HVAC&R MODULE Skills 120 FLAMMABLE Workshop LOWER TOXICITY

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This Skills Workshop is taken from the Institute of Refrigeration’s 2018 Safety Code of Practice. The object of this code is to define minimum Skills summary requirements for safety in the design, construction and installation, ■ What? commissioning, inspection and maintenance of vapour compression Properties of flammable refrigerants as refrigerating systems utilising flammable, lower toxicity refrigerants. listed in the Institute of Refrigeration’s 2018 Safety Code of Practice. These are classified as Group A2L, A2 or A3 refrigerants. ■ Who? This section of the code deals with the properties of these refrigerants. Relevant for every person with responsibility through ownership, The code of practice is intended to apply within the United Kingdom. consultancy, design, construction, installation, commissioning, However, the information is of general use in Australia as well. Where decommissioning, operation, maintenance, appropriate, relevant Australian standards have been noted next to the inspection, repair, modification or testing of a compression refrigeration system. British standards.

(LFL) and the Upper Flammability Limit (UFL) in Moisture solubility Relevant properties air and the Auto-Ignition Temperature (AIT). The Moisture is sparingly soluble in most refrigerants occupational exposure limit (OEL) indicates the of refrigerants at ambient temperature. The solubility decreases concentration of in the atmosphere that as the temperature reduces and excess Physical properties is allowable for continuous exposure during an can lead to the formation of ice or hydrate at the eight-hour working day. The PL for A2L, A2 and A3 Table 1 on page 17 shows some of the important expansion device, which could impair or stop the refrigerants is based on approximately 20% of the physical properties for the most common operation of the system. Moisture also increases LFL. Refrigerant detection devices should be set to flammable lower toxicity refrigerants. The normal the possibility of chemical reactions between the warn of concentrations of A2L, A2 or A3 refrigerants indicates the type of application for refrigerant, the oil and the system components and which approach the PL and the OEL. which the refrigerant should be used. The Practical in many refrigeration applications acids may form Limit (PL) of the refrigerant indicates the allowable The Figure below shows the pressure temperature which could damage the windings of hermetic or refrigerant charge related to the smallest human relationship of a selection of different refrigerants semi-hermetic compressors. Due to the chemical occupied space as defined in BS EN 378-1:2016. including which is an A3 Flammable make-up of , this is unlikely to occur Reference is made to the Lower Flammability Limit Lower Toxicity Refrigerant covered by this Code. with A3 refrigerants, but still applies to A2L and A2 refrigerants. Figure 1. Pressure temperature relationship of selected refrigerants 1000 Adsorbent desiccants (molecular sieves) which preferentially adsorb water in the presence of many refrigerants are generally applicable to most A2L, 100 A2 and A3 refrigerants provided the appropriate grades of adsorbent desiccant are selected. Conventional desiccants, such as activated alumina,

) 10 will adsorb moisture in the presence of most A2L, A2 and A3 refrigerants. However such desiccants

ar(A) do not retain moisture at higher temperatures as 1 Atmospheric Pressure well as the molecular sieve materials. Moisture removed during operation of the refrigerating CO2 system may therefore be returned to the system

Pressure (b 0.1 R-32 when it is switched off and warms up. It is strongly recommended that drier cores (or beads etc) specifically designated for the refrigerant are used. Propane 0.01 R-134a Lubricants In general, blends containing A2L or A2 refrigerants are not soluble in mineral or alkyl-benzene oils. 0.001 Special synthetic lubricants are recommended. -120 -100 -80-60 -40-12 0 20 40 60 80 100120 140 The most common type of synthetic lubricant for Temperature (°C) use with A2L or A2 refrigerants is the polyolester

April 2019 | www.airah.org.au/nation | HVAC&R Nation | 15 HVAC&R Skills Workshop oil (POE) (although the automotive industry Chemical properties and Excursions to concentrations above the commonly uses polyalkylene glycol (PAG) oils for potential hazards Occupational Exposure Limit values quoted in automotive air conditioning). It is a disadvantage Table 1 are permitted as defined by the short-term A risk assessment shall be carried out by a of these lubricants that they have a much greater exposure limit (STEL) where listed by the HSE or competent person prior to commencing any work. affinity for water than traditional mineral oils to other short-term limits as advised by refrigerant The following items should be considered – note the extent that they will absorb moisture from the manufacturers after risk assessment. atmosphere. They therefore have to be kept from this list is not exhaustive and a site specific risk assessment should be carried out. contact with the atmosphere as much as possible. The vapour of most refrigerants is colourless, odourless and denser than air. If inadvertently PAG oils have the additional disadvantage that they Reactivity are intolerant of trace quantities of chlorine. released to atmosphere it will initially collect at low A2L, A2 or A3 refrigerants do not react with steel, level, particularly in pits, trenches and basements. In general, pure A3 refrigerants can be used with copper, aluminium and brass in acceptably dry Suitable temporary forced ventilation which does a wider range of lubricants, particularly mineral refrigerating systems. Alloys containing more not provide a source of ignition shall be provided and alkyl-benzene oils. However, solubility than 2% magnesium will react with fluorine and to disperse the vapour rapidly. tends to be increased with A3 refrigerants chlorine atoms in A2L and A2 blends and so so it may be necessary to select a lubricant should only be used with pure A3 refrigerants. In Care shall be exercised on entering a pit, trench with a higher viscosity grade. Polyalphaolefin the presence of moisture, zinc and galvanised steel or basement where there is a possibility of a high (PAO) and polyalkylene glycol (PAG) are also are particularly susceptible to corrosive attack. concentration of refrigerant vapour. acceptable for use where approved by the compressor manufacturer. POE oils are also Thermal decomposition Fatal accidents involving refrigerants can occur acceptable but do exhibit an even higher A3 refrigerants are subject to thermal either as a result of asphyxiation or ignition. solubility with A3 refrigerants. It is a disadvantage decomposition at temperatures of the order of of these lubricants that they have a greater 450°C, and A2L and A2 refrigerants at temperatures Direct contact affinity for water than ordinary mineral oils and in excess of 250°C. In the presence of oil and other Where liquid refrigerants having boiling points therefore have to be kept from contact with contaminants they are subject to reaction and below zero Celsius at atmospheric pressure come the atmosphere as much as possible. decomposition at lower temperatures, particularly into contact with the skin or eyes, evaporation if impurities such as moisture are present in the may cause freezing of the skin or eye fluids and Care should be taken that the correct lubricant is system. Temperatures in refrigerating systems freeze burns may occur. Clothing saturated with selected for the application, for the compressor should be limited to about 135°C. Many A2L, A2 or liquid refrigerant may freeze to the skin. Higher and for the refrigerant used. Seek advice from the A3 refrigerants have low indices of compression, boiling point refrigerants have solvent actions compressor manufacturer if there is any doubt. which tend to produce low compressor discharge that can cause defatting and cracking of the skin. temperatures, although some can have higher Goggles, suitable temperature rated gloves and Materials compatibility discharge temperatures e.g., R32. other suitable clothing shall be worn whenever It is important to consider the compatibility of the there is a risk of exposure to refrigerant liquid. refrigerant and the compressor oils with system Since A3 refrigerants lack chlorine and fluorine materials such as plastics, elastomers, metals, etc. atoms there is no possibility of acid formation in the presence of moisture and therefore Potential sources of Virtually all common elastomer and plastic salt formation and subsequent blockage in refrigerant leakage materials used as ‘O’ rings, valve seats, seals appliances is unlikely. Thermal decomposition of The refrigerating system contains refrigerant and gaskets are compatible with A2L, A2 or A3 A3 refrigerants external to the system does not in both liquid and vapour states. It is possible refrigerants. Materials that are not compatible and produce harmful decomposition products, whilst under abnormal conditions for liquid refrigerant should not be used in HC systems include EPDM, decomposition of fluorinated refrigerants can to enter the compressor, for example by way natural rubbers and silicone rubbers. It should be produce toxic substances such as hydrofluoric acid of faulty valves or by overcharge of refrigerant noted that chloroprene (neoprene) products are which is harmful to human health at atmospheric to the system. A compressor is designed to specifically incompatible with unsaturated A2L, concentrations above 2 ppm v/v. A2 or A3 refrigerants (i.e. R1270, R1150, etc). compress refrigerant gas and not to pump liquid; Care shall be taken to exclude refrigerants where if excess liquid does enter a compressor, damage Whilst testing has been conducted on a any brazing, welding or other hot work is to be can occur, with possible release of refrigerant. number of selected materials with refrigerant undertaken. Systems shall not be installed in the Liquid refrigerant is liable to damage all types of and oil combinations it should be noted that same enclosure as flame producing equipment. compressors. there are numerous different grades available in the market and for this reason compatibility Inhalation Worn, poorly aligned and out of balance should be checked with the manufacturer or A2L, A2 and A3 refrigerants have a low order of machinery can cause excessive vibration and supplier of the component. toxicity but the inhalation of high concentrations premature failure of piping and components, can be dangerous. Practical limit values for again with possible release of refrigerant. Selection of refrigerant refrigerants in groups A2L, A2 and A3 are quoted Liquid refrigerant has a high coefficient of Refrigerants should be selected so that they in Table 1. Care shall be taken to select a suitable thermal expansion. Care should be taken to contribute to good system efficiency. The effect of leak detector, which shall not be a potential source ensure that liquid refrigerant is not trapped in temperature glide and composition shift on system of ignition. Exposure to high concentrations may pipelines or fittings between shut off devices. A performance should be considered when blended lead to one of more of three physiological effects: rise in ambient temperature may be sufficient to refrigerants are used. a. If the concentration of refrigerant vapour expand trapped liquid, generate excess pressure is very high, the atmosphere will become and rupture components, resulting in release of Refrigerant purity deficient in and unconsciousness or refrigerant. Refrigerant grade product should be used for death may result due to asphyxia. all refrigerating, air conditioning or heat pump b. Refrigerants at high concentrations can have a Hot works applications. Commercial grade hydrocarbons transient narcotic effect on the central nervous contain significant quantities of sulphur, water, Brazing, welding and all sources of flame in system (CNS effects). Returning the exposed and other impurities and could contribute to oil contact with a refrigerating system constitute person to fresh air will reverse the symptoms. degradation, shorten compressor life and invalidate a hazard. The probability exists of a flammable warranties. The composition of commercial LPG c. Cardiac sensitisation can result from refrigerant/oil/air mixture being present within is variable so the thermodynamic properties of inhalation of high concentrations of parts being modified. Precautions must be taken the fluid may vary significantly from cylinder to refrigerant vapour. If subsequently a cardiac before brazing, welding or any operation involving cylinder. Also, unlike commercial LPG, stimulant is used or is present, cardiac a source of flame in contact with a refrigerating refrigerants are not odourised. A2L and A2 arrhythmia can occur which can prove system. A risk assessment is required under WHS/ refrigerants are also not odourised. suddenly fatal. OH&S, AS/NZS 60079, and AS 2865 may also apply.

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Working in confined spaces Corrosion Internal metal surfaces of refrigerating systems The precautions to be taken before persons are Corrosion can occur on the external surfaces of characteristically have a protective oil coating, by permitted to enter a vessel or similar confined the steel piping and vessels used for refrigerating virtue of the compressor lubricating oil becoming space where there is a risk of them being overcome systems, reducing the strength of the containment entrained within the refrigerant flow. It is therefore by dangerous fumes are set out in AS 2865. and eventually resulting in leaks. Corrosion of rare to find internal corrosion in operating systems. These precautions should be followed in order unprotected steelwork can be rapid in wet or Systems out of operation for long periods can, to comply with the general requirements of damp conditions; such conditions often occur on however, corrode, particularly if they are open to the Australian WHS/OH&S legislation. AS 2865 the low‑pressure side of the system when metal atmosphere. In systems deliberately designed to be Confined Spaces, contains advice on the temperatures are below the dew point of the oil free, internal corrosion may occur. procedures and safeguards, which are essential to ambient atmosphere. Insulation where the vapour such work. Attention is drawn to the dangers of seal is defective or incomplete will not prevent Where heat-transferring liquids such as calcium entering or working on vessels which have formed condensation and may enhance corrosion; corrosion chloride or sodium chloride solutions are present part of a refrigeration system; even after air samples usually occurs relatively slowly on lines permanently they may form an additional source of corrosion. from the vessel appear clean, oil/refrigerant below 0°C but has been found to be particularly Chemical treatments of such solutions are mixtures remaining in the vessel can release rapid on pipes such as hot gas defrost lines where prescribed by the suppliers of chemicals and hazardous quantities of refrigerant when disturbed. dampness and heat are present together. should be adhered to rigorously.

Table 1. Refrigerant information

Toxicity Lower Flammability Reduced Practical (OEL) Limits (LFL) Safety Refrigerant Formula and Common AIT gravity Limit (ppm Group Number Name NBP (°C) (°C) (m/s2) (kg/m3) v/v) kg/m3 % v/v GWP ODP

A2L R-1234yf CF3CF=CH2 -29.4 405 29.7 0.058 500 0.289 6.2 4 0

A2L R-1234ze(E) CF3CH=CHF -19.0 368 29.7 0.061 800 0.303 6.5 7 0

A2L R-32 CH2F2 (methylene fluoride) -52 648 8.0 0.061 8500 0.307 14.4 675 0

A2L R-447B R32/R125/R1234ze(E) -50.1 to -46.0 n/a n/a 0.062 970 0.312 12.1 740 0

A2L R-452B R32/R125/R1234yf -51.0 to -50.3 n/a n/a 0.062 870 0.310 11.9 684 0

A2L R-454A R32/R1234yf -48.4 to -41.6 n/a n/a 0.056 690 0.278 8.0 238 0

A2L R-454B R32/R1234yf -50.9 to -50.0 n/a n/a 0.039 850 0.303 11.7 466 0

A2L R-454C R32/R1234yf -46.0 to -37.8 n/a n/a 0.059 620 0.293 7.7 148 0

A2L R-455A R744/R32/R1234yf -51.6 to -39.1 n/a n/a 0.086 650 0.431 11.8 148 0

A2 R-141b CH3CCl2F 32.0 532 — 0.053 1300 n/a 9.0 725 0.11

A2 R-142b CH3CClF2 -10.0 750 25.2 0.065 10000 0.329 8.0 2310 0.065

A2 R-143a CH3CF3 -47.0 750 19.2 0.056 53000 0.282 8.2 4470 0

A2 R-152a CH3CHF2 -25.0 455 13.1 0.027 14000 0.13 4.8 124 0

A2 R-413A R-218/134a/600a -29.4 to -27.4 n/a 26.2 0.08 2100 0.375 8.8 2053 0

A3 R-50 CH4 () -161.0 645 [-4.4] 0.006 1000 0.032 4.9 30 0

A3 R-170 C2H6 () -89 515 0.5 0.008 1000 0.038 3.0 6 0

A3 R-1150 CH2=CH2 () -104 425 [-0.3] 0.006 1000 0.036 2.7 4 0

A3 R-290 C3H8 (propane) -42 470 5.4 0.008 1000 0.038 2.1 3 0

A3 R-1270 C3H6 (propylene) -48 455 4.7 0.008 1000 0.046 2.5 2 0

A3 R-600 C4H10 () 0 ND 10.5 0.0089 600 0.038 1.5 4 0

A3 R-600a CH(CH3)3 () -12 ND 10.4 0.011 1000 0.043 1.8 3 0

A3 R-601 C5H12 () 36 ND — 0.008 600 0.035 1.4 5 0

A3 R-601a CHCH2(CH3)3 () 27 ND — 0.008 600 0.038 1.4 5 0

A3 R-E170 (CH3)2O () -25 ND 6.1 0.013 1000 0.064 3.4 1 0

Note 1: OEL are based on OES values detailed in EH40 published by the HSE, where they are available; otherwise they are based on short term exposure limits (STEL) as advised by refrigerant suppliers. Note 2: For practical limits, see AS/NZS 5149. This month’s Skills Workshop has been taken from the Institute Note 3: Reduced gravity in parentheses implies lighter than air, “-“ means liquid at atmospheric pressure. of Refrigeration’s 2018 Safety Note 4: For GWP values, see the Australian ozone protection and synthetic management Act (or IPCC 4th Assessment Report). Code of Practice. This code is Note 5: See AS/NZS 5149 for a fuller list of refrigerants available for purchase from www.ior.org.uk Note 6: ND = Not determined Note 7: N/A = figures not currently available

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