boilers types

8/3/2019 Boilers Types

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oiler Typese steam models utilize many different varieties of boilers ranging from the simple pot t

omotive type. Each boiler type can give excellent performance so long as it is operated with

sign envelope. Copper is the best material for small boilers. Brass should never be used

ler barrel, but is satisfactory for fittings.

ajor boiler types are discussed as follows:

ot Type

e pot boiler, show in Figure 2, is the simplest type and consists of a cylindrical copper tube

ayed end plates. The fire, which is typically from an alcohol burner, is applied to the extrface of the boiler. Its steaming ability can be significantly increased by the addition of a s

be and a stainless steel shield which encloses the burner and the lower portion of the boiler.

nfigured, the pot boiler can be a god steam generator in moderate temperatures and mild win

nk locomotives are good candidates for pot boilers since the tanks hide the fire shield. A su

n and blower are not needed for firing since there is no necessity for a forced draft. Pot b

ve large water capacity and simple to steam. However, pot boilers tend to discolor sinc

rner flame is in direct contact with the outer barrel surface. Either a wick or vaporizing type b

n be used.

ater Tube Type (Smithies)


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e water tube boiler was developed in the United Kingdom at the turn of the century by Mr.

mithies. It consist of a copper inner barrel with stayed end plates and water tubes at the ba

ttom, which extends from the front to the rear. This assembly slips into an outer casing wh

aped to resemble a locomotive boiler and firebox. There is an optimum sizing and arrangethe water tubes, which depends on the boiler's dimensions.

pically, the tubes should be greater than 5 mm in diameter and should be space so as to

enty of room for a flame path between them. Increasing the number of tubes may not increas

ler's ability to generate steam. If the flame path is restricted, the boiler cannot perform well

e draft cannot draw the flame forward toward the smoke box and increase flame temperature.

er surface of the outer casing is insulated with a ceramic sheet. It is important that the insu

es not obstruct the flame path near the throat plate.

operly designed Smithies boilers perform well in adverse weather conditions. If the boiler sh

n dry, the lack of draft will automatically extinguish the fire. A Smithies boiler is simple to build

erate, but it does require a suction fan and a blower since it is a forced draft system. The bi

advantage of the Smithies boiler is the limited water capacity of its inner barrel as compar

her boiler types with similar external dimensions.

ertical Type


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e vertical boiler is a simple type which consists of a firebox at the bottom and a copper barre

smoke tube. It typically is used to drive stationary engines and boats. Firing is accomplish

ohol or solid fuel pellets. More sophisticated versions of the vertical boiler contain many

bes and are sometimes fired by coal or charcoal. (Fig. 3)

enter Flue Type

e center flue boiler, show in Figure 4, has a large water capacity and a low center of gravity wakes it ideal for model boats. The center flue is surrounded by water and sometimes has seoss tubes to improve circulations. This type of boiler is usually fired by a gas burner, becausme is completely enclosed by the center flue. Therefore, the probability of an accidental fduced. It is necessary to maintain the proper water level in this type of boiler to avoid dame center flue. It offers good performance capabilities in adverse weather conditions.moke Tube Type


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e smoke tube boiler, show in Figure 5, consists of a copper barrel with stayed end platesveral curved smoke tubes extending from the front tube sheet to the rear bottom surface orrel. Its chief advantage is a greater water capacity than a comparable Smithies boiler,

aining good performance capability in adverse weather conditions. The sizing and numbbes is a function of the area of the smoke box tube plate. It is more expensive to build thamithies type and requires a suction fan and blower, since it is a forced draft system.ype C

e type C boiler, shown in Figurate 6, was developed by J. T. Van Riemsdijk. It consists

pper barrel with stayed end plates and several tubes running the length of the boiler. A stai

eel fire box with a duct is attached to the rear of the barrel. A multi-wick burner provides th

ich is drawn backwards by the draft, up through the duct and into the tubes. The inner surfae firebox and duct is lined with ceramic sheet. The outer surface of the duct can also be cov

h ceramic sheet to reduce cab temperatures.

e type C boiler has a good water capacity. It is easy to build and very strong. It requi

ction fan and blower since it is forced draft system. It has excellent performance capabilit


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verse weather conditions. Its name from the fact that it is the follows two other small scale b

veloped by Van Riemsdijk, the type A (center flue) and type B (smoke tube).

ixed Type (Smoke/Water Tubes)

e illustration above shows the Mixed Type of boiler developed by Dr. Seiichi Atonable. Iter tubes filled in the firebox of a locomotive type boiler in such as a way that the tubes a

ays. This configuration also increases the heating area and provides better water circulationplan locomotive type boiler. The Aster JNR D 51 and JNR 9600 utilize this type of boiler.ocomotive Type

e Locomotive type boiler, shown in Figure 8, consists of a copper barrel and an outer and

ebox attached to the rear of the barrel. Perfectly round pressure vessels carry pressure loa

veloping hoop tension stresses in the wall of the boiler. In this case, there is no tendency fo


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lls to bend. If a pressure vessel is not perfectly round, the walls will bend because the wal

nd attempting to form a perfect circle as it pressurizes. The results in a combined stress field

h stress levels. Since the firebox is not circular, it is necessary to provide additional stru

embers to strengthen non circular surfaces. This is the reason for stay bolts and structural b

the firebox assembly.

ermal stresses also occur as a result of thermal expansion, therefore a boiler must be design

rry both thermal and pressure loads. In a Belpaire type firebox, the outer wrapper and c

eet may be stiffened by beams or girder stayed to each other. Both side plates of the

ebox are cross stayed since they are flat. Flat surfaces on the back head and smoke box

ate can be stiffened or stayed. Sometimes a combination of both is used resulting in a very s

ler. If two or more stays are used, once can be hollow and used to route the blower line t

oke box. Tubes extend from the front tube plate in the smoke box to the rear tube plate, wh

ated at the front of the fire box.

is type of boiler can be fired by coal if grates are installed. Liquid fuel burners can als

mployed. The locomotive type boiler is the most difficult to build but is very efficient and allow

alism of a coal fire. It requires a suction fan and a blower, since it is a forced draft system

ter capacity may be less than a comparable type C boiler. The water level must be car

aintained so that the crown sheet is always covered, otherwise the boiler will be damaged.

addle Type


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e saddle type boiler, as shown in Figure 9, is used for the Aster Glaskasten. In order to provasonable running period, it was necessary to have a boiler with a minimum water capacity o Since space was limited, a unique boiler shape was required. The saddle type boiler consiarge diameter copper tube with end plates and a small cross tube. It uses features of the tyler as well as the Pot Type and Cross Water Tube Type. The inclined cross tube provides

tra water capacity and additional heating surface. They improve water circulation and also aays. The arc is filled a stainless steel firebox guiding the flame flow, so that the maximum heea is realized.

boilers types

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