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How Boilers Work


Quiz Questions

1.Boilers are pressure vessels designed to:
Heat water
Produce steam
All of the above
2. Boilers are classified into different types based on their working pressure and temperature, fuel type, draft method, size and capacity, and whether they condense the water vapor in the combustion gases. Boilers are also sometimes described by their key components, such as heat exchanger materials or tube design.
True
False
3.Two primary types of boilers include Firetube and Watertube boilers. In a Firetube boiler, hot gases of combustion flow through:
a series of tubes surrounded by water.
A series of tubes filled by water.
4.Alternatively, in a Watertube boiler, water flows in the inside of the tubes and the hot gases from combustion flow around the outside of the tubes.
True
False
5.Cast iron sectional boilers are advantageous because
they can be assembled on site, allowing them to be transported through doors and smaller openings.
They are made of cast iron
6.The main disadvantage of cast iron boilers is:
Because the sections are sealed together with gaskets, they are prone to leakage as the gasket age and are attacked by boiler treatment chemicals.
They are too heavy to move around.
7.Low-pressure boilers are limited to a maximum working pressure of _____ psig (pound-force per square inch gauge) for steam and _____ psig for hot water (2). Most boilers used in HVAC applications are low-pressure boilers.
15 psig    160 psig
50 psig    300 psig
8. High-pressure boilers are constructed to operate above the limits set for low-pressure boilers, and are typically used for power generation. Operating water temperatures for hot water boilers are limited to 250o F (2).
True
False
9.The pressure difference between the boiler combustion chamber and the flue (also called the exhaust stack) produces a draft which carries the combustion products through the boiler and up the flue. Natural draft boilers rely on the natural buoyancy of hot gasses to exhaust combustion products up the boiler flue and draw fresh air into the combustion chamber.
True
False
10.Which one the followings is/are considered key element of the Boiler.
burner,
combustion chamber,
heat exchanger,
exhaust stack,
controls.
All of the above
11.The combustion chamber, usually made of cast iron or steel, houses the burners and combustion process. Temperatures inside the combustion chamber can reach several hundred degrees very quickly.
True
False
12.Heat exchangers may be made from cast iron, steel tube bundles, or, in the case of some smaller boilers, copper or copper-clad steel.
True
False
13.Boiler safety is a key objective of the National Board of Boiler and Pressure Vessel Inspectors. This organization reports and tracks boiler safety and the number of incidents related to boilers and pressure vessels each year. Their work has found that the number one incident category resulting in injury was:
combustion chamber explosion
poor maintenance and operator error
14.Complete combustion results when a hydrocarbon fuel such as natural gas or oil burns and produces only carbon dioxide, water and heat. If there is insufficient oxygen and/or poor mixing of fuel and oxygen, then incomplete combustion will occur resulting in other products of combustion including carbon monoxide and unburned fuel.
True
False