Air bearings require clean, dry, oil-free air at adequate pressure. These conditions must be met whenever the bearing is pressurized; 99.9% conformance to these requirements won’t do.
Cleaning the compressed air to a 5-micron level is readily accomplished with a combination of particulate and coalescing filters. The coalescer also aids in removing oil droplets and mist. However, the vaporous oils, tars, and resins must also be removed; this can only be accomplished through use of an activated-charcoal filter.
The air may be dried in a variety of ways. Although most air drying technologies are well-proven and quite reliable, it is important to choose a system that will not put the air bearing at risk in the event of power interruption. Our recommendation is to use an automatic-cycle dryer only as a primary or whole-plant unit. A refrigerant-type dryer may be a good choice here. At the air bearing location, an additional point-of-use dryer that is not power-dependent serves to protect the bearing from the occasional dose of wet air. The single-tower deliquescent dryer is the ideal choice for this back-up unit, since it needs no power, and is not diminished by passing dry air through it.
Professional Instruments Company sells a model D4-A dryer-filter-regulator, which is a single-tower dryer with added particulate filters, coalescing filter, charcoal filter, and regulator. The model D4-A, when used in conjunction with a Humidity Alarm, provides a reliable, efficient, and inexpensive air-treating station. We use this dryer throughout our plants, and recommend it to all air bearing users.