POWER HOUSE BUILDING
The power house is situated adjacent to the North River on the block
bounded by West 58th Street, West 59th Street, Eleventh Avenue, and
Twelfth Avenue. The plans were adopted after a thorough study by the
engineers of Interborough Rapid Transit Company of all the large power
houses already completed and of the designs of the large power houses
in process of construction in America and abroad. The building is
large, and when fully equipped it will be capable of producing more
power than any electrical plant ever built, and the study of the
designs of other power houses throughout the world was pursued with
the principal object of reducing to a minimum the possibility of
interruption of service in a plant producing the great power required.
The type of power house adopted provides for a single row of large
engines and electric generators, contained within an operating room
placed beside a boiler house, with a capacity of producing,
approximately, not less than 100,000 horse power when the machinery is
being operated at normal rating.
[Sidenote: _Location
and General
Plan of
Power House_]
The work of preparing the detailed plans of the power house structure
was, in the main, completed early in 1902, and resulted in the present
plan, which may briefly be described as follows: The structure is
divided into two main parts--an operating room and a boiler house,
with a partition wall between the two sections. The face of the
structure on Eleventh Avenue is 200 feet wide, of which width the
boiler house takes 83 feet and the operating section 117 feet. The
operating room occupies the northerly side of the structure and the
boiler house the southerly side. The designers were enabled to employ
a contour of roof and wall section for the northerly side that was
identical with the roof and wall contour of the southerly side, so
that the building, when viewed from either end, presents a symmetrical
appearance with both sides of the building alike in form and design.
The operating room section is practically symmetrical in its
structure, with respect to its center; it consists of a central area,
with a truss roof over same along with galleries at both sides. The
galleries along the northerly side are primarily for the electrical
apparatus, while those along the southerly side are given up chiefly
to the steam-pipe equipment. The boiler room section is also
practically symmetrical with respect to its center.
A sectional scheme of the power house arrangement was determined on,
by which the structure was to consist of five generating sections,
each similar to the others in all its mechanical details; but, at a
later date, a sixth section was added, with space on the lot for a
seventh section. Each section embraces one chimney along with the
following generating equipment:--twelve boilers, two engines, each
direct connected to a 5,000 kilowatt alternator; two condensing
equipments, two boiler-feed pumps, two smoke-flue systems, and detail
apparatus necessary to make each section complete in itself. The only
variation is the turbine plant hereafter referred to. In addition to
the space occupied by the sections, an area was set aside, at the
Eleventh Avenue end of the structure, for the passage of the railway
spur from the New York Central tracks. The total length of the
original five-section power house was 585 feet 9-1/2 inches, but the
additional section afterwards added makes the over all length of the
structure 693 feet 9-3/4 inches. In the fourth section it was decided
to omit a regular engine with its 5,000 kilowatt generator, and in its
place substitute a 5,000 kilowatt lighting and exciter outfit.
Arrangements were made, however, so that this outfit can afterward be
replaced by a regular 5,000 kilowatt traction generator.
[Illustration: CROSS SECTION OF POWER HOUSE IN PERSPECTIVE]
The plan of the power station included a method of supporting the
chimneys on steel columns, instead of erecting them through the
building, which modification allowed for the disposal of boilers in
spaces which would otherwise be occupied by the chimney bases. By this
arrangement it was possible to place all the boilers on one floor
level. The economizers were placed above the boilers, instead of
behind them, which made a material saving in the width of the boiler
room. This saving permitted the setting aside of the aforementioned
gallery at the side of the operating room, closed off from both boiler
and engine rooms, for the reception of the main-pipe systems and for a
pumping equipment below it.
The advantages of the plan can be enumerated briefly as follows: The
main engines, combined with their alternators, lie in a single row
along the center line of the operating room with the steam or
operating end of each engine facing the boiler house and the opposite
end toward the electrical switching and controlling apparatus arranged
along the outside wall. Within the area between the boiler house and
operating room there is placed, for each engine, its respective
complement of pumping apparatus, all controlled by and under the
operating jurisdiction of the engineer for that engine. Each engineer
has thus full control of the pumping machinery required for his unit.
Symmetrically arranged with respect to the center line of each engine
are the six boilers in the boiler room, and the piping from these six
boilers forms a short connection between the nozzles on the boilers
and the throttles on the engine. The arrangement of piping is alike
for each engine, which results in a piping system of maximum
simplicity that can be controlled, in the event of difficulty, with a
degree of certainty not possible with a more complicated system. The
main parts of the steam-pipe system can be controlled from outside
this area.
The single tier of boilers makes it possible to secure a high and well
ventilated boiler room with ventilation into a story constructed above
it, aside from that afforded by the windows themselves. The boiler
room will therefore be cool in warm weather and light, and all
difficulties from escaping steam will be minimized. In this respect
the boiler room will be superior to corresponding rooms in plants of
older construction, where they are low, dark, and often very hot
during the summer season. The placing of the economizers, with their
auxiliary smoke flue connections, in the economizer room, all
symmetrically arranged with respect to each chimney, removes from the
boiler room an element of disturbance and makes it possible to pass
directly from the boiler house to the operating room at convenient
points along the length of the power house structure. The location of
each chimney in the center of the boiler house between sets of six
boilers divides the coal bunker construction into separate pockets by
which trouble from spontaneous combustion can be localized, and, as
described later, the divided coal bunkers can provide for the storage
of different grades of coal. The unit basis on which the economizer
and flue system is constructed will allow making repairs to any one
section without shutting off the portions not connected directly to
the section needing repair.
The floor of the power house between the column bases is a continuous
mass of concrete nowhere less than two feet thick. The massive
concrete foundations for the reciprocating engines contain each 1,400
yards of concrete above mean high water level, and in some cases have
twice as much below that point. The total amount of concrete in the
foundations of the finished power house is about 80,000 yards.
[Illustration: CROSS-SECTION OF POWER HOUSE]
Water for condensing purposes is drawn from the river and discharged
into it through two monolithic concrete tunnels parallel to the axis
of the building. The intake conduit has an oval interior, 10 x 8-1/2
feet in size, and a rectangular exterior cross-section; the outflow
tunnel has a horseshoe-shape cross-section and is built on top of the
intake tunnel. These tunnels were built throughout in open trench,
which, at the shore end, was excavated in solid rock. At the river end
the excavation was, at some places, almost entirely through the fill
and mud and was made in a cofferdam composed chiefly of sheet piles.
As it was impossible to drive these piles across the old timber crib
which formed the old dock front, the latter was cut through by a
pneumatic caisson of wooden-stave construction, which formed part of
one side of the cofferdam. At the river end of the cofferdam the rock
was so deep that the concrete could not be carried down to its
surface, and the tunnel section was built on a foundation of piles
driven to the rock and cut off by a steam saw 19-1/2 feet below mean
hightide. This section of the tunnel was built in a 65 x 48-foot
floating caisson 24 feet deep. The concrete was rammed in it around
the moulds and the sides were braced as it sunk. After the tunnel
sections were completed, the caisson was sunk, by water ballast, to a
bearing on the pile foundation.
Adjacent to the condensing water conduits is the 10 x 15-foot
rectangular concrete tunnel, through which the underground coal
conveyor is installed between the shore end of the pier and the power
house.
[Sidenote: _Steel Work_]
The steel structure of the power house is independent of the walls,
the latter being self-supporting and used as bearing walls only for a
few of the beams in the first floor. Although structurally a single
building, in arrangement it is essentially two, lying side by side and
separated by a brick division wall.
There are 58 transverse and 9 longitudinal rows of main columns, the
longitudinal spacing being 18 feet and 36 feet for different rows,
with special bracing in the boiler house to accommodate the
arrangement of boilers. The columns are mainly of box section, made up
of rolled or built channels and cover plates. They are supported by
cast-iron bases, resting on the granite capstones of the concrete
foundation piers.
Both the boiler house and the engine house have five tiers of floor
framing below the flat portion of the roof, the three upper tiers of
the engine house forming galleries on each side of the operating room,
which is clear for the full height of the building.
The boiler house floors are, in general, framed with transverse plate
girders and longitudinal rolled beams, arranged to suit the particular
requirements of the imposed loads of the boilers, economizers, coal,
etc., while the engine-room floors and pipe and switchboard galleries
are in general framed with longitudinal plate girders and transverse
beams.
There are seven coal bunkers in the boiler house, of which five are 77
feet and two 41 feet in length by 60 feet in width at the top, the
combined maximum capacity being 18,000 tons. The bunkers are separated
from each other by the six chimneys spaced along the center line of
the boiler house. The bottom of the bunkers are at the fifth floor, at
an elevation of about 66 feet above the basement. The bunkers are
constructed with double, transverse, plate girder frames at each line
of columns, combined with struts and ties, which balance the outward
thrust of the coal against the sides. The frames form the outline of
the bunkers with slides sloping at 45 degrees, and carry longitudinal
I-beams, between which are built concrete arches, reinforced with
expanded metal, the whole surface being filled with concrete over the
tops of the beams and given a two-inch granolithic finish.
[Illustration: 58TH ST. POWER HOUSE--GENERAL PLAN OF COAL BUNKERS AND
ECONOMIZERS.]
[Illustration: 58TH ST. POWER HOUSE--GENERAL PLAN OF MAIN OPERATING
FLOOR.]
The six chimneys, spaced 108 feet apart, and occupying the space
between the ends of the adjacent coal bunkers, are supported on
plate-girder platforms in the fifth floor, leaving the space below
clear for a symmetrical arrangement of the boilers and economizers
from end to end of the building. The platforms are framed of
single-web girders 8 feet deep, thoroughly braced and carrying on
their top flanges a grillage of 20-inch I-beam. A system of bracing
for both the chimney platforms and coal bunkers is carried down to the
foundations in traverse planes about 30 feet apart.
The sixth tier of beams constitute a flat roof over a portion of the
building at the center and sides. In the engine room, at this level,
which is 64 feet above the engine-room floor, are provided the two
longitudinal lines of crane runway girders upon which are operated the
engine-room cranes. Runways for 10-ton hand cranes are also provided
for the full length of the boiler room, and for nearly the full length
of the north panel in the engine room.
Some of the loads carried by the steel structure are as follows: In
the engine house, operating on the longitudinal runways as mentioned,
are one 60-ton and one 25-ton electric traveling crane of 75 feet
span. The imposed loads of the steam-pipe galleries on the south side
and the switchboard galleries on the north side are somewhat
irregularly distributed, but are equivalent to uniform loads of 250 to
400 pounds per square foot. In the boiler house the weight of coal
carried is about 45 tons per longitudinal foot of the building; the
weight of the brick chimneys is 1,200 tons each; economizers, with
brick setting, about 4-1/2 tons per longitudinal foot; suspended
weight of the boilers 96 tons each, and the weight of the boiler
setting, carried on the first floor framing, 160 tons each. The weight
of structural steel used in the completed building is about 11,000
tons.
[Sidenote: _Power House
Superstructure_]
The design of the facework of the power house received the personal
attention of the directors of the company, and its character and the
class of materials to be employed were carefully considered. The
influence of the design on the future value of the property and the
condition of the environment in general were studied, together with
the factors relating to the future ownership of the plant by the city.
Several plans were taken up looking to the construction of a power
house of massive and simple design, but it was finally decided to
adopt an ornate style of treatment by which the structure would be
rendered architecturally attractive and in harmony with the recent
tendencies of municipal and city improvements from an architectural
standpoint. At the initial stage of the power house design Mr.
Stanford White, of the firm of McKim, Mead & White, of New York,
volunteered his services to the company as an adviser on the matter of
the design of the facework, and, as his offer was accepted, his
connection with the work has resulted in the development of the
present exterior design and the selection of the materials used.
The Eleventh Avenue façade is the most elaborately treated, but the
scheme of the main façade is carried along both the 58th and 59th
Street fronts. The westerly end of the structure, facing the river,
may ultimately be removed in case the power house is extended to the
Twelfth Avenue building line for the reception of fourteen generating
equipments; and for this reason this wall is designed plainly of less
costly material.
The general style of the facework is what may be called French
Renaissance, and the color scheme has, therefore, been made rather
light in character. The base of the exterior walls has been finished
with cut granite up to the water table, above which they have been
laid up with a light colored buff pressed brick. This brick has been
enriched by the use of similarly colored terra-cotta, which appears in
the pilasters, about the windows, in the several entablatures, and in
the cornice and parapet work. The Eleventh Avenue façade is further
enriched by marble medallions, framed with terra-cotta, and by a title
panel directly over the front of the structure.
The main entrance to the structure is situated at its northeast
corner, and, as the railroad track passes along just inside the
building, the entrance proper is the doorway immediately beyond the
track, and opens into the entrance lobby. The doorway is trimmed with
cut granite and the lobby is finished with a marble wainscoting.
The interior of the operating room is faced with a light,
cream-colored pressed brick with an enameled brick wainscoting, eight
feet high, extending around the entire operating area; the wainscoting
is white except for a brown border and base. The offices, the toilets
and locker rooms are finished and fitted with materials in harmony
with the high-class character of the building. The masonry-floor
construction consists of concrete reinforced with expanded metal, and
except where iron or other floor plates are used, or where tile or
special flooring is laid, the floor is covered with a hard cement
granolithic finish.
In the design of the interior arrangements, the value of a generous
supply of stairways was appreciated, in order that all parts of the
structure might be made readily accessible, especially in the boiler
house section. In the boiler house and machinery portion of the plant
the stairways, railings, and accessories are plainly but strongly
constructed. The main stairways are, however, of somewhat ornate
design, with marble and other trim work, and the railings of the main
gallery construction are likewise of ornate treatment. All exterior
doors and trim are of metal and all interior carpenter work is done
with Kalomein iron protection, so that the building, in its strictest
sense, will contain no combustible material.
[Sidenote: _Chimneys_]
The complete 12-unit power house will have six chimneys, spaced 108
feet apart on the longitudinal center line of the boiler room, each
chimney being 15 feet in inside diameter at the top, which is 225 feet
above the grate bars. Each will serve the twelve boilers included in
the section of which it is the center, these boilers having an
aggregate of 72,000 square feet of heating surface. By these
dimensions each chimney has a fair surplus capacity, and it is
calculated that, with economizers in the path of the furnace gases,
there will be sufficient draft to meet a demand slightly above the
normal rating of the boilers. To provide for overload capacity, as may
be demanded by future conditions, a forced draft system will be
supplied, as described later.
As previously stated, the chimneys are all supported upon the steel
structure of the building at an elevation of 76 feet above the
basement floor and 63 feet above the grates. The supporting platforms
are, in each case, carried on six of the building columns (the three
front columns of two groups of boilers on opposite sides of the center
aisle of the boiler room), and each platform is composed of single-web
plate girders, well braced and surmounted by a grillage of 20-inch
I-beams. The grillage is filled solidly with concrete and flushed
smooth on top to receive the brickwork of the chimney.
Each chimney is 162 feet in total height of brickwork above the top of
the supporting platform, and each chimney is 23 feet square in the
outside dimension at the base, changing to an octagonal form at a
point 14 feet 3 inches above the base. This octagonal form is carried
to a height of 32 feet 6 inches above the base, at which point the
circular section of radial brick begins.
The octagonal base of the chimney is of hard-burned red brick three
feet in thickness between the side of the octagon and the interior
circular section. The brick work is started from the top of the
grillage platform with a steel channel curb, three feet in depth,
through which two lines of steel rods are run in each direction, thus
binding together the first three feet of brickwork, and designed to
prevent any flaking at the outside. At a level of three feet above the
bottom of the brickwork, a layer of water-proofing is placed over the
interior area and covered with two courses of brick, upon which are
built diagonal brick walls, 4 inches thick, 12 inches apart, and about
18 inches in height. These walls are themselves perforated at
intervals, and the whole is covered with hand-burned terra-cotta
blocks, thus forming a cellular air space, which communicates with the
exterior air and serves as an insulation against heat for the
steelwork beneath. A single layer of firebrick completes the flooring
of the interior area, which is also flush with the bottom of the flue
openings.
There are two flue openings, diametrically opposite, and 6 feet wide
by 17 feet high to the crown of the arched top. They are lined with
fire brick, which joins the fire-brick lining of the interior of the
shaft, this latter being bonded to the red-brick walls to a point 6
feet below the top of the octagon, and extended above for a height of
14 feet within the circular shaft, as an inner shell. The usual baffle
wall is provided of fire brick, 13 inches thick, extending diagonally
across the chimney, and 4 feet above the tops of the flue openings.
Where the chimney passes through the roof of the boiler house, a steel
plate and angle curb, which clears the chimney by 6 inches at all
points, is provided in connection with the roof framing. This is
covered by a hood flashed into the brickwork, so that the roof has no
connection with or bearing upon the chimney.
At a point 4 feet 6 inches below the cap of the chimney the brickwork
is corbeled out for several courses, forming a ledge, around the
outside of which is placed a wrought-iron railing, thus forming a
walkway around the circumference of the chimney top. The cap is of
cast iron, surmounted by eight 3 x 1-inch wrought-iron ribs, bent over
the outlet and with pointed ends gathered together at the center. The
lightning conductors are carried down the outside of the shaft to the
roof and thence to the ground outside of the building. Galvanized iron
ladder rungs were built in the brickwork, for ladders both inside and
outside the shaft.
The chimneys, except for the octagonal red-brick base, are constructed
of the radial perforated bricks. The lightning rods are tipped with
pointed platinum points about 18 inches long.
[Sidenote: _North River
Pier_]
Exceptional facilities have been provided for the unloading of coal
from vessels, or barges, which can be brought to the northerly side of
the recently constructed pier at the foot of West 58th Street. The
pier was specially built by the Department of Docks and Ferries and is
700 feet long and 60 feet wide.
The pier construction includes a special river wall across 58th Street
at the bulkhead line through which the condensing water will be taken
from and returned to the river. Immediately outside the river wall and
beneath the deck of the pier, there is a system of screens through
which the intake water is passed. On each side where the water enters
the screen chamber, is a heavy steel grillage; inside this is a system
of fine screens arranged so that the several screens can be raised, by
a special machine, for the purpose of cleaning. The advantages of a
well-designed screening outfit has been appreciated, and considerable
care has been exercised to make it as reliable and effective as
possible.
At each side of the center of the pier, just below the deck, there are
two discharge water conduits constructed of heavy timber, to conduct
the warm water from the condensers away from the cold water intakes at
the screens. Two water conduits are employed, in order that one may be
repaired or renewed while using the other; in fact, the entire pier is
constructed with the view of renewal without interference in the
operation for which it was provided.