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Page 25
Although nearly or quite 200,000 Parmelee automatic-sprinklers have been
installed, their manufacture has been supplanted by other forms; and the
total number of automatic-sprinklers in position at the present time
must be about 2,000,000.
When automatic-sprinklers were first introduced there were many
apprehensions that leakage, and also excessive water discharged upon
small fires, would be sources of damage. In England this opinion found
expression in increased insurance rates in buildings where
automatic-sprinklers were installed.
The logic of figures shows that this liability to damage is merely
nominal in the case of well-constructed sprinklers. An association of
underwriters who have given careful attention to the subject obtained
the facts that from the automatic-sprinklers installed in some
$500,000,000 worth of property insured by them, the average damage from
all causes, except fire, was $2.56 per plant per annum.
Although automatic-sprinklers have proved to be so reliable and
effective, yet, in order to provide for all possible contingencies,
their introduction should not displace other forms of fire-apparatus,
particularly stand-pipes in the stairway towers, with hydrants at each
story. The hose at these hydrants should be festooned on a row of pins,
or doubled on some of the reels made especially for such purposes.
Stand-pipes are not recommended to be placed in rooms or on
fire-escapes; and inside hydrants should not be attached to the vertical
pipes supplying automatic-sprinklers.
Fire-pumps are generally too small for the work required of them, 500
gallons per minute being the minimum capacity recommended. For a
five-story mill there should be an allowance of 250 gallons per minute
for an effective stream through a 1-1/8-inch nozzle, and for lower
buildings the estimate should rarely be less than 200 gallons for each
stream.
Contrary to the general assumption, a ring nozzle is not so efficient as
a smooth nozzle, the relative amount of discharge of ring and smooth
nozzles of the same diameter being as three is to four. For stand-pipes
7/8-inch nozzles are recommended, but for yard hydrant service the
diameter should never be less than one inch, and 1-1/8 inches generally
fulfils the conditions of best service.
The yard hydrants should be placed at a distance of fifty feet from
buildings, and covered with a house which should also contain hose,
axes, bars, nozzles and spanners.
Water-mains about a mill-yard should be of ample capacity not to cause
an excessive loss by friction, their diameter being based upon a limit
of velocity of ten feet per second for the maximum delivery.
RESULTS.
These methods of supervision, building and equipment do not refer to any
ideality, but to measures which have been widely carried into effect for
the purpose of reducing the fire-loss; the result of such action being
to diminish the cost of insuring industrial property engaged in such
normally hazardous processes as textile manufacture and other
industries, down to a yearly cost of less than one-fifth of one per
cent. This has been accomplished by the consideration of sources of
danger and their abatement, and by a course which has been in line with
sound engineering principles, and also practical methods of manufacture;
and it has thus been proved that it is cheaper to prevent a fire than to
sustain a loss.
There has been no attempt made to credit individuals with their share in
these features of mill development. They have been the outgrowth of a
continual profiting by experience, adopting some features and modifying
others. The concurrent action of the large number of minds engaged on
the same problem has led to duplication of methods; but the whole
progress has been a matter of slow, steady growth, advancing by hairs'
breadths, as the result of persistent efforts to adapt means to ends in
the endeavor to reduce the cost of manufacture.
FOOTNOTES:
[Footnote 6: Abstract of a paper by Mr. C.J.H. Woodbury, read before the
American Society of Mechanical Engineers.]
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