The Sun.
London, England, 1859-04-23 00:00:00

SUPE.7?HE4.TED ST I

.... •_.• a- +. ... ,1., X --...
A most important experimental ,improvement in
steam machinery, was on Thursday last tried for the
on board' the Peninsular . . t
.first time down the rii'er,-
the' Valetta.. The o,c; -.0
and Oriental Company's ship
tual nature of the improvement may be descri ' ..';,,t:
a few words as cen isting of a siMple apparat*: '.l. -,-ii,
working marine. ngines by ,means a superfie .: ....„3,-
steam ; but it is not too much to say thaf in 't int..pc
biln
0.,
success or failure of this. experiment are involve ,= .
results so important as to affect materially all ocean - r
going steamers—and, indeed, steam machinery- of •
all kinds. To be able to work machinery with super- , -
heated steam, means to command increased power
with a 30 per cent. reduction in the consumption of
fuel. A principle which can died such Important
changcs in the universal. application of steam has
not remained undiscovered to the present day. The
want of superheated steam haS long been felt, and
the enormous comparative advantages of workin:g,
engines on such a plan have long teen known. A
simple and effective working of the-principle, how-
ever, has been' an engineering difficultgr-Aqiie47
various expedients—all, however, sufficien4yowt-ix)
cessful to show the valueof the improvement-4944hr, t
`failed to obviate entirely. This obstacle has ,now,
we believe, been of by Mr; Penn, -
and the value of the improvement so clearly demon-.
strated that the general application of the principle
to steam machinery of every kind may now be re-
garded as certain. The idea of working engines by
superheated steam, and the immense saving of fuel
and increase of power it would effect, was, we be-
lieve, first started many years ago by Mr. Howard,
and subsequently by Dr. Haycraft. The difficulties
however, in the way of its adoption at that time,
and the undue estimate of the importance of the
principle, prevented those gentlemen from realising
very great practical results. •At a later period the .
matter was again taken Up by an American en-- •
ginecr—Mr. Weatherhead—who, however, only
superheated a portion of _ the steam and mixed it
with common steam inrits way to the cylinders. The
success which attended even this partial application
of the process. _ again revived the idea and
encouraged other engineers to turn their attention
to the subject. The result of these renewed efforts '
is that several methods of securing the great eco-
nomy to be effected by superheating the steam are
now under trial, and there is no doubt that a most
important step in the progress of steam, especially
as applied to ocean navigation, is now at least on
the point of being successfully accomplished. The
value of the improvement on the score of economy
in working may be best illustrated by a single fact
—namely, that the Peninsular and Oriental Com-
pany's bill for coal annually amoants to the enor-
mous sum of £700,000, and that by working their
vessels with superheated steam properly applied it
is become almost certain that, without any detri-
ment to the machinery from 28 to 30 per cent. of
this gigantic outlay may be saved. As to the various
proposed methods of superheating steam, it may be
briefly explained that the conditions required to be
fulfilled are perfect simplicity of arrangement with
ready control over the apparatus ; that it should
be so placed as not to be liable to accidental injury
in the engine-room; and that the heat employed
for superheating the steam should be waste heat
which has already done its duty in the boilers and
is passing away. All these conditions have been -
most satisfactorily fulfilled by Mr. Penn in the new
engines on board the Valetta, which were tried
down the Thames for the first time on Thursday.
The Valetta, as our readers may remember, was for
many years the mail-boat between Marseilles,
Malta, and Constantinople. While thus employed
she had Penn's engines of 400 horse-power, and to
work these up to an average speed of 15 miles an
hour required a consumption of fuel of from 70 to 75
tons of coal per day. At no time was it less than
from 45 to 55 tons. These engines have now been
removed to a vessel nearly double the tonnage of the
Valetta, and the latter fitted with engines by Mr.
Penn on the superheating principle. We may men-
tion that, besides this alteration, the Valetta has
been considerably improved. A poop and
forecastle _have been added, increased accom-
modation given to passengers, and the
whole vessel fitted up in the - richest style.
The saloon is one of the simplest and handsomest
things of the kind we have seen, sufficiently lofty,
capacious, and, above all, admirably ventilated on
the system which is now being adopted on all sea-
going steamers, and the merit Of devising which
belongs to Mr. Robinson, of the Peninsular and
Oriental Company. To return, however, to the
engines. Mr. Penn, at the repeated request of Mr.
Allen, the managing director of the Peninsular and
Oriental Company, undertook to apply to them the
principle of superheating, to which his attention
had many years before been seriously directed by
Dr. Haycraft. His method of doing this is to place
in the smoke-box of the boiler, 'through which the
hot air from the furnace first passes, as -large a num-
ber of small pipes as is consistent with allowing a
free draught from the furnaces. Through these all
the steam from the boilers passes in its way to the
cylinders. By this plan an immense heating surface
in the pipes is secured, the steam is in a subdivided
form, so as to be readily acted on, and the waste
heat from the furnace is utilised at the point where
its intensity is greatest, and where the greatest
conveniences exists for applying the apparatus. By
the means of three ordinary stop-valves the whole
contrivance can be shut in or off from the engines
at pleasure. In ordinary engines steam leaves the
boilers at about 250 deg., but declines from this
temperature in its way to the engines to 230 deg.,
undergoing from condensation a still greater and
more serious diminution of heat in the cylinders.
From these causes, and also from the immense
auantity of waste heat which escapes through the
smoke-box and up the funnels, there has always
been a theoretical loss of steam power amounting
to 40 per cent., as compared with the coal consumed.
It is this loss of power and waste of heat which
the superheating process is intended to prevent, and
which will, of course, allow a reduction of from 28

to 30 per cent. on the fuel now consumed. By the
superheating process the steam is raised in passing
along the pipes in the steam-pipes (where the heat
is about 650 deg.) from a temperature of 250
deg. to 350 deg., and so enters the cylinders at
100 deg. in excess of the temperature duo to its
pressure. This extra heat is, of course rapidly
communicated to the metals, and prevents the con-
densation in the cylinders or other parts of the
engines, which would otherwise, of course, take
place. Singularly enough, a smaller amount of cold
water is required to condense the steam at this
high temperature of 350 deg. than when at the ordi-
nary heat of common steam. The trial trip of the
Valetta on Thursday was most satisfactory, not only
ue rwheera t
Hi n
Hope,
enear
u r
e d m for
le
as regards the engines, but still more so as to the
atth ethseutprocess.theANtutrehe.
applicationmea
the result of repeated runs gave an average speed
of nearly 144 knots per hour, thus realizing with
engines of 260 horse-power, and a small consump-
tion of fuel, the same rate of speed as had been
gained with her previous engines of 400 horse-
power, and a consumption of 75 tons of coal per
day. The superheating apparatus evidently'
effected a most important saving in fuel, but until
an average of many days' working can be obtained
it would be difficult to estimate the exact amount
economized. There seem-, however, every reason to
believe that an average of 14 knots an.hour can,be
obtained with a consumption of only 24 to 26 tons
per diem. The thermometer during the trial indi-
cated in the steam pipes an addition to the ordi-
nary temperature of 100 deg., which Mr. Penn be-
lieves to be enough for all practical purposes of
superheating. Even when making from 33 to 34
revolutions per minute, and driving the vessel
against a strong head wind and tide, it was impos-
sible to consume all the steam generated, which
was blowing off from both boilers all the trip: The
engines are remarkable for the extraordimiry beauty
and simplicity of their proportions, qualities well
known in all engines from Penn and -5(41;2, and
which, combined with the strength of the mate-
rials 43, make this
and perfection of the workmanship,
of
firm the foremost in the world for machinery
oscillating, of
this description. Both cylinders are
of 4 feet 6
62 inches diameter, and with a stroke
n the feathering
inches. The paddles are o
principle, and the _
boilers of Lamb and Co.'s
patent. During the whole
t_
course
of the ole trials,
and when going at one time nearly 16 knots,
there wa no
perceptible vibration, even at the
s
end of the saloon nearest to the engines. When
it is remembered that the superheating process
which can effect such important results as capable,
as we have said, of application to steam machinery
of every kind, including even locomotives, it cannot
be doubted that the trial of Thursday and
its great
success is one of the most • important events for the
progress of steam which we have had to chronicle
for many years.

GREAT FIRE AT DEPTFORD.—Yesterday morn
ing, between two and three o'clock, a fire, attended with
grTheeatdliosscso.:efrpyrwopaesrtym, made by p happened
inoliNcee-mco'-nsstrteaebtl,e,Dwehpotford.
ob-
served smoke issuing from the premises belonging to Mr .
C. Knowles, baker, No. 30, in that street. The inmates
effected their es:ape with great difficulty, and in less than
ten minutes afterwards the entire building presented a
sheet of flame, and the house of Mr. Hughes, 'next door,
quickly shared a similar fate. At that time there seemed
no chance of saving any of the adjoining or even the oppo-
site houses, for the premises of Mr. Evans No. 32, as well
as Nos. 92 and 93, were already on fire. The engine from
the Dockyard was soon on the spot, and set to work ; but
the flames continued to spread, and a mounted polieeefri
was sent to London for additional assistance, whena.1!1,.....
Henderson started to the -spot with two engines, and )?±I
of firemen. All hands at once went to work, but fire-
menNo 33' severely
until Nos. 31 and 32 were burned down. .• ,
seriously uklureu•
damaged, and those opposite se
and policewere unable to get the flames exting,tushed
Mr.
, ferers were not insured.
Knowles was insured in the Sun Office, but the other suf-