Electric power for the many purposes of a modern city is generated in the enormous power station at Battersea, London. The power station is one of the most advanced of the great generating centres now in the service of the electrical engineer
ONE OF LONDON’S NEWEST LANDMARKS is Battersea Power Station, built on the south bank of the River Thames. The chimneys of the power station reach to a height of 337 ft 6-in. The building is a steel structure faced completely with warm buff bricks. It rests on a bed of concrete anchored to the London clay 40 feet below the surface.
AMONG the most efficient electric power stations in Europe, if not in the world, is the Battersea Power Station. In three years the station grew on the south bank of the River Thames until its buff chimneys reached up into the sky to a height of 337 ft 6 in. Each chimney, if it were laid on its side, would be large enough to serve as a tube station, for at the base it is 28 feet in diameter inside, tapering to 22 feet at the top. Thus a tube train could run through it, a platform could be built and passengers would find a loftier station than is usual on the tube railway of to-day.
The chimneys are typical of a building in which everything is so designed and balanced that its magnitude is not obtrusive. But it is the lips of the chimneys that tell of a miracle to those with eyes to see, for after three years of use they remain almost unmarked by soot. The ordinary industrial chimney stack holds up its grim, black mouth to heaven; yet day and night from the mouths of these two tapering chimneys white clouds billow out, resembling sprays of ostrich feathers, and it needs only the sun to give the feathery plumes a touch of loveliness.
Not until those who dreamed of this power house were able to prove that they would not sully London’s atmosphere with sulphur and smoke would the authorities permit the station to be built. The clean chimneys after years of use tell how successfully this difficult problem has been solved. It was overcome by adopting new methods to the latest scientific knowledge.
The Battersea Power Station is the child of nine of London’s electricity supply companies. Until a few years ago these companies were all operating as independent units, generating their own electricity to supply their own areas. Sir Francis Fladgate, by never-failing tact and persistence, smoothed out all the difficulties that existed between one company and another until they were all willing to co-operate. Thus was formed the London Power Company.
Nine of the stations generating electricity for the original companies were closed down between 1922 and 1928. Much of the current they had supplied came from a new power station built at Deptford West. Then in 1933 the great power house at Battersea materialized on the Thames.
The building itself, standing square and massive, gives an impression of power. The steel structures are completely faced with warm buff bricks, millions of which must have been used, which are pleasing to the eye. The chimneys are fluted in the manner of classical columns, and an austere decoration is achieved by setting back courses of bricks at the base of the chimney and the top of the main building to form perpendicular lines.
Before work started on the building, it was essential to bore and sink pits to study the subsoil. The contractors found that the ground was permeated with water which rose and fell with the tide of the river, and it was necessary to drive a series of piles until they were embedded in the London clay 40 feet below the surface. Then the station was built upon a gigantic raft of concrete which was anchored by the piles firmly to the London clay, the whole site being protected by strong containing walls of concrete which also went down 40 feet to the solid clay.
No stranger can enter this new power station without an official permit, which is carefully scrutinized by the gate-keeper. It must be in order, properly signed by the visitor under the clause which absolves the company from all liability in the event of an accident while going over the station—a clause suggestive of all sorts of hidden dangers lurking ahead.
A 5-TONS GRAB operated by an electric transporter crane picks up five tons of coal at a time to load on to the conveyer belt which leads to the bunkers of Battersea Power Station. The coal used is small coal, or slack, specially selected because of its low sulphur content The grab is taking coal from the reserve store of about 70,000 tons. enough to run the station for two months at normal load. Underneath these hills of coal is the intricate system of intakes which supply water from the Thames for the boilers.
A dull roar from the revolving turbines fills the power house and makes it necessary to raise the voice to talk. A slight vibration is noticeable under-foot, but neither noise nor vibration is excessive.
The turbine hall when fully lighted bears a resemblance to an ultra-modern restaurant as far as decoration is concerned. It is 475 feet long and 80 feet wide, a glass roof rising to an apex 100 feet above. Down either side of the hall is a long row of fluted columns faced with dull antique tiles of a greyish tint marbled with faint blue markings, the walls being faced with the same tiles made to resemble blocks of masonry. They obviate the expense of new decorations in the years to come, for a touch of soap and water will keep them clean as long as they last. For the same reason the handrails fencing the wells which give light to the floor below are made of specially processed steel that will retain its gleaming lustre without the need of replating from time to time.
The floors, made of compressed mosaic which is oil-proof, are kept clean by attendants who walk up and down, using electric washers and scrubbers which make it unnecessary for the men to wet their hands or bend their backs. Everything is so bright and spotless that it scarcely seems possible that the turbines could have been droning away for three years.
Down the centre of the hall are the three mammoth turbines that spin night and day to supply power for the thousand and one requirements of the modern age. They provide light for millions of lamps and work thousands of vacuum cleaners and electric irons. Thousands of homes in London depend upon them for cooking meals and working refrigerators. Factories depend upon them to supply the power for their electric motors. Girls touch switches to set electric sewing machines whirring to make dresses for the shops. Hairdressers rely upon them to dry the hair of modern woman and to give her a permanent wave.
Right down the hall the turbines stretch their length. The three pairs of huge pipes arching up to carry the steam to the low-pressure rotors give them rather a serpentine appearance that vaguely links these monsters of the new age with the monsters of the prehistoric era. They sing aloud to tell you they are working, but you cannot see them doing it. They are completely enclosed in dark grey and black casings with a cellulose finish which matches that of the finest motor car, and bands of stainless steel add a note of decoration to the joints.
These turbines are so big that it was not possible to assemble them all in the Manchester works where they were made. Until they were brought to Battersea in sections and set up in position no one had ever seen them work, but all the gears and parts had been built with such accuracy and precision that they fitted perfectly when the engineers assembled them, and worked satisfactorily at the first full test. It was a fine, tribute to the skill of modern engineers.
THE MAIN CONTROL BOARD in Battersea Power Station is a marvel of scientific co-ordination. Dozens of dials record the actions of machinery all over the building. Above the dials are illuminated diagrammatic plans which indicate the exact state of all the circuits in charge of the controlling officer. In front two engine telegraphs, resembling those in a ship, transmit orders instantly to the turbine engineers.
The last of the three turbines to be fitted was, early in 1937, the most powerful turbine in Europe. The first two turbines are giants of 92,000 horse-power. Either turbine develops 69,000 kilowatts, or 69,000,000 watts of electric power. Big and powerful as they are, they will not compare with the latest turbine, which develops 140,000 horse-power to give 105,000 kilowatts. These three turbines have therefore a combined output of 243,000,000 watts. They turn at 1,500 revolutions a minute, and a serious accident would happen if these gigantic masses of revolving metal went beyond the limits of endurance and flew asunder. But such a disaster could never happen. All the ingenuity of the engineers has been exercised to prevent it.
Over a century ago James Watt used a governor to control the rate at which his steam engine worked. The idea was quite simple - just two, three or four spheres or weights of metal on the ends of rods which were attached to a central pivot by hinges which enabled the rods to rise and fail. At rest, the weights hung down against the central pivot. When the engine was started they went round and swung higher and higher as the speed of the machine increased. The governor acts in the same way as when a boy swings round his head a cord with a weight on the end. The faster he swings it the higher the weighted cord goes.
It was a simple matter for the engineer to find out how high the arms or rods of the governor rose when his machine was working at its maximum safe speed. It was easy to install a trigger or trip, or use some other device at this limit, so that, if the arm of the governor came into contact with it, it actuated another device which stopped the machine. This old safety device, the centrifugal governor, which is still the best, is installed in these modern turbines. Their working speed is 1,500 revolutions a minute.
The governor is set to give them a margin of 10 per cent above this speed, so if the machines were to exceed a speed of 1,650 revolutions a minute, the governor would close the steam inlet and cut off steam, thus stopping the turbine. The governor would also cut off steam and prevent the turbine from seizing up and wrecking itself if oil ceased to flow through the bearings.
Cascade of Golden Oil
ALTHOUGH all this relentless movement is going on, there is nothing moving to he seen in the turbine hall, no men rushing thither and hither. It might be a deserted city but for the hum and vibration which tell of the machines at work. At the foot of each turbine, however, may be seen an oval of plate glass beneath which a cascade of golden oil is pouring ever downward.
That is the oil gushing from the turbine after having circulated through the working parts. It passes into the machine at about 90 degrees Fahrenheit and it emerges at 112 degrees Fahrenheit; so it rises about 22 degrees Fahrenheit in temperature while passing through the machine. The oil supplies the magic touch to make everything run smoothly. Without that cascade of oil the machine would come to a stop.
There are six tanks, with a total capacity of 7,200 gallons of oil, to supply the three turbines. As the oil gushes from the machines it passes through the coolers to rid it of its excess heat before it flows into the machines again.
It seems difficult to realize that these turbines are a development of the little turbine, now in the South Kensington Science Museum, which the late Sir Charles Parsons invented and built.
Parsons revived an idea over 1,900 years old. About A.D. 50 Hero of Alexandria invented the reaction turbine. A primitive impulse turbine was invented by Giovanni Branca in 1629. Both machines were little more than toys. Parsons, in the face of much scepticism, clearly demonstrated that the principle involved was capable of successful practical application.
In the old type of steam engine the steam moved a piston backwards and forwards, which wasted a great deal of power, because at the end of each stroke the piston had to stop before it started back in the reverse direction. Then these to-and-fro movements had to be converted into a rotary movement, which wasted more power. In the turbine the steam, by impinging on the blades, is made to give a direct rotary movement to the shaft itself. Sir Charles Parsons fortunately had enough money to develop his idea, for the benefit of the whole world.
ERECTING THE STATOR for one of the 69,000-kilowatts turbo-alternators in the turbine hall of Battersea Power Station. The turbines were designed on so large a scale that they had to be brought from the manufacturers in sections and assembled in the power station. They had been built with such accuracy and precision that they worked satisfactorily at the first full test.
Just as running water will wear away a stone, so high-pressure steam will eat away the metal blades of a turbine. The wearing of blades in this way leads to a big loss in efficiency and their replacement costs time and money. Meanwhile the machine has to stand idle.
All that science can suggest and the metallurgists have been able to create to obviate this defect has been incorporated in the turbines at Battersea Power Station. Of the thousands of turbine blades, some are made of rolled stainless steel, others of rust-less steel, and others are cut out of solid bars of stainless steel. The use of the metals has been suited to the positions the blades occupy and the steam pressure they have to stand.
High-pressure steam, at 600 lb to the square inch, rushes into the high-pressure cylinder of the turbine through nickel steel nozzles, the metal best suited to withstand the wear and tear. From the high-pressure cylinder the steam is led in a pipe beneath the floor into the intermediate-pressure cylinder; this is larger than the first cylinder to allow for the expansion of the steam, which passes into this cylinder at a pressure of about 240 lb. From the second cylinder the steam is led overhead through the gigantic black pipes into the low-pressure cylinder, which is the largest of the three because by now the steam hits expanded enormously. When it has emerged from this cylinder it enters the condenser, in which there is a partial vacuum. Thus the turbines use almost the whole power of the steam.
Stepped Up to 66,000 Volts
COUPLED to the shaft of the turbine is the generator which transforms the mechanical energy developed by the turbine into electric power. The fixed portion of the main generator of the largest set weighs 148 tons, and the moving portion, or rotor, mounted on the shaft, weighs 82 tons.
This colossal mass, the armature, turning on the continuation of the turbine shaft at 1,500 revolutions a minute, generates current all the time from the magnetic fields set up by the magnets in the casing, or fixed portion, of the generator. The armature passes through three magnetic fields to give a three-phase current, which means that as one current reaches its maximum strength and starts to die away, another starts to grow stronger until it reaches the peak of its impulse. While the armature is moving from the influence of this magnetic field it is simultaneously entering another that is increasing to maximum.
The current collected in this way passes from the generator, or alternator, at 11,000 volts into a transformer which steps it up, or increases its electrical pressure to 66,000 volts.
From the transformer the current flows to the main bus bars from which it can be switched through various cables and transformers and sent to any area in the system. In other power stations the bus bars are visible as wide and massive bars of copper, fenced on and protected from human interference, because to touch them means death.
At Battersea, however, an entirely new system of bus bars has been installed. The gleaming masses of copper have vanished, and their place has been usurped by a series of black pipes with a pitch-like covering through which a wire winding may be detected. In the centre of these pipes is a copper pipe charged with the electricity and properly insulated. Before the privileged visitor can examine the bus bars, he is compelled to wriggle between two of them. It comes as a shock to realize that he has been sitting astride a bus bar. with his back pressing against another while they have been carrying current at 66,000 volts., In the old type a touch was death, but here they are so perfectly insulated that the engineers crawl between them to go in to examine the gear without giving it a second thought. But harmless as the bus bars appear to be, there is demoniacal power locked up inside them.
TWO OF THE ROTORS of the 105,000-kilowatts turbine set in the builders’ workshop before being sent to Battersea. In the foreground is the intermediate-pressure rotor, with its eighteen rings of thousands of stainless steel blades. The rings increase in size to allow for the expansion of the steam as it flows through the turbine. In the low-pressure turbine the steam enters at the centre and passes to left and right, which accounts for the smallest rings of the low-pressure rotor (in the background) being in the centre.
All this power is controlled by switches of a magnitude that is difficult for the average man to comprehend. Beside them a house switch is infinitesimal. Even those giant switches which take all a man's strength to operate are as nothing at all. A dozen men, indeed, would strive in vain to open the main switches. They weigh about 31 tons, and are so enormous that they are opened and closed by two travelling cranes which span the whole roof of the building which houses the switches.
At first sight they bear no resemblance to switches. Each one is composed of three enormous cylinders, painted a battleship grey, standing taller than a man, surmounted by other massive containers rather resembling an inverted water bottle with the neck cut off. The top halves contain the immense bayonet-shaped tongues of copper that are thrust into the connectors in the centre of the bottom cylinders. On the framework of the bottom cylinders are set four big pillars of steel, pointed in the same way as pencils, that fit into holes in the framework of the upper half to guide the switches home and ensure that proper contact is made.
THE bottom drums are each filled with 400 gallons of golden oil in which the switches are immersed, so there is not the slightest possibility of fire. The oil is tested regularly in a machine to ensure that it is free from water or any foreign matter which is likely to cause a reduction in its insulating value. The positive and negative points of a circuit are immersed in a beaker of oil, a current is passed through, and if a spark should form and leap the gap when they are within a quarter of an inch of one another the oil is withdrawn for purification.
It is part of the routine that before work can be started on any cable in the system or on any switch or cable in the power house, a permit card must be obtained from the controlling officer, who signs it. All current is then cut off from the point on which work is to take place, and the current must not be switched on again until that card is back in the hands of the controlling officer. By the adoption of this measure, the safety of those working on the lines is ensured.
Taking out one of the 66,000-volts switches for examination is an interesting process. One of the cranes, which are worked by electricity, as is everything else in the station, moves noisily along its rails at the top of the switch house into position over the switch. Connexions are made, and there is a clatter of gears as the 31-tons switch is lifted clear of the floor. Then the crane moves down the switch house to the big inspection space, where the whole switch is lowered to the floor.
Other couplings are then made, and in about a minute the top half of the switch is lifted out of the bottom half, to be transported across the floor to the other side of the building where it can be set on a frame to enable the engineers to examine it and do what is necessary. It is all done so calmly, with such an absence of fuss, that the onlooker is apt to forget the men are handling a mass of metal and oil weighing 31 tons.
THE COAL CONVEYER BELT at Battersea Power Station is composed of rubber-faced material and is curved upwards at the edges to prevent the coal from spilling off. Coal from colliers alongside the jetty seen in the background is loaded on to the conveyer belt which carries the coal to a hopper in the weighing tower. Having been weighed, the coal is moved up another band conveyer to the bunkers at the top of the building.
The quiet competence displayed about the power house is impressive. Something of the efficiency of the machines they control seems to inspire the men. It is similar to the spirit which inspires the crew of a battleship. There is something reminiscent of a ship about the power house. Officers are always on duty night and day. They sit at desks with their log sheets before them recording the performance of the machines under their control. Complete sets of readings are inserted on the log sheets every half-hour.
In front of them, on the control panel, the automatic recorders work quietly from midnight to midnight, inscribing in lines and graphs the performances of the machines for the twenty-four hours
These recorders are among the wonders of the place. By turning a handle at any moment the officer in charge can find out anything he wishes to know about a dozen things that concern the safe running of the machine.
THE automatic recorders for the boiler house are ruled paper disks about the size of gramophone records. At a distance they might be mistaken for clock faces, but upon examination the red and black and green lines inscribed by the stylus are plainly seen. The recorders are silent, implacable witnesses, on the watch all the time to ensure that duty is done.
The control room of the power house embraces all the upper side of the turbine hall. It is a spotless place, with marble walls, polished hardwood floor and artistic ceiling lights. The side overlooking the turbine hall is a series of bay windows through which the three turbines, two being 102 feet and the largest 120 feet long, can be seen at a glance, as can the two cranes spanning the top of the hall, ready to traverse the whole length to handle the machinery at any point.
Half-way down the room is the control board, set well away from the wall. There are dozens of dials that give the officer in control necessary information. Above the dials are diagrammatic plans which indicate to the controlling officer the exact state of all the circuits in his charge. The live parts of the system are indicated by a red line of light. Green means that a section is earthed and out of commission, and yellow that a switch is open. In front of the control panel are two telegraphs resembling those in a ship. and by them the officer can signal his orders instantly to the officers in charge of the three turbines.
The tall desk standing here marks the extent of modern progress. It has a ground glass top. If anything went wrong in the system a bell would ring instantly and keep on ringing until the officer switched it off. At the same time a section of the desk about 4 in wide would light up and tell him where and what the trouble was. “Earth Fault”, he might read. “Willesden 2, Over-current”; “Station Transformer, Earth Fault” - these and many more troubles that may come unexpectedly are all charted in this magic desk which signals to ear and eye when a hitch occurs.
There seems no end to the marvels of London’s great power station. On the river frontage is a jetty that will accommodate two seagoing colliers of 2,000 tons. The London Power Company owns seven colliers. The river has been specially dredged to allow them to draw in at any state of the tide. Three cranes run along the jetty to operate grabs that pick up five tons of coal at each mouthful.
The coal is dropped upon a moving band of rubber-faced material that curves up at the edges to prevent it from spilling off. From the jetty the coal travels up an inclined plane to the top of a tower, where it is spilled into a hopper which automatically weighs it and records the weight. At the correct weight the full hopper automatically moves downwards and an empty hopper takes its place.
IN THE MAIN TURBINE HALL at Battersea there are in all three turbo-alternator units. Two of the turbines are of 92,000 horse-power, developing 69,000 kilowatts, or 69,000,000 watts of electricity. The third turbine develops 105,000 kilowatts.
At the bottom of the weighing tower the coal is shot upon another band conveyer, which carries it up, round three sides of a rectangle, until it reaches the bunkers at the top of the building. Here the bands of coal run up over two tipping machines which collect the coal as it comes from the bands and direct it down funnels through the floor gratings into the coal hoppers which feed the furnaces.
The coal is quite small. It would be called slack by most people, and it comes from two special pits in Scotland and Wales. This coal has been specially tested and selected because it has a low sulphur content. Obtaining it was one of the first steps that the London Power Company took in its campaign to prevent pollution of the atmosphere.
The coal slides down automatically through the hoppers to the furnaces on the firing floor far below. There are four coaling hoppers to each furnace, and the main pipe of each hopper divides into several feeding pipes, so that each furnace is fired regularly at twenty different points, the coal being distributed evenly over the whole surface.
FROM the front of the furnaces not a spark of fire can be seen. The stranger might find it difficult to believe that these were furnaces at all, for there is no great heat to betray them, only the slow motions of the mechanical stokers moving round as inexorably as fate, with the rams driving the coal charge home in the furnace and not a bit of coal dropping to show what they are doing. It is an object lesson in how the specialist has ceased to allow heat to run to waste outside the furnace and conserves nearly all of it to turn water into steam. Thousands of water tubes form a ceiling to the furnace; thousands more line the back and sides behind a vitreous covering, so, instead of the flames heating solid masses of fire-brick, they create steam. There are six boilers in use which, when working normally, can turn 250,000 lb of water an hour into steam at a pressure of 615 lb to the square inch. At their maximum, when the demand is at its peak, they can evaporate 330,000 lb of water an hour, the temperature of the steam being from 875 degrees to 900 degrees Fahrenheit. The heating surface of the boiler totals 26,580 square feet, the superheater has 10,920 square feet, the economizer 17,826 square feet and the air heater 57,208 square feet.
The furnaces burn 17½ tons of coal an hour. If all six were worked at full pressure they would use up 2,500 tons a day. The heat in the furnace is so intense, and the incandescence is so bright, that those who tend the fires dare not look at them with the naked eye through the special door at the side. To look into a furnace resembles looking into the heart of the sun; so a shield must be held before the face. In this shield is set a strip of purple glass through which the inferno can be viewed. Even through the purple glass the incandescence is almost unbearably bright to look at, and the bluish names dance in their myriads on every side.
AN ENORMOUS TURBINE in the main hall of Battersea Power Station. The pair of huge pipes arching over the centre of the set carries steam from the intermediate cylinder to the low-pressure rotors. The turbines are completely enclosed in dark grey and black casings.
The gases given on flow up the flue to the top of the economizer, through which they are drawn downwards and out of the bottom into the air heater. From the air heater they rise again to enter the grit collector, which rids them of all solids. Then the giant fans suck them out into the gas washing chambers, where they run the gauntlet of the sprays of water.
These curtains of spray eventually rob the gases of everything injurious or offensive, but previously they flow into the main flue, which runs the whole length of the top of the building from the base of one chimney to the other, and through the downtakes and uptakes, whence they rise out of the tops of the chimneys in the form of steam, created in passing through the screens of water. The main body of water through which the flue gases are passed in this scrubbing process runs down into the treatment plant on the ground, where it is properly clarified and filtered.
From the boilers the high-pressure steam goes to forged steel receivers, whence it passes through 9-in pipes to the turbines. These pipes are lagged (coated with insulating material in the form of asbestos) to prevent any of the heat from escaping into the atmosphere, and they are painted with red bands to indicate that they are the live steam pipes. When the steam has done its work in the turbines, it flows into the condensers, where it comes into contact with miles of brass tubes through which cold water is passing.
Miles of Brass Tubes
THIS water, on its way back to the boiler through the economizer, is passed through five heaters which are operated by steam from the low-pressure turbine and the intermediate-pressure turbine. In this way the boiler water is heated until it is delivered into the boilers at 355 degrees Fahrenheit, which enables the furnaces to generate steam rapidly.
Prodigious quantities of water are needed in the condenser tubes to keep them cool enough to do their work. The twin condensers, whose miles of brass tubes have a cooling surface of 60,000 square feet, or nearly 1½ acres, are worked by four pumps, each of which can pump 2,000,000 gallons an hour. All the time they are circulating cold water through the tubes in the condensers and discharging the warm water back to the river.
This water is drawn from the Thames. The intake is situated under the jetty and is surrounded by a screen of metal bars to prevent floating stuff from entering. In addition, fine band screens are provided through which the water passes before entering the main inlet culvert to the pumps.
All the electrical power is carried away from the station in seven 66,000-volt cables, two to Deptford, two to Willesden and three to Grove Road, and eight 22,000-volt cables go to four other distributing stations. In. addition the station supplies power to the Central Electricity Board, which owns four cables that go out to Woking, in Surrey.
The whole side of the Battersea Power Station is covered with sheets of corrugated iron, acres and acres of it, painted black. Battersea Power Station, as it stands, is only half a dream come true. Not until all that corrugated iron has been stripped away and another building of the same size has been joined to it, with two more gigantic chimneys pointing to heaven, will the whole dream be realized.
AN ELECTRIC TRANSPORTER CRANE with a grab is used to handle the enormous quantities of coal used for the furnaces at Battersea Power Station. The furnaces for the six boilers burn 17½tons of coal an hour. If all six boilers were worked at full pressure, they would use 2,500 tons a day. All the machinery at Battersea is operated by electricity supplied from auxiliary generators.
[From part 5 and part 6, published 30 March and 6 April 1937]