Wheeling Sunday register. [volume] (Wheeling, W. Va.) 1882-1934, 1895-03-03
IN THE CAISSON.
What is the Greatest Air Pressure That
Can stand?

What is the Greatest Air Pressure That
Can Stand?
Messrs. Sooysmith & Co.. of New
York. the well-knOwn contracting en-
gineers. who, for years. have made a
speciality of difficult foundations and
tunnelliug requiring the use of COM
pressed air, tell us that the full ability
of properly equipped and properly be-
haved men. under the most favorable
OnditiOus. to resist caisson disease, has
never been tested. The highest work
ing pressures recorded have been close
to 30 pounds per square inch; but with
extreme care i'm the selection OF men
ande corresponding care on the
part of the mn, it is very
probable that this limit may be
considerably exceeded. For the aver
age pressure under average con-
ditions, the top limit may be placed at
about 40 pounds, the time Of working
varying from four to six hours per
shift. according to conditions. In the
cases where higher pressures might be
used and shifts for the man should be
restricted to two. of two hours each,
separated by considerable interval
As an example of heavy pressure work
under favorable conditions as to ven
tilation, without very bad effects on
the men. MessTs. SOOysmith 4 Co. had
an experience with a work on which
men were engaged in siN-hOur shifts,
separated into two parts by half-hour
intervals for lunch. This work was
excavation in open. seamy rock. car
ried on for several weeks under about
45 pounds pressure.
Thecharactero of the material through
which the caissOn is being sunk, or
upon which il may be resting at any
time bears quite largely upon the abil-
fly OF the men to stand the pressure
necessary to hold back the water at
that point. If the material be so
porous as to admit a considerable leak
age of air through it, there will natur-
ally result a continuous change OF air
i'm the working chamber, and a core-
spending relief of the menfrom the
deleterious effects which are produced
nearly always by oveTUsed air; in other
words. a system of ventilation is kept
no by the porous material. On the
other hand. If the caiSsOn is passing
through an impervious such
asthrough clay. vetilatiOn is much o6-
structed and the consequent bad effects
ON the men are very noticeable. As it
is usually necessary to carry the high
est pressure when the caiSson has
reached it's final position and
while the air-chamberr is being
FILLED with concrete and sealed up, the
worst result usually results at these
times. thus. very often at the time
when the pressure is greatest the ven
tilation is the worst. As an example.
evDerience has shown that, in one
known instance, at least, during eXca-
yation at great depths the leakage OF
air through the seams and crevlces OF
tho rock permitted of the men standing
very high pressures. The physical con-
ji+ion of the men is a very important
factor in the whole matter. Men who
are thoroughly sound organically and
v-bo are not ieshy can endure much
biober pressures than men who have
not these physical conditions. More
o-er the degree to which pressure men
observe hygienic rules, preserve regu-
larity of conduct and abstain from dis
sinafiou affects largely their capacity
- sndure the effects of compressed air.
1,ba extent. also. to which pressure
,,on adhere TO the rules for entering
,,ressrre for conduct while at work, for
evit IN the ordinary atmosphere and
for behavior Immediately after coming
ONT Influences their physical sensitive
nsss TO these effects