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1.10. Flammable Refrigerant Detection
CAUTION
Do not use potential sources of ignition when
detecting refrigerant leaks. Do not use a halide torch
or any other detector that employs a naked flame
The following leak detection methods are deemed
acceptable for systems containing flammable refrigerants.
•
Use electronic leak detectors to detect flammable
refrigerants
NOTE:
The sensitivity of electronic leak detectors may
not be adequate or may need re-calibration.
Detection equipment must be calibrated in a
refrigerant-free area. Ensure the detector is not a
potential source of ignition and is suitable for the
refrigerant used. Leak detection equipment must
be set at a percentage of the LFL of the refrigerant
and must be calibrated to the refrigerant in use
and the appropriate percentage of gas (25 %
maximum) is confirmed. Leak detection fluids are
suitable for use with most refrigerants, but the use
of detergents containing chlorine must be avoided
as the chlorine may react with the refrigerant and
corrode the copper pipe-work.
•
Remove or extinguish all naked flames if a leak is
suspected
•
If a leakage of refrigerant is found and requires
brazing, all refrigerant must be recovered from the
system or isolated (by means of shut off valves) in
a part of the system that is remote from the leak.
Oxygen-free nitrogen (OFN) must then be purged
through the system both before and during the
brazing process.
1.11. Remove/Evacuation of Refrigerant
Use conventional procedures when breaking into the
refrigerant circuit to make repairs or for any servicing
purpose. It is important to follow best practices since
flammability is a possibility. The following are high level
instructions for removing and evacuating refrigerant.
1. Remove refrigerant
2. Purge the circuit with inert gas
3. Evacuate
4. Purge again with inert gas
5. Open the circuit by cutting or brazing
Refrigerant Removal or Evacuation Tips
•
The refrigerant charge must be recovered into the
correct recovery cylinders.
•
The system must be flushed with OFN to render the
unit safe. This process may need to be repeated
several times.
•
Do not use compressed air or oxygen for this task.
•
Flushing is achieved by breaking the vacuum in
the system with OFN and continuing to fill until
the working pressure is met, then vented to the
atmosphere, and pulling down to a vacuum. This
process must be repeated until no refrigerant is
within the system.
•
The system must be vented down to atmospheric
pressure in order to service the unit after the final
OFN charge is used. This operation is absolutely vital
if brazing operations on the pipe-work is planned.
•
Verify the outlet for the vacuum pump is not close to
any ignition sources and there is ventilation available.
1.12. Charging Procedures
In addition to conventional charging procedures, the
following requirements must be met:
•
Ensure that contamination of different refrigerants
does not occur when using charging equipment.
•
Hoses or lines must be as short as possible to
minimize the amount of refrigerant contained in them.
•
Cylinders must be kept upright.
•
Ensure that the refrigeration system is grounded 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 must be pressure
tested with OFN. The system must be leak tested on
completion of charging, but prior to commissioning. A
follow-up leak test must be executed prior to leaving
the site.
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