8
CAUTION
7.
Leak detection methods
Electronic leak detectors shall be used to detect flammable refrigerants, but the sensitivity may not be adequate, or may need re-
calibration.
(Detection equipment shall be calibrated in a refrigerant-free area.)
Ensure that the detector is not a potential source of ignition and is suitable for the refrigerant used.
Leak detection equipment shall be set at a percentage of the LFL of the refrigerant and shall be calibrated to the refrigerant
employed 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 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 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.
8.
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.
9.
Charging procedures
In addition to conventional charging procedures, the following requirements shall be followed.
- Ensure that contamination of different refrigerants does not occur when using charging equipment.
- Hoses or lines shall be as short as possible to minimize 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 over fill the refrigeration system.
Prior to recharging the system it shall be pressure tested with OFN (refer to #7).
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.
Electrostatic charge may accumulate and create a hazardous condition when charging and discharging the refrigerant.
To avoid fire or explosion, dissipate static electricity during transfer by grounding and bonding containers and equipment before
charging/discharging.
10.
Decommissioning
Before carrying out this procedure, it is essential that the technician is completely familiar with the equipment and all its details.
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.
g)
Start the recovery machine and operate in accordance with manufacturer’s instructions.
h)
Do not over fill cylinders. (No more than 80 % volume liquid charge).
i)
Do not exceed the maximum working pressure of the cylinder, even temporarily.
j)
When the cylinders have been filled correctly and the process completed, make sure that the cylinders and the
equipment are removed from site promptly and all isolation valves on the equipment are closed off.
k)
Recovered refrigerant shall not be charged into another refrigeration system unless it has been cleaned and checked.
Electrostatic charge may accumulate and create a hazardous condition when charging or discharging the refrigerant.
To avoid fire or explosion, dissipate static electricity during transfer by grounding and bonding containers and equipment before
charging/discharging.
