KROHNE H250 M40 ATEX II3G Ex nA EN - Manual (Page 8)

2
DEVICE DESCRIPTION
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H250 M40
www.krohne.com 01/2012 - 4001485201- MA H250/M40-Ex-II3G-AD R01 en
2.7 Ambient temperature / temperature classes
Due to the influence of the product temperature, variable area flowmeters with built-in electrical
equipment (electric variants) are not assigned to any fixed temperature class. The temperature
class of these devices is rather a function of the product temperature and ambient temperature
that is present and the specific device version. The classification is outlined in the following
tables.
The tables take into account the following parameters:
• Installed equipment
• Ambient temperature T
amb.
• Product temperature T
m
• Nominal DN
• Standard or high temperature version (HT)
• Standard or heating jacket version
• Heat resistance of the connecting cable
When there is more than type of built-in equipment, the data of the most unfavourable
equipment should be used.
For certain device version, lower values apply due to differing boundary conditions (e.g. lining
materials). Here the user should consult the technical data sheet.
INFORMATION!
The maximum permissible product temperatures listed in the tables are valid under
the following conditions:
• The measuring device is installed and operated in accordance with the manufacturer's
installation instructions.
• It must be ensured that the flowmeter is not heated by the effects of additional heat radiation
(sunshine, neighbouring system components) and thus operated above the permissible
ambient temperature range.
• Insulation must be limited to the piping.
Unobstructed ventilation of the indicator part must be ensured.
To do this, the variant with a projecting indicator (HT version) is preferable.
• For device versions with a heating jacket, that the temperature of the heating medium does
not exceed the maximum permissible product temperature.
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