Combustibility
Refrigerant is non-flammable. It actually has a fire-resistant or fire
extinguishing effect. Refrigerant decomposes when exposed to
flames or red-hot surfaces. UV light (occurring for example during
electric welding) also causes refrigerant decomposition. The re‐
sultant decomposition products are toxic and are not to be in‐
haled. However, irritation of the mucous membranes provides an
adequate and timely warning.
Charge Factor
A vessel must have space for vapor as well as liquid. As the tem‐
perature rises, the liquid expands. The vapor-filled space be‐
comes smaller. At a certain point, there will only be liquid in the
vessel. Beyond this, even a slight increase in temperature causes
great pressure to build up in the vessel as the liquid attempts to
continue expanding despite the absence of the necessary space.
The forces that result are strong enough to rupture the vessel. To
prevent a vessel from being overfilled, the regulations regarding
compresses gasses specify how many kilograms of refrigerant
that may be added to a vessel per liter of interior volume. Multi‐
plying this filling factor with the interior volume gives the permitted
filling capacity. The figure for refrigerant used in vehicles is 1.15
kg / liter.
Leak Detection
External damage, for example, can cause a leak in the refrigerant
circuit. The small quantity of refrigerant escaping from minor leaks
can be detected for example using an electronic leak detector or
by introducing a leak detection additive into the refrigerant circuit.
Electronic leak detectors are capable of registering leaks with re‐
frigerant losses of less than 5 g per year.
Note
Use leak detectors designed for the type of refrigerant. For ex‐
ample, a leak detector for R12 refrigerant will not work with R134a
because R134a refrigerant has no chlorine atoms so the leak de‐
tector will not respond to it.
1.1.3 Refrigerant R134a Vapor Pressure Ta‐
ble
The vapor pressure table for every refrigerant is published in lit‐
erature for refrigeration system engineers. This table makes it
possible to determine the vapor pressure acting on the column of
liquid in a vessel if the temperature of the vessel is known.
Because each refrigerant has its own characteristic vapor pres‐
sure table, refrigerant can be identified by measuring the pressure
and temperature.
Note
♦
At absolute pressure, 0 bar corresponds to absolute vacuum.
Normal ambient pressure (positive pressure) equals 1 bar ab‐
solute pressure. 0 bar pressure corresponds to an absolute
pressure of one bar on most pressure gauges (indicated by -1
bar below 0).
♦
Pressure is measured in different units: 1 MPa (mega Pascal)
corresponds to 10 bar positive pressure or 145 psi, 1 bar ab‐
solute pressure corresponds to 0 bar positive pressure and
thus to the ambient pressure (atmospheric pressure).
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Refrigerant R134a Servicing - Edition 01.2011
4 Rep. Gr.00 - General, Technical Data
