The daily morning journal and courier., 1897-12-22
CLEANED BY SAND BLAST
NOVEL WORK ON W.ASELNGTON
 VIADUCT.

The Great Steel Structure Attacked by
 Rust-New Means Used to Clean It.
 Quick Work by the Sand Blast-Experi- l ments With Rust-proof Paint.
 The great Western Heights steel via duct over the elevated railroad station at 155th street and Eighth avenue is the scene of an important and interesting work made necessary by the destructive effect of the steam and gases from the elevated railroad locomotives. says the New York sun" The destructive ef- feet was first noticed when the elevated railroad people complained that water was dripping from the Viaduct above the station. An examination of the viaduct showed a thick coating of rust on all that part of the structure above the elevated railroad station, and it was apparent that radical measures weres necessary to protect the viaduct.
 When the viaduct was built, about cred with four coats of paint. Where the painted work was exposed to only the ordinary weather conditions 1t af- l forded adequate protection, but over the l station it seemed to have served as q medium to catch and retain the destruc- | tive gases from the engines where they l could do the most harm.
 Much of the paint was found to be scaling off with the rust. Whether the rust had got beyond a surface attack and had eaten it's way into the riveted joints of the big lattice glrders and so threatened the actual safety of the structure, no one could tell until the work of cleaning was under way. The usual way of cleaning such a structure is to break away the loose rust scale and paint with hammers and then scrape the the rest down to the metallic surface with hand scrapers or scrub it off with wire brushes and sand. This is tedious and expensive method, and
 particularly difficult where there are complications of parts such as those of lattice work girders and columns.
 E. P. North, the engineer of the de-
 partment of public works in charge of the viaduct was inclined to follow ,his
 plan, when his assistant, MT. Evans, suggested the use of the sand blast.
 Not long before the sand blast had been
 successfully used at the navy yard in
 Brooklyn to clean the bottoms of some
 of Uncle Sam's ships of war. The con-
 cern that cleaned the warships was in-
 vited to try the sand blast on the via
 duct steel work. The proposition was
 accepted and the result has been so
 satisfactory that MT. North predicts
 that his method will supercede all oth-
 CTS for such purposes.
 A great platform of matched boards
 was first built under the viaduct and
 suspended from it. The platform was
 enclosed with canvas and what has
 been going on there has been only a matter of conjecture for most of the people who have been f1ocking into and
 out of 155th street station since that platform was built Those who have
 gone peering about to satisfy their cu-
 rosty have been rewarded principally
 by getting dust in their eyes In fact, Q goodly lot of dust has escaped from the
 platform every day while the sand blast machines have been at work
 These machines embody one of the many uses of compressed air A steam engine squeezes the air into a reservoir,
 
 blast machine Here, between the point
 where the air enters and the nozzle
 through which it issues, the sand is fed | into it in such manner that the blast
 of air picks up the sand and drives it
 forth with great velocity. Each grain
 of sand cuts off a thin bit of whatever it strikes, but the number of grains !, driven forth is so great that blast of
 y,-in hn1 oh
 faster than the stone could be chiseed
 away. From the mixing machines to the nozzles the air and sand were fed } through two and one-half inch hose lined with soft rubber, and the elastic lining would be unharmed, unless there was a kind in the pipe, while the chilled l cast iron nozzles were worn out by the l dozens. These nozzles were plain tubes about eight inches long and an inch in diameter, with a hole nine-sixteenth of an inch in diameter. From these the ) air issued with roar at a speed of 1 l5O f feet a second, or more than thirteen s miles a minute. The sand struck the steel viaduCt at a speed of two hun l dred and fifty or three hundred feet a 2 second. Two men were required to l hold each nozzle. While they worked l the air was filled with the dust of sand Q and rust and iron, and the men would ) soon have been stifed and blinded but . for masks of iron and glass which they 9 wore over their faces The nozzles were l held close to the steel and little slant
 ing, and the rapidity with which the sharp sand cleaned the steel work was l marvellous. Each nozzle cleaned abou, ], eighteen square feet of steel surface an n hour.
 The sand cut with a. peculiar noise - and the quality of this sound was a V guide to the workmen as to how to hold
 the nozzle. As the rust and paint dis | appeared before the sand blast a beau D tiful effect appeared on the cleaned
 steel This took on a mottled finish ot - a fine drab color and looked exactly as T If it had just received a coat of drat
 paint There was no crevice or pit IT '' the surface of the steel too fine for the 0 sand to get at, and when it's work was q done the steel was left clean.
 Q If the weather were dry this surface r would not show a sign of rusting agair e for many hours, but if there were mois = ture about it would catch it and begr I to turn red in very little while. A:
 the purpose of this thorough cleaning Q was to get a perfect metallic surface tC paint upon, the painters followed the
 sand blast workmen almost as fast al