UEERA0014 — Design ammonia refrigerated systems

Elements & performance criteria

Performance evidence

• understanding required operating functions and parameters from the design specification
• developing the design within the safety, regulatory and functional requirements and budget limitations
• documenting and presenting design effectively
• negotiating design alteration requests successfully
• obtaining approval for final design
• dealing with unplanned events
• applying relevant work health and safety (WHS)/occupational health and safety (WHS/OHS) requirements, including using risk control measures
• designing ammonia refrigeration systems
• preparing to design ammonia refrigeration systems.

Knowledge evidence

• ammonia refrigeration system design, components and piping design requirements, safe working practices and relevant standards, codes and regulations, including:
• technical standards, codes and regulations:
• environmental and safety considerations in the use and disposal of ammonia refrigerant:
• toxicity of ammonia, the effects on human health and the legislative limitations imposed on ammonia refrigerant as a result
• flammability of ammonia, concentration and lower explosive limit (LEL)
• environmental effects
• safe disposal
• safety data sheets (SDS)/material safety data sheets (MSDS) samples
• registration requirements for transport and on-site use
• relationship between ammonia system refrigerant charge and dangerous goods storage regulations
• engine ventilation requirements and determination of ventilation rates
• scrubbers for elimination of the harmful effects of ammonia
• ammonia refrigeration system design requirements:
• applications of ammonia refrigerant (NH3) in industrial refrigeration:
• introduction to industrial ammonia refrigeration applications and systems
• applications in industrial refrigeration: cool and cold storage, food processing, beverage manufacturing plants, fertilizer plants and second compression stage of CO2 systems
• application in environment control and air conditioning: large scale reticulated water/secondary refrigerant systems
• advantages and disadvantages of ammonia refrigerant compared with other natural and synthetic refrigerants
• properties, application and limitations of ammonia refrigerant:
• general classification of ammonia refrigerant according to AS/NZS 1677 Refrigerating systems SAA refrigeration code refrigerating systems
• common contaminants in ammonia refrigeration systems, water, oil, non-condensable and the effects of same on cycle efficiency and system wear
• refrigeration machine oils soluble in ammonia, oil type, applications and reactions with water
• thermal and transport properties of ammonia in comparison with other natural and synthetic refrigerants, including the behaviour in a vapour compression cycle
• application concepts and principles:
• single stage vapour compression cycles with dry expansion refrigerant feed
• single and dual stage vapour compression cycles with liquid overfeed
• single stage vapour compression cycles with screw compressors and liquid overfeed
• cascade ammonia/CO2 systems with dry expansion and liquid overfeed
• single and dual stage vapour compression cycles with gravity flooded refrigerant feed
• single and dual stage vapour compression cycles with ammonia used as a volatile secondary refrigerant
• dual stage vapour compression cycles with multiple (>2) saturation temperature levels
• automatic defrost principles, including off-cycle air defrost, ambient air defrost, hot gas defrost, electric defrost and water defrost
• selection and sizing of ammonia pumps for liquid overfeed systems
• selection and sizing of high pressure and low-pressure vessels
• refrigerant pipe sizing using ammonia refrigerant
• selection of suitable refrigerant oil
• ammonia refrigeration system components and piping:
• corrosion and material selection:
• materials compatibility table
• thermal and other properties of materials in use
• pipe material and jointing methods/materials
• compressors
• pumps, impellers and seals
• isolation and control valves
• heat exchangers
• pipe and insulation materials, pipe stresses and pipe suspension methods:
• mild steel pipe
• stainless steel pipe
• sharpy tested pipe
• post-installation insulation (in situ foaming, formed insulation and closed cell flexible insulation)
• pre-insulated pipe material
• vapour barrier – importance and maintenance
• heat exchangers:
• finned air coolers or evaporators - induced draught; forced draught; stainless steel/aluminium; mild steel galvanized; all aluminium; stainless steel/AlMg3; all stainless steel; description of what materials are used where and for what reason; various refrigerant feed methods including advantages/disadvantages i.e. top feed, bottom feed, vertical up flow/down flow of air; fin spacing; fin thickness and impact of geometry on fluid pressure drops
• condensers – evaporative, air cooled, air cooled adiabatically assisted, water cooled shell and tube, water cooled plate/plate, water cooled plate and shell, cascade shell and tube, cascade plate/plate, cascade plate and shell, material selection for condensers, and importance of discharge temperature for condenser design
• cooling towers
• intercoolers and economisers of the closed type, sizing of liquid sub-cooling coils and tube bundles
• liquid coolers or evaporators – plate/plate, plate/shell, shell and tube, material selections, refrigerant feed methods and oil management
• screw compressor oil coolers – plate/plate type, shell and tube type, water cooled, refrigerant cooled and surface enhancement options
• heat recovery – shell and tube de-superheaters, plate/plate de-superheaters and heat recovery condensers of various types
• system control and monitoring:
• compressor capacity control – pressure and temperature signals
• room temperature and humidity control – understanding the principle of cooling and re-heating air streams to control absolute moisture contents
• control of condensers – optimisation of overall plant C.O.P
• floating condensing pressures
• control of fluid temperatures within the system – oil, secondary refrigerants and sub-cooling
• control of flows – thermostatic expansion valves, low pressure floats, high pressure floats, motorised valves, electronic expansion valves, hand regulating valves, and oil return systems between compressor oil separators and compressors
• pressure controllers - evaporating pressure controllers, thermostatic controllers, hot gas bypass valves, crankcase pressure regulators, overflow valves, ammonia pump pressure control, flow controllers and defrost pressure controllers
• defrost control
• programmable logic controller (PLC) control systems
• supervisory control and data acquisition (SCADA) systems
• water treatment and desiccant dehumidifiers:
• condenser water treatment – purpose and legislative requirement
• treatment of secondary refrigerant loops including monitoring
• desiccant dehumidifiers and their role in infiltration minimisation, defrost control and energy savings
• equipment selection:
• use computer software and manufacturers’ data to select major components of an ammonia refrigeration plant
• problem-solving techniques
• relevant job safety assessments or risk mitigation processes
• relevant manufacturer specifications
• relevant WHS/OHS legislated requirements
• relevant workplace budget, quality, policies and procedures
• relevant workplace documentation.

Unit content sourced from training.gov.au — © Commonwealth of Australia, licensed under CC BY 4.0. Auditori is not affiliated with the Department of Employment and Workplace Relations.

Questions about assessing UEERA0014