Steffen Reichel
Member
Well, there is not many about Titanics propusion plant in the web, and their are very little books, which represent technical background informations.
So an 'steam engineers handbook' seems to be what sometimes is needed.
So, speculative, I would like just to tell how such a propulsion power plant operated, and you might correct some parts or add some word, just to give the board reades a possibility to get informations about: How Titanic engine worked!
Well, first for all steam engines, steam is requiered. In Tatanic coal was the fuel and stokers or firemen used shovels to put the coal from a store hill at the boilers into the firetube.
WEll, marine boilers often look like a steel box or steel tube or vessel. They got usually two doors at the lower bottom front: The upper door is the fire door, the door below the ash door. Both doors give a way into a long and large tube, which got in its middle a grid iron and which the fire was enlighted and fired with coal. the grid iron was not as long as the tube, commonly shorter and endet at a steel screen, to prevent burning coal falling down into the ash part of this so called fire or flame-tube. Fresh air enterd commonly though a small opening at the opposite side of the tube, the secondary air, and the primary air entered through a flap or a couple of flaps close to the ash door from the front. Bot air inlets could be adjusted by handles. So what happend here? The coal set a flame, and the hot smoke, as the hot air flow through the flame-tube through the boilers vessel into a part at the other side of the boiler, the combustion chamber. Here the smoke was directed back into a couple of smaler tubes, which were often grouped into a couple of sets, and in the combustion chamber often a superheating unit was placed. So the hot air and smoke flow back into the boiler vessel, now through smaller tubes and then found the smoke box, or another combustion chamber. In three pass boilers the otehr combustion chamber now turned again the direction of the smoke and hot air, again through a couple of small tubes, back through the boiler int o the smoke box. Two pass boilers had this not, and so we are at the smoke box, were above the exhaust channel, or funnel channel or funnel tube is attached. Also commonly here the entrie of the superheating tubes is found and a water preheating unit could be placed. 'Preheating of teh water is important, because cold water will lead to massive boiler metall problems and preheating makes the boiler more effective and spares coal.
So the boiler is manually feed with coal, and the smoke in the tubes which go through the boiler vessel heat up the surrounding water. So water inside the boiler vessel heats up, boils and gets into steam. Because the boilers is closed to the free room or air, pressure of the steam in the boiler upper parts prevents further water to turn into steam, so the water temperature rised, releases more steam, and pressure starts to rise insode the boiler. So at 16 kg per square centimeter, which is 16 bar, the water has a temperature of about 200°C. So if now the boiler valve is opened, the pressure quickly decreases, and the water will not be able to boil and turn into steam much better, so staem is quickly released from the hot water.
In boiler explosion nearly all that water turn into steam, and this is a very massive power, will tear the boiler parts apart.... So as example: At 16 bars and 8 cubicmeters water inside the boiler a boiler explosion will release more than 1 GigaWatts Power, if the explosion will take one second. But, a boiler explosion is a 'BANG', shorter than a second, so for the example we can consider 4 or more gigaWatt Power if this boilers blasts, so be aware os steam power, and marine boilers often had more water in the boiler vessel...
But, to prevent this, safety valves at the boiler were installed, which open automatically if pressure is to high, releasing the steam into the free air or a funnel tube... Safety valves are spring loaded, so close automatically after boiler pressure is in the boiler pressure range...
The steam from the boiler is now a foggy thing, is is steam, and rough useable, but the small droplets in the steam quickly settle on the inner tube walls, cool down and the steam is for this reason not good for transportation and not very effective in machinery purposes. So the steam from the boiler is taken out through a main boiler valve, and then divided into small tubes and those tubes were then again surrounded by hot smoke and air, so superheat the stem inside the tubes. Superheated steam is nothing else than transforming the water completely into a moleculary gas, so 'water gas' might be a hint to keep in mind....
This steam is now at a pressure, and from all boilers the steam enters now a collection tube, to bring the steam to the machinery. Here we often found a secondary main valve, just to shut up machinery from boilers, as we find bypasses and other things for maintainance.
The steam now enters the recipoking engine.. this is tricky thing, because it works completely different than our modern gasoline or diesel engines.
A steam engine is a set of a cylinder pair, each a vessel with entry and exhaust openings. The first, often longer, but thinner cylinder is the piston valve cylinder, here the steam from the boiler enters.
Well, a pair of valves, commonly piston valves in this cylinder now allows the steam to enter into the steam cylinder, only one time from above or atbottom, while the other valve in the same moment lets teh steam from the steam cylinder to the exhaust or compound tube.
Steam engines are double action engins. In gasoline engins the combustion of the fuel in the cylinder 'hammers' the piston down, in Steam engines the steam pushes the piston down, and if down steam enters below the piston and pushes it up, then steam enters atop and pushed the piston down again, and so on. The valves of the valve gear control now, when an how much steam atop or atbottom should enter.
In our example we found, that the piston is atop, so the upper valve opens right now the entry valve, and the botton valve conncets the room below the pistom to the exhaust, and here to the compound tube... So the steam enters, and pushes the piston down, while the main shaft is turned by the piston rod, connected to the crank at the crank shaft.. Turning the shaft moves now the rods of the gear, starting to close the valve atop, clsing the valve atbottom of the cylinder, further opening the bottom valve and connceting the top valve with the compound tube (exhaust). So the pressure of the boilers will 'rush' through the tubes and push the piston down, very ineffectife and steam consuming. It ist much better, to close the entry valve at the point when the piston is 2/3 or less of its downward way gone, and letting the steam expand and pushing it that power further downwards. Steam has under pressure the tendency to get in atmosphaeric pressure again. Steam under pressure need less room, than under lower pressure, so you can put far more steam of 16 bar into a cubic-inch room, than if the steam has 10 or less bar in pressure. So in a room, like the cylinder room, all walls are immobile, except the wall which is the piston area. This wall is mobile and the steam can push it away.
So if we now let the piston move about 1/3 of its way move downward, this room is filled with fresh steam in nearly boiler pressure. If now the valve closes, the steam will start to loose pressure, and this process, called expansion will need space, because with lower pressure the amount of steam will need more space, and thus the steam pushes the piston the whole rest of the downward way down.
Same will no happen in upward move. Engineers say: The engine is running at a expansion set or filling ot 30%, or the gear is at 30%. As higher the percent number, as longer the way which steam can enter the steam cylinder, as little the expansion, as lower the percent, as more expansion will need. Role of thumb: Below a special percent number, in example 20% the engine will not move proplerly, because it produces to less power to turn, and as higher the percent, as more steam will be 'sucked' by the engine and as more coal the boilers will eat, but the engine will run at maximum power output!!!
So an engineer starts his engine with ah giant wheel, setting the gear into the desired direction, in our case the gear as in other mobile engines controls also the direction. So by letting the steam once upwards in, or once downwards in, the engine will start turning left or right ways, just bythe engineers turn at the control wheel. In motion, the engineer will quickly set the gear to low percents if the engine has the first complete rounds done, and if desired, he can change from turning right to full left in a couple of seconds, just by turning the wheel to the opposite end. This switches the valves. In our expample: The top valve was open, steam enters, piston is pushed down, shaft turns, down valve lets the steam from below the piston flow out into the compound tube (exhaust). If we now switch the gear, we switch the valve: Top valve will be connected suddenly to the compound tube (exhaust), so the fresh steam in the cylinder will stop pushing the piston down immediately, and rush through the top valve into the compound tube. At same time the dwon valve, connected to the compund tube is closed and opens to fresh steam entry, so fresh steam enters immediately to the room below the piston, and trying to push the still downward moving piston upwards. Horrible force to the piston area, rods and cranks were now set free, stopping the downward piston move nearly immediately and starting with pushing the piston upwards, thus changing the shafts turning direction to left turn....
So what happens to the exhaust steam, which exhausts from the cylinder? Well, in single cylinder engines the steam now comes to the condensator, or will go to the chimney, in Titanics case, the steam will come into an compound tube, because in Titanic the steam was used three times in three different sized cylinders. Because the steam loses pressure in the first cylinder, so to having in the second cylinder the same force at the piston, well the piston surface must be larger, because to have the same force. So the compound tube from the first, so called high pressure or HP-cylinder, will now at the second, immediate pressure (or IP-Cylinder or MP-Cylinder) cylinder the steam entry, and the exhaust ist again an compound tube to the thrid, low-pressure or LP-cylinder. All cylinders work in the same way, have only differend cranks, to make the force of the cylinders to the crank shaft smooth and soft. As we see: If the second cylinder was larger than the first, the thrid must be even larger than the second, in Titanics fact the piston surface needed was that large, that the machinery constructeur divied the thrid cylinder into two cylinder, so Titanic hat one HP, one MP and Two LP cylinders, so four cylinders at all. This we call a four Cylinder triple expansion engine! For cylinder is clear, triple expansion, because the steam for the engine is used three times, and can expand three times in the different cylinders...
But were not at the end! In Titanic the steam will be expand to very low pressure, than entering the turbine. Here a special effect happens: the steam will expand more, so still high in temperature the steam will take more space than commonly need, so the pressure drops slightly below 0 bar, so that is called 'counterpressure'. This will now having a special effect: Steam pushes in high pressure, but below 0 steam 'sucks' other steam, so in example of our piston: High pressure steam atop the piston pushes by expansion the piston down, counter pressure steam drags the piston up....
So the turbine is moved other way: the steam from the engine will go into the turbine, and a nozzle focuses the steam to a propellerlike wheel, with many, many little winglets. So the steam flows around the winglets and drags and pushes those little winges aside, like in a windmill, and thus turns the turbine shaft. Counterpressure steam does same, onyl counterdirectional to the winglets, will losing not pressure, but losing temperature and speed.
So with very low speed and temperature and at a presure of, I guess -0.5 to -1 bar the steam enters the condensator. The condensator is a vessel with many tubes in, like the boiler, but here in the tubes not smoke can be found, no, in the tubes cold sea water flows, sooling down the surounding steam to water. The water is no taken by a pump out of the condensator vessel, holding the below zero pressure in the condensator still upright, and the pump will 'feed' that water again to the boilers. And here we had begun....
Commonly those pumps are driven by the main shaft of the engine, so work only if the engine is in march, what makes sense, because not to get a to high counterpressure and damage the condensator vessel and sealings.
As not all steam can be condensated, becasue some steam will move to the free air through the sealings, fittings and bearings, and sometimes to valves in the free air, fresh water had to be pumped into the boiler: For this case as special driven feed-water-pump is mounted, pumping water from the bunker, through the water preheating units into the boilers, often water-treatment is on the way before, to remove lime and salt of the fresh water, before it will enter the boilers...
so two pumps can be found in Titanic basicly: Main water march pump driven by the crank shaft of the recipoking engines, and fresh water feed pump with its own steam engine attached...
And more you basicly do not know, and this is how it works, basicly!!!
Hope, this helps thos of you, who do not know how Titanics or any other expansion steam engine works.
So an 'steam engineers handbook' seems to be what sometimes is needed.
So, speculative, I would like just to tell how such a propulsion power plant operated, and you might correct some parts or add some word, just to give the board reades a possibility to get informations about: How Titanic engine worked!
Well, first for all steam engines, steam is requiered. In Tatanic coal was the fuel and stokers or firemen used shovels to put the coal from a store hill at the boilers into the firetube.
WEll, marine boilers often look like a steel box or steel tube or vessel. They got usually two doors at the lower bottom front: The upper door is the fire door, the door below the ash door. Both doors give a way into a long and large tube, which got in its middle a grid iron and which the fire was enlighted and fired with coal. the grid iron was not as long as the tube, commonly shorter and endet at a steel screen, to prevent burning coal falling down into the ash part of this so called fire or flame-tube. Fresh air enterd commonly though a small opening at the opposite side of the tube, the secondary air, and the primary air entered through a flap or a couple of flaps close to the ash door from the front. Bot air inlets could be adjusted by handles. So what happend here? The coal set a flame, and the hot smoke, as the hot air flow through the flame-tube through the boilers vessel into a part at the other side of the boiler, the combustion chamber. Here the smoke was directed back into a couple of smaler tubes, which were often grouped into a couple of sets, and in the combustion chamber often a superheating unit was placed. So the hot air and smoke flow back into the boiler vessel, now through smaller tubes and then found the smoke box, or another combustion chamber. In three pass boilers the otehr combustion chamber now turned again the direction of the smoke and hot air, again through a couple of small tubes, back through the boiler int o the smoke box. Two pass boilers had this not, and so we are at the smoke box, were above the exhaust channel, or funnel channel or funnel tube is attached. Also commonly here the entrie of the superheating tubes is found and a water preheating unit could be placed. 'Preheating of teh water is important, because cold water will lead to massive boiler metall problems and preheating makes the boiler more effective and spares coal.
So the boiler is manually feed with coal, and the smoke in the tubes which go through the boiler vessel heat up the surrounding water. So water inside the boiler vessel heats up, boils and gets into steam. Because the boilers is closed to the free room or air, pressure of the steam in the boiler upper parts prevents further water to turn into steam, so the water temperature rised, releases more steam, and pressure starts to rise insode the boiler. So at 16 kg per square centimeter, which is 16 bar, the water has a temperature of about 200°C. So if now the boiler valve is opened, the pressure quickly decreases, and the water will not be able to boil and turn into steam much better, so staem is quickly released from the hot water.
In boiler explosion nearly all that water turn into steam, and this is a very massive power, will tear the boiler parts apart.... So as example: At 16 bars and 8 cubicmeters water inside the boiler a boiler explosion will release more than 1 GigaWatts Power, if the explosion will take one second. But, a boiler explosion is a 'BANG', shorter than a second, so for the example we can consider 4 or more gigaWatt Power if this boilers blasts, so be aware os steam power, and marine boilers often had more water in the boiler vessel...
But, to prevent this, safety valves at the boiler were installed, which open automatically if pressure is to high, releasing the steam into the free air or a funnel tube... Safety valves are spring loaded, so close automatically after boiler pressure is in the boiler pressure range...
The steam from the boiler is now a foggy thing, is is steam, and rough useable, but the small droplets in the steam quickly settle on the inner tube walls, cool down and the steam is for this reason not good for transportation and not very effective in machinery purposes. So the steam from the boiler is taken out through a main boiler valve, and then divided into small tubes and those tubes were then again surrounded by hot smoke and air, so superheat the stem inside the tubes. Superheated steam is nothing else than transforming the water completely into a moleculary gas, so 'water gas' might be a hint to keep in mind....
This steam is now at a pressure, and from all boilers the steam enters now a collection tube, to bring the steam to the machinery. Here we often found a secondary main valve, just to shut up machinery from boilers, as we find bypasses and other things for maintainance.
The steam now enters the recipoking engine.. this is tricky thing, because it works completely different than our modern gasoline or diesel engines.
A steam engine is a set of a cylinder pair, each a vessel with entry and exhaust openings. The first, often longer, but thinner cylinder is the piston valve cylinder, here the steam from the boiler enters.
Well, a pair of valves, commonly piston valves in this cylinder now allows the steam to enter into the steam cylinder, only one time from above or atbottom, while the other valve in the same moment lets teh steam from the steam cylinder to the exhaust or compound tube.
Steam engines are double action engins. In gasoline engins the combustion of the fuel in the cylinder 'hammers' the piston down, in Steam engines the steam pushes the piston down, and if down steam enters below the piston and pushes it up, then steam enters atop and pushed the piston down again, and so on. The valves of the valve gear control now, when an how much steam atop or atbottom should enter.
In our example we found, that the piston is atop, so the upper valve opens right now the entry valve, and the botton valve conncets the room below the pistom to the exhaust, and here to the compound tube... So the steam enters, and pushes the piston down, while the main shaft is turned by the piston rod, connected to the crank at the crank shaft.. Turning the shaft moves now the rods of the gear, starting to close the valve atop, clsing the valve atbottom of the cylinder, further opening the bottom valve and connceting the top valve with the compound tube (exhaust). So the pressure of the boilers will 'rush' through the tubes and push the piston down, very ineffectife and steam consuming. It ist much better, to close the entry valve at the point when the piston is 2/3 or less of its downward way gone, and letting the steam expand and pushing it that power further downwards. Steam has under pressure the tendency to get in atmosphaeric pressure again. Steam under pressure need less room, than under lower pressure, so you can put far more steam of 16 bar into a cubic-inch room, than if the steam has 10 or less bar in pressure. So in a room, like the cylinder room, all walls are immobile, except the wall which is the piston area. This wall is mobile and the steam can push it away.
So if we now let the piston move about 1/3 of its way move downward, this room is filled with fresh steam in nearly boiler pressure. If now the valve closes, the steam will start to loose pressure, and this process, called expansion will need space, because with lower pressure the amount of steam will need more space, and thus the steam pushes the piston the whole rest of the downward way down.
Same will no happen in upward move. Engineers say: The engine is running at a expansion set or filling ot 30%, or the gear is at 30%. As higher the percent number, as longer the way which steam can enter the steam cylinder, as little the expansion, as lower the percent, as more expansion will need. Role of thumb: Below a special percent number, in example 20% the engine will not move proplerly, because it produces to less power to turn, and as higher the percent, as more steam will be 'sucked' by the engine and as more coal the boilers will eat, but the engine will run at maximum power output!!!
So an engineer starts his engine with ah giant wheel, setting the gear into the desired direction, in our case the gear as in other mobile engines controls also the direction. So by letting the steam once upwards in, or once downwards in, the engine will start turning left or right ways, just bythe engineers turn at the control wheel. In motion, the engineer will quickly set the gear to low percents if the engine has the first complete rounds done, and if desired, he can change from turning right to full left in a couple of seconds, just by turning the wheel to the opposite end. This switches the valves. In our expample: The top valve was open, steam enters, piston is pushed down, shaft turns, down valve lets the steam from below the piston flow out into the compound tube (exhaust). If we now switch the gear, we switch the valve: Top valve will be connected suddenly to the compound tube (exhaust), so the fresh steam in the cylinder will stop pushing the piston down immediately, and rush through the top valve into the compound tube. At same time the dwon valve, connected to the compund tube is closed and opens to fresh steam entry, so fresh steam enters immediately to the room below the piston, and trying to push the still downward moving piston upwards. Horrible force to the piston area, rods and cranks were now set free, stopping the downward piston move nearly immediately and starting with pushing the piston upwards, thus changing the shafts turning direction to left turn....
So what happens to the exhaust steam, which exhausts from the cylinder? Well, in single cylinder engines the steam now comes to the condensator, or will go to the chimney, in Titanics case, the steam will come into an compound tube, because in Titanic the steam was used three times in three different sized cylinders. Because the steam loses pressure in the first cylinder, so to having in the second cylinder the same force at the piston, well the piston surface must be larger, because to have the same force. So the compound tube from the first, so called high pressure or HP-cylinder, will now at the second, immediate pressure (or IP-Cylinder or MP-Cylinder) cylinder the steam entry, and the exhaust ist again an compound tube to the thrid, low-pressure or LP-cylinder. All cylinders work in the same way, have only differend cranks, to make the force of the cylinders to the crank shaft smooth and soft. As we see: If the second cylinder was larger than the first, the thrid must be even larger than the second, in Titanics fact the piston surface needed was that large, that the machinery constructeur divied the thrid cylinder into two cylinder, so Titanic hat one HP, one MP and Two LP cylinders, so four cylinders at all. This we call a four Cylinder triple expansion engine! For cylinder is clear, triple expansion, because the steam for the engine is used three times, and can expand three times in the different cylinders...
But were not at the end! In Titanic the steam will be expand to very low pressure, than entering the turbine. Here a special effect happens: the steam will expand more, so still high in temperature the steam will take more space than commonly need, so the pressure drops slightly below 0 bar, so that is called 'counterpressure'. This will now having a special effect: Steam pushes in high pressure, but below 0 steam 'sucks' other steam, so in example of our piston: High pressure steam atop the piston pushes by expansion the piston down, counter pressure steam drags the piston up....
So the turbine is moved other way: the steam from the engine will go into the turbine, and a nozzle focuses the steam to a propellerlike wheel, with many, many little winglets. So the steam flows around the winglets and drags and pushes those little winges aside, like in a windmill, and thus turns the turbine shaft. Counterpressure steam does same, onyl counterdirectional to the winglets, will losing not pressure, but losing temperature and speed.
So with very low speed and temperature and at a presure of, I guess -0.5 to -1 bar the steam enters the condensator. The condensator is a vessel with many tubes in, like the boiler, but here in the tubes not smoke can be found, no, in the tubes cold sea water flows, sooling down the surounding steam to water. The water is no taken by a pump out of the condensator vessel, holding the below zero pressure in the condensator still upright, and the pump will 'feed' that water again to the boilers. And here we had begun....
Commonly those pumps are driven by the main shaft of the engine, so work only if the engine is in march, what makes sense, because not to get a to high counterpressure and damage the condensator vessel and sealings.
As not all steam can be condensated, becasue some steam will move to the free air through the sealings, fittings and bearings, and sometimes to valves in the free air, fresh water had to be pumped into the boiler: For this case as special driven feed-water-pump is mounted, pumping water from the bunker, through the water preheating units into the boilers, often water-treatment is on the way before, to remove lime and salt of the fresh water, before it will enter the boilers...
so two pumps can be found in Titanic basicly: Main water march pump driven by the crank shaft of the recipoking engines, and fresh water feed pump with its own steam engine attached...
And more you basicly do not know, and this is how it works, basicly!!!
Hope, this helps thos of you, who do not know how Titanics or any other expansion steam engine works.
