Naval Boilers - Grates Under Pressure

[Music] [Music] so this month the two choices made on patreon for extended videos were history of naval enigma which we've already done or rather the breaking of it and also naval boilers which I suppose is a fairly appropriate subject for this time of year because it's usually pretty cold outside I mean being in the UK it's just very very damp but a boiler will always keep you warm even if you're in the middle of the ocean now to be clear we're not going to be talking about a ship's engines single expansion double expansion triple expansion turbines diesels etc because that's an entire subject for an entirely different video but we are going to be talking about the boilers at the first part of the ship's power plant now what is the purpose of the boiler you might ask well very simply you take the fuel from the ship and you set fire to it whether that fuel is coal or oil or whatever else you might be using in more recent times and from that fire you get heat but that heat doesn't drive the ship directly so you have to turn that heat into something else and what it's turned into in the period for naval boilers is steam the steam can then be sent to the engines to propel them and thus as the engines move such as the propeller shaft thus the propeller moves and thus the ship moves or as far as been very very early times the paddle wheel but never mind but you can have all the fancy engines you like but if the steam isn't arriving in enough quantities are now high enough pressure you're not going to go anywhere fast and so the history of naval boilers could perhaps be shortly summarized as mankind's efforts to fit pressure bombs of increasingly worrying amounts of destructive power into the hearts of their ships in an effort to make them go faster because at the end of the day if you get your boiler wrong that is basically what you've created a gigantic steam powered pipe bomb one other thing to clear up here at the start is what exactly steam is in terms of naval boilers and thus marine engineering what we're talking about is actually what we would call superheated steam now you might think steam is something that you see coming out the top of a kettle no that this is not steam in the engineering sense that is a mixture of true steam which is a colorless gaseous form of water and water vapor droplets in the air and that visible part of what is commonly called steam is actually incredibly dangerous for ships engines because unlike a gas water is incompressible so if you have this visible type of quote-unquote steam in the reciprocating piston of a reciprocating engine then as the drive shaft comes down it's going to encounter liquid water which is incompressible or near enough is make no difference which is going to cause all sorts of hideous damage to the engine to give a more commonly understood example think about driving your car through particularly high flood water and if the Pistons in your car's engine get flooded that causes a lot of damage to your car and bless your car obviously shorts out which it's more likely to do these days before water gets in because believe it or not put under enough pressure the metal of your car engine will give out before the water does and the same thing in marine engines and when you go from triple-expansion door double expansion or basically reciprocating engines over to turbines it's even worse news because well there's a reason you can use the more commonly thought of version of steam in things like steam cleaners and steam paint strippers to get rid of all sorts of wonderful things including rust and that's before you account for stuff that might be in that water various minerals and such and so if you've lost a jet of what is in all do likelihood a mild acid over some very sensitive high-speed metalwork it's gonna eat into that turbine pretty quickly and again you're gonna have failure of turbo and that can be quite spectacular so what we're looking at is the ability for boilers to generate what's called superheated steam which has said is that incredibly hot see-through gas that comes out of let's say a kettle if you look very closely at the very spouts and that's why sticking your hand into the column of quote-unquote steam rising out of your kettle spout it say 2 3 feet above it makes you slightly warm and makes your hand slightly damp whereas whilst your kettle is boiling if you stick your hand right over the spout and please don't do this that way lies flesh being stripped from bone and extreme pain and possibly death if depending on how powerful your kettle is and of course how long you stick your hand there for and that's just with the kettle a less alone something like a naval boiler so with all that said and done let's get on to naval boilers themselves now the boiler to power a steam engine had in fact gone through a number of technological developments before they arrived in the first warships to be steam powered the very earliest boilers were literally gigantic rectangular or cubic metal tanks full of water that you stuck a fire under this is of course incredibly inefficient as if you consider the area where the fire is you've got the ground you've got the upper surface which is the underside of the boiler and you've got four sides through which the heat can escape plus obviously the ground will absorb some heat so it's a very inefficient way of heating the boiler and it only heats the underside of the boiler at any given time which means only a limited amount of the water within the boiler is being heated that heated water obviously then has to pass up through all the cold water so it takes an awful long time to boil and uses an awful lot of fuel and doesn't generate all that much steam the size of the boilers needed along with the size of the accompanying steam engines and the relatively small amount of work that could be done as a result was basically of no use in ships and so these kind of boilers were pretty much an experimental and occasionally seen in the very earliest uses of steam engines such as some mine workings the next stage was the development of the so-called flood boiler and this was where a flue or effectively a pipe was run from the firebox which was now almost entirely enclosed except for a hatch at the front where you'd shovel in more fuel in most of the time this would be cold and the hot gases from the combustion of the fuel would pass through a cylindrical pipe or flue of fairly large diameter which itself I ran through a body of water which was in a tank this was somewhat more efficient and could be made more efficient still with the invention of the double flue boiler where the flue doubled back on itself so the length of the flue or pipe was slightly more than double what it could otherwise be in a single flue boiler by enclosing the fire and then passing the heat through the body of water rather than just on the underside you increased the overall surface area that was contacted by the heat which improved the efficiency of the boiler by a considerable margin a further revision of this was the use of corrugated metal instead of plate metal when making the flue which of course increased the surface area in contact with the water but whilst this offered so increase in power and was good for some early steam locomotives it was still nowhere near efficient enough in terms of fuel usage or power generated to be of any particular use aboard a warship however as this technology advanced the power output and fuel efficiency did reach a point where it could be useful in some commercial steam ships and so it was this kind of boiler that would see first service aboard ocean-going and river going steam craft the next interim step in development was where warships first started she used boilers and this was the multi flute oiler now the flues were still fairly large and in most cases they were rectangular but with multiple flus running through the same water tank there was of course a much greater amount of surface area ink on with the water from the multiple clues and the amount of water in the tank at any given time was less which meant it was easier and faster to boil that water and hence to create steam however their efficiency was still such that the boilers and the engines that companied them needed to be quite tall and this was a concern for the Admiralty because they recognized that as we said before they'd effectively invited steam powered pressure bombs onto their ships which were powered by fire neither of these things were particularly attractive on board wooden warships which were of course the first recipients of the steam engine and its associated boilers and they responded particularly badly to having holes poked in them by high-velocity metal projectiles like say cannon fire and so the Admiralty was rather keen that these boilers and the engines should be kept below the waterline at where at all possible because at that time cannonballs were incredibly likely to punch through at the side of a ship and below the waterline and thus the boilers would be safe well at least until the ship began to flood and water got in and there was a massive steam explosion but at that points things were probably already quite bad anyway and indeed even if a cannonball the punch through a boiler didn't set off some kind of explosion or spread fire everywhere it would at the very minimum set a bunch of a very very hot water vapor i steam flooding through the ship's engine compartments and other parts of the ship which tended to do nasty things to the ship's crew as well as caused the loss of all power and of course with your engineering crew all freshly parboiled there would be nothing much they could do to stop the spread of fires from the boiler through the rest of the ship and so the next advancement was very welcomed by the Admiralty and this was the invention of the firetube boiler in this boiler the larger rectangular flus were replaced by smaller cylindrical tubes these could be more tightly packed together thus ensuring a greater efficiency of heat transfer because there were more of them and thus more surface area in contact with the water and also thanks to their lack of corners far less susceptible to being degraded at points over time by the superheated gas that was being come through them they were also significantly stronger thanks to their cylindrical shape which meant you could run them at higher pressures the more compact nature of this type of boiler meant that the height of the boiler could be reduced and thus the Admiralty's fears could be somewhat allayed and so this kind of box boiler was seen in quite a number of ironclads across many nations during the 1850s and 1860s it was so called and because as you can see the oval shape of the boiler was a simple box shape with the furnace underneath sending its gases through the tubes and then up through the exhaust to the funnels one particular feature of this kind of boiler was two sets of safety valves one set was fairly obvious in case the steam got too too high pressure these safety valves would pop open and release the steam before the boiler exploded but there were another set of safety valves that opened inwards onto the boiler and these were in place because with this kind of boiler once the fires were quenched and the boiler went out of use the steam that was left in the boiler particularly in the tubes would start to condense back into water and taking up far less volume this would create a vacuum over the surface area of the average naval boiler this could create enough vacuum pressure for the atmosphere to actually crush the sides of the boiler in and so these safety rails were designed to let air into the boiler should the pressure fall too low but as ships got larger through the late 1850s and into the 1860s and targeted speeds became higher engines even needed even more steam and at even higher pressures to drive themselves fast enough and with enough power to push these new ships through the water this meant that the Box boiler was no longer suitable as the water contained in the Box tank was now generating steam at a sufficiently high pressure that the would fail before the necessary steam pressure was reached and so boilers transitioned over to a cylindrical type as the cylinder was much stronger this had obviously already been found with the fire tubes themselves but now the water tank which was generating the steam was also cylindrical this allowed steam pressure to rise from about 25 pounds per square inch in the 1850s to about 45 pounds per square inch by the end of the 1860s additional improvements were made in the 1870s this consisted of running the exhaust gases from the fires through the water in the boiler three times once on the underside of the boiler to the so called combustion chamber along this path it would do a degree of preheating to the water in the boiler the combustion chamber was where the final combustion of the fuel would take place as distinct from the firebox and where the temperature would really get going then the combustion gases would pass through the various tubes as per at regular firetube boiler the water that had been preheated was thus closer to boiling point and so less energy was needed to get it up to boiling and thus into steam the combustion gases would then pass through a final large flue at the top of the boiler which would further preheat water that was held in saddle tanks on either side of the boiler as well as providing a very hot surface at the top of the boiler which of course is where the steam was exiting and this would help to superheat the steam corrugation also made a reappearance now in the cylindrical fire tubes which increased the strength of the fire tubes as well as improving at the surface area in contact with the water yet again with these refinements and advancements boiler pressure had gone up yet again with some boilers being used in the 1880s and early 1890s aboard small ships like torpedo boats which needed to move very quickly reaching between 120 and 180 pounds per square inch of pressure however this was approaching the limits of what could be done by simply setting fire to a bunch of Birnbaum materials and erecting that exhaust through various pipe work on land this problem could be solved by allowing the steam to escape via the funnel as if you're a locomotive there'll be water towers along the route once you've run out of water because you pulled it all the way and for a factory or similar you can always make sure you're connected to a water supply however at sea ironically enough you're not in this position let's not say you're not surrounded by water you must definitely are however seawater contains all sorts of wonderful minerals and constantly taking in seawater would result in large amounts of in crustaceans and blockages forming within the boiler which would rapidly lead to loss of efficiency and then potentially also problems at like again explosions fresh water is generally slightly less full of mineral contaminants than seawater but it's still not really suitable for long-term using steam engines however on land filtering and purifying water is a relatively easy thing to do whereas at sea setting up a water filtration and distillation plant aboard a warship he uses pressure space that you really really don't have also in the very earliest parts of steam boiler usage having a filtration and distillation plant was also something that you didn't have at any rate in a form that you could fit in a ship and so a steam ship would set out with a certain amount of boiler water which was hopefully relatively clean and you might have to top that up with seawater but ideally you wanted to keep as much pure water as possible and this is where the surface condenser came in the surface condenser was not strictly part of the boiler but it needs mentioning to explain pot the problem that they were facing this takes the steam at the end of its cycle after it's powered the engines and condenses it from steam back into water which can then be fed back into the ship's tanks where it can be reboil de ghin and the energy transferred again using the same most pure water some water is obviously going to be lost and over time boiler water could become contaminated with the necessary injections of seawater to top it up but this extended the lifespan of Euler's quite considerably and it also meant that small distillation plants later on could be set up aboard ships to try and keep from having to use sea water at all except in emergencies now the reason this is directly relevant to the development of naval boilers was that without the steam exhausting out of the system there was no additional pool that could be harnessed beyond natural convection of the exhaust gases to suck air into the furnaces as of course if you do suck air into the furnaces that means more oxygen is flowing across the fuel for any given amount of time which increases the combustion rate which increases the temperature and more temperature means more steam which means more pressure which means you can go faster the solution to this introduced around 1880 was forced or induced draught the two are of a similar concept but different in execution with induced draught as the gases run up the funnel there is a fan installed in the funnel to drive the gases out as obviously the fan imparts additional energy to the gases this creates a vacuum below the funnel which sucks more air up from the area of the combustion chamber and the firebox which in turn it sucks air more greedily from the engine room and thus with the greater airflow you get the greater combustion as described earlier whereas with forced draft this is effectively done at the other end in this an area of the ship around the boiler potentially all the way up to the entire boiler room is made airtight and then fans again are used to pump air into this volume which results in a positive pressure since this volume is airtight the only place that this positive pressure can go to equalize with the outside air pressure is through the firebox and through the boiler and up out through the funnel which again increases air flow and thus increases your pressure this then represented pretty much the epitome of the firetube boiler design with the so-called Scotch boiler being a relatively popular type that was used and refined throughout the last three decades of the 19th century as well as having now approached a cap on the pressure that could be achieved with the fire boiler there were a number of other ongoing problems with this kind of design because there was a relatively large amount of water relative to the volume of the fire tubes it took quite a while to raise steam pressure which meant that ships could take quite some time to get up to any kind of useful speed for this same reason the large volume of water in the boiler it was very difficult to respond quickly to a need to change the overall pressure so in say a battle where you might want to be speeding up and slowing down well you might eventually work your way up to your top speed but to slow down you couldn't just damp the fires slightly you'd have to blow off a large amount of steam pressure at which point you would go slower but it would take you a lot longer to build back up again which could render you tactically vulnerable thus as the century turned from the 19th to the 20th the next step up in boiler technology began to be deployed across warships this was the water to boiler as with most other kinds of boiler it had been in use on land for considerable amounts of time in various guises before it made its way on to warships as generally the needs of warships were very specific so outside of a few circumstances they generally adopted Boyle technology somewhat later than their land-based counterparts in a water tube boiler the vast bulk of the boiler is now occupied with the hot combustion gases from the furnace and the tubes are now actually running water through this incredibly hot environment and turning at the water then into steam as the individual tubes are considerably smaller than the overall volume of the boiler as a whole they can be operated at significantly higher pressures however whilst the tubes in a firetube boiler are vulnerable to buildup of things like soot from the exhaust gases the tubes in a water tube boiler are much more vulnerable to the build-up of mineral deposits in calcification amongst other things from the water being flash boiled into steam and while most fire tube boilers could be cleaned relatively easily by opening a hatch at the front while when the fires were down and effectively doing a horizontal chimney sweep getting in to a water-tube boilers system is much more complicated and getting rid of calcification and other mineral build-up as a result of water operating through is a considerably harder job as anybody who's had to clean a pipe in a hard water area or lost a kettle to limescale will understand as there's a much smaller volume of water being heated for a given boiler it means that steam is produced a lot quicker and the boiler can respond a lot faster to changes in demand which means that ships can get up to steam faster and they can also slow down and speed up faster as it's much easier to control the relative temperature of the water tubes and whilst running a water tube boiler on impure water can make life very difficult it does allow you to run the boiler with impure fuels much much more easily as with a large of combustion volume the deposits have passioned suchlike tends to build up in areas that are much more easy to clean have less effect on the take a lot longer to affect the water tubes themselves and as a result of the greater volume also take a lot longer to affect anything much of the boilers operation they are however considerably more expensive nonetheless water-tube boilers were definitely the way forward and initially they operated as you can see here with a water drum at the base of the boiler which would then feed water up through the tubes up into a working steam chamber with a super heater attachment to one side this was all well and good except that with the introduction of turbine engines the need for ever more steam and ever higher pressures was growing more and more and so the development of the three drum boiler proceeded apace this took various forms in various navies with various makers having their own particular takes on it but as you can see in this diagram they all followed generally the same layout and this had to feed water drums one on either side at the base and these would run pipes up towards a single chamber at the top this of course increased the amount of steam that could be generated in a given boiler without increasing the footprint all that much the overall efficiency of this layout is not perhaps as great as some other designs but other designs of what reported that are more efficient take up significantly more space and as we said space is at a premium aboard a ship it was in part the development of these boilers that allowed ships speeds to jump considerably using battleships as an example with the old fire tube boilers ships could generally be expected to hit 14 to 16 knots with the new water-tube boilers the average speed of a capital ship went up to about 18 knots and once you introduce turbines into the equation to take a more advantage of the superheated steam that was being generated the average battleship speed went up still further to 21 knots with some of them able to reach slightly higher speeds up to 23 knots naval boiler technology then plateaued somewhat for a while during the 1900s and 1910s and in some cases going into the 1920s as refinements to this kind of boiler layout were sort of tinkering with an established design and the main change in terms of generated power came from the introduction of oil fuel instead of coal this is because a given amount of oil can generate more energy than a given amount of coal as it is a more volatile substance and this burn rate can be increased not only through the use of forced or induced draught but also by spraying it which creates an aerosolized mr. fuel which obviously has a much greater surface area in contact with the air which accelerates the speed of the combustion and so using these advances it was possible to start pushing capital ships up to 25 knots or even more if you're prepared to throw in a lot of extra boilers and engines which allows for things such as the queen elizabeth-class and the various battle cruisers of the first world war however as indicated previously the tubes in a water-tube boilers slightly larger than they strictly could be partly as a result of feed water issues and partly as a result of technological issues it was possible to increase the pressure and thus the power of the boilers by using smaller tubes but this ran at several risks obviously poor feed water could block up a small tube much faster than it could block up a larger tube the tubes themselves will be more vulnerable to damage from the heat as there would be substantially less water in them which meant that the tubes themselves would get much much hotter this was of course brilliant for generating steam but as most of you will know once you start heating up metal to a significantly high temperature it starts to exhibit rather unwelcome properties such as ductility and the last thing you want is a ductile pipe that's full of high pressure steam nonetheless change was coming and over the late 1910s and 1920s and into the 1930s the so called small tube boilers began to be used more and more one of the biggest attractions of the small tube boiler to navies at the time was that it allowed for considerably more power to be generated whilst using a significantly smaller amounts of the ship's overall volume and with fewer boilers there was less weight used which meant weight could be diverted to other purposes on ships that were being refitted which during 1920s and 1930s with a lot of legacy World War 1 era shipping around was a very very imp and feature this could allow for a number of things you could maintain the same amount of power using significantly fewer boilers and thus keep the same speed but divert that extra weight saved into other things making a ship more heavily-armed more heavily armored etc as with HMS Warspite so for example when she was launched she used 24 boilers to generate 75 thousand shaft horsepower whereas after her refit she generated almost as much shaft horsepower on a total of six boilers this allowed for all sorts of new equipment to be installed and significant amounts of additional armor to be installed on her decks almost at the other end of things were the Kongo class which has launched used 36 boilers to generate 64,000 shaft horsepower for a top speed of a between 27 and 28 knots during their refits they had slightly more boilers installed a total of 11 boilers but these generated a staggering 136,000 shaft horsepower just under a third as many boilers but generating twice as much power as they were still fewer boilers being used this allowed speed to increase substantially up to almost 31 knots whilst also allowing for improved deck armor as well as various other improvements to the upper works of the ship likewise the Italians managed to take the quantity Kivar class including the Giulio Cesare up from 21 and a half knots using 24 boilers at 31,000 shaft horsepower to 27 knots using only 8 boilers generating 75,000 shaft horsepower albeit they did have to ditch a main gun turret in order to do so although it was never done for obvious reasons the refit planned for HMS hood would likewise have replaced her 24 older-style boilers generating 144 thousand shaft horsepower with much more modern units which would take up significantly less space while still generating slightly more shaft horsepower which would keep her at her design speed of around 32 knots whilst allowing for significant improvements in her protection as well as obviously radar and new fire control systems as we've discussed in a drydock comparing the Megumi's powerplant and the hoods which were of comparable power output despite Megumi's at being significantly smaller thus illustrating the advantages of more modern boilers a straight for one-for-one replacement of old boilers with new would have resulted in ships that would go ridiculously quick indeed probably far too fast for their hull designs and it was this proliferation of small tube boilers that was the main change between World War 1 and World War 2 we're almost at the end of this very abbreviated history of naval boilers as gas turbines diesel engines and nuclear power would predominate quite significantly after the Second World War and into the modern era however there was one last advance to be made in the field of naval boiler technology you now had the small tube boiler but it was possible in theory to get them up to even higher pressures the problem with this was that you needed to have a very fine control over the boilers themselves as well as have them built to extremely fine manufacturing tolerances as if you didn't you'd end up with broken boilers and a broken ship there were two navies who really took the lead in this field of high-pressure small water-tube boilers and that was the German Craig's Marina and the US Navy the advantage of course was that compared to even at normal small water-tube boilers you could get a significantly higher power output which in turn led to even smaller machinery spaces or higher speed for the same machinery space in this endeavor the US Navy had somewhat more success long-term than the Germans although the Craig's marina initially took the lead in deploying high-pressure machinery it tended to be a very high-maintenance and very fiddly to keep running without a very experienced and well-trained crew who knew exactly what all the foibles of that particular powerplant were a ship could break down in rather spectacular manner rather quickly as indeed the prince organ did once it was taken into US Navy service temporarily at the end of the Second World War whilst initial American attempts met with substantially less success than the early German attempts they took this as a motivation to actually get it right and so by the time of the Second World War entering full swing many American ships possessed very efficient very reliable high pressure small water-tube boilers which allowed them to operate as we said with significantly more power output for a given square footage of machinery space partially through their own developments and partially through in some cases adopting American technology other navies would catch up sooner or later but with other navies generally operating at 400 to 500 pounds per square inch the fact that the US Navy's power plants could reliably operate at 600 pounds per square afforded them a number of advantages which would only be realized across the rest of the globe's navies in the late 1940s and so that brings us to the end of this very abbreviated approximately half hour look at the history of naval boilers there is of course as with the development of naval armor a fantastically greater amount of detail to this subject but I thought that this is probably the most compact I could make it covering and the main highlights of the development of naval boy'll attack without getting into extreme fine detail in terms of marine engineering but if you'd like to learn about this in significantly more detail then I can suggest two books one is a short history of naval and marine engineering by Edgar C Smith this was published in 1938 so it doesn't cover the lost advances in high-pressure machinery that occurred in the run-up to and during World War two but it does give a fairly substantial background into the history and development of naval boiler technology up to that point and the other one is the somewhat imaginatively titled naval boilers by Robert F Latham who published that for the United States Naval Academy Department of Marine Engineering in 1956 and so that does cover that final period and both of these are available on most good online bookstores and hopefully that will give you a little bit more insight into the material that had to cut down for this video that's it for this video thanks for watching if you have a comment or suggestion for a ship to review let us know in the comments below don't forget to comment on the pinned post for drydock questions

Channel: Drachinifel

Views: 488,804

Rating: 4.9190617 out of 5

Keywords: wows, world of warships, naval boiler, fire-tube, water-tube, box-boiler, steamship

Id: Qveycr0-WMU

Length: 36min 45sec (2205 seconds)

Published: Wed Dec 25 2019

Reddit Comments

[u/RCTommy]

For any naval history fans not familiar with Drach: subscribe to him now. You won't regret it.

[u/CautiousKerbal]

Drach got coal for his Christmas?

[u/OpanaPointer]

Last boilers I dealt with were made by Combustion Engineering. About thirty feet high.