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1 - INTRODUCTION
Never cover any protection devices.
This applies to the relief valves in the refrigerant or heat transfer
medium circuits, and the pressure switches.
Ensure that the valves are correctly installed, before operating the
unit.
DO NOT OBSTRUCT ANY PROTECTIVE DEVICES:
This applies to any fusible plugs, rupture disks and valves fitted
on the refrigerant or heat transfer fluid circuits. Check whether the
original protection plugs are still present at the valve outlets. These
plugs are generally made of plastic and should not be used. If they
are still present, please remove them. Fit devices at the valve or
discharge piping outlets to prevent the penetration of foreign
bodies (dust, building debris, etc.) and atmospheric agents (water
can form rust or ice). These devices, as well as the discharge
piping, must not impair operation or lead to a pressure drop that
is higher than 10% of the set pressure.
CLASSIFICATION AND CONTROL:
In accordance with the Pressure Equipment Directive and national
usage monitoring regulations in the European Union, the protective
devices fitted to these machines are classified as follows:
Refrigerant Side
(3)
High pressure safety loop
(4)
External relief valve
Rupture disk
Heat transfer fuid side
External relief valve
(1) Classified for protection in normal service situations.
(2) Classified for protection in abnormal service situations. These accessories are
sized for fires with a thermal flow of 10kW/m². No combustible matter should be
placed within 6.5m of the unit.
(3) High pressure safety loop = SRMCR as described in component section of this
manual and in electrical diagram.
(4) The instantaneous overpressure limitation of 10% of the operating pressure
does not apply to this abnormal service situation.
The control pressure can be higher than the service pressure. In this case, either
the design temperature or the high pressure switch ensures that the service
pressure is not exceeded in normal service situations.
(5) The selection of these relief valves must be made by the personnel responsible
for completing the hydraulic installation.
All factory-installed relief valves are lead-sealed to prevent cany
calibration change. The external relief valves must always be
vented to outside if the units are installed in a closed space. Refer
to the installation regulations, for example those of European
standard EN 378 and EN 13136. These pipes must be installed
in a way that ensures that people and property are not exposed
to vented refrigerant. As the fluids can be diffused in the air, ensure
that refrigerant is discharged away from building air intakes, relief
valves must be checked periodically. The valves must be checked
periodically.
The safety device shall be tested at least once a year to verify
good operation and cut out value.
An example of test procedure without removing the pressure
switch is given in Section 13.8 of this manual.
If the relief valves are installed on a change-over manifold, this is
equipped with a relief valve on each of the two outlets. Only one
of the two relief valves is in operation, the other one is isolated.
Never leave the change-over valve in the intermediate position,
i.e. with both ways open (locate the control element in the stop
position). If a relief valve is removed for checking or replacement
please ensure that there is always an active relief valve on each
of the change-over valves installed in the unit.
All factory-installed relief valves are lead-sealed to prevent any
calibration change.
The external relief valves are designed and installed to ensure
damage limitation in case of a fire.
Device for damage
Safety
limitation in the event of an
(1)
device
external fire
X
X
X
(5)
(5)
In accordance with the regulations applied for the design, the
European directive on equipment under pressure and in
accordance with the national usage regulations:
- These relief valves (and rupture disk if used) are not safety
accessories but damage limitation accessories in case of a
fire,
- The high pressure switches are the safety accessories.
The relief valve must only be removed if the fire risk is fully
controlled and after checking that this is allowed by local
regulations and authorities. This is the responsibility of the
operator.
When the unit is subjected to fire, safety devices prevent rupture
due to over-pressure by releasing refrigerant. The fluid may then
be decomposed into toxic residues when subjected to the flame:
- Stay away from the unit
- Set up warnings and recommendations for personnel in
charge to stop the fire.
- Fire extinguishers appropriate to the system and the
refrigerant type must be easily accessible.
The external relief valves must be connected to discharge pipes
for units installed in a room. Refer to the installation regulations,
for example those of European standards EN-378.
These standards include a sizing method and examples for
(2)
configuration and calculation. Under certain conditions they permit
connection of several valves to the same discharge pipe.
Carrier recommends using flexible hose to connect the relief valves
to discharge pipe. Special care shall be taken so that coupling to
discharge pipe is not creating mechanical stress on relief valve
connection.
These pipes must be installed in a way that ensures that people
and property are not exposed to refrigerant leaks. These fluids
may be diffused in the air, but far away from any building air intake,
or they must be discharged in a quantity that is appropriate for a
suitably absorbing environment (Note that the R1234ze(E) and
R515B refrigerants are heavier than air).
It is recommended to install an indicating device to show if part of
the refrigerant has leaked from the valve. The presence of oil at
the outlet orifice is a useful indicator that refrigerant has leaked.
Keep this orifice clean to ensure that any leaks are obvious.
The calibration of a valve that has leaked is generally lower than
its original calibration. The new calibration may affect the operating
range. To avoid a nuisance tripping or leaks, replace or re-calibrate
the valve.
Periodic check of the relief valves: See paragraph "Maintenance
safety considerations".
Provide a drain in the discharge circuit, close to each relief valve,
to avoid an accumulation of condensate or rain water.
Ensure good ventilation, as accumulation of refrigerant in an
enclosed space can displace oxygen and cause asphyxiation or
explosions.
Inhalation of high concentrations of vapour is harmful and may
cause heart irregularities, unconsciousness, or death. Vapour is
heavier than air and reduces the amount of oxygen available for
breathing. These products cause eye and skin irritation.
Decomposition products are hazardous.
5
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