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Safety Information (continued)
CABLING
Check that cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp edges or any other adverse environmental
effects. The check shall also take into account the effects of aging or continual vibration from sources such as compressors or fans.
DETECTION OF FLAMMABLE REFRIGERANTS
Under no circumstances shall potential sources of ignition be used in the searching for or detection of refrigerant leaks. A halide torch (or
any other detector using a naked ame) shall not be used.
LEAK DETECTION METHODS
The following leak detection methods are deemed acceptable for systems containing ammable refrigerants. Electronic leak detectors
shall be used to detect ammable refrigerants, but the sensitivity may not be adequate, or may need recalibration. (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 con rmed. Leak detection uids 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 pipework.
If a leak is suspected, all naked ames 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 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 ammability is a consideration. Opening of the refrigeration systems shall not be done by
brazing. 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 ushed 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 ll until the working pressure is
achieved, then venting to atmosphere, and nally pulling down to a vacuum. This process shall be repeated until no refrigerant is
within the system. When the nal 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 pipework are to take place.
□ Ensure that the outlet for the vacuum pump is not close to any ignition sources and there is ventilation available.
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 ll 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.
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.
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