Leser 411 Instructions De Service page 24

In addition AD 2000-Merkblatt A2 requires that
"safety valves must correspond to the state-of-
the-art and be suitable for the purpose for
which they are deployed".
Under the following conditions it is possible to
deviate from the upright installation direction,
and in our view it is also permissible.
E.g., the safety valves have been granted type
approval for non-upright installation and a note
to this effect is found in the VdTÜV-Merkblatt.
If adequate experience of installing safety valves
E
in a direction other than upright is available over
an extended period, this type of installation
is permissible if agreed between operator,
manufacturer and the technical inspector, who
authorises the installation. If applicable,
additional measures may need to be taken with
regard to this installation.
Therefore safety valves may, according to the
information provided above, be installed in
directions other than the one specified in AD
2000-Merkblatt A2.
If the conditions mentioned above have been
fulfilled, the following points have to be
observed when installing the valve in a direction
other than upright:
• Drainage has to be fitted to drain medium or
condensation from components which are
important for the function of the valve.
• Servicing procedures should be modified,
e.g., the functioning of the drainage system
must be ensured.
• LESER must be informed about the type of
installation in order to be able to agree to a
direction deviating from upright.
12.6 Flow-through
The flow direction must be observed during
installation. It can be recognised by the
following features:
• Flow direction arrow on the body
• Diagrams in the
– Complete Catalogue
– Operating instructions
– Data sheets and
– Assembly instructions.
12.7 Condensation
Medium or condensation must be drained from
the outlet chamber of the safety valve or such
components, which are important to the
functioning of the valve (spring, bellows etc.).
The following points should be noted:
• Drainage should always be carried out via the
blow-off pipe, which should be installed sloping
downwards so that it can drain itself (figure 3).
• Directly downstream of the safety valve there
must be no upward bend as in this case
correct drainage would not be possible
(figure 4).
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• The blow-off pipe must be provided with a
sufficiently large condensation drainage pipe,
which must be attached to the lowest point
of the pipe. For pipes larger than nominal
diameter 40 mm the drainage pipe must
have a nominal diameter of at least 20 mm.
(In case of steam applications even larger
diameters may be necessary. In such cases
the regulations must be observed).
• LESER safety valves are not provided with a
drain hole as the drainage must be executed
via the blow-off pipe.
Exceptions: Certain regulations require
drainage holes (e.g., on ships with variable
orientation in the water and a pipe slope).
Safety valves which are intended for such
purposes are equipped with a drainage hole.
Such designs are only manufactured if they
are specifically ordered.
• It is possible to drill a drain hole later at the
place intended for this purpose.
Caution: swarf can cause damage which
may lead to leaks or to the failure of safety
valves.
• Drainage pipes must be installed sloping
downwards; these pipes must have no
restrictions such as locally reduced
diameters. There must be an unobstructed
view of the drain outlet; any risks resulting
from leaking medium must be prevented.
(e.g., by fitting condensation traps, drip
container, filters, etc.)
• Unused drainage holes must be closed.
12.8 Transfer of vibrations from the installation
Any vibrations which might be transferred to the
safety valve must be prevented. If this is not
possible the safety valve must be decoupled
from the installation, e.g., via bellows, pipe
bends, ...
Pressure variations or surges in the medium
also may lead to dangerous vibrations of the
safety valve. This also has to be prevented.
If the transfer of vibrations cannot be
prevented, damping systems can be built in,
e.g., o-ring dampers.
12.9 Discharge pipe
When a safety valve blows off, in addition to the
general hazards from the medium, the following
hazards have to be expected (refer to section 2):
• High flow rates
• High temperatures
• Noise emissions
In this context the following points should be
noted:
• For steam or gases the blow-off pipe should
point upwards in order to allow blowing off
without danger.