The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-11-21
CLEANED BY SAND BLAST.
NOVEL WORK ON THE WASHING
TON HEIGHTS TIADUCT.


IN. cr.,t steel structure Attacked by Rust
view Means Used 20 Clean It-ouick work
~ ,he sand nIast-Experiments by Severn
,s., P~nIntmRkers with Rust-Proor Pnints
The great Washington Heights steel viaduct
overt the elevated railroad station at 155th street
md Eighth avenue is the scene of an impor-
tant and interesting work made necessary by
tho destructive effect Of the steam and gases
from tho elevated railroad locomotives. This
destructive effect was first noticed when tho
o,cvatod railroad people complained that
water was dripping from the viaduct above the
station. An examination of the viaduct show
cd n thick coating of rust on oil that part of
tho structure above the elevated railroad sta
,ion and II was apparent that radical meas
ures were necessary to protect tho viaduct.
when the viaduct was built, about four years
AGO. the steel work was covered with four coats
Of paint. Where the painted work was OK
posed to only the ordinary weather conditions
Il afforded adequate protection, but over tho
station it seemed to have served Us q medium
TO catch and retain the destructive gases from
the engines where they could do the most harm.
Much of the paint was found to be scaling
Off with the rust. Whether the rust had got
bcyond q surface attack and had eaten its
way into the riveted joints Of the big lattice
eirders and 80 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
tho loose rust scale and paint with hammers
and then scrape the rest down to the metallic
surface with hand scrapors or scrub 1t of with
wire brushes and sand. This is q tedious and
expensive method. and particularly difficult
where there are complications Of parts such as
those OF lattice work girders and columns. E:
+. North, the engineer OF the Department. or
Public Works in charge of the viaduct, was in.
clined to follow this plan, when his assistant,
Mr.. Evans, suggested the use of tho sand blast.
Not long before the sand blast had been sue.
to clean tho bottoms of some OF Uncle Sans
ships, of war. Tho concern that cleaned the
warships was invited to try the sand blast on
accepted, and tho result has been SO %satisfac;;
tory that Mr.. North declares that this method
will supersede all others for such purposes.
A great platform of tIatched boards was
first built under the viaduct and suspended
from it., The platform was inclosed with can
vas, and what has been going on there has been
only n matter Of conjecture for most of the peo-
ple who have been flocking into and out of the
155th street station since that platform was
built. Those who have gone pcering about to
satisfy their curiosity have been rewarded
principally 9GSaI by ,d getting ~ G5s aq bas in 6s tnG,r e frem thu ba
platform every day while the sand blast ma
chimes have been at work.
These machines embody one of the many uses
Of compressed air. A steam engine saueczes
the air into small compass, and under high
c eaIssui into I the sand blast machine. Here. be.
tween the point where the air enters and the
nozzle through which it issues, the sand is fed
picks up the sand and drives 1t forth with
great velocity. Each grain of sand cuts of a
! OF grains driven forth is SO great that a blast Of
this sort will eat n hole, through rock faster
than the stone could DO chiselled away. From
the mixing machines to the nozzles the air and
sand were fed through 21e-inch hose lined with
soft rubber, and tho elastic lining would be un-
while the chilled sast-iron MOBILES were worn out
by the dozens. These MOBILES were plain tubes
about eight inches long and nd an inc inch !, outside
ter. From these the air issued with n roar ut
a speed of 1.15O feet a second, or more than
steel viaduct at a speed of $50 or 300 feet a sec
ond., Two men were required to hold each
n9z5le :. Will i they sSy,G To nId 1.-THE the a air was ;rn, f aSd
the men would soon have been stified and
blinded but for masks of iron and glass which
held close 10 the steel and u little %slanting, and
the rapidity with which the sharp sand
nozzle cleaned about eighteen square feet of
steel surface an hour.
The sand cut with a peculiar noise and the
men as to how to hold the nozzle. As the rust
and paint disappeared before the sand blast a
This took on a notified finish of a fine drab
color and looked exactly as if II had just re-
crevico or pit in the surface Of the steel too fine
for the sand to get at. and when its work was
done r. t the w steel was ws left G clean This sur,,co wou,d
hours, but If there we're moisture about It
would catch it and begin to turn red in a very
little while. AS the purpose of this thorough
cleaning was to get a perfect metallic surface
to paint upon, the painters followed the sand
were stopped and the cleaned sections were
A few years ago it was believed that a paint
which contained an insoluble oxide of iron was
there are no end of theories as TO the best way
to n. make ;ko a paint for the paIRpGSe: ohout no,rt =,
said Engineer North yesterday, but when VIC
got ready TO do this work and ADVERT sed fol-
blind by paint men, until had to throw W
body a chance to prove what he. sald."
The result was that a very interesting OK
pertinent, was. begun. Seventeen different
paint.mqking, houses, all of high reputation
signed to it, upon which its paint is to be tested
Some of the firms. will put on two or more
kinds of paint. There arc oxide paints, sub
oxide paints, varnishes, and plain paints o.
white lead, red lead, or zinc. When thes,
paints have been in use a year It is believed
GERS as q guido for further experiments. Som'
are cheap and others cost eight times as much
Tho section OF the yiaduct which was rusted
included seventeen bents, and was about II;
feet, in length: Each bent Is supported BY
lattice truss rs feet long ana y feet deep. owe
these trusscs are steel girders and these in turn
support steel plates on which the stone pave
ment Of tho roadway and the asphalt of tn
sidewalks are laid. 1t was found that the rus
had not attacked the riveted work and it wa
not necessary TO replace any Of the steel.
Much difference was found In the cutting
power Of different sands. Ordinary building
sand was first tried. Then sand was brough
from Huntington Harbor. Long Island, whicl
was dug in twenty feet Of water. This wa
washed free from salt. and screened until
would go through meshes of one-tenth inch
but not through others of fifty to the inch
When this had been used 1t was swept UP an,
used again until 1t had been through the nozzl
three times. BY that time 1t was as fine a
flour, and was thrown away. 1t took .abou
one-third Of q cubic foot of sand each time I
clean a square foot Of steel surface, and the worl
cost at first as much as 20 cents a foot. Late
this cost was reduced to about 9 cents. Thi
was after tho men had gained experience and
new sand was put into use. This sand Is "A by
product of Edison's latest project, tho 'Ogdel
mine iron works. 1t consists OF tho sharl
particles of Tho crushed Jersey rocks, out o
which Edison has drawn all the iron ore. .Thi
sand is in demand for building purposes also.
Tho work on the viaduct is nearly done, an!
in a few days The scaffoiding will be removed
The trouble from leakage which led to the ex
animation of the viaduct was caused by
loosening Of some of the sidewalk and pavemen
l Al Aha a.