Transactions

CLARKE, W HITE, UPTHEGROVE—CONDENSER TUBES AND T H E IR CORROSION 529
improvement in the quality of tubes, metallurgically, physically,
and mechanically, so that there are available today condenser
tubes embodying a standard of quality impossible to obtain two
or three decades ago.
Consider for instance the old practice: Admiralty tubes made
from cast shells; the alloy melted in pit fires with natural draft;
small unit melts which resulted in wide variations in analysis and
quality; cast in iron molds with a built-up core of hay, sand, and
clay; and, at one time, horse manure mixed with molasses as one
of the core materials, and cold drawn to the finished size.
The next step in the improvement of admiralty was the turning
or machining the inside and outside of the shell casting, also the
use of the “cupping” process.
Today, this, as well as other tube alloys, are cast in large units
from electric furnaces under accurate temperature control. Each
“heat” is analyzed. The exterior surface of the billets is removed;
the billets are then forged and extruded under high pressure
and the resultant “extruded” tube carefully examined before
receiving subsequent cold-working and drawing. Dies and tools
are chrome-plated or made from tungsten-carbide steel.
Final inspection, as it exists today, on the resultant product is
so severe, so searching, and of such a high quality, that it is
doubtful if one tube, manufactured under the methods in vogue
years ago, would be “accepted” today. Therefore, if tube life
was wholly dependent upon quality alone, we would not be faced
with the condenser-tube-corrosion problems which exist today.
We all recall that in the early days, in the minds of engineers,
when tubes failed, it was not a prima facie case of bad tubes but a
conclusive case.
We sincerely trust that the problem will be approached, in the
future, to even a greater degree than now, on the basis of an
analysis of all the facts; that engineers will continue to endeavor
to design condensers and plan their installations in such a manner
that the failure of condenser tubes will cease to be a matter of
such grave concern as it is at present.
W . R. W e b s t e b .17 There is probably no important engineering
material concerning which there have been as many exparte
claims, regarding the importance of this, that, or the other composition,
treatment, or procedure, unaccompanied by any sufficient
supporting evidence, as is the case with the condenser tube.
This paper is therefore welcome in that it reports the results of a
scientific investigation intended to determine facts. It amply
confirms one already well-established belief, namely, that aluminum
brass is superior in corrosion resistance to admiralty metal
under normal conditions. It does not, however, support another
belief widely held that cupronickel is superior to both. The complete
accuracy of these tests is, however, open to some question,
due to wide variation in results from sample to sample. This
may be because, in all probability, all tubes did not receive an
identical exposure to the corroding media. On no other grounds
can the differences observed in the case of tubes of approximately
the same characteristics be explained, although the law of averages
would correct this situation as between tubes of widely different
characteristics.
It is regretted that the opportunity was not embraced to test
the condenser. This could readily have been done since it would
have been an easy matter to make sufficient tubes to equip it
from one casting, all manufacturing operations being controlled
with extreme accuracy. Should these tubes then have shown as
wide variations in corrosion resistance, as occurred in the original
test, it would be difficult to avoid the conclusion that each tube
had been subjected to a different intensity of exposure. It is
hoped that the authors will arrange to conduct such a test since it
would add much to the value of the present paper and might help
11 Bridgeport Brass Company, Bridgeport, Conn. Mem. A.S.M.E.
to controvert a widely held belief that the causes of unsatisfactory
performance always reside in the tubes.
It is noted that the results give no support to the long-held
grain-size theory which never had any evidence to substantiate
it, although much to refute it. It is hoped that it is now dead
beyond resurrection.
Certain omissions are noted, the addition of which would add
greatly to the value of the paper, among which are chemical
analyses of the various samples. This is particularly true of the
cupronickels as the presence of manganese and iron are known
substantially to increase corrosion resistance. In Table 4, of the
paper, the presence of tin is indicated, although this ingredient
is not normally found in the cupronickels. It is also noted that
the 20 per cent nickel does not show the poorest performance of
the nickel tubes although experience indicates that it is markedly
inferior to the 30 per cent.
It is questionable whether the impingement test represents
true impingement attack, as this requires the presence of air in
quantity. Further, if air were present in the test it would be
doubtful if it were uniformly distributed from jet to jet.
In the final summary, conclusion 7 is not supported by any
data coordinating any manufacturing procedure with any variation
in performance. It is, therefore, irrelevant to this discussion
and in addition has no more application to condenser tubes than
to any other high-grade material.
A u t h o r s ’ C l o s u r e
The discussion of this paper as given by the various contributors
is much appreciated.
The discussions by Messrs. LaQue and Crawford relate almost
exclusively to the findings with respect to the copper-nickel
tubes. They are at a loss to account for the relatively poor showing
of the tubes of this type in comparison with the tubes of the
aluminum-brass type. The authors of the paper were equally
surprised at the results of the test. They expected copper-nickel
tubes to show an outstanding superiority over the aluminumbrass
and admiralty tubes.
Regret was expressed that the composition of the water was
not given. This was purposely omitted for the reason that no
one analysis would tell the true story. The cooling water used
for condensing is virtually at head tide. This means that at
high tide there would be a tendency for the water to be slightly
alkaline, although possibly not greatly so because of the small
rise and fall of the tide at that point, and at low tide the water
would be slightly acid in character because of the fact that the
water would be essentially that of the Providence River and its
tributaries which collect sewage and waste from many of the textile
plants and communities which lie along their shores.
The authors agree with the thought that these tests may not
apply to service in condensers wherein an erosion or dezincification
is the principal factor determining the life of the tubes. It
must be remembered that, in initiating this investigation, it was
the feeling of the authors that through an impingement and
condenser test it might be possible to get some idea as to the
relative merits of condenser tubes of the aluminum-brass and
admiralty compositions. A few copper-nickel tubes were added,
with the feeling on the part of all of those concerned in planning
the test that there would be no question about the outstanding
superiority of the copper-nickel tubes, though with some doubt in
the minds of those engaged in the work as to whether or not the
extra cost of these types of tubes could be justified, especially if
the aluminum-brass tubes made a good showing. The authors
are as much disturbed over these findings as are Messrs. LaQue
and Crawford, for they agree that, in most instances of severe
service, there is no better tube composition than the copper nickel.
The rating of the tubes, as given in Table 8 of the paper, was