Moist Air from the compressor enters into the Pre filter through the top manifold. Water and oil coalesces here. The condensate with water and oil is drained by the Drain valve. The drain valve is periodically opened by the controller. The specially designed drain valve discharges only a fixed volume of condensate and minimizes air loss. The air then passes through the Inlet Shuttle valve and the Drying tower. In the drying tower, Activated Alumina adsorbs the water vapour present in the air and sends out Dry air of required Dew point. Fine Alumina powder which may come from the bed of desiccant is removed by the After filter. Clean and dry compressed air is let out through the outlet shuttle valve and Purge Control valve.
The Purge Control Valve Diaphragm senses the outlet flow and accordingly the Purge Air port size area is varied. This varies the amount of Purge Air during regeneration in proportion to the flow of compressed air through the dryer. It is also a function of the inlet pressure and hence only uses purge air in proportion to the moisture load.
The two towers operate alternately in the drying and regeneration phases. In the regeneration phase dry purge air is passed through the tower under regeneration and released into the atmosphere. Under given operating conditions (service pressure of 10.5 Kg/cm2 (g)) 10% of the airflow is used for regeneration. A fixed quanity of air is purged during very low flows. The regeneration phase is shorter than the drying phase in order to allow the regenerated tower to return to service pressure before a new cycle starts. The purge is 10% for units with Auto Adjust purge control valve and fixed 15%without Auto Adjust purge control valve.
Trident Locomotive dryers are designed exclusively for the railroad industry for the following applications :