By Grant Laidlaw
Many people ask for assistance in the understanding of theoretical and practical aspects of the industry. I will endeavour to enlighten.Many people ask for assistance in the understanding of theoretical and practical aspects of the industry. I will endeavour to enlighten.
Chris asks: Grant,we are beginning to see a lot of R290 in the commercial refrigeration space and in particular the cold drink type fridges. We were wondering, what changes to tooling and basic procedures do we need to make as this is a problem for us. Any advice would be appreciated. Also, are we allowed to transport these new flammable refrigerants in our vehicles? Again, what additional procedures do we need to implement a professional driving permit (PDP)? As equipment may only use 150g of hydrocarbons is this really viable for air conditioning systems or only for larger refrigeration systems?
Hi Chris, let us begin with the tooling, yes there are of course some changes necessary.
Some standard tools and equipment, including gauge manifold sets, can be used safely with flammable refrigerants. Although, South Africa is still in the process of updating the national standards pertaining to Hydrocarbons. Looking at the English and European EN Codes we find the following:
Safety procedure for the work area where HC systems are being serviced:
- There must be no source of ignition (compressor contactors, klixons, electrical connections) within 3m of the system.
- The area must be well-ventilated.
- The area must be monitored with a hydrocarbon leak detector.
A3 are refrigerants with a higher flammability risk than A2L-refrigerants. The main difference is that a relatively weak spark can ignite a flammable mixture. Static sparks typically occur from clothing, poor electrical earthing, or lighting an oxy-acetylene torch.
Avoiding sparks, good ventilation and no leakage are key points to avoid a dangerous situation. When working with A3 refrigerants, use a leakage detector and remember that the vacuum pump, ventilation fan, recovery unit and leak detector will need to be suitable and not constitute an ignition source.
As far as the tooling is concerned let us begin with vacuum pumps. The best option is to use vacuum pumps approved for use with A2L, A2 or A3 (flammable) refrigerants. Having said that, at the moment it is difficult to source these pumps from our local suppliers. This situation will improve as the market develops.
What if a vacuum pump approved for flammable refrigerants is not available?
Vacuum pumps with brushless motors can be used if the pump is switched on by an external power source and not by the on/off switch mounted on the pump. Check that the on/off switch is the only source of ignition in the pump. If this is the case, the vacuum pump can be safely used with flammable A2L-refrigerant if the on/off switch is not used:
Move the switch to the on position and plug the pump into a socket outside a minimum 3m radius from the unit and control the vacuum pump from this socket.
In Addition, keep the vacuum pump in a well-ventilated area or outside. The flammable refrigerant discharged by the pump should be able to safely disperse and should not result in a flammable situation.
Vacuum pumps with a brushed motor should not be used because of the high energy sparks they create within the motor.
Standard recovery machines cannot safely recover flammable refrigerants and therefore must not be used. Unlike vacuum pumps there are several sources of ignition (on/off switches, relays, pressure switches).
A leak would result in a flammable zone around the machine. As these hazards cannot be avoided; the correct recovery machine must be used. Again, currently these machines are not freely available from South African suppliers.
It is important to note the following:
- Evacuate the recovery cylinder to remove air before filling it with flammable refrigerant.
- Do not mix flammable refrigerants with other types of refrigerant in a recovery cylinder.
- When recovering hydrocarbon refrigerants, do not fill the recovery cylinders with more than 45% of the HFC safe fill weight.
- Label the recovery cylinder to show it contains a flammable substance.
- A2L synthetic refrigerants (as HFOs and R32) must be recovered as with the HFC refrigerants and not vented to the atmosphere.
Most electronic leak detectors used for HFC and HCFC leak detection are not safe or sufficiently sensitive for use with flammable refrigerants. This of course means that we will need to use electronic detectors specifically for flammable gases.
Flammable refrigerant systems must be leak-tested using a method that is safe and sensitive: for example, service cylinders.
The standard for Hydrocarbons used is:
- A red shoulder (donating: flammable gas).
- Left hand thread (an adapter piece is required to connect manifold).
- Minimum test pressure = 4800 kPa.
- Fill rate for recovery cylinders should be noted as they differ from HFCs, HCFCs.
In general, all service tools that are being used for HFCs can be used for hydrocarbon refrigerants.
Recommended procedure for recovering Hydrocarbon refrigerants from small refrigeration units:
- Ventilation fan 3m from the working area and position at floor level.
- Recovery unit 3m from the working area to recover the hydrocarbon refrigerant.
- When the desired low pressure is reached or the low-pressure lamp illuminates, switch the unit to low pressure override and allow it to run for two minutes (to remove refrigerant from the oil).
- Pressurise the system with nitrogen to just above atmospheric pressure.
- Using an HC sensor, check that no hydrocarbon refrigerant is in the air before using the brazing torch.
- Open or cut the connections and complete the service operation.
- Braze back the connections.
- Cylinders for flammable refrigerants have left thread connections. They differ from the traditional HFC refrigerant cylinders to avoid use of the incorrect fittings and underline the type of refrigerant being used.
- Recommendations for vacuum, recovery and leak checks for A2L-refrigerants are valid for A3-refrigerants.
For small quantities of hydrocarbons to be evacuated from a system, normal practice recommends venting, but always refer to national legislation. Regardless, venting needs to be conducted in a well-ventilated area, away from any ignition source.
Chris this brings us to the next aspect and that is the transport of flammable gases in cylinders and equipment.
Let us consider both the transport of flammable gases in cylinders, for example by the contractor, and the transport of refrigeration and air conditioning systems which are charged with flammable refrigerants. The most
common requirements of service companies and manufacturers are covered as follows:
Transportation of cylinders by road
When dealing with South Africa’s road legislation around transport of propane we find that reference is made to SANS 10231 and in particular to table C.1.
SANS 10231 establishes rules and procedures for the safe operation and handling of all road vehicles that are used for the transport of Dangerous Goods in accordance with the load constraints.
The procedures include requirements for the consignor, the consignee, the operator, the driver, the qualified person as well as en route procedures and cargo handling.
Studying the standard, we find that the hazardous class is 2.1 and propane is exempt from the legislation up to 100kg.
That being said we should remain attentive.
The Regulation applies to everyone carrying gases in the course of his or her work in a vehicle. cylinders have a capacity or the maximum weight of product. If the total load is below the 100kg threshold basic legal safety regulations apply, above the 100kg threshold the full legislation applies.
Most service companies will not exceed the threshold.
The basic safety requirements for a load below the threshold (small load exemptions) carried in a closed vehicle are as follows:
- Drivers should be aware of the hazards of the products, how to safely handle them, emergency procedures and the use of firefighting equipment;
- Vehicles should be well ventilated;
- One 2kg fire extinguisher should be carried;
- Cylinder valves should be closed, and adaptors disconnected;
- Cylinders should be secure and clearly labelled.
Transportation of charged systems
Given that the maximum amount of R290 in a single system is 500g, refrigerating machines and refrigerating machine components are considered exempt.
An excerpt from the standard reads as follows “the transport of machinery or equipment not specified in this clause and which contain dangerous goods in their internal or operational equipment, provided that measures have been taken to prevent any leakage of contents in normal conditions of transport”.
Looking again at the European requirements we find more detail. Flammable liquefied gases shall be contained within refrigerating machine components. These components shall be designed and tested to at least three times the working pressure of the machinery. The refrigerating machines shall be designed and constructed to contain the liquefied gas and preclude the risk of bursting or cracking of the pressure containing components during normal conditions of carriage.
Basic guidelines are:
- Cylinders must never be laid down. Always keep cylinders upright and well secured.
- Never tamper with a cylinder or valve. If excess force is needed to open or close the cylinder valve, or if the valve is damaged in any way, have it replaced.
- If a leak from the cylinder valve is detected, move the cylinder to a safe location at least 20 metres from any sources of ignition until empty.
- Ensure that cylinders are always kept away from sources of ignition.
- Should there be a fire, use a dry chemical fire extinguisher as these are suitable to extinguish flammable refrigerant fires.
- In the event of fire, a cylinder should be removed from the heat source. If this is not possible, keep the cylinder cool by spraying water on to it. However, if flames are threatening to engulf the cylinder, the area should be evacuated, and emergency services notified immediately.
- No cylinder larger than 9kg should be carried inside a passenger vehicle.
- Ensure cylinder valve is tight prior to transportation.
Chris, I hope that this assists you with the use of flammable refrigerants. They have arrived and are certainly here to stay. The last part of your question will be addressed in the next issue but please note: the maximum limit for a single contained system has been changed from 150g to 500g.
To finish this off I would like to pose the following question: We have been transporting propane in our cars, bakkies, caravans for years, what does the legislation say on the matter?
I quote: “The requirements of this standard shall not apply to the following:
The transport of dangerous goods by private individuals where the goods in question are packaged for retail sale and are intended for their personal or domestic use or for their leisure or sporting activities.
NOTE: Dangerous goods in IBCs, large packaging or tanks in excess of exempted quantities are not considered to be for personal or domestic use or for their leisure or sporting activities.