AN IMPROVED METHOD OP AND MEANS FOR PREVENTING THE CORROSION OF STEAM BOILERS
Year: 1869

page_text: LETTERS PATENT to George Hawxhurst and James Pollock, both of
San Francisco, California, United States of America, for the
Invention of "AN IMPROVED METHOD OP AND MEANS FOR PREVENTING
THE CORROSION OF STEAM BOILERS."
Sealed the 29th June 1869, and dated the 26th April 1869.
PROVISIONAL SPECIFICATION left by the said George Hawxhurst
and James Pollock at the Office of the Commissioners of Patents,
with their Petition, on the 26th April 1869.
We, GEORGE HAWXHURST and JAMES POLLOCK, both of San Francisco,
California, United States of America, do hereby declare the nature of
the said Invention for "AN IMPROVED METHOD OF AND MEANS POR PREVENTING
THE CORROSION OF STEAM BOILERS," to be as follows:-
The object of our Invention is to prevent the corrosion of the
material of steam boilers from the use of distilled or condensed water
therein.
The nature of the said Invention consists in mingling with the
distilled water within the boiler or upon its way thereto a strong solution

page_text: of caustic lime in such quantity and at such intervals of time that the
water contained in the boiler will be a weak solution of the same.
It is a well known fact that surface condensation as now practised
has the great disadvantage of being accompanied with more or less
corrosion or waste of the boilers and particularly of the tubes, and as
tubular boilers have become almost indispensable in sea-going steamers,
it is a matter of great importance to obviate this source of trouble and
expense.
The cause of this particular corrosion is involved in mystery, and
indeed the corrosion of iron in all other forms and under varied cir-
cumstances has been the subject of much thought and research among
scientific men and without unanimity of opinion.
It is therefore superfluous to describe herein the various theories
presented, inasmuch as the object of this Invention is simply to produce
the practical result of obviating the difficulty, and in this connection
has more reference to the daily duties of the engineer than to the province
of analytical chemistry.
In practising our Invention we take the ordinary quicklime of
commerce preferring that which is fresh burned, and by leaching or
any other known method procure a strong solution of the same in water
which we keep in close vessels to prevent the absorption of carbonic
acid and other substances. We prefer the solution above described to
the crude quicklime for the reason that it is more conveniently kept,
transported, and applied, and because the residuum of the crude material
would, if introduced into steam boilers, furnish material for a large
amount of scale. When in using a steam boiler which is fed with
distilled water, we judge that corrosion is going on or about to commence
by reason of the peculiar and not well understood action of heated
distilled water upon iron and other metals of which boilers are usually
composed, we introduce small quantities of the aforesaid lime water by
means of pumps, hollow plug cocks, or other devices suitable for the
purpose. The quantity of lime used to make the solution is of course
to be determined by the amount of condensed water that is derived from
the condenser and pumped into the boiler. A consumption of one
pound of lime per day of twenty-four hours for each one hundred and
fifty (150) horses power developed in usual practice, will be a fair
criterion for the engineer to guage the quantity to be used, taking care
rather to use too much than too little, as in the case of using the lime

page_text: in excess the result of the production of a thin scale on the tube is not
objectionable. In fact it has been common heretofore to endeavour to
form a similar scale by pumping salt water into the boilers, thereby
protecting the tubes to a considerable extent but at a great expense in
fuel, and with uncertain results. But referring again to the un-
determined causes of corrosion, it would seem that this new Invention
operates as an actual neutralizing agent to that principle in the
condensed water which causes the corrosion, and also causes a protecting
scale to be precipitated on the surface of the tubes.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Hawxhurst and James Pollock in the
Great Seal Patent Office on the 23rd October 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, GEORGE
HAWXHURST and JAMES POLLOCK, both of San Francisco, California,.
United States of America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-sixth day of April, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said George Hawxhurst and James Pollock,
Her special licence that we, the said George Hawxhurst and James
Pollock, our executors, administrators, and assigns, or such others as:
we, the said George Hawxhurst and James Pollock, our executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention of "AN IMPROVED METHOD
OF AND MEANS POR PREVENTING THE CORROSION OF STEAM BOILERS," upon the
condition (amongst others) that we, the said George Hawxhurst and
James Pollock, our executors or administrators, by an instrument in
writing under our, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that we, the said George Hawxhurst and James
Pollock, do hereby declare the nature of our said Invention, and in what
manner the same is to be performed, to be particularly described and
ascertained in and by the following statement (that is to say)
The object of our Invention is to prevent the corrosion of the material
of steam boilers from the use of distilled or condensed water therein.
The nature of our Invention consists in mingling with the distilled
water within the boiler or upon its way thereto a strong solution of
caustic lime in such quantity and at such intervals of time that the
water contained in the boiler will be a weak solution of the same. It is
a well known fact that surface condensation as now practised has the
great disadvantage of being accompanied with more or less corrosion or
waste of the boilers and particularly of the tubes, and as tubular boilers
have become almost indispensable in sea-going steamers it is a matter
of great importance to obviate this source of trouble and expense.
The cause of this particular corrosion is involved in mystery, and
indeed the corrosion of iron in all other forms and under varied cir-
cumstances has been the subject of much thought and research among
scientific men and without unanimity of opinion.
It is therefore superfluous to describe herein the various theories
presented, inasmuch as the object of the Invention is simply to produce
the practical result of obviating the practical difficulty, and in this
connection has more reference to the daily duties of the engineer than
to the province of analytical chemistry.
In practising our Invention we take the ordinary quicklime of
commerce, preferring that which is fresh burned, and by bleaching or
any other known method procure a strong solution of the same in water,
which we keep in close vessels to prevent the absorption of carbonic
acid and other substances. We prefer the solution above described to
the crude quicklime for the reason that it is more conveniently kept,
transported, and applied, and because the residuum of the crude material
would, if introduced into steam boilers, furnish material for a large
amount of scale. When in using a steam boiler which is fed with
distilled water we judge that corrosion is going on or about to
commence by reason of the peculiar and not well understood action of
heated distilled water upon iron and other metals of which boilers are
usually composed, we introduce small quantities of the aforesaid lime
water by means of pumps, hollow plug cocks, or other devices suitable

page_text: for the purpose, or the lime can be put in the fresh water tank or hot
well and from there pumped into the boiler. The quantity of lime used
to make the solution is of course to be determined by the amount of
condensed water that is derived from the condenser and pumped into
the boiler. A consumption of one pound of lime per day of twenty-
four hours for each one hundred and fifty (150) horse power developed
in usual practice, will be a fair criterion for the engineer to guage the
quantity to be used, taking care rather to use too much than too little,
as in the case of using in excess the result of the production of a thin
scale on the tube is not objectionable. In fact it has been common
heretofore to endeavor to form a similar scale by pumping salt water
into the boilers, thereby protecting the tubes to a considerable extent,
but at a great expence in fuel and with uncertain results.
But referring again to the undetermined causes of corrosion, it would
seem that this new Invention operates as an actual neutralizing agent
to that principle in the condensed water which causes the corrosion as
well as by forming a protecting scale precipitated on the surface of the
tubes. We are aware that water holding salts of lime, such as carbonates
and sulphates, have heretofore been introduced along with distilled water
into boilers for the purpose of protecting them from corrosion, and do
not claim that as our Invention; but what we do claim is, the use of
an artificial solution of quicklime in distilled water as a liquid from
which steam is generated by heat, substantially as and for the purposes
described.
In witness whereof, we, the said George Hawxhurst and James
Pollock, have hereunto set our hand and seal, this Ninth day of
June, in the year of our Lord, One thousand eight hundred and
sixty-nine.
GEORGE HAWXHURST. (L.S.)
JAMES POLLOCK.
(L.S.)