Membrane air dryer for vehicle air brake system
An air drying system for a vehicle including a membrane air dryer is provided. The air dryer is supplied with a stream of compressed air that has a low and constant concentration of oil vapor. A coalescing filter element may be used to maintain the oil vapor concentration. The filtered material may be discharged from the coalescing filter by a pressure swing drain valve, which discharges the filtered material upon unloading of the compressor.
1. A method of drying a compressed air stream on a vehicle, comprising the steps of:
supplying the compressed air stream to a coalescing filter element, wherein said coalescing filter element is disposed within a filter housing;
filtering the compressed air stream with said coalescing filter element;
supplying the compressed air stream to a membrane air dryer;
drying said compressed air stream;
delivered the dried compressed air stream to one or more downstream components; and
draining filtered material from said filter housing, wherein draining is preformed by a pressure swing drain valve; wherein said pressure swing drain valve is activated by a pressure swing within the coalescing filter housing caused by the unloading of a compressor.
2. An air drying system for a compressed air system of a vehicle, comprising:
a coalescing filter element located downstream from a vehicle compressor, wherein said coalescing filter element is disposed within a coalescing filter housing;
a membrane air dryer attachable to the vehicle, wherein said membrane air dryer receives a compressed air stream from said coalescing filter element; and
a pressure swing drain valve attached to said coalescing filter housing, wherein said pressure swing drain valve is activated to discharge filtered material from said coalescing filter element when there is a pressure swing within the coalescing filter housing caused by the unloading of a compressor.
3. The air drying system of claim 2 , wherein said pressing swing drain valve is actuated each time the compressor unloads.
4. The air drying system of claim 2 , wherein said pressure swing drain valve includes a restriction orifice.
5. The air drying system of claim 4 , wherein said restriction orifice is between about 0.04 inches and about 0.06 inches.
6. The air drying system of claim 2 , wherein said membrane air dryer comprises a supply end cap, a membrane air dryer core, and a delivery end cap, wherein said membrane air dryer core includes a plurality hollow fiber membrane tubes.
7. The air drying system of claim 6 , wherein said membrane air dryer further comprises a metering orifice for creating a backflow of air through said membrane air dryer core.
8. The air drying system of claim 7 , wherein said metering orifice allows between about 15 and about 20 percent of the compressed air stream exiting said plurality of hollow fiber membrane to flow back through said membrane air dryer core.
9. The air drying system of claim 6 further comprising a check valve disposed within said delivery end cap, said check valve regulating the flow of the compressed air stream between the membrane air dryer and one or more downstream components.