A high pressure watertube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace. In smaller boilers, additional generating tubes are separate in the furnace, while larger utility boilers rely on the water-filled tubes that make up the walls of the furnace to generate steam. High Pressure Water Tube Boiler: The heated water rises into the steam drum. Here, saturated steam is drawn off the top of the drum. In some services, the steam will reenter the furnace through a superheater to become superheated. Superheated steam is defined as steam, heated above the boiling point at a given pressure. Superheated steam is a dry gas and therefore used to drive turbines, since water droplets can damage turbine blades. Cool water at the bottom of the steam drum returns to the feedwater drum via large-bore'downcomer tubes', where it pre-heats the feedwater supply.. To increase economy of the boiler, exhaust gases are used to pre-heat the air blown into the furnace and warm the feedwater supply.
Such watertube boilers in thermal power stations are called steam generating units. The older fire-tube boiler design, in which the water surrounds the heat source and gases from combustion pass through tubes within the water space, is a much weaker structure and is used for pressures above 2.4 MPa. A significant advantage of the watertube boiler is that there is less chance of a catastrophic failure: there is not a large volume of water in the boiler nor are there large mechanical elements subject to failure. A water tube boiler was patented by Blakey of England in 1766 and was made by Dallery of France in 1780. “The ability of watertube boilers to generate superheated steam makes these boilers attractive in applications that require dry, high-pressure, high-energy steam, including steam turbine power generation”. Owing to their superb working properties, the use of watertube boilers is preferred in the following major areas: Variety of process applications in industries Chemical processing divisions Pulp and Paper manufacturing plants Refining unitsBesides, they are employed in power generation plants where large quantities of steam having high pressures i.e. 16 megapascals and high temperatures reaching up to 550 °C are required.
For example, the Ivanpah solar-power station uses two Rentech Type-D watertube boilers. Modern boilers for power generation are entirely water-tube designs, owing to their ability to operate at higher pressures. Where process steam is required for heating or as a chemical component there is still a small niche for fire-tube boilers, their ability to work at higher pressures has led to marine boilers being entirely water-tube. This change began around 1900, traced the adoption of turbines for propulsion rather than reciprocating engines – although watertube boilers were used with reciprocating engines. There has been no significant adoption of water-tube boilers for railway locomotives. A handful of experimental designs were produced, but none of these were successful or led to their widespread use. Most water-tube railway locomotives in Europe, used the Schmidt system. Most were compounds, a few uniflows; the Norfolk and Western Railway's Jawn Henry was an exception, as it used a steam turbine combined with an electric transmission.
LMS 6399 FuryRebuilt after a fatal accidentLNER 10000 "Hush hush"Using a Yarrow boiler, rather than Schmidt. Never successful and re-boilered with a conventional boiler. A more successful adoption was the use of hybrid water-tube / fire-tube systems; as the hottest part of a locomotive boiler is the firebox, it was an effective design to use a water-tube design here and a conventional fire-tube boiler as an economiser in the usual position. One famous example of this was the USA Baldwin 4-10-2 No. 60000, built in 1926. Operating as a compound at a boiler pressure of 2,400 kilopascals it covered over 160,000 kilometres successfully. After a year though, it became clear that any economies were overwhelmed by the extra costs and it was retired to become a stationary plant. A series of twelve experimental locomotives were constructed at the Baltimore and Ohio Railroad's Mt. Clare shops under the supervision of George H. Emerson, but none of them was replicated in any numbers; the only railway use of water-tube boilers in any numbers was the Brotan boiler, invented in Austria in 1902 by Johann Brotan and found in rare examples throughout Europe.
Hungary, was a keen user and had around 1,000 of them. Like the Baldwin, this combined a water-tube firebox with a fire-tube barrel; the original characteristic of the Brotan was a long steam drum running above the main barrel, making it resemble a Flaman boiler in appearance. While the traction engine was built using its locomotive boiler as its frame, other types of steam road vehicles such as lorries and cars have used a wide range of different boiler types. Road transport pioneers Goldsworthy Gurney and Walter Hancock both used water-tube boilers in their steam carriages around 1830. Most undertype wagons used water-tube boilers. Many manufacturers used variants of the vertical cross-tube boiler, including Atkinson, Clayton and Sentinel. Other types include the Clarkson'thimble tube' and the Foden O-type wagon's pistol-shaped boiler. Steam fire-engine makers such as Merryweather used water-tube boilers for their rapid
Leyland Motors Limited was a British vehicle manufacturer of lorries and trolleybuses. The company diversified into car manufacturing with its acquisitions of Triumph and Rover in 1960 and 1967, respectively, it gave its name to the British Leyland Motor Corporation, formed when it merged with British Motor Holdings in 1968, to become British Leyland after being nationalised. British Leyland changed its name to BL in 1986 to Rover Group. Although the various car manufacturing businesses were divested or went defunct due to the troubled existence of BL and its successors, the original Leyland Trucks business still exists as a subsidiary of Paccar. Leyland Motors has a long history dating from 1896, when the Sumner and Spurrier families founded the Lancashire Steam Motor Company in the town of Leyland in North West England, their first products included steam powered lawn mowers. The company's first vehicle was a 1.5-ton-capacity steam powered van. This was followed by a number of undertype steam wagons using a vertical fire-tube boiler.
By 1905 they had begun to build petrol-engined wagons. The Lancashire Steam Motor Company was renamed Leyland Motors in 1907 when it took over Coulthards of Preston, making steam wagons since 1897, they built a second factory in the neighbouring town of Chorley which still remains today as the headquarters of the Lex Autolease and parts company. In 1920, Leyland Motors produced the Leyland Eight luxury touring car, a development of, driven by J. G. Parry-Thomas at Brooklands. Parry-Thomas was killed in an attempt on the land speed record when the car overturned. Rumours that a chain drive broke were found to be incorrect when the car was disinterred late in the 20th century as the chains were intact. At the other extreme, they produced the Trojan Utility Car in the Kingston upon Thames factory at Ham from 1922 to 1928. Three generations of Spurriers controlled Leyland Motors from its foundation until the retirement of Henry Spurrier in 1964. Spurrier inherited control of Leyland Motors from his father in 1942, guided its growth during the postwar years.
Whilst the Spurrier family were in control the company enjoyed excellent labour relations—reputedly never losing a day's production through industrial action. During World War II, Leyland Motors, along with most vehicle manufacturers, was involved in war production. Leyland built the Cromwell tank at its works from 1943 as well as medium/large trucks such as the Hippo and Retriever. After the war, Leyland Motors continued military manufacture with the Centurion tank. In 1946, AEC and Leyland Motors form British United Traction to build trolleybuses. In 1955, through an equity agreement, manufacture of commercial vehicles under licence from Leyland Motors commenced in Madras, India at the new Ashok factory; the products were branded as Ashok Leyland. On the other hand, Leyland Motors acquired other companies in the post war years: 1951: Albion Motors 1953: Collaboration with Danish Automobile Building, a bus manufacturer with a majority stake in the 1970s 1955: Scammell—military and specialist lorry manufacturer 1961: Standard Triumph, cars and some agricultural machinery interests Donald Stokes Sales Director, was appointed managing director of Leyland Motors Limited in September 1962.
A Leyland student apprentice he had grown up with the company. He became chairman in 1966. In 1968 Leyland Motors merged with British Motor Holdings to form the British Leyland Motor Corporation. BMH, the product of an earlier merger between the British Motor Corporation, the Pressed Steel Company and Jaguar, brought with it into the new organisation more famous British goods vehicle and bus and coach marques, including Daimler, Guy, BMC, Austin and Morris. Leyland diesel engines were used in Finnish Vanaja lorries and buses in 1960s. Chronologically, the growth of Leyland Motor Corporation was as follows: 1962: Leyland Motors aquires Associated Commercial Vehicles, which incorporated AEC, Park Royal Vehicles and Charles H Roe. 1962 a new group holding company was incorporated to own Leyland Motors Limited, ACV and new acquisitions 1965: Minority interests in Bristol Commercial Vehicles and Eastern Coach Works 1966: Rover cars and their Subsidiary, aero-engine and armoured fighting vehicle manufacturers Alvis 1967: Aveling-Barford was acquired This company made road rollers and dumper trucks.
The BLMC group was difficult to manage because of the many companies under its control making similar products. This, other reasons, led to financial difficulties and in December 1974 British Leyland had to receive a guarantee from the British government. In 1975, after the publication of the Ryder Report and the company's bankruptcy, BLMC was nationalised as British Leyland and split into four divisions with the bus and truck production becoming the Leyland Truck & Bus division within the Land Rover Leyland Group; this division was split into Leyland Bus and Leyland Trucks in 1981. Leyland Trucks depended on British sales as well as export markets Commonwealth and ex-Commonwealth markets; the early 1980s were hard, with export sales drying up in many places such as oil-dependent Nigeria. In 1986, BL changed its name to Rover Group; the equity stake in Ashok Leyland was controlled by Land Rover Leyland International Holdings, sold in 1987. At this point, while building about 10,000 trucks per annum, Leyland was more and more depending on outside engines as production of their own 98-series was declining.
The 1986 closure of Bedford's he
A pistol boiler is a design of steam boiler used in light steam tractors and overtype steam wagons. It is noted for the unusual shape of the firebox, a circular design intended to be self-supporting without the use of firebox stays; the name "pistol boiler" derives from the smooth curve of the outer firebox flowing into the boiler barrel, a supposed resemblance to the stock of an early 19th-century pistol. The locomotive boiler had become well established since Stephenson's day. If the top crown sheet of the inner firebox was made flat, so as to maintain a constant water depth above it, this required complex and expensive girder stays to support it; these stays were a safety-critical part of the boiler and many past boiler explosions had been caused by their failure. This was so for boilers that were to be used at all carelessly, or by crews who were less skilled or well-trained; the market for small steam traction engines could make use of a novel boiler design that avoided these problems. Following the lead of the London & Birmingham Railway's Bury locomotives, some small portable engines were using cylindrical stayless fireboxes.
These combined a cylindrical vertical drum with a domed top, both shapes that could support themselves well under pressure. In extreme cases for larger railway locomotives, these became the massive brass-clad'Haycock' fireboxes that were so distinctive on early Great Western Railway locomotives; the firm of Robey & Co. well-known builders of both large stationary engines and small steam tractors, developed its own version of this stayless domed firebox as the pistol boiler. As the boiler was small, with a barrel diameter of only 2', it was practical to form the curved plates for the inner and outer firebox with a hydraulic press; the inner firebox was formed in one piece as a truncated cone with a domed top. Although a small boiler, this gave a large grate area; the front face of this cone was flattened inwards. 54 1½inch fire-tubes were used. The boiler barrel was cylindrical, but the lower part of the rear end was cut on a diagonal, rather than straight across; the lower part of the outer firebox was conical and wrapped over this diagonal edge.
The foundation ring was circular. The upper corner of the outer firebox was a separate plate a quarter of a sphere. Rather than the time-consuming and costly flanging of flat plates, these curved plates could be pressed and riveted together immediately; the number of boiler plates was reduced, from the usual eight to only five. A high working pressure of 250 psi could be used; the firebox door was of novel design. As the backplate sloped so steeply, the door was top-hinged and opened inwards, rather than outwards; this had the effect of acting as a deflector plate, directing the cold draught down onto the firebed, rather than directly across and into the tubes. Robey used this design of boiler on their 6-ton steam wagons and'Express' steam tractors their tandem steam rollers. One of these rollers was the first artefact to be preserved by the Robey Trust; when the boiler was re-barreled in 1988, this was the last boiler to be constructed by the Robey factory before closure. On their larger engines, Robey used a conventional boiler.
A similar pistol boiler was used by Foden in their'O-type' Speed Six and Speed Twelve steam wagons. They were used by Ransomes for their overtype steam wagons in the 1920s; the firm of Garrett sought a reliable stayless firebox for their smaller boilers at around the same time in the 1920s. Their solution was more conventional: a conventional outer firebox enclosed an inner firebox, where the inner crown sheet was formed into a curved valley. For a small firebox, this acted as a girder stay between the end sheets of the firebox and was sufficient to be self-supporting; the portable engines used this pattern alone. For the more powerful road tractor boilers, the inner firebox was still self-supporting but the outer wrapper now required crosswise sling stays to support it, where it would have been supported by the stays to the inner firebox. "Robey steam wagon, 42657". Steam Scenes. 30 May 2010. "Side view of Robey Tandem Road Roller, 41593". Steam Scenes. 24 Jul 2003
A fire-tube boiler is a type of boiler in which hot gases pass from a fire through one or more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and creating steam; the fire-tube boiler developed as the third of the four major historical types of boilers: low-pressure tank or "haystack" boilers, flued boilers with one or two large flues, fire-tube boilers with many small tubes, high-pressure water-tube boilers. Their advantage over flued boilers with a single large flue is that the many small tubes offer far greater heating surface area for the same overall boiler volume; the general construction is as a tank of water penetrated by tubes that carry the hot flue gases from the fire. The tank is cylindrical for the most part—being the strongest practical shape for a pressurized container—and this cylindrical tank may be either horizontal or vertical; this type of boiler was used on all steam locomotives in the horizontal "locomotive" form.
This has a cylindrical barrel containing the fire tubes, but has an extension at one end to house the "firebox". This firebox has an open base to provide a large grate area and extends beyond the cylindrical barrel to form a rectangular or tapered enclosure; the horizontal fire-tube boiler is typical of marine applications, using the Scotch boiler. Vertical boilers have been built of the multiple fire-tube type, although these are comparatively rare. In the locomotive-type boiler, fuel is burnt in a firebox to produce hot combustion gases; the firebox is surrounded by a cooling jacket of water connected to the long, cylindrical boiler shell. The hot gases are directed along a series of fire tubes, or flues, that penetrate the boiler and heat the water thereby generating saturated steam; the steam rises to the highest point of the steam dome, where it is collected. The dome is the site of the regulator. In the locomotive boiler, the saturated steam is often passed into a superheater, back through the larger flues at the top of the boiler, to dry the steam and heat it to superheated steam.
The superheated steam is directed to the steam engine's cylinders or rarely to a turbine to produce mechanical work. Exhaust gases are fed out through a chimney, may be used to pre-heat the feed water to increase the efficiency of the boiler. Draught for firetube boilers in marine applications, is provided by a tall smokestack. In all steam locomotives since Stephenson's Rocket, additional draught is supplied by directing exhaust steam from the cylinders into the smokestack through a blastpipe, to provide a partial vacuum. Modern industrial boilers use fans to provide induced draughting of the boiler. Another major advance in the Rocket was large numbers of small-diameter firetubes instead of a single large flue; this increased the surface area for heat transfer, allowing steam to be produced at a much higher rate. Without this, steam locomotives could never have developed as powerful prime movers. For more details on the related ancestor type, see Flued boilers; the earliest form of fire-tube boiler was Richard Trevithick's "high-pressure" Cornish boiler.
This is a long horizontal cylinder with a single large flue containing the fire. The fire itself was on an iron grating placed across this flue, with a shallow ashpan beneath to collect the non-combustible residue. Although considered as low-pressure today, the use of a cylindrical boiler shell permitted a higher pressure than the earlier "haystack" boilers of Newcomen's day; as the furnace relied on natural draught, a tall chimney was required at the far end of the flue to encourage a good supply of air to the fire. For efficiency, the boiler was encased beneath by a brick-built chamber. Flue gases were routed through this, outside the iron boiler shell, after passing through the fire-tube and so to a chimney, now placed at the front face of the boiler; the Lancashire boiler has two large flues containing the fires. It was the invention of William Fairbairn in 1844, from a theoretical consideration of the thermodynamics of more efficient boilers that led him to increase the furnace grate area relative to the volume of water.
Developments added Galloway tubes, crosswise water tubes across the flue, thus increasing the heated surface area. As these are short tubes of large diameter and the boiler continues to use a low pressure, this is still not considered to be a water-tube boiler; the tubes are tapered to make their installation through the flue easier. The Scotch marine boiler differs from its predecessors in using a large number of small-diameter tubes; this gives a far greater heating surface area for the weight. The furnace remains a single large-diameter tube with the many small tubes arranged above it, they are connected together through a combustion chamber – an enclosed volume contained within the boiler shell – so that the flow of flue gas through the firetubes is from back to front. An enclosed smokebox covering the front of these tubes funnel. Typical Scotch boilers had a pair of furnaces, larger ones had three. Above this size, such as for large steam ships, it was more usual to install multiple boilers.
A locomotive boiler has three main components: a double-walled firebox.
A vertical boiler is a type of fire-tube or water-tube boiler where the boiler barrel is oriented vertically instead of the more common horizontal orientation. Vertical boilers were used for a variety of steam-powered vehicles and other mobile machines, including early steam locomotives. Many different tube arrangements have been used. Examples include: Fire tubesVertical fire-tube boiler Vertical boiler with horizontal fire-tubesWater tubesVertical cross-tube boiler Field-tube boiler Thimble tube boiler Spiral watertube boiler The main advantages of a vertical boiler are: Small footprint – where width and length constraints are critical, use of a vertical boiler permits design of a smaller machine. Water-level tolerance – The water level in a horizontal boiler must be maintained above the crown of the firebox at all times, or the crownplate could overheat and buckle, causing a boiler explosion. For a vehicle application expected to traverse hills, such as a railway locomotive or steam wagon, maintaining the correct water level when the vehicle itself is not level is a skilled task, one that occupies much of the fireman's time.
In a vertical boiler, the water is all sitting on the top of the firebox, the boiler would need to be low on water before a gradient could cause a risk by uncovering the firebox top. Simpler maintenance – A vertical boiler is mounted on a frame on the vehicle, allowing easy replacement. Horizontal boilers, such as those on railway locomotives and traction engines, form an integral part of the vehicle – the vehicle is built around the boiler – and hence replacement requires the dismantling of the entire vehicle; the main disadvantages of a vertical boiler are: Size – The benefits of a small footprint are compromised by the much greater height required. The presence of over-bridges limits the height of steam vehicles, this in turn restricts the size of the boiler. Grate area – This is limited to the footprint of the boiler, thus restricting the amount of steam that may be produced. Short tubes – Boiler tubes must be kept short to minimise height; as a result, much of the available heat is lost through the chimney, as it has too little time to heat the tubes.
Sediment – Sediment may settle on the bottom tube sheet insulating the water from the heat and allowing the sheet to burn out. Several manufacturers produced a significant number of vertical boiler locomotives. Notable amongst these were: Alexander Chaplin & Co. of Glasgow, who produced a range of steam-powered industrial products which included steam cranes, locomotives and winding engines, ship's deck engines and sea water distilling apparatus. Between 1860 and 1899, it delivered 135 vertical boiler locomotives similar to the East London Harbour 0-4-0VB to customers around the world. De Winton of Caernarfon, who produced at least 34 narrow gauge locomotives for use in the slate quarries of Wales. Sentinel Waggon Works of Shrewsbury, who produced a large number of shunters using their high-pressure vertical boilers; these were used on industrial railways in Britain. Société anonyme John Cockerill produced 891 standard gauge shunting locomotives between 1867 and 1942 using a standard design with five sizes.
The Sentinel Waggon Works produced a range of road lorries based on their high-pressure vertical boilers The Best Manufacturing Company of San Leandro in California produced a range of steam tractors that used vertical boilers. Certain designs of steam roller departed from the conventional traction engine style of a horizontal boiler with an engine mounted above. Vertical-boilered rollers were built around a substantial girder frame chassis, with the boiler being mounted low down between the front and rear rolls; such designs were not common in the UK. The traditional form of steam donkey married a vertical boiler with a steam engine on a rigid base fitted with skids for mobility. Since the ground to be traversed would be rough and level, the water-level -tolerant design of the vertical boiler was an obvious choice. Construction equipment such as steam cranes and steam shovels used vertical boilers to good effect. On a rotating base, the weight of the boiler would help to counterbalance the load suspended from the shovel bucket or crane jib, mounted on the opposite side of the pivot from the boiler.
The compact boiler footprint permitted smaller designs than would have been the case for a horizontal type, thus allowing use on smaller worksites. Some steam boats smaller types such as river launches, were designed around a vertical boiler; the small footprint of the boiler permitting smaller, more space-efficient designs, with less of the usable vessel being occupied by the means of propulsion rather than the payload. Vertical types such as the Cochran boiler provided useful, small footprint, package solutions for many stationary applications, including process and space heating. Rowland A. S. Abbott. Vertical Boiler Locomotives. Oakwood Press. ISBN 0-85361-385-0. Ian Allan ABC of British Railways Locomotives. Ian Allan. 1948
A boiler stay is an internal structural element used inside boilers. Where the shell of a boiler or other pressure vessel is made of cylindrical or spherical elements, the internal pressure will be contained without distortion. However, flat surfaces of any significant size will distort under pressure. Stays of various types are used to support these surfaces by tying them together to resist pressure; some boiler configurations require a great deal of staying. A large locomotive boiler may require several thousand stays to support the firebox. In water tube boilers, stays were sometimes used between their main chambers, could themselves be water tubes. A cylindrical firebox may be self-supporting without stays because of its shape
The Sentinel boiler was a design of vertical boiler, fitted to the numerous steam waggons built by the Sentinel Waggon Works. The boiler was designed for use in a steam wagon: it was compact, easy to handle whilst driving, its maintenance features recognised the problems of poor feedwater quality and the need for it to be maintained by a small operator, rather than a major locomotive works. Although this design was used in most of Sentinel's products, they produced larger boilers of quite different types for their railway locomotives. Sentinel boilers are vertical, as was common for many designs of steam wagon, so as to reduce the effects of tilting due to hill climbing or uneven roads disturbing the water level, it provides a compact boiler that leaves adequate space in the cab for the crew and coal bunker, whilst leaving as much as possible of the wagon's overall length available for the useful load. The boiler is a watertube boiler, with these tubes contained within a vertical, cylindrical outer drum.
This drum is double-walled and forms a water jacket around the boiler, with a large vertical flue within. The inner flue has a complex cross section, it is stepped in three diameters. The central region is square in section, rather than round; the main heating surface is provided by water-tubes in this squared section. These tubes are short and pass between the flat faces of the squared section in a grid pattern. There are eight layers of four banks of six each way. A space is left in the centre of the water-tube banks for the firing chute; the firebox is top-fired through this chute and there is no side firedoor. The lower part of the water-jacketed barrel surrounds the firebox; the narrow waterspace here encourages rapid steam raising. Firing is simple, with a thick fire relative to its area and fuel poured down. Beneath the grate is a water-filled ashpan, to prevent hot embers falling onto the road. Draught is controlled by a damper in the side between the grate and the water tray. Above the tube nest the water space widens to form an increased reservoir, protecting against tilting.
Sentinel's drawings permitted a hill climb gradient of 1 in 6. Modern regulations for buses require a safe tilt of 35°; the narrowed flue in this area is used, where fitted. An unusual feature of the Sentinel boiler was the "exhaust drying box", a small reheater, in the upper part of the boiler flue before the blastpipe nozzle; this heated the exhaust steam to avoid it condensing into a visible white plume. It was a requirement of the Highways and Locomotives Act 1878 that engines should "consume their own smoke". By the nature of their use, steam wagons were required to use feedwater, either dirty or contaminated with dissolved minerals. Untreated, this builds up boiler scale on the tubes and deposits sludge in the lower parts of the boiler. Both of these disturb circulation and risk local overheating and damage, scale reduces boiler efficiency and wastes fuel; the Sentinel boiler was designed to cope with these problems, to permit easy cleaning of the waterspace. As well as the usual blow-down cock for daily use, the entire boiler could be dismantled easily.
The outer shell was in two sections and outer drum, were joined by a bolted ring joint at top and bottom. Regular servicing was to separate the water-tubes in their drum from the boiler outer shell, so that they could be cleaned. Sludge dropped free on opening the shell and the short, straight tubes could be cleaned with brush or scraper. Several other vertical boilers, such as the Straker, had similar arrangements for lifting their shells off the tube nest; the Sentinel though instead dropped the tube nest downwards. This had the advantages that it required simpler lifting gear: the waggon would be raised on ramps or over a pit, the bolts removed and the tube bank lowered with a block and tackle from a fixed beam, without requiring a mobile crane that could lift it and move it sideways. Secondly the many pipe connections to the outer shell were left undisturbed, making the operation quicker. Dropping the firebox was not required at every washout and was recommended at intervals of 2 to 12 months, depending on water quality.
Sentinel's best-known flue design was the square-section, but at one time they used a circular corrugated design, with the water-tubes arranged in a spiral. Manufacture of these was sub-contracted to the well-known boilermakers Galloway of Manchester; when Galloway closed in 1932, Sentinel switched back to their square pattern. The boiler was used from the earliest to the last, it was used for their steam tractors and other vehicles. Mann's of Leeds used a derivation of the Sentinel boiler in their "Express" wagon, launched in 1924; this particular boiler design was not used for Sentinel's railway locomotives. Narrow-gauge locomotives used it. LNER Class Y1 LNER railmotorsTheir larger locomotives used a range of boiler designs, but all with water-tubes. Straker boilera direct precursor of the SentinelRobertson boilera comparable fire-tube design Sentinel-Doble boilerSentinel recruited the American steam car developer Abner Doble to develop an advanced monotube boiler for them. Woolnough boilera three-drum water-tube boiler used for their larger locomotives.locomotive boilerused on the handful of overtype steam waggons built by Sentinel