Orifice Tubes
The orifice tube is the dividing point between the high pressure and low pressure side of a CCOT system. Orifice tubes are probably the most commonly used refrigerant metering devices.The orifice tubes in use today measure approximately three inches in length and consist of a small brass tube, surrounded by plastic, and covered with a filter screen at each end. The oring on the orifice tube ensures that refrigerant only passes through the small fixed orifice area. The larger surface areas of the filter screen prevents the small brass "orifice" from becoming clogged. Looking at the debris found on the screen can indicate overall system health. Large amounts of debris can indicate compressor problems and/or system contamination.
While it is not uncommon for the orifice tube filter screen to become partially clogged with small debris. They are inexpensive, and should be inspected any time the system is opened for service. A clogged orifice tube will starve a compressor of oil. An orifice tube restriction or "failure" is usually indicated by very low suction side pressures.
