The Johnson design was developed by the British engineer J. Johnson in the late 1920s.[2] A patent was granted in 1931,[3] and one of these boilers was installed in the RMS Empress of Britain.[2] This was a time when water-tube boilers were being adopted in fast turbine ships, such as naval warships and passenger liners. There was also a shift to oil firing rather than coal burning. Oil had several advantages for a fast ship, particularly a warship that needed to combine both efficiency for long range with the ability to generate high power on demand when full speed was needed. Oil required fewer stokers, and a smaller crew required less space aboard given over to mess spaces. Refuelling was also quicker and cleaner with oil than with coal.[4]
The Johnson boiler was the first of the O-type boilers, a class of water-tube boilers characterised by single steam and water drums vertically above each other, with curved vertical water tubes to the sides forming an overall cylindrical volume. There is no grate at the base of this furnace space, so they are fired by liquid burners, rather than a solid fuel furnace producing ash.[4]
The large radiant heating area available allows a combustion rate, for a given furnace volume, of around twice that for a contemporary boiler, such as the Yarrow.[5] The end walls of the furnace may be either water walls with more tubes, or else simple firebrick. The small amount of brickwork for the Johnson design, without requiring a furnace base, was seen as an advantage by the Navy.[5]
The Royal Navy trialled a Johnson boiler in 1936, when the H-class destroyerHMS Hyperion was built with two Admiralty 3-drum boilers and a Johnson, rather than the three Admiralties used for the rest of the class.[5][6] This boiler had a water wall at the non-firing end. The initial design had poor circulation until external cold downcomers were added, increasing the weight by 10%.[5]
Babcock-Johnson boilersedit
RMS Windsor Castle, and her sister ship RMS Arundel Castle, were both four-funnelled liners refitted in 1937 with Babcock-Johnson boilers and only two funnels
The Babcock-Johnson is the developed form of the Johnson design, constructed by Babcock. The end walls of the furnace are tube-walled and there are large external downcomers.[7]
The boiler and its exhaust uptake is enclosed in an overall downward air duct, supplied through an air preheater in the exhaust stack.[7]
Early versions of this design used a thick tube nest, split into two layers and with the superheater placed as axially-parallel tubes between these.[7]
Later designs had thinner tube nests of only four rows of tubes, with the superheater placed in the uptake to the funnel. Working conditions would be '850/850', with a working pressure of 850 pounds per square inch (59 bar) and a steam temperature of 850 °F (454 °C).[7] The superheater would be placed in one side of the uptake, with a reheater between the high and low pressure turbines placed in the other.[7]
Fairfield-Johnson boilersedit
The Fairfield-Johnson boiler is a further development of the Babcock-Johnson type. The working pressure of the boiler is reduced from around 58 bar to 30 bar, but the steam temperature after the supheater remains the same at around 825 °F (441 °C).[8]
The engineering change for these boilers is to reduce the work done in the boiler's steam generating tubes, in favour of increased superheating. Radiant heating of the boiler tubes is the same, but there is less convective heat transfer, giving a higher superheater gas inlet temperature.[8]
Referencesedit
^Smith, Edgar C. (2013) [1937]. A Short History of Naval and Marine Engineering. Cambridge University Press. pp. 313–315. ISBN978-1107672932.
^US 1816780, "Water tube boiler", published 28 July 1931
^ abMilton, J. H. (2013) [1953]. "Chapter 4: Water Tube Boilers". Marine Steam Boilers (4th ed.). London: Newnes. pp. 150–153. ISBN978-1483102283.
^ abcdRippon, Commander P.M., RN (1998). The evolution of engineering in the Royal Navy. Vol. 1: 1827-1939. Spellmount. pp. 245–246. ISBN0-946771-55-3.{{cite book}}: CS1 maint: multiple names: authors list (link)
^. Grey Funnel Line. Archived from the original on 2016-04-25.
johnson, boiler, water, tube, boiler, used, ship, propulsion, johnson, design, developed, british, engineer, johnson, late, 1920s, patent, granted, 1931, these, boilers, installed, empress, britain, this, time, when, water, tube, boilers, were, being, adopted,. The Johnson boiler is a water tube boiler used for ship propulsion 1 The Johnson design was developed by the British engineer J Johnson in the late 1920s 2 A patent was granted in 1931 3 and one of these boilers was installed in the RMS Empress of Britain 2 This was a time when water tube boilers were being adopted in fast turbine ships such as naval warships and passenger liners There was also a shift to oil firing rather than coal burning Oil had several advantages for a fast ship particularly a warship that needed to combine both efficiency for long range with the ability to generate high power on demand when full speed was needed Oil required fewer stokers and a smaller crew required less space aboard given over to mess spaces Refuelling was also quicker and cleaner with oil than with coal 4 HMS Hyperion The Johnson boiler was the first of the O type boilers a class of water tube boilers characterised by single steam and water drums vertically above each other with curved vertical water tubes to the sides forming an overall cylindrical volume There is no grate at the base of this furnace space so they are fired by liquid burners rather than a solid fuel furnace producing ash 4 The large radiant heating area available allows a combustion rate for a given furnace volume of around twice that for a contemporary boiler such as the Yarrow 5 The end walls of the furnace may be either water walls with more tubes or else simple firebrick The small amount of brickwork for the Johnson design without requiring a furnace base was seen as an advantage by the Navy 5 The Royal Navy trialled a Johnson boiler in 1936 when the H class destroyer HMS Hyperion was built with two Admiralty 3 drum boilers and a Johnson rather than the three Admiralties used for the rest of the class 5 6 This boiler had a water wall at the non firing end The initial design had poor circulation until external cold downcomers were added increasing the weight by 10 5 Babcock Johnson boilers edit nbsp RMS Windsor Castle and her sister ship RMS Arundel Castle were both four funnelled liners refitted in 1937 with Babcock Johnson boilers and only two funnels The Babcock Johnson is the developed form of the Johnson design constructed by Babcock The end walls of the furnace are tube walled and there are large external downcomers 7 The boiler and its exhaust uptake is enclosed in an overall downward air duct supplied through an air preheater in the exhaust stack 7 Early versions of this design used a thick tube nest split into two layers and with the superheater placed as axially parallel tubes between these 7 Later designs had thinner tube nests of only four rows of tubes with the superheater placed in the uptake to the funnel Working conditions would be 850 850 with a working pressure of 850 pounds per square inch 59 bar and a steam temperature of 850 F 454 C 7 The superheater would be placed in one side of the uptake with a reheater between the high and low pressure turbines placed in the other 7 Fairfield Johnson boilers editThe Fairfield Johnson boiler is a further development of the Babcock Johnson type The working pressure of the boiler is reduced from around 58 bar to 30 bar but the steam temperature after the supheater remains the same at around 825 F 441 C 8 The engineering change for these boilers is to reduce the work done in the boiler s steam generating tubes in favour of increased superheating Radiant heating of the boiler tubes is the same but there is less convective heat transfer giving a higher superheater gas inlet temperature 8 References edit Smith Edgar C 2013 1937 A Short History of Naval and Marine Engineering Cambridge University Press pp 313 315 ISBN 978 1107672932 a b Smith 1937 p 313 US 1816780 Water tube boiler published 28 July 1931 a b Milton J H 2013 1953 Chapter 4 Water Tube Boilers Marine Steam Boilers 4th ed London Newnes pp 150 153 ISBN 978 1483102283 a b c d Rippon Commander P M RN 1998 The evolution of engineering in the Royal Navy Vol 1 1827 1939 Spellmount pp 245 246 ISBN 0 946771 55 3 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link G and H class Destroyers Grey Funnel Line Archived from the original on 2016 04 25 a b c d e Milton Marine Boilers pp 150 151 a b Milton Marine Boilers pp 152 153 Retrieved from https en wikipedia org w index php title Johnson boiler amp oldid 1208432796, wikipedia, wiki, book, books, library,
