait until the downstream pressure is
stabilised. Then proceed as §3.3.2. Close
the bypass.
After start up, please check the tightness of
the installation. Check also that the maxi-
mum flow of the meter is not exceeded.

4 Transmitters

The MZ is equipped as option with 2 Low
Frequency (LF), Reed switches and an anti-
tampering switch; with inductive medium or
high frequencies (HF) transmitters. A Cyble
sensor can be also installed onto the to-
taliser, see Annex 3.
Remarks about using the meter in poten-
tially hazardous areas (ATEX)
• Pulse transmitters must be connected to
circuits intrinsic safe circuits, according
to EN 60079-11.
• All exposed aluminium parts must be
suitably protected (using paint, varnish,
etc) if a film of rust is possible from dust
in the environment.
• The meter must be earthed.
• Tools used for installing, removing, or
repairing the meter on site must be ap-
propriate for use in the hazardous area
bearing in mind that the hazardous area
classification during meter replacement
5