Flammability And Explosive Ness
The majority of refrigerants common areas are non-combustible and nonexplosive. Again, die notable exceptions are ammonia and direct hydrocarbon refrigerants. Ammonia is slightly flammable, but becomes explosive when mixed widi air at a concentration of 15 to 27% by volume. Nevertheless, widi reasonable precautions to die hazards associated with the use of ammonia as a refrigerant can be reduced to an acceptable level. In contrast, the right of hydrocarbons always highly flammable and explosive. They are used as refrigerants, is allowed only in special applications, which are under the supervision of an experienced service personnel. Because of their excellent thermal properties, die right hydrocarbons often work in ultra-low temperatures.
Are toxicity and Flammability characteristics of a number of refrigerants. Refrigerants are divided into two groups (A and B) according to their degree of toxicity. Class A means, refrigerants, which are not considered in toxic concentrations up to and including 400 parts per million (ppm).
Class defines refrigerants that there are some signs of toxicity at concentrations below 400 ppm. Flammability is determined by one of diree classes. Class 1-refrigerants that do not show of flame propagation test in the air at 14.7 psi (101.3 kPa) and 65F (18.3C). Class 2 defines refrigerants with lower Flammability limit (LFL) more dian force that accounts for 0.00625 lb/ft3 (0.10 kg/m3) to 14.7 psi and 70 F (101,3 kPa and 21C). and heat of combustion less than 8,174 BTU/lb (more than 19 000 kJ/kg). Class 3 indicates refrigerants diat is highly flammable, having LFL) less than or equal to the force that accounts for 0.00625 lb/ft3 (0.10 kg/m3) to 14.7 psi and 70F (101,3 kPa and 21C) or the heat of combustion is equal to or more than 8,174 BTU/lb (more than 19 000 kJ/kg). Based on this information, refrigerants, listed in the Group 1 are the least dangerous as those listed in Group B3 are the most dangerous.
Some refrigerants actually a composite of two or more different refrigerants. In zeotropic mixture is a mechanical mixture of refrigerants with different saturation temperature in die same pressure. Therefore, under certain conditions, refrigerants can separate into their individual components. This unwanted separation can cause a change in the Flammability or class of toxicity of the mixture. Therefore, zeotropic refrigerants classified using dual rating separated by a solidus. The first ranking member of the class of the mixture, as it is formulated. The second ranking-class under the worst case the composition of diat can occur if the individual components (fractionalize).
ASHRAE Standard 15, Security Code for Mechanical Refrigeration, detail the conditions and circumstances under which different refrigerants can be safely used. Most of the local laws and regulations governing die the use of refrigeration equipment based on diis code, the development of which together ASH RAE and die the American national Standards Institute (ANSI)...