Winter freeze-up had been the source of numerous maintenance headaches and at least one extensive repair job at a New York facility until the yacht club installed an inexpensive sparger system to prevent ice formation around its floating docks.

The two docks rise and fall a distance of about 7 ft. depending on the tide. When ice builds up around the dock and support pilings, the pilings tend to lift with the tide. During severe cold periods, the two docks- 60 ft. and 45 ft. respectfully- can become dislodged. A few years ago, during a severe cold period, encrusted ice was so hard it actually lifted several of the pilings completely free from their foundations. The cost of replacing only one of the eight pilings is about $500, and the cost of installing a new dock was estimated at well over $15,000.

In addition to the damage sustained by the dock facility, ice buildup on the shore during the spring thaw had been another problem calling for considerable maintenance work to restore the shore line. To economically alleviate the freeze-up problem, the club installed a sparger system consisting of only 200 ft. of polyvinylchloride (PVC) piping and a Rotron DR404 regenerative blower. The cost of the entire system would have to be well within reach of those who maintain their own private docks.

The system has been trouble-free since its installation last December despite having faced one of the worst winters of the century. The system also provided the added advantage of allowing boat owners to leave their craft in the water during the winter rather than having them dry-docked.

Installation called for running a 2 in. diameter PVC pipe from the regenerative blower located on the inner dock along the length of the two docks to their outer edges near the support pilings. Approximately one hundred 3/32 inch holes were drilled into the pipe at 15 inch intervals for the air flow. Heater hose was used for the system's flex joints. The entire installation was conducted by four men and required eight hours of labor time.

The Rotron Regenerative Blower was well suited for the sparger assembly because of its ability to deliver high volumes of air at relatively low pressures, along with its simple yet efficient, maintenance-free design. This system operates at about 1 PSI and 75 CFM of air. Another advantage was the relatively low cost of the regenerative blower in comparison to standard centrifugal blowers.

Regenerative blowers differ from centrifugal models in their basic method of air delivery. Centrifugal blowers impart air by outward radical acceleration from a central point. The regenerative principal also employs centrifugal force, but by throwing and re-throwing the air at the outside of an enclosed ring (where centrifugal force is greatest) it causes the air to build pressure with relative ease.

Since the DR404 has only one moving part - its impellor - and a motor with sealed, lubricated bearings, it requires virtually no maintenance. In addition, due to its design, it is unlikely the air will pick up oil from the motor or shaft bearings.

Relatively large clearances between vanes and housing mean that frictional contact is limited to the motor bearings. The clearance and the flat shape of the vanes also make it possible for the regenerative blower to tolerate the small amounts of dirt that will be taken in when the unit is installed outdoors without impairing overall performance. Consequently, maintenance requirements with these types of airmovers are minimal, a feature which should make the system economical to operate for some time to come.