Chapter 6 (Pages 165 thru 176)

What types of boilers use predominantly forced draft systems?

Low pressure boilers.

What is another means of controlling natural draft?

Controlling the temperature of the gases of combustion.

Draft system?

A boiler system that regulates the flow of air to and from the burner.

Manometer?

A device that measures draft by comparing pressures at two locations.

Damper?

A device used to create resistance in order to regulate the flow of air and gases of combustion in a boiler.

What is required for there to be a direction of flow?

A difference in pressure.

Breeching?

A duct used for the transport of gases of combustion from the boiler to the stack.

What phenomenon causes air or gases to flow and the direction of the flow?

Air or gases flow from a location with higher pressure to a location with lower pressure.

What is balanced draft?

Combination forced and induced draft, is mechanical draft from fans located before and after the boiler.

Natural draft?

Draft produced by the natural action resulting from temperature differences between air and gases of combustion.

Mechanical draft?

Draft produced using a mechanical device such as a fan or blower.

How is draft measurement expressed?

In inches of water column (in. WC.)

How is draft measured?

In inches or tenths of an inch of a vertical column of water using a draft gauge (manometer).

What is the benefit of mechanical draft systems?

It provides greater control of the combustion process.

Induced draft?

Mechanical draft from air pulled through the boiler furnace with fans located in the breeching.

Forced draft?

Mechanical draft from air pushed through the boiler with fans located in the front of the boiler furnace.

Stack condensation in conventional boilers?

Most likely to occur in heating boiler installations where light loads and intermittent firing case a cool stack condition.

What are the two types of draft?

Natural draft and Mechanical draft.

What determines the rate of combustion?

The amount of draft in the furnace.

What term (stack or chimney) is used when they are not used interchangeably?

Stack refers to a metal structure, and chimney refers to a brick structure.

Draft?

The flow of air or gases or combustion caused by a difference in pressure between two points.

What causes the amount of natural draft to increase?

The height of the chimney.

What is the relationship between combination draft systems and high pressure boilers?

They always use combination draft systems.

What is the relationship between the terms "stack" and "chimney?"

They are often used interchangeably.

What is the relationship between low pressure boilers and induced draft systems?

They occasionally use them.

When are different controls required for regulating draft?

When burning fuel oil, gas boilers or stokers.