Expansion Block/Orifice Tube: Description and Operation

Orifice (Expansion Tube):

The orifice tube is a plastic assembly containing a fixed diameter tube with a mesh filter screen at either end. It is located in the evaporator inlet line. The fixed diameter tube creates a restriction to the high pressure liquid refrigerant, metering the flow to the evaporator as a low pressure liquid (see accompanying figure).

When system diagnostics indicate a restricted orifice tube, it may not be necessary to replace it. Metal chips, flakes or slivers found on the screen may be removed with shop air and the orifice may be reused provided:

^ Plastic frame is not broken.

^ Brass orifice tube is not damaged or plugged.

^ Screen material is not torn.

^ Screen is not plugged with fine gritty material.