TRAINING
Characteristics of some flammable refrigerants can be seen in table 2.
Saturation temperature at atmospheric pressure Practical limit, the limit that if exceeded is deemed unsafe and might lead to asphyxiation
LFL (lower flammability limit), the minimum quantity mixed in air required to create a flammable mixture
UFL (upper flammability limit), this is the maximum quantity mixed in air required to create a flammable mixture
Density in air at 21°C MIE Minimum ignition energy in mJ
Replacing a high GWP with a low GWP refrigerant is a good idea with regard to direct global warming however, the indirect effect needs to be considered as well. Therefore, the efficiencies and cooling capacities of refrigerants need to be compared to evaluate the characteristics of the refrigerants.
During the training course one of the subjects covered is to ensure that all attendees have an in depth understanding of the charge limitations and additional control measures required under EN 378. The technician will be given a variety of
scenarios using A2L and A3 refrigerants and be asked to calculate the charge limits by ascertaining the access category (A, B or C) and then the location classification (I, II or III). From this information they should be able to
undertake the required steps to enable them to work out the maximum charge allowable.
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The candidate will then ascertain whether or
not the equipment is suitable or if alternative provisions are required. Provisions include ventilation/extract systems and/or permanent leak detection. The requirement within the UK is that
anyone enrolling on the new ‘Flammables Qualification’ would need to hold a current and valid F-Gas certificate, many of the practical activities can be omitted from the syllabus as they will already have proven competency. Practical areas will be covered if they differ significantly from the requirements of the F-Gas assessment, including carrying out a location specific risk assessment to allow identification of hazards that could affect safe working practices when installation, commissioning, servicing and de- commissioning of RACHP systems. Recovery of flammable refrigerants will be covered so the attendees understand the health and safety implications and can select suitable recovery equipment. Technicians may not be equipped with a new recovery unit and will therefore need to recognise if their equipment is suitable or not. Attendees will need to show competency
creating a suitable working environment, ensuring that a flammable mixture cannot exist during service and maintenance. The image below is purely an example. The area of potential flammability will vary dependent upon refrigerant used, charge size, potential leakage points etc. The extent should be calculated with a risk assessment under The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR). It is a requirement that all refrigerating
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systems are installed, commissioned and repaired in accordance with the findings of a DSEAR assessment, even if the system does not use a flammable refrigerant. If the system has been charged with a flammable refrigerant, any ‘hot works’ would obviously impose the greatest risk. The technician would need to ensure that prior to Oxy-fuel brazing, a flammable mixture cannot be present. This is achieved by the following process: Evacuate the systems to a pressure below the refrigerant boiling point at the ambient temperature
Agitate the oil in the compressor (use the oil pump, crankcase heater etc)
Purge with inert gas (place flammable gas detector near outlet of purge) Repeat as necessary
Upon completion of the training and assessment, the candidate will be issued with a certificate of competence to the safe handling of A2, A2L and A3 refrigerants which will be valid for five years.
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