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By Grant Laidlaw

Many people ask for assistance in understanding theoretical and practical aspects of the industry. I will endeavour to enlighten. We are going back to basics as I have questions coming in that indicate that the basic understanding necessary to work in industry is not in place.

Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy (ACRA) in Edenvale. He holds a Bachelor of Business Administration and an associate degree in educational administration. He has a National TechnicalDiploma and completed an apprenticeship with Transnet. He has dual-trades status: refrigeration and electrical. He has been involved with SAIRAC for over two decades and served on the Johannesburg committee as chairman and was also president between 2015 and 2018. Currently he is the SAIRAC national treasurer.

Hi Stanley. At the moment in South Africa, the highest percentage of equipment using hydrocarbon refrigerants would be the domestic and light commercial sectors. However, the impact of the Montreal Protocol and in particular the Kigali amendment will most certainly see an increase in the quantity and scope of equipment using hydrocarbon refrigerants. This is especially true of R290. In the overseas markets the use of R290 extends into and from the unitary air conditioning market right up to and including large capacity indirect industrial chillers.

Stanley, the release of natural refrigerants including R290 is virtually harmless to the global environment, but we must consider all our options. In addition, while venting is permissible, we have to consider the health and safety aspects. As you may be aware, when dealing with hydrocarbons (R290, R600a) flammability and/or asphyxiation are hazards which must be considered.

In the last issue we dealt with the venting of hydrocarbons and will now move on to recovery. Hydrocarbon refrigerant venting should only be carried out as an alternative to recovery if the charge size is smaller than 500g. We are now looking at quantities greater than 500g that should be recovered.

Conventional recovery procedures, as used for any other refrigerant, are for the most part applicable when dealing with hydrocarbon refrigerants. However, attention should be paid to certain aspects such as:

The recovery machine used must be suitable for use with flammable refrigerants in general and not have any potential sources of ignition

Hoses should be complete with leak-free disconnect couplings and be in good condition

Before using the recovery machine, check that it is in satisfactory working order, has been properly maintained and that any associated electrical components are sealed to prevent ignition in the event of a refrigerant release. Consult the manufacturer if in doubt

• The recovery cylinder must be suitable for the refrigerant used, specifically, in terms of the pressure rating and the compatibility with the refrigerant
• Ensure that the correct number of cylinders for holding the total system charge are available
• Ensure all cylinders to be used are designated for the recovered refrigerant and labelled for the refrigerant (i.e. special cylinders for the recovery of refrigerant). Cylinders shall be complete with pressure-relief valve and associated shut-off valves in good working order
• When connecting hoses between the refrigeration system, manifold gauges, recovery machine and recovery cylinder, ensure that the connections are secure and there are no potential sources of ignition nearby
• A fire extinguisher must be available

Purge the hoses, manifold and recovery machine prior to recovery to avoid the ingress of air.

Take care to minimise the emission of refrigerant but also make sure that there is always sufficient ventilation to dilute the release by using a fan to disperse any refrigerant.

Note:

Enriched oxygen content in the surrounding workplace environment must be avoided (e.g. recovery in the immediate surrounding of brazing equipment). The minimum ignition energy can be greatly reduced at elevated oxygen levels or temperatures. The flammability limits are widened at elevated temperatures and elevated pressures.

Process for the recovery of refrigerant

Tools required:

• Evacuated appropriate recovery cylinder with pressure relief and shut-off valves
• Recovery cylinder valve adapter
• Recovery unit for the use with flammable refrigerants
• Four-way valve manifold gauge set for the refrigerant in use with hoses
• Access valves/tool in order to access system
• Refrigerant weighing scale
• Vacuum pump and refrigerant vent-line
• Inline filter drier place inline at inlet of recovery machine
• Blower for the ventilation of working area with capacity of 700 m³/h.
• Suitable flammable refrigerant gas detector
• Personal protection equipment (PPE)
• Safety area warning signs

Preparation for recovery

Safety precautions:

• Inform owner and/or supervisor and obtain permit of work if required
• Isolate the refrigeration system
• Place the warning signs within the work area
• Connect a ground strap between recovery unit, recovery cylinder and operator to prevent static electricity, build up
• Wear Personal Protection Equipment as required.
• Check all equipment is in good working order
• Label the recovery cylinder with the correct type and maximum filling weight of the refrigerant to be recovered
• Place the recovery cylinder on a calibrated scale
• Place the end of the vacuum pump vent-line at a safe place within outside ambient
• Switch on the gas detector (leak finding device) in ‘fresh air outside condition’ and place it in the floor area next to the equipment arrangement
• Check that all temporary refrigerant hose connections are tightened
• Maintain air circulation with blower

Recovery

Then do as follows:

• Operate the recovery unit according to the manufacturer’s operation instructions
• Observe operational parameters at manifold gauge, recovery unit and gas detectors
• Fill the recovery cylinder carefully and monitor the weight of the cylinder – and therefore the transferred refrigerant – with the scales
• 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, considering 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/dm³ and the density of R600a at 50°C is 0.517 kg/dm³. 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
• Monitor the discharge pressure to ensure that the maximum allowable pressure of the recovery cylinder is never exceeded. When 0 kPa level is observed on the low side manifold gauge, close both side manifold valves and turn off the recovery unit to prevent possible entry of air during recovery process. Do not pull the system into a vacuum with the recovery equipment
• When pressure on low side manifold gauge starts to rise, repeat operation
• Electric heating with the crank-case heater can be used to accelerate this process
• When the low side manifold gauge remains at 0 KPa, close all cylinder, manifold and hose valves
• Note the actual recovered refrigerant amount and update the recovery cylinder label
• Remove the recovery cylinder from the weighting scale, put sealing caps on connection ports
• Connect a suitable vacuum pump and evacuate the system to 1000 Microns in order to remove residues of refrigerant from the system
• Once the complete evacuation is complete flush the system through with nitrogen rendering the refrigerant circuit inert
• Prepare and execute subsequent repair/service work
• Fill system logbook with relevant data

After recovery

The recovered refrigerant should be returned to the refrigerant supplier in the correct recovery cylinder. Do not mix refrigerants in cylinders. If compressors or compressor oils are to be removed, ensure that they have been evacuated to an acceptable level to make certain that flammable refrigerant does not remain within the lubricant. The evacuation process shall be carried out prior to removing the compressor from the system. When oil is drained from a system it must be disposed of in the correct manner.

Check the filled recovery cylinder for the existence of non-condensibles by doing a temperature/pressure comparison.

This is done by placing the cylinder in a stable environment for 10 hours or overnight. Measuring temperature of the bottom quarter of the refrigerant cylinder. Place a manifold gauge set on the vapour service valve on the cylinder, open the value and record the pressure. The pressure should correspond with temperature on the pressure temperature chart for the specific refrigerant. Should the pressure reading be higher than what is indicated there are non-condensibles present in the cylinder. Following all the safety rules applicable to venting flammable refrigerants, vent the non-condensibles out of the cylinder until the pressure corresponds with the temperature as indicated on the chart.

Marking of recovery cylinders with flammable refrigerants

The cylinder containing recovered refrigerant should be marked to note any special conditions, for example: ‘HC R-290 – Recovered’. A red band on the shoulder or top of the container should designate flammable compounds, or mixtures that could become flammable in the event of a leak.

First aid measures

Should exposure to a refrigerant occur the following first aid measures should be followed:

General:

• Remove the victim to a safe area with fresh air and keep at rest in a comfortable position for breathing, if respiratory arrest occurs, provide resuscitation by trained personnel. Note: It may be dangerous for the person providing aid to give mouth-to-mouth resuscitation
• If unconscious, place in recovery position and get medical attention immediately. Maintain an open airway. Loosen tight clothing such as a collar, tie or belt
• Get medical attention

Eye contact:

• Immediately flush eyes with plenty of water, occasionally lifting the upper and lower eyelids
• Check for and remove any contact lenses and continue to rinse for at least 10 minutes
• Get medical attention

Contact with skin:

• Dermal (relating to the skin) contact with rapidly evaporating liquid could result in freezing of the tissues or frostbite
• Flush contaminated skin with plenty of water
• Remove contaminated clothing and shoes. To avoid the risk of static discharges and gas ignition, soak contaminated clothing thoroughly with water before removing it
• In case of contact with liquid, warm frozen tissues slowly with lukewarm water and get medical attention. Do not rub affected area

Ingestion is unlikely because of the low boiling point of the refrigerant. Should it occur, discomfort in the gastrointestinal tract from rapid evaporation of the refrigerant and consequent evolution of gas would result. May cause burns like frostbite. If frostbite occurs, get medical attention. Never give anything by mouth. Do not induce vomiting. It is crucial to seek medical attention, regardless of the severity of exposure. Provide the medical professionals with information about the type of refrigerant involved, the duration of exposure, and any other symptoms.

Stanley, I hope that this helps with your understanding of the recovery of flammable refrigerants and natural refrigerants in general.

REFERENCES:

1. ACRA
2. The Deutsche Gesellschaft für Internationale Zusammenarbeit GmbH