Manual for Refrigeration Servicing Technicians - UNEP - Division of ...

4
Servicing Practices
Volumetric charging by graduated cylinder
Using graduated charging cylinder is one of the most popular charging
methods, an example is shown here:
Graduated charging cylinder
It uses a glass tube liquid level indicator, which allows a technician
to transfer refrigerant into a system and measure the amount on
a scale. Some cylinders are electrically heated to speed up the
evaporation and maintain pressure in the cylinder. This process of
electrically heating cylinder is usually done with an electrical insert.
In some cases, the compressor itself is heated, using a heat gun so
the refrigerant and oil will circulate and be purged more easily.
In both cases, it is extremely important that a pressure control relief
valve and thermostat be used to provide the required temperature
and pressure safety controls. The system has a pressure gauge
and hand valve on the bottom for filling the charging cylinder liquid
refrigerant into a system. It also has valve at the top of the cylinder.
This valve is used for charging refrigerant vapour into the system.
Mass charging by balance
CHAPITRE 4
PAGE 16
Using an electronic weight balance, such as the one shown here:
Electronic weight
balance is typically one
of the most accurate
ways to charge
refrigerant. System
charging could be
performed in vapour
or liquid phase. This
is generally done in
smaller systems, which
are more sensitive to
charge size. Therefore it is important to be aware of the additional
refrigerant within the refrigerant hoses, and the artificial weight of
the hoses themselves on the balance reading, so that the actual
mass added to the system is not erroneous.
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