Chapter 15: Equipment of the Subway
Rapid Transit in New York City and in the Other Great Cities · Chamber of Commerce, 1906
Cost of Equipment. According to the conditions of the contract, the contractor was to supply the entire equipment. This comprised the power houses, conductors, train equipment, signalling apparatus, and the like. The outfit is part of the cost to be borne by the builder; and at the expiration of the fifty years, the period for which the contract runs, is to be turned over to the city as part of the subway plant. The equipment as it stands to-day represents an expenditure by the Interborough Company of between $15,000,000 and $20,000,000, thereby making its total investment about $60,000,000.
Before proceeding with its installation, a very thorough examination was made of all the prominent generating stations of this country and of Europe. This preliminary study resulted in the creation of not only the largest power house in the world-- measured according to the horsepower capacity-- but also the most complete one so far as each individual part is concerned.
It will be re-called that both Contract No. 1 and Contract No. 2 are controlled by the same interests. Therefore when the company received the second contract, in 1902, it immediately prepared plans for an electrical capacity sufficient to provide for the operation of the Brooklyn extension of the road.
Power House. The power house occupies the site bounded by Fifty-eighth and Fifty-ninth streets and Eleventh and Twelfth avenues. The building is 200 feet wide on Eleventh avenue, and is divided into a boiler house 83 feet wide, and an engine room 117 feet wide, separated by a partition wall. Provision was made for six generating sections, with space remaining for a seventh. Each section has one chimney, together with the following equipment: 12 boilers, 2 engines direct-connected to a 5,000-kilowatt alternating generator, 2 condensing plants, 2 feed pumps, and all the appliances necessary to make each section complete in itself. All this required a structure 694 feet in length.
Interior and Exterior, Power House, N. Y. Subway.
Arrangement of Building. The advantages of this plan are thus summed up:* [* From the book on the "New York Subway" published by the Interborough Rapid Transit Company.]
"The main engines, combined with their alternators, lie in a single row along the center 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 the 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 engines. 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."
Coal Handling Plant. In the top of the building immediately over the boilers are seven coal bunkers, five of which are 77 feet and two 41 feet in length, all being 60 feet wide at the top. The total capacity is 18,000 tons. The six chimneys placed along the center of the boiler house separate the bunkers from each other. The chimneys are placed 108 feet apart, and are carried on plate-girder platforms in the fifth floor, the entire space below being thus left clear. The framing for both the chimney platforms and the bunkers is extended down to the foundation.
Both coal and ashes are handled by belt conveyors. Thirty-inch belts convey the coal along the dock where it is received, and by a tunnel to the southwest corner of the power house. From there it is raised 110 feet to the top of the boiler house, at the rate of 250 tons per hour, and distributed along the bunkers. The conveyors have automatic trippers which distribute the coal evenly in the bunkers. Another set of conveyors is placed under the bunkers for delivering different grades of coal from any particular bunker to the chutes in front of the boilers. All the conveyors are operated by electric motors.
The boiler room is intended to receive, ultimately, 72 boilers of the water-tube type, which will have a combined heating surface of 432,576 square feet. Fifty-two are now erected in batteries of two each, and between each pair is a 5-foot passageway. Thirty-six of the boilers are hand fired and have shaking grates. Twelve are furnished with automatic stokers.
Forced draft is provided in order to burn fine anthracite coal in sufficient quantity to obtain boiler rating with hand firing, and also to secure excess over the rating with other coal. The blowers deliver the air at a pressure of 2 inches of water.
Steam Piping. The steam piping from six boilers to one main engine is thus described:
"A cross-over pipe is erected on each boiler, by means of which and a combination of valves and fittings the steam may be passed through the superheater. In the delivery from each boiler there is a quick-closing 9-inch valve, which can be closed from the boiler room floor by hand, or from a distant point individually or in groups of six. Risers with 9-inch wrought iron goose-necks connect each boiler to the steam main, where 9-inch angle valves are inserted in each boiler connection. These valves can be closed from the platform above the boilers, and are grouped three over one set of three boilers and three over the opposite set. The main from the six boilers is carried directly across the boiler house in a straight line to a point in the pipe area where it rises to connect to the two 14-inch steam downtakes to the engine throttles. At this point the steam can also be led downward to a manifold to which the compensating tie lines are connected. These compensating lines are run lengthwise through the power house for the purpose of joining the systems together as desired. The two downtakes to the engine throttles drop to the basement, where each, through a goose-neck, delivers into a receiver and separating tank and from the tank through a second goose-neck into the corresponding throttle."
Engines. There are nine main engines from 8,000 to 11,000 horsepower direct connected to 5,000-kilowatt generators, and three steam turbines direct connected to 1,875-kilowatt lighting generators, and two 400-horsepower engines direct connected to 250-kilowatt exciter generators. The main engines are of the compound type, having cylinders 42 and 86 inches and stroke of 60 inches, working under a steam pressure of 175 pounds.
The steam turbines are of the multiple expansion parallel flow type, consisting of two turbines arranged tandem compound. Each unit is of 1,700 electrical horsepower.
Condensers and Pumps. Each engine has its own condenser outfit, and each has a circulating pump and vacuum pump which, for the sake of flexibility, are cross connected with each other so as to be used interchangeably. Each circulating pump has a capacity of 10,000,000 gallons of water per day, so that the combined capacity is 120,000,000 gallons per day. Two electrically driven compressors supply air throughout the power house for cleaning electric machinery and other purposes.
The operating room is supplied with one 60-ton and one 25-ton electric traveling crane; the area over the oil switches with one 10-ton hand crane, and the center aisle of the boiler room with one 10-ton hand crane. Both the electric cranes have a span of 74-1/3 feet and travel the entire length of the building.
The subway electric system comprises alternating generation and distribution with direct current car motors. The current is generated at a voltage of 11,000, and is delivered through three-conductor cables to transformers and converters in sub-stations, where it is transformed into direct current of 625 volts for delivery to the third rail. In the book above referred to we find the following:
Electrical Power Required. "Calculations based upon contemplated schedules indicated that there would be needed for traction purposes and for heating and lighting the cars, a maximum delivery of about 45,000 kilowatts at the third rail. Allowing for losses in the distributing cables, in transformers and converters, this implies a total generating capacity of approximately 50,000 kilowatts; and having in view the possibility of future extensions of the system it was decided to design the power house building for the ultimate reception of eleven 5,000 kilowatt units for traction current in addition to the lighting sets. Each 5,000 kilowatt unit is capable of delivering during rush hours an output of 7,500 kilowatts or approximately 10,000 electrical horsepower, and, setting aside one unit as a reserve, the contemplated ultimate maximum output of the power plant is 75,000 kilowatts, or approximately 100,000 electrical horsepower." A generating unit of this size was adopted "because it is practically as large a unit of the direct-connected type as can be constructed by the engine builders unless more than two bearings be used-- an alternative deemed inadvisable by the engineers of the company. The adoption of a smaller unit would be less economical of floor space and would tend to produce extreme complication in so large an installation, and, in view of the rapid changes in load which in urban railway service of this character occur in the morning and again late in the afternoon, would be extremely difficult to operate." The company's engineers made a close study of steam turbines as prime movers for the alternators, and decided in favor of the reciprocating engine.
Dynamos. The alternators have a stationary armature exterior to the field; they are three-phase machines delivering current at a potential of 1,000 volts. The revolving part weighs 332,000 pounds, and the design is such as to eliminate the fly-wheel. The switches are electrically operated, and the circuits are made and broken under oil. "Provision is made for an ultimate total of twelve substations, to each of which as many as eight feeders may be installed, if the development of the company's business should require that number. But eight sub-stations are required at present, and to some of these not more than three feeders are necessary. The aggregate number of feeders installed for the initial operation of the subway system is 34."
Exterior, Sub-Station, N. Y. Subway.
Interior, Sub-Station, N. Y. Subway.
Electric Conductors. The conductors pass to the sub-stations through vitrified clay ducts built into the subway structure. The sub-stations are located at City Hall place, East Nineteenth street, West Fifty-third street, West Ninety-sixth street, West One-hundred-and-forty-third street, West One-hundred-and-thirty-second street, Hillside avenue, and Fox street. In these stations the high potential alternating current is transformed into direct current at a potential of 625 volts; this current is conveyed to the contact rails by insulated cables.
The contact rails are carried upon block insulators resting upon malleable iron castings. The track rails are 33 feet long and weigh 100 pounds to the yard. One rail of each track is used for the operating current and the other for signal purposes. The third rail is guarded by a plank placed in a horizontal position directly above it.
After a thorough consideration of the question, the company decided to adopt a car with end platforms such as those generally used on American railways. The standard car is 51 feet long over all, 40 feet long in the clear inside, and 7 feet 10 inches wide in the clear, with a seating capacity of 52. The following is from the report of the Chief Engineer to the Commission, dated January 1, 1905:
Composite Cars. "In order to eliminate or reduce to the minimum all danger from fire, the result of which filling the subway with smoke would be disastrous, it was realized that the new cars should be made as nearly fireproof as possible. An all metal car of reasonable weight was unknown, and at first did not seem practicable. A composite car was therefore designed having the sills of 6-inch steel channels for side sills, and 5-inch I-beams for center sills, and the superstructure of wood, but covered on the sides with copper so as to protect, for a while at least, the wood from taking fire by radiant heat. Great care was taken with the wiring details. All junctions and fusible plugs were located in asbestos-lined boxes, while the underside of the floor was covered with "transiter," a heavy asbestos board made for the purpose, and both fire and electric proof. Such a car, while not absolutely fireproof, is at least slow burning, and believed to be fireproof against any accident likely to occur in the subway. All details of construction were made more strong and heavy than is usual in cars for similar service, so that the weight of the car body is 27,650 pounds, as against 20,500 pounds for the car bodies on the Manhattan elevated."
Composite Car and Interior, N. Y. Subway.
Steel Car and Interior, N. Y. Subway.
All-Metal Cars. "While such cars as above described were being built, Mr. George Gibbs, consulting engineer to the company, and who was specially charged with equipment design, was studying a type of all-metal car, and finally evolved such a car of the same general dimensions as the composite car, the weight of the body being 28,500 pounds. In general the details of this car are center sills of I-beams, 17.25 pounds; side sills of angles 5 by 3 by 1/2 inches, 12.8 pounds; with a plate of steel for the sides, which, with the side sills and a longitudinal angle (spiraled bulb angle) 4-1/2 to 2-3/4 inches, at the level of the window ledge, forms a plate girder to take the place of the ordinary iron body truss. The upper side and roof framing is of steel, while the interior lining of the car is aluminum. The floor is a cement compound. The only wood used is in the window sashes, doors and in the post furring, which is fire-proofed."
"On October 27, the date of the opening, there were delivered on the line 103 metal cars and 502 composite cars. At the end of the year 97 metal cars in addition had been furnished, and there were outstanding contracts for 100 metal cars. It is the intention to make the metal cars the motor cars, and the composite cars the trailers, until such time as the latter will be entirely superseded by the former."
Train Make-Up. "As equipped electrically the motor cars have each two motors of a nominal capacity of 200 h. p. each, working on two axles of one truck. The total weight, on track, of a metal motor car completely equipped, but exclusive of passengers, is 76,925 pounds, and a composite trailer with ordinary trucks 51,300 pounds. The ordinary make-up of a local train is five cars, of which three are motors and two trailers, while an express train consists of eight cars, five motors and three trailers. The former therefore weighs empty 333,384 pounds, and has a total energy of 1,200 h.p., while the latter weighs 528,540 pounds with an energy of 2,000 h.p. In both cases the energy figures are a nominal rating and are capable of standing considerable overload, especially during the period of acceleration."
Signals. "For the regular train signals, automatic devices were adopted. The express lines were divided into blocks, the length of each being the distance in which a train traveling at full speed could be brought to rest with current cut off and emergency brakes applied. As this distance is obviously dependent upon the profile of the road, and as to whether the gradient is ascending or descending, the blocks are of varying length, from 450 feet to 1,000 feet. The ordinary arrangement of home and distant signals is established, but always with an overlap block; that is, each home signal guards not the next block, but the one after, so that there is always at least one whole block distance intervening between the home signal and the next train ahead."
"At each signal box and connected with the home signal there is a mechanical trip set in the center of the track. When a home signal is at danger the trip is erect, so that if a motor-man for any cause overruns a home signal at danger the trip will cut off his power, set his brakes, and automatically bring the train to a stop before passing off the next block."
"On the local tracks home danger signals are located to guard all station approaches, curves, and any other point obstructing a free view of trains ahead."
Lighting. In order to maintain lights in the subway entirely independent of any temporary interruption of the power used for lighting the cars, a separate plant was installed in the power house. This is composed of three turbine-driven alternators, receiving steam from a special supply, and not from the supply for the large units. The primary current at 1,000 volts is led to transformers placed in fireproof compartments near the station platforms. The current is then delivered to two separate systems of wiring at 120 and 600 volts; the first provides the general lighting of the stations, while the second lights the subway between stations. In addition to this, and as a still further precaution, there are in each station a number of lamps connected to the contact rail circuit.
Lack of space will not permit an extended description of the many admirable features of the equipment of the subway provided by the Interborough Company. As it stands to-day it represents not only the best practice in electrical generation and distribution, but in many characteristics it is far in advance. The planning has been wisely and conservatively done and the construction has been thorough in all respects.