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This is the name given to an assembly of vane air swirler plates etc fitted within the boiler casing in association with each burner ,its functions is to divide air into primary and secondary streams and to direct them such as to give the correct air flow pattern. The air must pass through the air check to enter the register . In some cases the check can be formed by the swirl vanes themselves by rotating them about their axis, in other cases a sliding sleeve is used. The inner primary air flows until it reaches the tip plate ( stabiliser ) then spills over to form a series of vortices which reduces the forward velocity of the air. This retains the primary flame within the quarl . The outer , secondary air passes over the swirler vanes which causes the air to rotate thus assisting the mixing of air and fuel. The secondary air shapes the flame, short and fat for side fired, longer and thinner for roof fired. A small amount of cooling air is allowed to flow to the tip plate and atomiser tip. It is important that the air check forms a tight seal otherwise thermal shock can damage the quarls when the burner is not in use The front plate is usually insulated , the complexity of the air control is related to the TDR .The steam jet types have the steam providing additional energy for the mixture of air and fuel.

Related Terms

BOILER OPERATING PRESSURE

Depending upon the design of the boiler, the constant pressure maintained at the steam drum or the superheater outlet.

BOILER FULL POWER CAPACITY

The required number of pounds of steam generated per hour to develop contract shaft horsepower and maintain the specified pressures and temperatures in the plant, when divided by the number of installed boilers.

AIRFLOW TRANSMITTER

A diaphragm type airflow transmitter, used in the boiler combustion control system receives its high-pressure signal from the boiler windbox.

WATER COLUMN

A vertical tubular member connected at its top and bottom to the steam and water space respectively to a boiler, to which the water gage, gage valves, high and low water alarms and fuel cutoff may be connected.

TRY VALVE

One of three valves mounted on a boiler or water column within the visible range of the gauge glass and used to check the water level.

PORCUPINE BOILER

A boiler having dead end tubes projecting from a vertical shell.

PLATEN

1.A flat plate against which something rests or is pressed. 2. The rubber-covered roller of a typewriter against which paper is pressed when struck by the typebars. 2. A flat surface for exchanging heat in a boiler or heat exchanger which may have extended heat transfer surfaces.

OPERATING WATER LEVEL

The water level in a boiler drum which is normally maintained above the lowest safe level.

OPEN-CYCLE ENGINE

An engine in which the working fluid is discharged after one pass through boiler and engine.

ONCE-THROUGH BOILER

A boiler in which water flows, without recirculation, sequentially through the economizer, furnace wall, and evaporating and superheating tubes.

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