PRISM membranes will not be permanently damaged by liquid water. The membrane performance can be restored by flowing warm, dry air through the membrane until all the liquid water is removed. The membranes will not be affected by oil vapor in the feed stream; however, the membranes will be permanently damaged by liquid oil entering or condensing in the membrane.
Air Products typically provides a standard performance warranty for one year from start-up or eighteen months from purchase date, provided the membrane and equipment have been properly operated and maintained. The warranty may be extended for Preferred Partners.
The weight is strongly dependent upon the system performance required. Separators weighing 5 to 20 pounds have been considered for various OBIGGS applications. Air Products can select from several materials to design and build membrane separators. These materials can save weight while meeting temperature and pressure requirements. In addition, we have developed manufacturing processes and designed custom components to keep the membrane separator weight to a minimum.
The dew point varies slightly with nitrogen purity. At 95% purity, the nitrogen will have at least a -70°F dew point. Operating at 99% will further lower the dew point to below -100°F. For systems requiring extremely low moisture levels, Membrane air dryers can be installed in series with nitrogen-generating PRISM membranes.
No. Some membranes made by other companies are susceptible to oil vapors. A carbon filter is used upstream of those membranes to remove the oil vapor, and often a final filter is added to remove any carbon dust carried over from the carbon filter.
Membrane dryers have a wide range of drying capability, while desiccant dryers dehydrate air by adsorbing water on a solid granular desiccant. Because the desiccant must be regenerated, two desiccant towers are used, and the air to be dried is periodically switched between the two towers. Maintenance is required on the switching valves, and there is the issue of desiccant carryover into the dried air as well as desiccant life.
A refrigerated dryer dehydrates air by cooling it down to condense the water. A refrigerated dryer typically dries your compressed air to a 35°F pressure dew point. The membrane dryer operates on a principle of dew point depression, so the outlet dew point is not limited to 35°F. The refrigerated air dryer also consumes electricity.