How Bendix Pura-Guard Air Dryer works, these units are fitted to Kenworth T360 & T360A models. This video explains how the system operates and describes the cycles of the air dryer. Visit www.roadtrains... to read the full technical article on air dryer operation.
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Charge Cycle
The principle behind a desiccant dryer is to remove moisture and contaminants before the air reaches the first reservoir tank - commonly known as the ‘wet tank’. How they work involves a simple procedure; air travels through the end cover assembly - called the charge cycle - it’s direction in flow changes several times, reducing the temperature and causing contaminants to condense and drop in the bottom of the sump. After exiting the end cover, the air flows into the desiccant cartridge. Once in the desiccant cartridge, air first flows through an oil separator located between the inner and outer shells of the cartridge. The separator removes water in liquid form as well as oil and solid contaminants.
Air, along with the remaining water vapour, is further cooled as it exits the oil separator and continues to flow upward between the outer and inner shells. Upon reaching the top of the cartridge, the air reverses direction of flow and enters the desiccant drying bed. The air is drawn through a bed of clay beads. The special clay attracts water molecules which adhere to the beads’ surfaces. The moisture is “adsorbed” onto the beads’ surface rather than absorbed by soaking into the beads. Keeping moisture on the beads’ surface allows the moisture to be removed, greatly extending the life of the desiccant.
Purge Cycle
As the air brake system pressure reaches the cutout setting of the governor, the governor unloads the compressor - air compressor stopped - and the purge cycle begins. Water and contaminant in the end cover sump are expelled immediately when the purge value opens. Oil and solid contaminants collected by the oil separator are removed by air flowing from the purge volume through the desiccant drying bed to the open purge value. The purge cycle takes about 30 seconds. This is fast, considering that thousands of beads must be stripped of moisture.
The desiccant itself needs periodic changing. How often this is (or should be) done depends on the size of the desiccant bed. As most air-dryers are manufactured in the US, desiccant is measured in pounds, with 2 to 5 pounds used in the various models available from many suppliers. Basically, the bigger the cartridge, the longer it will last. In general, a desiccant cartridge will last two to five years in normal highway operation. However depending on the humidity and type of operation, especially where a lot of air passes through it, the cartridge may need changing more often.
Turbo Cut-off valve
The primary function of the turbo cut-off value is to prevent loss of engine turbocharger air pressure through the air-dryer in systems where the compressor intake is connected to the engine turbocharger. The turbo cut-off valve also removes the “puffing” of air out the open purge exhaust when a naturally aspirated, single cylinder compressor, equipped with an inlet check valve, is in use.
Servicing is usually done by removing one or two bolts and lifting or spinning off the cartridge. Some models require the entire dryer to come off the truck. A label on the unit may include instructions otherwise check with the manufacturer.
Негізгі бет Ойын-сауық How a Bendix Pura-Guard Air Dryer works
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