PRESSURE-TEMPERATURE RELATIONSHIP
The relations between pressure and corresponding temperatures in Fahrenheit degrees of R-12 and R-22 are given in the chart below. For example, at a pressure of 21 psi, the temperature of R-12 will be 20°F. If the pressure is increased to 77 psi, the temperature will increase to 75°F, etc.
The reason why a torch should not be used to heat a tank of refrigerant is evident. The torch flame temperature is so high that pressures above the tank safety capacities can too easily be reached. The tank could rupture and explode.
Pressures at or below the tank safety limits may still be too high for the connection hoses when the tank valve is opened. For safety's sake, use nothing warmer than hot water if you wish to warm a refrigerant drum or tank.
CARE IN HANDLING REFRIGERANTS
In the foregoing discussion it has been observed that one of the requirements of an ideal refrigerant is that it must be nontoxic. In reality, however, all gases (with the exception of pure air) are more or less toxic or asphyxiating. It is therefore important that wherever gases or highly volatile liquids are used, adequate ventilation should be provided, because even nontoxic gases can produce a suffocating effect, by displacing the oxygen in the air.
R-12 is not irritating and can be inhaled in considerable concentrations for a short period without serious consequences. It should be remembered, however, that liquid refrigerants will freeze or remove heat from anything with which they come in contact when released from a container, as in the case of an accident. In other words, liquid refrigerant spilled on any part of the body will produce freezing. A physician should be called immediately to treat the affected area.
HANDLING REFRIGERANT CYLINDERS
It is of the utmost importance to handle cylinders of refrigerant with care (see Fig. 1), and to observe the following precautions :
1. Never drop cylinders nor permit them to strike each other violently.
2. Never use a lifting magnet or a sling (rope or chain) when handling cylinders.
3. Caps for valve protection, when provided, should be kept on the cylinders except when the cylinders are in actual use.
4. Never overfill cylinders. CAUTION: Never recharge throwaway type cylinders. To do so may result in serious injury or possible death. Whenever refrigerant is discharged from or into a cylinder, immediately thereafter weigh the cylinder and record the weight of the refrigerant remaining in the cylinder.
5. Never mix refrigerants in a cylinder.
6. Never use cylinders as rollers, for supports, or for any purpose other than to carry refrigerants.
7. Never tamper with the safety devices in valves or cylinders.
8. Open cylinder valves slowly. Never use wrenches or tools except those provided or approved by the manufacturer.
9. Make sure that the threads on regulators or other unions are the same as those on cylinder valve outlets. Never force connections that do not fit.
10. Regulators and pressure gauges provided for use with a particular gas must not be used on cylinders containing other gases
11. Never attempt to repair or alter cylinders or valves.
12. Never store cylinders near highly flammable substances such as oil, gasoline, waste, etc.
13. Always wear safety goggles when working with refrigerants.
14. Never heat cylinders with an open flame to remove refrigerant; tank rupture or explosion could result.
Refrigerant Container Color
& Class by Refrigerant
Refrigerant Color
11 Orange
12 White
I13 Light Blue (Sky)
13B1 Pinkish-Red (Coral)
14 Yellow-Brown (Mustard)
22 Light Green
23 Light Blue-Grey
32 Light Blue-Green
113 Dark Purple (Violet)
114 Dark Blue (Navy)
116 Dark Grey (Battleship)
123 Light Blue-Grey
124 Deep Green (DOT Green)
125 Medium Brown (Tan)
134a Light Blue (Sky)
236fa Dark Grey (Battleship)
245fa Maroon
401A Pinkish-Red (Coral)
401B Yellow-Brown (Mustard)
401C Blue-Green (Aqua)
402A Light Brown (Sand)
402B Green-Brown (Olive)
403B Light Purple (Lavender)
404A Orange
407A Lime Green
407B Cream
407C Medium Brown (Brown)
407D Dark Brown (Chocolate)
407F Green-Yellow-White
408A Medium Purple (Purple)
409A Medium Brown (Tan)
410A Rose
411A Dark Purple (Violet)
411B Blue-Green (Teal)
413A Deep Blue
414A Beige
414B Medium Blue (Blue)
416A Yellow-Green (Lime)
417A Green
422A Yellow-Orange
422D Green-Yellow
423A Wedge Wood Blue
424A Black
426A Pastel Orange
427A Green-Blue (Jungle Green)
428A Traffic Yellow
434A Sulfur Yellow
437A Royal Blue
438A Blue Jay
442A Night Blue
500 Yellow
502 Light Purple (Lavender)
503 Blue-Green (Aqua)
507A Blue Green (Teal)
508B Dark Blue (Navy)
SUMMARY
The quantity of matter which a body contains is called its mass.
The space a body occupies is called its volume.
The quantity of matter contained in a given volume is called its density.
The specific gravity of a solid or liquid is the ratio between its weight for a given volume and the weight of the same volume of water.
Atmospheric pressure is considered to be 14.7 psi at sea level.
Gauge pressure is that pressure above atmospheric pressure.
Absolute pressure is the sum of gauge pressure and atmospheric pressure.
With temperatures constant, the volume of a given weight of gas decreases as its pressure increases.
At a constant pressure, the volume of a gas increases as its temperature increases.
At a constant volume, the pressure of a gas increases as its temperature increases.
With the volume held constant, the temperature of a gas will decrease if its pressure is decreased.
Power is the rate of doing work.
One horsepower is the power required to raise 33,000 pounds one foot in one minute.
A BTU is the measure of a quantity of heat.
One BTU is the amount of heat energy that must be added to one pound of water to raise its temperature one Fahrenheit degree.
All matter contains heat in lesser or greater quantities.
Heat will pass only from a body at a higher temperature to a body with a lower temperature.
Water boils at 212° F at sea-level pressure.
Water freezes at 32° F at sea-level pressure.
Specific heat is the capacity of a substance for absorbing heat.
Sensible heat is that heat that can be detected and felt and measured with a thermometer.
Latent heat is hidden heat which brings about a change of state in a substance with no change in pressure or temperature.
Refrigerants are mediums which absorb heat at a low temperature level and release heat at a higher temperature level.
Class 1 refrigerants are used in home refrigerators, dehumidifiers, air conditioners, etc.
Fluorocarbon refrigerants are colorless, nearly odor-free, nontoxic, noncorrosive, nonirritating, and nonflammable.
All gases are more or less asphyxiating and can cause death under certain conditions by displacing the oxygen in the air to cause smothering.
Liquid refrigerant spilled on any part of the body will produce freezing.
Throwaway-type refrigerant cylinders must never be recharged under any circumstances.
Care should be exercised in handling and storing refrigerant cylinders.
Never heat a refrigerant tank or drum with a flame or torch.