Yarrow boilers is an important class of high-pressure water boilers. They are developed by Yarrow & amp; Co (London), Shipbuilders and Engineers and widely used in ships, especially battleships.
The Yarrow boiler design is a three-drum boiler characteristic: two straight edge water tubes arranged in a triangle row with a single stove between them. A single steam drum was installed at the top between them, with a smaller water drum at the base of each bank. Circulation, both up and down, takes place inside this same bank of tubes. The hallmark of Yarrow is the use of straight tubes as well as circulation in both directions that occur entirely inside the bank tube, rather than using external downcomers.
Video Yarrow boiler
Boiler watertube awal
The early use of water-tube boilers at the Royal Navy was controversial at times, resulting in the 'Battle of the Boilers' around 1900. The first boilers, such as Belleville and Niclausse, were large. tube design, with simple straight tube of about 4 "diameter, at shallow to horizontal angle.This tube is connected to the cast iron header and gives many problems with leakage at this connection.At that time, the assumption is that the thermal expansion in this straight tube is tense joints, these boilers are also large, and although fitted to many warships pre-warships, can not be fitted to small torpedo boats and destroyers early then under very active developments.
To provide a lighter boiler for smaller vessels, the type '' Express' is developed. It used smaller water tubes of about 2 "in diameter, giving a larger ratio of heating areas to volume (and weight).Most of this is a three-drum pattern, mainly from Du Temple and the Normand design.This gives more settings vertical of the water-tube, thereby prompting the circulation of the thermosyphon in this narrow tube.The previous problem of tube expansion is still a theoretical concern and the tube is either curved, or even convoluted into the hairpin and S shape, thus improving the heating.In practice these forms raises two more practical issues: difficulty in cleaning the tube and also the difficulty in forming a reliable connection into the water drum, especially where the tube enters the drum at various angles.
Maps Yarrow boiler
Yarrow tube water boiler
Alfred Yarrow developed his boiler in response to others who have developed water-tube boilers. This is a long process based on theoretical experiments rather than the evolution of practical boilers. The work began in 1877 and the first commercial boiler was not supplied until 10 years later, a torpedo ship in 1887.
Despite this long age, the origin of the boiler seems most direct. Yarrow's initial conversation with William Crush, head of the boiler department, was noted to have incorporated a rather straightforward approach and Yarrow's statement, "We have to get up about boiler tubes of water", "Why not boilers like this?" (putting his fingers together as if praying), and "Tube straight?" already stated two of the three basic design principles of the boiler.
Straight tube
The early water tube designers have been concerned with the expansion of the boiler tubes when heated. Efforts are made to enable them to expand freely, especially so that those closest to the furnace can expand relatively more than the farther away. Usually this is done by arranging the tubes in a large looping curve, such as for the Thornycroft boiler. It has difficulties in manufacturing and requires the support used.
Yarrow acknowledged that the temperature of tubes containing water held relatively low and consistent between them, provided they remained full of water and boiling was not allowed to occur inside the tube itself. High temperatures and variations only appear when the tube becomes filled vapor, which also disrupts circulation.
The conclusion is that a straight water tube is acceptable, and has a clear advantage for the manufacture and cleaning of the service.
Getting a tube that is able to withstand boiler pressure is getting harder and most of the makers are already having problems with welds in the tube. The benefit of the less obvious clear tubes is that they can use newly developed seamlessly developed tubes that are now manufactured for bicycle manufacturing.
Yarrow circulation experiment
It has been acknowledged that boilers of water tubes depend on a continuous flow through a water-tube, and this should be with a thermosyphon rather than a non-practical effect requiring a pump.
The hot water tube is a large number of small diameter tubes mounted between large drums: drum water below and a steam drum above it. The Fairbairn study has shown the importance of tube diameter and how small diameter tubes can easily withstand much higher pressures than large diameters. Drums can withstand pressure under strong construction. Manhole mounted on them allows regular internal inspection.
The assumption is that the flow through the water-tube will be upward, due to their heating by the furnace, and that a downward flow of offset will require unheated heat downcomers. In most water tube designs, these are some large-diameter external pipes from the steam drum to the water drum. This large diameter pipe is a problem for reliability due to its stiffness and strength.
Alfred Yarrow conducted a famous experiment in which he denied this assumption. The source is unclear whether he found this during the experiment, or experimented only to show the theory he has held.
A vertical U-shaped tube is arranged so that it can be heated by a series of Bunsen burners on each side. A simple flow meter shows the direction and approximate strength of any flow through the tank at the top connecting the two arms of U.
When only one side of U is heated, there is a flow of hot water that is expected upward in the arm of the tube.
When heat is also applied to unheated arms, conventional theory estimates that the flow of circulation will slow down or stop completely. In practice, the actual flow is increasing . As long as there is some asymmetry for heating, Yarrow's experiments show that circulation can continue and heating cooler downcomers can even increase this flow.
Yarrow then repeated the experiment, first with a U-tube at a shallow angle to the horizontal, eventually with the whole system under pressure. The result is the same and the circulation is maintained.
Thus, Yarrow boilers can issue separate external downcomers. The flow is entirely inside the heated watertubes, upward inside that is closest to the furnace and down through that is on the bank's outer row.
Description
Yarrow's production boilers have a simple and distinctive design that remains unchanged after that. Three drums are arranged in a triangular formation: a large single steam drum at the top and two smaller water drums below. They are connected by watertubes straight in a multi-row bank into each water drum.
The furnace is placed in the space between the bank of the tube. The initial boiler is manually fired coal, then fired oil. The boiler is enclosed in a sealed steel casing, lined with bricks. The final walls lined stones into this casing holds firedoor or quarls of burner oil, but lacks a heating surface. Uptake uptake from the boiler is at the top of the casing, the flue gas passing around the steam drum. To reduce corrosion of the flue gas above the drum, it is sometimes wrapped in a simple deflector sheath. Usually the bottom of the water drum is exposed outside the casing, but only the tip of the steam drum appears. The water level is about one-third the diameter of the steam drum, sufficient to cover the tip of the submerged tube.
The weight of the boiler is put on the drum of water, and thus on the support of the flat deck shooting. Steam drums are only supported by watertubes and allowed to move freely, with thermal expansion. If superheated, a superheater element is suspended from this drum. Compared to earlier Scotch boilers and locomotives, boiler water cylinders with reduced water volume are considered light and do not require extensive support.
Next evolution in design
Drum water
The first Yarrow water drum or "trough" is D-shaped with a flat tubeplate, thus providing easy installation for the tube. Tubeplate is bolted to a trough and can be dismantled for maintenance and cleaning of the tube.
This D shape is not ideal for drum pressure, because pressure will tend to turn it into a more circular part. The experience of boiler explosions has shown that the sharp internal angle inside the boiler is also susceptible to erosion by grooving.
Then the boiler uses a more rounded part, despite the difficulty of inserting and sealing the ends of the tubes when they are no longer perpendicular. These drums have a hole in the end for access.
Downcomers
Circulation in the Yarrow boiler depends on the temperature difference between the inner and outer tube lines of the bank, and especially at the boiling level. While this is easy to maintain at low strength, higher pressure Yarrow boilers will tend to have fewer temperature differences and thus will have less effective circulation. This effect can be neutralized by providing external downcomers, outside of the heated exhaust area.
Although most Yarrow boilers do not require downcomers, some are installed with them.
Double boiler ends
The first double-ended boiler was built in 1905 for the Spanish government. The design is appropriate to be fired from both ends and it is known that the double-ended boiler is slightly more efficient in its use.
Yarrow shipyard is always limited in the size of the ship that can be built. Many of their boilers are meant for larger warships and Yarrow supplies these as components to the building yard with a larger launch pad.
Superheaters
The early Yarrow boilers were not superheated, but with the introduction of steam turbines, there was a growing demand for steam temperatures.
Asymmetric boiler
Yarrow superheater consists of a hairpin tube, parallel to the existing steam generator tube. One generator tube bank is separated into two, with a bottom water drum each for them. The superheater is placed in the gap formed between this, with both ends of the tube connected to a single superheater header drum, and an internal baffle to separate the wet and dry vapors.
The secondary effect of the superheater is to increase the temperature difference between the inside and outside tubes of the bank, thus encouraging circulation. Two water drums are often associated with unheated downcomers, to allow this flow among the drums. This effect is then pushed in the Admiralty boiler, where the tubes of a bank are curled apart to leave room for the superheater, while maintaining a single water drum.
Controlled flow
Only one superheater has ever been installed, just on one side of the boiler. The simplest, and the smallest, boilers move their exhaust to this side, passing all the exhaust through the bank with a superheater. The now-asymmetric boiler can pass all its exhaust gases through the super-hot side as a single flow type. Other banks are still used for pure heating of radiation, often with fewer tube lines.
Alternatively, 'double flow' boilers retain full gas flow through both sides, although only one contains a superheater. A controlled baffle on the non-superheated side can be closed to increase flow through the superheater. These boilers usually incorporate additional feed water heaters in the updraught above this baffle.
Boiler three drum admiralty
The next development of Yarrow is the Admiralty three-drum boiler , developed for the Royal Navy among the wars.
It's widely similar to Yarrow's high-pressure and oil-fueled version. Waterdrum is cylinder and downcomers sometimes, but not always, used. The only big difference is in the tube bank. Instead of a straight tube, each of the tubes is mostly straight, but rotates toward the end. These are installed in two groups within the bank, so they form a gap between them inside the bank. Superheaters placed inside this gap. The advantage of putting a superheater here is that they increase the temperature difference between the inside and outside tubes of the bank, thus encouraging circulation.
Sea use
HMSÃ, Hornet (1893), Havock class destroyer. HMSÃ, Havock Ã, (1893), the main class ship, built with the current locomotive boiler shape, Hornet with Yarrow boilers for comparison.
The first Yarrow boiler is intended for small destroyers and fills the entire width of the hull. In the starting class, three boilers are used together, each with a separate funnel. The next set is reserved for capital boats using multiple boilers and these are often grouped into sets of three, share uptake.
Land-based boiler
In 1922, Harold Yarrow decided to exploit an increasing explosion for power generation as a market for Yarrows to build land-based boilers. The first boiler, at Dunston Power Station and Brighton, has the same ocean pattern. As for the success of their navy, they are recognized to have a large radiant heating area and to be quick to improve steam.
Large ground turbines require high efficiency and increased superheat, so the marine pattern is revised to a typical land-based Yarrow boiler. It becomes asymmetric. One wing is enlarged and receives most of the gas flow. The banks in the tube remain and receive radiant heat from the furnace, but the gas then flows through one of them, passes the superheater bank, then through the third additional bank to increase the extracted heat.
Working pressure also increased. From a working pressure of 575 psi in 1927, in 1929 an experimental boiler operated at 1,200 psi.
Engine 10000
Only one "Yarrow" boiler used in railroad locomotives, experimental machine Nigel Gresley 10000 in 1924 for LNER company. After observing the benefits of higher pressure and compound machines in marine practice, Gresley was interested in experimenting with this approach in railroad locomotives. As with ground-based boilers, Harold Yarrow is eager to expand the market for Yarrow boilers.
Boiler is not a regular Yarrow design. In operations, especially circulation paths, boilers have more in common with other three drum designs such as Woolnough. It has also been described as an evolution of the Brotan-Deffner tube water-tube, with an extended fire box to become an entire boiler.
References
Source of the article : Wikipedia
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