www. refrigerationandaircon. co. za RACA Journal I May 2025 41
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• Set of refrigerant transfer hoses with plastic hose of appropriate length for use as vent line( approximately 15m)
• One set of access valves in order to minimise refrigerant release during equipment connection at appliances / system service ports( if required)
• Flammable refrigerant gas detector depending on risk assessment
• Floor standing fan to disperse any refrigerant leakage
• PPE according to risk assessment
• Safety area warning signs
Preparation for venting:
• Inform owner, supervisor and obtain permit for work( if required)
• Wear PPE as required
• Place the warning signs within the work area
• Switch off the refrigerating system
• Switch on the leak detector( leak finding device) at fresh air outside condition and place on the floor area near the equipment
• Use the correct refrigerant manifold and connect refrigerant transfer hoses as required
• Use a small floor fan to vent the area around the equipment and disperse and accidental leakage to below the refrigerants lower flammability limit
Venting process:
• Use a floor fan and connect the manifold gauges
• Check that all temporary refrigerant hose connections are tightened( all connections are Temporary Flammable Zones)
• The gauges show the standing pressure in the system
• If the system is pressurised, open valves on the manifold gauge set to begin venting
• Set to a low flow rate through the vent-line to ensure the refrigerant is well diluted on exit
• Check flow of hydrocarbon refrigerant( pressure indications, sight glass on manifold, vent-line outlet)
Continue venting refrigerant until pressure gauges indicate 0 kPa( atmospheric pressure). Do not hurry, allow the refrigerant to flow out of the refrigerating appliance completely. Remember that refrigerant is absorbed into the compressor oil and the system still contains refrigerant at atmospheric pressure.
Flame proof vacuum pump suitable for use with flammable refrigerants
Once venting is complete:
• Close all valves
• Evacuate the system using a suitable vacuum pump for use with flammable refrigerants
Once the complete evacuation process is completed, purge with nitrogen( allow nitrogen to flow through system). If purging with nitrogen is not possible, the system should be pressurised with nitrogen and the evacuation procedure repeated, to ensure that there is minimal HC refrigerant remaining inside the system. Mark the system‘ Empty’. Stanley, moving on to flammable refrigerant recovery. For systems with refrigerant charges larger than 500g, in most circumstances it is recommended to recover the refrigerant, as opposed to venting.
For this you will need recovery cylinders which are specially designed for the extraction of refrigerants( and oil) from refrigerating systems. Recovery cylinders should have a dual-port valve for liquified and vapour refrigerant. They are constructed according to international and local standards. Note: These recovery cylinders are typically not recommended for the use with R-32 refrigerant.
Do not exceed the maximum charging capacity of the cylinder. When a container is filled with refrigerant, the maximum charge should always be observed by using a calibrated weighting scale, taking into account that possible refrigerant mixtures have a lower density than pure refrigerant. The usable container capacity should therefore be reduced. It should be noted that the density of R290 at 50 ° C is 0.449 kg / dm ³ and the density of R600a at 50 ° C is 0.517 kg / dm ³.
The charging capacity is a result of the internal volume of the container and the liquid density of the refrigerant at a reference temperature( 70 % liquid by volume at 50 ° C). Do not exceed the allowable pressure of the container, even temporarily, during any operation. Special valves may be fitted to the refrigerant container to avoid the possibility of over-filling. Container filling to be carried out according to national regulations. Do not mix different refrigerants, refrigerant should not be placed in a container that contains a different or an unknown refrigerant. An unknown refrigerant already in a container should not be vented to the atmosphere but reclaimed and disposed of in the correct manner.
Refrigerant recovery cylinders that are over-filled exceeding the allowable charge amount may vent refrigerant through their safety valves. Large quantities of vented hydrocarbon refrigerant into for example a vehicle represents a major safety hazard. In addition severely overfilled cylinders can explode with catastrophic consequences.
Refrigerant charging into cylinders must be monitored with the use of calibrated charging scales and all processes involving temporary connections and systems under pressure should never be left unattended.
Warning of non-condensable gases( typically nitrogen and air): In the case of non-condensable gases entering HCFC and HFC cylinders, although undesirable, could more easily be dealt with. In the case of flammable refrigerants, it is of fundamental importance to avoid transfer of non-condensable gases into the recovery cylinder. Air has to be especially avoided as it contains
www. refrigerationandaircon. co. za RACA Journal I May 2025 41