Glossary of Boiler Terms

Question 1

Attended boiler

Answer 1

A boiler that is only operated when a qualified operator is present to watch over and control the various boiler functions.

Question 2

Baffle

Answer 2

A wall, barrier, or panel used to change the direction of flow of a liquid or a gas.

Question 3

Blowoff / Blowdown valve

Answer 3

Valves locate on a line leading from the lowest part of the water side of a boiler

Question 4

Boiler failure

Answer 4

A ruptured tube or crack which allows high pressure steam or water to escape.

Question 5

Boiler rating:

Answer 5

The heating capacity of a boiler expressed in boiler horsepower, Btu/ hour, or pounds of steam/hour.

Question 6

Burner

Answer 6

A device for the introduction of fuel and air into a furnace at the desired velocities, turbulence and concentration.

Question 7

Check valve

Answer 7

A valve that has a hinged disk that is allowed to swing freely back and forth when pushed and allows one way flow only.

Question 8

Chimney

Answer 8

A brick, metal or concrete stack.

Question 9

Combustion chamber

Answer 9

An area of the boiler where air and fuel combine in a chain reaction to cause sustained burning.

Question 10

Combustion gases or flue gasses

Answer 10

The hot gaseous products from burning

Question 11

Dry steam

Answer 11

Steam containing less than 0.5% moisture.

Question 12

Drum

Answer 12

The boiler shell together with the heads which contains the fluid being heated. This term is used more often for watertube boilers.

Question 13

Efficiency

Answer 13

The ratio of output energy (steam heat) to input energy (fuel).

Question 14

Externally fired boiler

Answer 14

A boiler that has a furnace located outside of the boiler space, usually in brickwork.

Question 15

Feedwater

Answer 15

The water that is fed into a steam boiler to replace water which has been converted to steam and drawn off from the boiler.

Question 16

Firetube boiler

Answer 16

A boiler consisting of a drum containing straight tubes through which the hot combustion gases from the fire travel. Water in the drum surrounds the tubes and the heat from the hot gases passes through the tube walls to the water.

Question 17

Fitting

Answer 17

Any valve, gauge, regulating or controlling device, flange, or other attachment on the boiler.

Question 18

Flue gas

Answer 18

The gaseous product of combustion.

Question 19

Generally supervised boiler

Answer 19

A boiler that can operate without continual control by an operator.

Question 20

Handhole

Answer 20

Small, hand sized inspection, cleaning and maintenance port leading from the outside into the pressured area of the boiler which is covered during operation.

Question 21

Heating surface

Answer 21

Consists of all parts of the boiler through which heat from the burning fuel is transferred to the water side of the boiler. It includes all parts of the boiler plates and tubes which have water or steam on one side and fire or hot combustion gases on the other side.

Question 22

High pressure steam boiler (power boiler)

Answer 22

A boiler that operates at pressures above 103 kPa

Question 23

Horizontal Return Tubular (HRT) boiler

Answer 23

A firetube boiler usually supported in a brick combustion chamber. The hot gases from combustion sweep along the underside of the shell then return through the fire tubes to the chimney connection.

Question 24

Hot water boiler

Answer 24

A closed vessel completely filled with water to which heat is added to raise the temperature of the water. No steam is generated.

Question 25

Internally fired boiler

Answer 25

A boiler that has the combustion chamber located within the shell of the boiler, or the furnace is surrounded by water tubes.

Question 26

Low pressure steam boiler

Answer 26

A boiler that operates as a pressure under 103 kPa

Question 27

Manhole

Answer 27

An opening or hatch through which a person may enter into the shell or drum of a boiler.

Question 28

Operating pressure

Answer 28

The pressure at which a boiler is operated.

Question 29

Oxidization

Answer 29

Chemical combination with oxygen

Question 30

Packaged boiler

Answer 30

A boiler supplied by the manufacturer completely equipped and mounted on its own base.

Question 31

Port

Answer 31

An opening though which fluid passes.

Question 32

Pressure vessel

Answer 32

A closed vessel or container designed to hold a fluid at a pressure above atmospheric.

Question 33

Rupture disk

Answer 33

A safety device that acts like a safety valve to protect against excessive pressure buildup in a system. This disk ruptures when its maximum rated pressure is reached and must be replaced each time it activates.

Question 34

Safety valve

Answer 34

This fitting prevents the pressure within a steam boiler from exceeding safe units. It will pop open when the pressure inside the boiler reaches a certain point, until it is reduced to a lower preset pressure, then it will close.

Question 35

Setting

Answer 35

The brickwork used to support a boiler and the combustion chamber.

Question 36

Shell

Answer 36

The cylindrical portion of a pressure vessel.

Question 37

Smoke

Answer 37

Small gas borne particles of carbon or soot, less than 1 micron in size, resulting from incomplete combustion of carbonaceous materials and of sufficient number to be observable.

Question 38

Soot blower

Answer 38

A device used to blow accumulated soot (unburned carbon particles) off tubes and heating surfaces in a boiler.

Question 39

Stack

Answer 39

The hollow duct through which combustion gases are elevated for discharge to the atmosphere.

Question 40

Steam

Answer 40

The vapor phase of water, unmixed with other gases.

Question 41

Steam boiler

Answer 41

A closed container partially filled with water that is evaporated to steam under pressure by the application of heat.

Question 42

Vertical tubular boiler

Answer 42

A small sized firetube boiler with vertical firetubes.

Question 43

Water column

Answer 43

Water in a gauge (sight) glass to give visual indication of the water level.

Question 44

Water line

Answer 44

The actual level of water in a boiler. This is the point at which water and steam are separate.

Question 45

Watertube boiler

Answer 45

A boiler consisting of drums and headers that circulate water through tubes which are heated by fire and the products of combustion. The heat from the fire is transmitted through the tubes to the water.

Question 46

Steam wetness

Answer 46

Percentage of water (droplets) in steam.

Question 47

Windbox

Answer 47

The box surrounding the burner damper on a boiler. The fan blows combustion air into this box and the damper regulates and directs the air into the burners.