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TURBO-AIR COMPRESSOR REPAIRS.

By COMMANDER R. L. IRVINE, U. S. N., MEMBER.

The following description of repairs undertaken and completed at the Puget Sound Navy Yard to two turbo-air compressors for the U. S. S. Nevada may prove interesting from an engineering viewpoint. These two turbo-air compressors are horizontal, multiple centrifugal pressure staged, direct connected to the motive end, and designed to deliver 2350 cubic feet per minute at 100 pounds pressure. There are thirteen (13) pressure stages, six (6) of which are on one shaft in the low pressure end, and seven (7) on a separate shaft in the high pressure end.

The side discs of practically all stages became badly corroded away near the periphery, causing great loss of efficiency and unbalance and necessitating the renewal of practically all stage wheels. In the stages the impeller elements were corroded to the extent that the scale deposits averaged about 140 mils in thickness over the entire plate surface.

It was considered at first to send these rotors to the manufacturers works for repairs, but this being impracticable and the bids for the manufacture of the necessary parts and proposed delivery dates being greatly in excess of the yard estimate, the Bureau of Engineering directed that the yard perform the work.

When the very accurate dimensions and contours and the thinness of the discs, etc., that were necessary in this work are considered, it is apparent that to produce efficient results very delicate workmanship was required and special methods had to be devised. The plan dimensions are given to thousandths of an inch and these dimensions and the contours of the parts forming the air passages must be strictly adhered to in order to secure efficient operation. The impellers are approximately

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FIG. 1-IMPELLER DISC FINISHED ON BLADE SIDE AND IN BORE.

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FIG. 2.-MACHINING THE RADIUS ON THE OUTSIDE OF IMPELLER COVER.

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FIG. 4. ROUGHING OUT THE BLADE AND RIVET OF THE BLADE.

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FIG. 6.-SLOTTING OUT ONE SIDE OF THE BLADE.

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FIG. 7.-BLADE DISC SHOWING BLADES CUT OUT ON ONE SIDE.

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