Midea MPPD40C User Manual page 10

Leak detection fluids
are suitable for use with most refrigerants but the use of detergents containing
chlorine shall be avoided as the chlorine may react with the refrigerant 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
o 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.
12.Removal and evacuation
When breaking into the refrigerant circuit to make repairs or for any other purpose
conventional procedures shall be used. However, it is important that best practice is
followed since flammability is a consideration. The following procedure shall be
adhered to: Remove refrigerant; Purge the circuit with inert gas; Evacuate; Purge
again with inert gas; Open the circuit by cutting or brazing.
The refrigerant charge shall be recovered into the correct recovery cylinders. The
system shall be flushed with OFN to render the unit safe. This process may need to
be repeated several times. Compressed air or oxygen shall not be used for this task.
Flushing shall be achieved by breaking the vacuum in the system with OFN and
continuing to fill until the working pressure is achieved, then venting to atmosphere,
and finally pulling down to a vacuum. This process shall be repeated until no
refrigerant is within the system. When the final OFN charge is used, the system shall
be vented down to atmospheric pressure to enable work to take place. This
operation is absolutely vital if brazing operations on the pipe-work are to take place.
Ensure that the outlet for the vacuum pump is not close to any ignition sources and
there is ventilation available.
13.Charging procedures
In addition to conventional charging procedures, the following requirements shall be
followed. Ensure that contamination of di erent refrigerants does not occur when
using charging equipment. Hoses or lines shall be as short as possible to minimise the
amount of refrigerant contained in them. Cylinders shall be kept upright.
Ensure that the refrigeration system is earthed prior to charging the system with
refrigerant. Label the system when charging is complete (if not already).
Extreme care shall be taken not to overfill the refrigeration system. Prior to
recharging the system it shall be pressure tested with OFN. The system shall be leak
tested on completion of charging but prior to commissioning. A follow up leak test
shall be carried out prior to leaving the site.
14.Decommissioning
Before carrying out this procedure, it is essential that the technician is completely
familiar with the equipment and all its detail. It is recommended good practice that
all refrigerants are recovered safely. Prior to the task being carried out, an oil and
refrigerant sample shall be taken in case analysis is required prior to re-use of
reclaimed refrigerant. It is essential that electrical power is available before the task
is commenced.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure ensure that: Mechanical handling equipment is
available, if required, for handling refrigerant cylinders;All personal protective
equipment is available and being used correctly; The recovery process is supervised
at all times by a competent person; Recovery equipment and cylinders conform to
the appropriate standards.
d) Pump down refrigerant system, if possible.
e) If a vacuum is not possible, make a manifold so that refrigerant can be removed
from various parts of the system.
f) Make sure that cylinder is situated on the scales before recovery takes place.
09