Report 3 (of 6): Back to the Future

Introduction

Life on earth has been safeguarded for thousands of years because of a life-protecting layer in the atmosphere. This layer, composed of ozone, acts as a shield to protect the earth against the harmful ultraviolet radiation from the sun. Any damage that is done to the ozone layer will lead to increased amounts of the dangerous ulraviolet radiations perforating the filter and reaching the earth's surface.

The depletion of the ozone layer results in dangerous levels of ultraviolet radiation reaching the earth's surface, which causes alarming increases in risks to human health through skin cancer, eye cataracts, and immune system suppression. An increased level of ultraviolet radiation also endangers crops, forests, plants, marine life, and wildlife, and contributes to the rapid deterioration of plastics and other materials widely used by society. Climate change is causing drastic increases in natural disasters such as floods, violent storms, fires, heat waves and cold spells, as well the spread of infectious diseases.

Chlorofluorocarbons (CFCs)

"Greenhouse" gases such as chlorofluorocarbons (CFCs) are contributing to the reduction of the earth's ozone layer. CFCs are widely used in cooling systems and in the blowing of insulation foam for refrigerators. Some CFCs have atmospheric lives of over 100 years and therefore, once these chemicals are emitted, they will influence the process of ozone depletion for a long time. By forces of air circulation, they spread around the globe until they eventually reach the stratosphere (the upper part of the atmosphere) where they are exposed to powerful ultraviolet radiation which break apart the refrigerant chemical, releasing the chlorine. As the chlorine reacts with ozone, oxygen is created which, in turn, allows more ultraviolet light to pass toward the earth. The chlorine atom acts as a catalyst which means that it is not used up in the reaction but can continue to convert ozone to oxygen through thousands of similar reactions.

The dual atmospheric crises of ozone layer depletion and global-warming are a great threat to the well-being of human life on our planet. The depletion of the ozone layer spurred the international community to enact the Montreal Protocol for the Protection of the Ozone Layer in 1987 to phase out the use of CFCs and other major ozone depleting substances. One of the challenges now facing the world is meeting human needs with technologies that are environmentally sustainable.

Hydrocarbons

Hydrocarbons are environmentally safe, efficient, and technologically reliable refrigerants and insulation foam-blowing agents. Hydrocarbons (HCs) were used during the early decades of modern refrigeration in the 1920s and 1930s, but were eventually replaced with the advent of CFCs in the 1940s. The need to find substitutes for CFCs during the 1990s has led industry back to using hydrocarbons which have no impact on the ozone layer and insignificant contribution to global warming.

Hydrocarbons are naturally occurring substances formed from fossilized plant matter, and found throughout the world as oil and natural gas. The gases that make up the hydrocarbon family, including propane, cyclopentane, butane, and isobutane, are used as fuels and raw materials in manufacturing, and as refrigerants. Hydrocarbons are relatively cheap to produce and they are readily available in most parts of the world.

Since 1992, hydrocarbon refrigeration has become the technology of choice in many domestic markets in Western Europe. In Germany, 100 per cent of the industry has already converted to hydrocarbon technology. All of the major European companies, such as Bosch/Siemens, Electrolux, Liebherr, Miele, Quelle, Vestfrost, Whirlpool, Bauknecht, Foron, and AEG are selling hydrocarbon refrigerators. They are available in many sizes, and a wide variety of models, including some with no-frost freezer compartments. There are over 100 different hydrocarbon refrigerator models on the European market.

Flammability

The concern with hydrocarbons is that, unlike CFCs, HCFCs, and HFCs, they are flammable. Their flammability is an important safety concern in the manufacture and servicing of refrigerators. Modern innovations have greatly improved the safety of hydrocarbon technologies. Most consumers in Southern countries are already familiar with hydrocarbons in the form of LPG (liquid petroleum gas a propane and butane mix), as it is widely used for cooking in the home. The amount of propane or butane in a domestic hydrocarbon refrigerator is only 40 to 60g equivalent to two to six cigarette lighters, depending on the size of the refrigerator.

Combustion

Hydrocarbons are flammable when mixed with air, if the concentration of hydrocarbon in the air is at a certain level. For example, if there is less than 1.95% of hydrocarbon blend in air then there is insufficient fuel (from the refrigerant) for combustion. If there is more than 9.1% there is insufficient oxygen (from the air) for combustion.

It is very unlikely that combustion will occur inside a refrigeration system as there will be insufficient air. If the hydrocarbon refrigerant leaks out of the system, combustion will occur if the correct mixture exists and if there is an ignition source.

For combustion to happen an ignition source hotter than 430° C is needed to ignite the air/hydrocarbon mixture. For example, a flame from a brazing torch, halide torch leak lamp, match, or lighter; a spark from an electrical component, such as compressor overload protectors, relays, pressure switches, thermostats, on/off switches, and loose connections; or static electricity. Potentially hazardous situations are when:

• refrigerant leaks into the air around the system and is ignited by sparking electrical components on the system;
• refrigerant leaks into the food compartment or any sealed space and is ignited by sparking electrical components inside the space;
• cyclopentane is emitted during the foaming process; and
• refrigerant is emitted during the refrigerant charging process during manufacture or servicing; and
• refrigerant which was left in an open system is emitted during the repair of an appliance.

Safe Design

When creating a new appliance or modifying existing ones, a flammable mixture of hydrocarbon and air should never be allowed to occur, either at the back of the appliance or in the food compartment. The design should ensure that if a leak does occur, it will be diluted to prevent the gases from reaching a flammable mixture. There must also be no potential sources of ignition. In order to ensure dilution and prevent ignition, the following design guidelines should be followed:

1. Minimize the number of joints, which will reduce the potential for leaks.
2. Use brazed joints instead of flared connections to minimize leaks.
3. Eliminate, move to a safe position, or use intrinsically safe electrical components.
   The main ways to make potential ignition sources safe are to:
   • replace electrical component with a sealed component; or
   • replace electrical component with a solid state component; or
   • enclose the electrical components in a sealed box; or
   • relocate electrical components away from the refrigeration unit; and
   • ensure all wiring connections cannot work lose.

4. Use specially designed compressors with safe electrical components.
5. The weight of hydrocarbon refrigerant will be about 40 per cent of CFC weight.
6. For hydrocarbon blends, use R12-size compressors with safe (usually sealed) electrical components.
7. Label the appliance to show what coolant has been used so that it can be safely repaired.

Safety During Handling

• CFCs, HFCs, and HCs all have a boiling point of well below 0° C at atmospheric pressure, so liquid refrigerant will cause a freeze burn on skin. Gloves and goggles should be worn, as well as clothing that covers the whole body. Contact with skin or eyes should be treated by flushing affected area with cold or tepid water for at least 15 minutes, followed by medical attention.
• CFCs, HFCs, and HCs are heavier than air which means that these refrigerants can asphyxiate. Enclosed areas must be well ventilated, and access to areas below ground level sealed off. Anyone who has inhaled refrigerant should be moved to an uncontaminated area, and kept warm and still. If breathing has stopped or shows signs of failing, commence artificial respiration. Summon immediate medical attention.
• Cylinders of hydrocarbon should be labelled clearly, with both the contents and a flammability warning. Fit the valve cap when the cylinder is not being used. Do not modify or repair cylinders or their valves. Do not refill cylinders unless they are specifically for recovered refrigerant. To check if a cylinder is empty weigh it, as pressure is not an accurate indication.
• Cylinders should only be transported with the valve closed and capped.
• Do not heat the cylinders, or leave unprotected in the sun.
• Transport cylinders in open vehicles. Ensure cylinders are safely fixed in an upright, stable position.
• Store cylinders outside, protected from the sun and in a fenced-in area.
• Do not smoke where hydrocarbon is stored.

Servicing Appliances Safely

The servicing of hydrocarbon appliances requires stringent safety practices. The working area should be well ventilated and an LPG gas alarm should be used. In addition, the measures below are designed to monitor the hydrocarbon concentration in the working area during the venting and charging of the system.

1. Replace damaged electrical components with sealed or solid state components, and do not reposition them.
2. Vent, evacuate, and charge refrigerants outside or in a well-ventilated area.
3. Recover the refrigerant from an appliance and ensure that any residue is vented outside the building.
4. Evacuate the system before brazing or unbrazing joints.
5. Use a vacuum pump with an encapsulated power switch or install a new spark-free power switch.
6. When charging refrigerant:
   • ensure that the charging equipment is safe for hydrocarbon refrigerants;
   • evacuate or purge carefully all lines before charging; and
   • take liquid hydrocarbon, not gas, from the cylinder when charging the hydrocarbon blend.

Safe Handling of Hydrocarbons

For safe handling of hydrocarbons, the following conditions are strongly recommended:

• effective ventilation of the room
• use of closed apparatus and vessels/containers
• removal of emerging vapours by suction
• solvent-resistant (non-corrosive materials) equipment and floor covering
• prevention of the entry of CP into drains
• protection against excessive pressure
• regular pressure-testing of pipelines
• precautions against electrostatic discharge
• personal protection for the respiratory organs, hand, and eyes
• no smoking during work
• keeping away from the sources of ignition
• disposal of waste material in accordance within regulations
• use of brass alloy and spark-free tools for opening the drum
• avoidance of open handling
• provision of escape and emergency routes
• protection against general traffic hazards (control access)
• avoidance of pits and ditches in the area of the plant
• earthing of all parts of the installation including jump leads over flange connections and during discharge of vehicles
• installation of fire and explosion alarms
• provision of fire-fighting equipment, mobile fire extinguishers, pressurized fire hoses, a sprinkler system, and a sump for extinguishing fluid
• emergency procedures evolved in consultation with the local fire officer
• provision of access for the fire brigade to critical areas
• provision of a vapour return system with a flash-back safety mechanism

This material is taken from the video and booklet 'Back to the Future: Working safely with Hydrocarbons', available from January 1999 from UNEP's OzonAction Programme or through the National Ozone Units. The video and booklet is a cooperative undertaking between the OzonAction Department of the United Nations Environment Programme (UNEP), the ProKlima Department of the German Government's Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ), and the Greenfreeze Project and Global Climate and Ozone Layer Protection Campaign of Greenpeace International. For more information, try the following web-sites: http://www.unepie.org/ozonaction.html and http://www.greenpeace.org/

Further reading available from ITDG Development Bookshop

How to Look After a Refrigerator
Jonathan Elford
Written specifically for primary health workers in developing countries, this revised edition contains information on kerosene, electric, gas and solar refrigerators for vaccine storage in health centres.
£5.50, 1992, 58pp., paperback. (AHRTAG) ISBN 0907320201

Refrigeration and Air-conditioning Technology
Norman Cook
£9.99, 1995, paperback, (Macmillan) ISBN 0333609581

Refrigeration Equipment: A servicing and installation handbook
A.C. Bryant
£19.99, (Butterworth-Heinemann) ISBN 0750636882

Refrigeration: A practical manual for apprentices
G.H. Reed
£32.50 (Elsevier Science Ltd) ISBN 0853346054

To order any of these books from ITDG Development Bookshop, send a Sterling Cheque (adding 15% for postage and packing to European addresses, 25% elsewhere), or credit card details (American Express, Visa or MasterCard) to:

or visit our website at http://www.developmentbookshop.com/

TVE/ Practical Action gratefully acknowledge support for the HANDS ON programmes from the UK's Department for International Development (DFID), the European Commission (EC), the UN Foundation and UNDP/The Equator Initiative in collaboration with the Government of Canada, IDRC, IUCN, BrasilConnects and the Nature Conservancy.