Publication: Electrical World
New York, NY, United States
DEVELOPMENTS ON SPOKANE RIVER, WASH. — II.
Steam-Turbine Relay Station, Switching Stations and Substations of the Washington Water Power Company.
Interconnection of the Company's Various Stations and Method of Operating System, Which
Possesses a High Load-Factor--Description of General Transmission System
Embracing Circuits of Various Voltages.
A DESCRIPTION of the newer developments of the Washington Water Power Company at Little Falls and at Long Lake was given in last week's article on the system. In the present article the steam-turbine station and the Post Street and Twenty-ninth Avenue substations will receive attention, as well as the general method of operating the system. As having a bearing on the steam-station design, it should be mentioned that slack coal at Spokane costs $4,23 a ton—a factor of considerable importance.
STEAM-TURBINE RELAY STATION.
When the flow of water in the Spokane River is unduly slack it has been found advisable under the present condition of development to operate a steam station as a relay to the hydroelectric properties. To help carry the load at such times or in emergencies there has been erected, at a place called Ross Park, within the city limits and on the Spokane River, a modern steam-turbine station capable of generating some 14,000 kw. The illustrations published herewith give a fair impression of the station design, its location and layout. It has not been used, however, to any extent since its erection, all told probably not more than six months; but it has amply proved its worth.
The building is of red brick resting upon a reinforced-concrete foundation. The walls of the turbine room rise 76 ft. 4 in. above the turbine-room floor, and the walls of the boiler room are 53 ft. 3 in. above the boiler-room floor. All trenches and well covers are made watertight so that exceptionally high water is not liable to flood the turbine room. Two large main doorways, one in the east end of the boiler room and the other in the northerly end of the turbine room, are provided for bringing in heavy material. An annex built on the western side of the turbine room contains the oil room, blower room, tool and supply room, workshop, etc. Located directly over the office is a storage-battery room, energy from which is used for operating the switchboard lamps and motor-driven switches. Abundant natural illumination is obtained throughout the entire structure.
The turbine room is equipped with a 40-ton Case traveling crane, having a span of 37.5 ft. The motors, of which there are four, the main hoist being rated at 40 hp and the auxiliary hoist at 25 hp, are of the direct-current, 110-volt series type, receiving energy from the exciter bus. Located in the northerly end of the turbine-room annex is the laboratory. There is provided the necessary apparatus for performing the simpler and common tests on oils, fuels and flue gases. The equipment comprises coal-sampling apparatus, flue-gas sampling apparatus, flue-gas analyzer, fire and flash test machines, reduction oven, Parr calorimeter, viscometer, chemical balance and weights.
The boiler-room equipment comprises twelve water-tube boilers of the Aultman & Taylor type, set in batteries of two and rated at 500 hp each. The boilers are suspended from steel supports and are equipped with superheaters and eight of them with stationary grates. The settings are built of common red brick, firebrick-lined, and are cement capped, the steam drums being covered with cement arches for heat insulation. The four last boilers to be installed differ somewhat in arrangement from the other eight in that they are equipped with rocking instead of stationary grates and the steam drums are covered by means of vitrobestos instead of cement. The settings are also 1 ft. higher. As will be noted from Fig. 2, the boilers are arranged on either side of the room with a firing aisle in the center.
The boiler feed-water system includes two Cochrane open feed-water heaters and three Epping-Carpenter feed-water pumps. The heaters receive their water supply directly from the hot-water tank into which the condensate and make-up water find their way. The heaters are inter-connected by a 4-in. equalizing pipe, and from the bottom of both there is an 8-in. water line which makes a circuit beneath the floor level and passes to the feed pump room located at the western end and beneath the boiler room. From this 8-in. line the three boiler-feed pumps take their supply. The three pumps feed a 6-in. cast-iron header built on the loop system from which 2.5-in, brass pipes branch vertically to the boiler room. The connections to the boilers are taken from these feed riser loops. Inserted in each of the connections is a combination stop and check valve which automatically closes in case there is a reversal of flow.
The arrangement of valves in the heater and feed-pump connections is such as to give the utmost flexibility and permit cleaning and repairs without disturbing the system. The feed-water heaters are rated at 3000 hp each.
The coal-handling facilities at the station consist of a spur from the Great Northern Railroad which, crossing over scales at an elevation, branches, one branch descending and passing directly to the turbine room and the other branch ascending to the coal embankment and trestle. The cars upon the trestle may be unloaded manually or by an unloader of special design similar to that employed in unloading grain cars. If the coal is unloaded in hopper cars, they simply dump their fuel into the yard beneath the trestle.
Coal is delivered to the boiler room by an Exeter Machine Company's bucket conveyor driven by a 30-hp induction motor through a triple gear reduction. The coal can be crushed if necessary by a coal cracker driven by a 30-hp induction motor. The buckets of the conveyor are loaded by a bucket loader so arranged on a track that the buckets may be filled from the coal cracker directly or from a storage hopper. Two movable bucket-tripping devices are located on the upper ingoing side of the bucket circuit, one for dumping the buckets into the storage hopper and the other for dumping the buckets into the weighing hopper. The latter is suspended from a movable truck and from it the fuel is dumped to the floor below.
For the disposal of ashes there are two tunnels almost the full length of the boiler room, whose axes are directly beneath the centers of the ash pits. The latter consist of concrete hoppers protruding into the tunnels and provided at their lower ends with double clamshell gates. Running transversely with the boiler room and extending outside of the building line is a third tunnel whose southerly end comes up to the street level and whose northerly end serves temporarily for housing the boiler from which the plant is heated during the winter months when the station is not in use. 24-in. gage track embedded in the concrete floor of all three tunnels serves for the ash cars, and at the junctions of the lateral tunnels with the trunk tunnel are ball-hearing turntables. At the point to the south side at the center line of the building and coal conveyor is an elevator shaft. The ashes are drawn out of the ash pits into cars which are dumped on the low land outside the station and adjacent to the river; or the ashes can be hoisted 60 ft. to a storage bin and clumped thence into standard cars. The operating mechanism for the elevator was made up of materials left from the, construction plant and is. driven by a worm shaft connected to a 5-hp induction motor.
STACKS, FLOORS AND BREECHINGS.
Running lengthwise of the boiler room, are two steel breechings passing between the rear end of the settings and the outside walls, being connected with each 'setting by a steel thimble provided with a butterfly damper. At the central point of each breeching there is an uptake connecting it with the bower intake chamber. The blowers are of Buffalo Forge Company's build and are driven by simple piston-valve engines. The fans are of the overhung type.
Rising vertically from the wall sides of the blower casings are two steel stacks 5.5 ft. in diameter and extending 84 ft. 2 in. above the grates. Regulators are inserted in the supply line to each engine, which are in turn controlled by damper regulators in such manner that the speed of the blowers varies inversely with the variation in steam pressure. All of the surfaces of the blowers and breechings are lagged in order to keep down the temperature of the boiler room during warm weather.
HIGH—PRESSURE STEAM SYSTEM.
The high-pressure steam piping includes two systems complete with traps and trap lines, namely, a superheated steam system and a saturated steam system, each of which is independent 'of the other during normal operation but so built that they can be interconnected if necessary.
The two main generating units are supplied with steam from the superheater headers, while the auxiliaries receive their supply from the saturated steam lines. The pipe joints on the superheated lines are of the Van Stone & Crane lap type and all valves and fittings are of steel. Valves 8 in. and over are of the rising-stem type with nickel steel stems and trimmings, and valves 50 in. and 12 in. in size are provided with by-pass valves.
All valves 8 in. and above in the boiler connections and the main headers, except the stop and automatic check valves, may be closed from the boiler-room floor.
The main header is divided by valves into sections corresponding to each battery, the central section of each main header comprising an expansion loop made up of four To-in. quarter bends. An 8-in. chain-operated gate valve is placed near each boiler superheater and an 8-in. stop and automatic check valve is placed in the boiler connection with the main header. An 8-in. quarter bend placed between these valves completes the boiler connection to the superheated steam header. There are two 4-in. saturated steam headers which combine into one 6-in. header in the turbine room for supplying the auxiliaries.
All of the various auxiliaries, including the blower engines and the feed-water pumps, exhaust into a common header leading to both heaters and also with the atmospheric exhaust from the turbines. The exhaust from one of the circulating pumps can be turned into the third stage of the turbine to which it is connected.
The two main generating units-are of the General Electric type, one being a four-stage, 5000-kw machine running at 720 r.p.m. and directly connected to a 10-pole, 60-cycle, three-phase, 13,200-volt generator by means of a one-piece shaft guided by an upper, middle and lower bearing, and with the entire weight of the unit carried on a step bearing. The turbine is provided with an overspeed tripping device which operates when the speed becomes excessive, in which case the generator will run as a synchronous motor until normal conditions can be re-established. The upper end of the generator is provided with a hood and connection to a forced system of ventilation.
The second unit is a five-stage, 9000-kw machine of the same general characteristics as the other machine, but connected to the generator by means of a flexible shaft. The latter is made in two pieces, the lower piece carrying the steam turbine and having at its top a flexible-disk diaphragm coupling which is keyed to the shaft. The field structure of the generator is placed on the upper part of the shaft by means of a taper fit which will allow the field structure to slip a small amount in case of shocks produced by severe short-circuits.
To keep down the generator temperatures at heavy loads a system of ventilation has been provided and two motor-driven blowers, one rated at 30 hp and the other at 40 hp, installed. The blowers discharge into an underfloor air duct which rises up through the turbine-room floor near the intake wells. From the floor level for a distance of about 10 ft. is a rectangular sheet-iron duct provided with two connections extending to the ventilating hood of each main generator.
The energy for excitation is supplied from two exciter units, one an 85-kw motor-driven set and the other a 75-kw steam-turbine set. The latter is operated non-condensing and,is equipped with a 125-volt interpole generator running at 2400 r.p.m.
The condensing system includes, besides the condensers for the turbo-generators, the necessary auxiliary apparatus, Both units are fitted with Worthington surface condensers. Circulating water is taken from the Spokane River by an engine-driven centrifugal pump, an intake tunnel leading from the river to a well beneath the pump. The rest of the equipment comprises a steam-driven vacuum pump and. a duplex hot-well pump discharging into the feed-water heaters. In order to shorten the time for priming the circulating pump a weight-closed check valve is attached to the submerged end of the circulating discharge pipe, which valve closes automatically with the cessation or reversal of flow. A 4-in. flooding line from the house-service system enters the circulation head of the condenser and may be brought into service in emergencies. The hot-well pump of the larger condenser is driven by means of an induction motor.
The step bearings of the two main units are floated and lubricated by means of a high-pressure oiling system, comprising three high-pressure, steam-driven pumps and two 50-gal. accumulators. The low-pressure, or guide-bearing, oil system is provided with lubricant taken from the oil filters and delivered at a pressure of 125 lb. by two steam-driven pumps. From this system the guide bearings and also both governors are supplied, the latter through equalizing tanks. The high-pressure and low-pressure pumps are equipped with relief valves so that the pressure cannot rise above the predetermined limit.
The majority of the ordinary bearings on the auxiliaries are lubricated by sight-drop gravity oil cups, but all steam cylinder lubrication is by means of sight-feed force pumps„ All of the high-speed main bearings are equipped with a-ring oiling system. Two 750-gal. tanks and one 500-gal. tank store the oil, which may be forced into the oil filters by air pressure.
When the load assumes a constant daily value and the shifts are regular, the crew necessary for the operation of the station comprises one station foreman, one operator per shift, one engineer per shift, one conveyor engineer per shift, two oilers per shift, one fireman per boiler per shift, one extra fireman per shift, two laborers per shift, one mechanic's helper per shift, three water tenders, one mechanic and a janitor. Where the loads assume a fairly constant nature with intermittent peaks of short duration, steaming conditions give best results with one boiler per 1000 kw normal load, plus one boiler with a second boiler banked but not cut in. Loads in excess of 4000 kw are carried more easily and more economically on the larger unit, which also operates with less vibration and noise under full speed.
TELEPHONE AND ALARM-BELL SYSTEMS.
Telephone connections with the main office building of the company are had over a local connection to the company's local central and another over the transmission telephone line. Both sets of telephones are located in an insulated booth on the switchboard floor. The local telephone connection has a repeating coil inserted, so that the plant office telephone or the engineer's telephone located in the turbine gallery booth can be connected with the company's local central or the three plant telephones can be used locally without disturbing the rest of the system. The transmission telephone system is connected with the system operator's office and at the steam-plant end is provided with duplicate telephones and switch-over devices, together with alarm attachments and high-tension fuses. The ringing of either telephone operates a mercury-contact telephone drop which causes a bell to ring until the drop is restored. A watchman's time detector and fire-alarm system are also in use.
A direct-current 5-hp, 110-volt series, motor-driven, duplex, single-acting, portable air compressor furnishes air at a pressure of 75 lb. for forcing oil from the storage tanks to the oil filters and for maintaining air in the guide bearing tanks. Compressed air is also used for cleaning the electrical apparatus and after the spring high-water season for agitating and removing the deposit from the mouths of the intake and discharge tunnels.
SPOKANE HYDROELECTRIC STATION.
The Spokane hydroelectric station is located at Monroe Street and the river, where a head of 70 ft. is available on the lower falls. The output of the station is used chiefly in Spokane, and the station itself will eventually be displaced by a more modern plant on the upper falls, which will use the drop of both the upper and lower falls and