Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-11-08
SCALE IN STEAM BOILERS.
Consideration of Some of the Benefits
Derivable From It.
From the Engineering News.

From the Engineering News.
Is scale in steam boilers benefit an
injury? That It is generally assumed to be
the latter we are well aware. and there is
no doubt, of course. that the scale which
forms In boilers using hard water is very
great nuisance and one which involves
large expense in caring for it. But sup
pose, for the sake of argument, that boilers
were supplied with water absolutely free
from mineral matter, let us say with rain
water or distilled water. Would not the
troubles that would be experienced far
exceed those that are now caused by scaler
To put the question I'm another form, is not
the scale which forms in a steam boiler
fed with fairly pure water really benefit
in protecting the interior of the boiler from
the rapid corrosion which would otherwise
take place?
In paper by Mr. NJ E. Wells, chief boil
er inspector of the Burlington and Missouri
River railroad, the fact is pointed out that
boiler tubes piled outdoors and exposed to
the weather rust out faster than tubes in
side a boiler. The statement is made by
Mr.. Wells that perfectly pure water is the
most corrosive that is put inside a boiler.
mature has provided incrusting matter In
water that the inside of the sheets of boil
ers may be coated with a layer of it, and
thus be protected from oxidation"
% lar as we are aware, tUlS lQed mas
never before been set forth in technical lit
erature. We do not mean by this that the
fact that boiler scale protects from corro-
sion has not been noted and put on record
but that the general Importance of scale in
boilers as protection and preservative has
never been recognized by any of those who
have studied steam DO Ter construction and
written treatises upon it.
Very likely many engineers will question
the soundness of Mr.. Wells statement
above quoted. but there seems to us to be
much evidence In its support. We know
that boiler shells which have been in serv-
Ice for years when protected from external
corrosion often show scarcely any diminu-
ton in thickness, whereas if the same ma
terfal were immersed in river or pond il
would be rusted very rapidly. Again. prac-
tical experience has shown that boilers in
which rain water alone is used have given
trouble from internal corrosion, and II has
been frequently ascribed to ac.d gases alb
sorbed by the water from the air. But may
not the true expla natfon be that no scale is
deposited by such water to protect the
metal surfaces?
The question may be asked of what prac-
heal benefit would be a general knowledge
of the protective power of SCALE One bene-
fit might be the more intelligent care of
boilers. Many large power plants are now
using the same feed water over and over
again by the use of surface condensers or
cooling towers. There will usually be suf-
ficient makeup water used in such plants
to protect the boiler surfaces, Yet there NAV
De cases WHeTe internal c0rrOSiOn is going
on unknown to those in charge of the
plant.
Another field that has never been exploit
ed Is the possible use of scale to protect
other metal surfaces than boilers from cor
rosion. Any one who has tried to remove
calcium sulphate scale from boiler fiues or
stays knows with what tenacity ii will
often adhere. 1t might be practicable to
treat various metal articles, such as fence
posts or water mains, by immersing them in
a closed tank containing a saturated solu-
ton of calcium sulphate and then partially
evaporating the solution. Certainly the de-
mand for better and more effective methods
of protecting iron surfaces from corrosion
Is great enough to encourage experiments
In this field.