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11.8.1.1 The orifice tube
Operation:
The orifice tube is a tube with a given length and
cross-section which expands the refrigerant but, un-
like the expansion valve, is unable to regulate flow
rate and superheating.
The orifice tube is always associated with an accu-
mulator at the evaporator outlet.
11.8.1.2 The accumulator
From condenser
Fine mesh
filter inlet
O-Ring
Fixed small
diameter
bronze tube
(rextriction)
To evaporator
The accumulator has a similar function to the
receiver drier but works on the gaseous side of
the A/C loop.
The accumulator protects the components of the
system; it is located on the low pressure
side of the circuit between the evaporator outlet
and the compressor suction port.
Roles:
1. To provide compressor protection, preventing
compressor failure due to liquid slugging
2. To retain moisture and contaminants from the
system (during the accumulators life time)
3. To ensure oil return and assure that only refrige-
rant is returning to the compressor.
11. The components
of the A/C Loop
58
Orifice tubes are made up of three main parts:
g
A metal tube with a chamfered inlet
g
A plastic tube body
g
An inlet and outlet filter
Gaseous
refrigerant
Oil
Gaseous
refrigerant
Oil
Liquid
refrigerant
Contaminants
A/C system
Evaporator
Condenser
Orifice tube
Compressor
Accumulator
From condenser
Replacement:
If the A/C loop is contaminated, then the
orifice tube becomes clogged.
In this case, replace the orifice tube. The
orifice tube must always be replaced when
another important part of the circuit is
replaced (compressor, condenser, evapora-
tor, receiver drier).
Warning !
Flush the A/C loop before
installing a new orifice tube.
Advice on replacing accumulators:
The accumulator is a drier filter that
must be replaced every 3 years or
whenever the circuit is opened.