Combustibility Of Hfc-134A; Leak Testing; Bulk Delivery And Storage; Filling And Charging Operations - Electrolux Side by Side Refrigerator Service Manual

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Section E

Combustibility Of Hfc-134a

HFC-134a is nonflammable at ambient temperatures and atmospheric pressure.
However, tests have shown HFC-134a to be combustible at pressures as low as
5.5 psig (139.3 kPa absolute) at 177°C (350°F) when mixed with air at
concentrations generally greater than 60% volume air. At lower temperatures,
higher pressures are required for combustibility. (HCFC-22 is also combustible at
pressures above atmospheric in the presence of high air concentrations). Test
results and calculations have shown:
• At ambient temperature, all concentrations of HFC-134a in air are
nonflammable at pressures below 15 psig (205 kPa absolute).
• Combustible mixtures of air and HFC-134a will not form when liquid HFC-
134a is pumped into closed vessel if initial air pressure in vessel is limited
to one atmosphere absolute and final pressure is limited to 300 psig (2,170
kPa absolute). If initial air pressure is greater than one atmosphere,
combustible mixtures may form as tank is filled.
Based on above information, the following operating practices are recommended:

Leak Testing

• Equi pm ent shoul d NEVER be leak tested with a pressurized mixture of HFC-
134a and air. HFC-134a may be safely pressured with dry nitrogen.

Bulk Delivery and Storage

• Tanks should normally be evacuated at start of filling, and should never be
filled while underpositive air pressure.
• Tank pressure should never be allowed to exceed 300 psig (2,170 kPa) when
filling with HFC-134a. Relief devices on either tanks or HFC-134a supply
system usually prevent this.
• Tank pressures should be monitored routinely.
• Air lines should never be connected to storage tanks.

Filling and Charging Operations

• Before evacuating cylinders or refrigeration equipment, any remaining
refrigerant should be removed by recovery system.
• Vacuum pump discharge lines should be free of restrictions that could
increase discharge pressures above 15 psig (205 kPa) and result
in formation of combustible mixtures.
• Cylinders or refrigeration equipment should normally be evacuated at start of
filling,and should never be filled while under positive air pressure.
• Final pressures should not exceed 300 psig (2,170 kPa).