Schmidt
Mess- und Regeltechnik
©2014 Schmidt
Mess- und Regeltechnik
Fon 0 67 32 - 91 91 20 Fax 0 67 32 - 96 24 42 [email protected]
6
8.1
Description of function
Type device DW-U-EX is a combination of a flow switch and meter with analogue display of the
current flow and a flow switch with adjustable switch-point. However, the type device DW-N-EX
is a flow-switch with adjustable switch-point without an additional flow indicator of the current
flow. Each device, type DW-U and type DW-N, is also available with gold-plated contacts for
intrinsic safe circuits without EX-switch. A model with two independent adjustable switches is
also available.
The devices can be used as follows:
a. In Zone 2 (Gas-Ex, Category 3G) in the Explosion group IIA und IIB
b. In Zone 22 (Dust-Ex, Category 3D) at dusts with minimum ignition energy (MIE) > 3 mJ
c. In Zone 1 (Gas-Ex, Category 2 G) in the Explosion group IIA und IIC
d. In Zone 21 (Dust-Ex, Category 2D) at dusts with minimum ignition energy (MIE) > 3 mJ
e. Usually there is no zone within the measuring tube. Here, Zone 1 may be set as maximum.
The qualification regarding the surface temperature is T4; for all gases, vapours, mists with an
ignition temperature > 125°C, the mentioned devices are no ignition source.
In the dust-EX category, the reference temperature is 110°C. Other measures concerning the
safety distance from glow temperature, etc. must be performed by the operator.
8.2 Assembly units
The devices Type DW-U and Type DW-N consist of following units:
Z
Description
Assessment
of ignition risk
Remarks
1 Lower part with baffle plate, metal
bellows, flanges
included
2 Upper part with mechanics and indication
included
3 Switch
Company Stahl
Manufacturer’s declaration / BA
4 Switch as simple apparatus
arbitrary
500 volts to earth
8.3. Identification (label)
Type: DW-N-EX resp. DW-U-EX
TFR: 04ATEX 010 Nr.:/No.: ……………… CE year of construction
II 2GD c IIB T4 IP65 T125°C
-20°
C ≤ Ta ≤ 70°C
Operation Manual
Flowmeter / Flow Control DW-U
Flow monitor after the baffle plate principle for liquids
