ITRON MTZ, Инструкция по эксплуатации, Страница: 5 / 44

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ENGLISH
• (6) Dirt particles may damage the tur-
bine wheel therefore the use of starting
sieve and filter are recommended .
• (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 .
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