Series NKS-N, NKSP-N
Page
8
9520-021-en
Revision 17
TM 10477
Edition 05/2022
3
Safety notes for applications in potentially explosive areas
based on the Directive 2014/34/ EC (ATEX)
The valves are intended for use in a potentially
explosive area and are therefore subject to the
conformity assessment procedure of the directive
2014/34/EC (ATEX).
As part of this conformity assessment, an ignition
hazard analysis to EN 13463-1 to satisfy the
fundamental safety and health requirements was
conducted with the following result:
♦
The valves do not have any ignition source of
their own and can be operated both manually
as well as mechanically/electrically.
♦
The valves are not covered by the scope of
application of the ATEX directive and therefore
do not need to be identified accordingly.
♦
The valves may be used in a potentially
explosive area.
Supplementary notes:
♦
Electric/mechanical
actuators
must
be
subjected to their own conformity assessment
to ATEX.
It is imperative to observe the individual points of
intended use for application in a potentially explosive
area.
3.1 Intended use
Improper operation, even for brief periods, may
result in serious damage to the valve.
In connection with explosion protection, potential
sources of ignition (overheating, electrostatic
and induced charges, mechanical and electric
sparks)
may
result
from
these
improper
operation;
their
occurrence
can
only
be
prevented by adhering to the intended use.
Furthermore, reference is made in this connection to
the Directive 95/C332/06 (ATEX 118a) which
contains the minimum regulations for improving the
occupational health and safety of the workers who
may be at risk from an explosive atmosphere.
A difference is made between two cases for the use
of chargeable liquids (conductivity < 10
-8
S/m):
1. Chargeable liquid and non-conductive lining
Charges can occur on the lining surface. As a
result, this can produce discharges inside and
outside the valve.
a) Discharges inside the valve
However, these discharges inside the valve
cannot cause ignitions if the valve is completely
filled with medium.
If the valve is not completely filled with medium,
e.g. during evacuation and filling, the formation of
an explosive atmosphere must be prevented, e.g.
by superimposing a layer of nitrogen. It is recom-
mended to wait 1 hour before removing the valve
from the plant in order to permit the elimination of
static peak charges.
This means that, to safely prevent ignitions, the
valve must be completely filled with medium at all
times or else a potentially explosive atmosphere
must be excluded by superimposing a layer of
inert gas.
b) Discharges outside the valve
At the points where the non-conductive lining e.g.
protrudes on the sealing surfaces to the outside or
gets contact with the atmosphere on the outside,
it may lead to discharges from the lining to nearby
valves or attachments.
To safely avoid explosion hazards and accidents,
therefore, the atmosphere surrounding the valve
must not be explosive.
2. Chargeable liquid and conductive lining
No hazardous charges can occur as charges are
discharged direct via the lining and shell (surface
resistance < 10
9
Ohm, leakage resistance < 10
6
Ohm)
If non-conductive versions of individual compo-
nents are installed in the valve, it may restrict the
permitted ATEX zone and explosion subgroup
when operating the valve despite the conductive
lining of the armor plating (see “Technical rules for
hazardous substances: Avoidance of ignition
hazards due to electrostatic ch
arges” (TRGS
727)).
In these cases, consult the manufacturer.
Static discharges of non-conductive linings
are only produced through the interaction with
a non-conductive medium and are therefore
the responsibility of the plant operator.
Static discharges are not sources of ignition
which stem from the valves themselves!
♦
The temperature of the medium must not exceed
the temperature of the corresponding temperature
class or the maximum admissible medium tem-
perature as per the operating manual.
♦
If the valve is heated (e.g. heating jacket), it must
be ensured that the temperature classes pre-
scribed in the Annex are observed.
