Rusted Air Cylinders Scoured On Shop-Made Tumbler

Rusted Air Cylinders Scoured On Shop-Made Tumbler

Tumbler built by the Fort Lauderdale Fire Department is used for removing rust from air cylinders.Aluminum oxide gravel poured into cylinder before tumbling, scours rust from cylinder walls.Tanks are sealed with masking tape to contain gravel. Motor drives tumbler to rotate tank.

Rust in air cylinders brought on by Florida’s weather was a problem for the Fort Lauderdale Fire Department until Driver/Engineer Franklin H. Brown designed and built a tumbler for cleaning them.

Members of the fire department utilize two cascade recharging systems, one of which is mobile and located in a step van quartered at Central Station, the other at No. 4 Station and Training Center. While charging and repairing the breathing apparatus, fire fighters noticed that all of the units coming in for repair and normal maintenance had rust building up in the cylinders. While the most severe of the rusted tanks were out of service for hydrostatic tests and tumbling, they inspected all of the remaining 145 cylinders and found rust problems of varying degrees.

Climate a problem

The severe climatic conditions of the area—humid and salt-laden atmosphere—called for more preventive maintenance than is normal. The interstage coolers and separators were allowing moisture to build up in the cascade cylinders and subsequently transfer to the 45-cubic-foot cylinders. The compressors were modified by the addition of more and larger cooler separators, thus solving the primary problem; but not the existing problems with the smaller in-service units throughout the department. Since there were still 145 cylinders to be tumbled at approximately $15 per cylinder, the department decided to go ahead with the expense of having its own tumbler.

Using his mechanical and welding expertise, Brown constructed the tumbler in somewhat less than one week. The frame was made of 3-inch channel iron in a 2 X 5-foot rectangle. Intermediate bearing surfaces were made of 2-inch angle iron. Nine 2 1/2 -inch rollers with ½-inch shafts were mounted in three rows on pedestal bearings. The center shaft and rollers are powered while the outboard ones are driven by the cylinders being tumbled. Power is supplied through a flex-coupling driven by a 1/10-hp, 60-rpm electric Gearmoter (Model 3M138) from Dayton Electric, Chicago.

The total investment of $556.65 and 40 hours of work has paid for itself and will save much money in the future.

As many as six 45-cubic-foot cylinders or one 300-cubic-foot cylinder may be tumbled at one time. Prior to the 48hour tumble cycle, aluminum oxide gravel is placed in the cylinders and the necks taped shut (25 pounds of gravel in the 45-cubic-foot and 1200 pounds of gravel in the 300-cubic-foot cascade cylinders, slightly more than 50 percent of volume of the cylinder).

After tumbling is completed, the gravel is removed and the cylinders are completely flushed with fresh water. A second rinse of distilled water and a rust preventive is conducted prior to “blow-

ing” out with dried breathing air. The main cylinder control valve should be reinstalled immediately and the cylinder charged.

The air tanks are in no way damaged by this procedure and unless severely rusted, would not have to be hydrostatically tested unless the last test date so dictates.

Tumbler can handle up to six 45-cubic-foot cylinders or two 300-cubic-foot tanks that are used in the cascade system

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