relevant refrigerant. The leak tracing
equipment must be set and calibrated for
the relevant refrigerant, to ensure that the
gas concentration is a maximum of 25%
of the lowest combustible concentration
(Lower Flammability Limit, LFL) of the relev-
ant refrigerant.
Leak detection fluids are suitable for use
with most refrigerants but the use of deter-
gents containing chlorine shall be avoided
as the chlorine may react with the refriger-
ant and corrode the copper pipe-work.
If a leak is suspected, all naked flames shall
be removed/extinguished.
If a leakage of refrigerant is found which
requires brazing, all of the refrigerant shall
be recovered from the system, or isolated
(by means of shut off valves) in a part of
the system remote from the leak. Oxygen
free nitrogen (OFN) shall then be purged
through the system both before and during
the brazing process.
Removal and draining
When a cooling circuit is opened for repairs
– or for another reason– work must be
carried out in a conventional manner. Due
to the risk of fire it is important that best
practice is applied. Follow the procedure
below.
1.
Drain the refrigerant.
2.
Flush the circuit with inert gas.
3.
Drain the circuit.
4.
Flush again with inert gas.
5.
Open the circuit by cutting or burning.
Collect the refrigerant in the intended
container. Flush the system with oxygen-
free nitrogen to make the device safe. This
process may need to be repeated several
times. Compressed air and oxygen may not
be used.
Flush the system by breaking the vacuum
with oxygen-free nitrogen, and filling the
system to working pressure, relieving the
pressure to atmospheric pressure and fi-
nally pumping to vacuum. Repeat the pro-
cess until no refrigerant remains in the
system. After the final filling of oxygen-free
nitrogen, relieve the pressure in the system
to atmospheric pressure, so that work can
be carried out. This type of flushing must
be carried out if hot work is to be per-
formed on the pipe system.
Ensure that the vacuum pump's outlet is
not near to ignition sources and that there
is satisfactory ventilation by the outlet.
Filling
In addition to the conventional filling pro-
cedures, the following actions must be
taken.
■
Ensure that different refrigerants are not
mixed when filling equipment is used.
Hoses and lines must be as short as pos-
sible to minimise the enclosed refrigerant
volume.
■
Containers must be stored upright.
■
Ensure that the cooling system is groun-
ded before the system is filled with refri-
gerant.
■
Mark the system once filling is complete
(if not already marked).
■
Take extra care not to overfill the cooling
system.
Before refilling the system, pressure test it
with oxygen-free nitrogen. Leak test the
system after filling but before using the
system. Perform an additional leak test
before leaving the installation.
Decommissioning
Before performing this procedure, the
technician must be familiar with the
equipment and all its component parts.
7Chapter 1 | Important informationNIBE F470
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