KROHNE H250 M40 NEPSI Ex d-Ex t - Manual (Page 6)

2
DEVICE DESCRIPTION
6
H250 M40
www.krohne.com 06/2013 - 4002868601 MA H250-M40-NEPSI-Ex-d-R01-
2.4 Flammable products
Atmospheric conditions: Atmospheric conditions: Atmospheric conditions: Atmospheric conditions:
An explosive atmosphere is a mixture of air and flammable gases, vapours, mists or dusts under
atmospheric conditions. The following values define it
T
atm
= -20...+60°C / -4...+140°F and P
atm
= 0.8...1.1 bar.
Outside of this range, no key data are available as to ignition behaviour for most mixtures.
Installation conditions: Installation conditions: Installation conditions: Installation conditions:
Variable area flowmeters operate outside of atmospheric conditions, which means that
explosion protection – regardless of the zone assignment – is fundamentally not applicable due
to the lack of key safety data for the interior of the measuring section.
2.5 Device category
Variable area flowmeters are designed in accordance with GB 3836.1-2010, GB 3836.2-2010 and
GB 12476.1-2000.
WARNING!
Operation with flammable products is only permitted as long as no explosive fuel/air mixture
builds up on the inside of the flowmeter under operating conditions. The operator is responsible
for ensuring that the flowmeter is operated safely as regards the temperature and pressure of
the products used. In case of operation with flammable products the measuring units must be
included in the periodic pressure tests of the system. When using the device version H250/C...
(PTFE-liner, nonconductive) the min. conductivity of the medium must be 10
-8 S/m, in order to
avoid the electrostatic charge.
INFORMATION!
Definition of zone 1 acc. to EN 1127-1, Appendix B:
An area in which an explosive atmosphere may occasionally occur as a result of the mixture of
flammable substances in the form of gas, steam or mist with air under normal operation.
Definition of zone 21 acc. to EN 1127-1, Appendix B:
An area in which an explosive atmosphere may occasionally occur in the form of a cloud of
flammable dust in the air under normal operation.
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