Cast Iron Sectional And Modular Boilers

Front 1

How are cast-iron sectional boilers generally used?

Back 1

The cast-iron sectional boiler is generally used for steam and hot water heating systems in small and medium sized buildings.

Front 2

What is the basic construction of cast-iron boilers?

Back 2

The boiler is built up from a number of hollow, cast-iron sections which are connected to each other by means of push nipples in the upper and lower part of the sections. Water and steam can flow freely from one section to the other through the push nipples.

Front 3

What are the two possible arrangements?

Back 3

The sections are placed either side by side like slices in a loaf of bread (vertical) or stacked one above the other like pancakes (horizontal).

Front 4

Describe the foundation of Vertical Sectional Cast-Iron Boilers

Back 4

The sections are placed on a rigid supporting base that also contains the gas burners.

Front 5

How are the sections of Vertical Sectional Cast-Iron Boilers connected?

Back 5

Push nipples and tie rods

Front 6

What is the pathway of the combustion gases in Vertical Sectional Cast-Iron Boilers?

Back 6

The hot combustion gases travel upwards between the sections to the collector hood which guides the gases to the draft hood from where they rise into the uptake.

Front 7

Describe the covering of Vertical Sectional Cast-Iron Boilers

Back 7

The boiler is enclosed by an insulated sheet metal casing with removable panels to provide access.

Front 8

What is aimed for in determining the shape of Vertical Sectional Cast-Iron Boilers?

Back 8

The sections of cast-iron boilers come in a wide variety of shapes. However, all are designed to obtain maximum heat transfer from the hot gases to the heating surface. This is accomplished by exposing as large a surface as possible to the hot gases or by lengthening the time of contact between the gases and the heating surface.

Front 9

How do the front and rear section of Vertical Sectional Cast-Iron Boilers differ from the intermediate sections?

Back 9

The front and rear sections of cast-iron boilers differ in design from the intermediate sections since they are only fitted with push nipples on one side and have cleanout plugs on the side facing the outside of the boiler.

Front 10

How are flue gases prevented from escaping?

Back 10

To prevent the flue gases from escaping, the spaces between the sections are sealed with high temperature asbestos rope. Some boilers have cleanout slots between the sections; these openings are closed off during operation by covers that are also sealed with asbestos rope.

Front 11

Describe how flue gases travel in Horizonal Sectional Cast-Iron Boilers?

Back 11

The sections are stacked on top of each other and only one nipple connects two sections. The nipples are placed at alternate ends so that the water is forced to travel back and forth through the boiler from the bottom up. The hot gases travel upwards in a zigzag pattern through the gas passages in the sections.

Front 12

What is a disadvantage of using Cast-Iron Boilers?

Back 12

Cast-Iron boilers are limited in the maximum pressure they can endure.

Front 13

What are the advantages of using Cast-Iron Boilers?

Back 13

1. High resistance to corrosion

2. Ease of assembly

3. Choice of assembly location

4. Possibility of enlarging the boiler capacity

Front 14

What are two options for boiler capacity when a large load needs to be carried?

Back 14

1. To specify one or two large boilers able to carry the full load during the coldest weather.
2. To specify a number of small boilers to be operated in parallel with a total capacity matching the heating load.

Front 15

What are the advantages of using multiple boilers operating in parallel instead of a single large boiler?

Back 15

1. Should one boiler fail, the other boilers will be able to carry the full load except during extremely cold weather. A malfunction of the boiler in a single boiler plant shuts down the entire heating system.
2. Burners and controls for small capacity boilers are relatively simple and cheap.
3. The water content of a low capacity boiler is quite small. This makes the boiler far less destructive should a pressure part fail.
4. Less space is required for a number of small capacity boilers than for a single large boiler of equal total capacity.
5. Small boilers are relatively light; no strong foundation is required.
6. Most of the low capacity boilers can be moved through standard size doorways and can be installed or removed without any rigging.

Front 16

Describe the basic construction of Cast-Iron Modular Boilers

Back 16

A number of horizontal sectional cast-iron boilers have been integrated to form a single unit, the modular boiler. The boilers, or modules, are connected in parallel between the supply and return header of the hot water heating system and the flow through all modules is continuous. Each individual module has its own burner system and controls.

Front 17

How is the operation of the burner of each module controlled?

Back 17

The operation of the burner of each module is controlled by a step controller which starts or stops modules in sequence as load demand increases or decreases.