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City of Omaha 3rd Grade N.A.P.E. Stationary Engineers Test
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City of Omaha 3rd Grade N.A.P.E. Stationary Engineers Test
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City of Omaha 3rd Grade N.A.P.E.Stationary Engineers Test
At what pressure is the use of cast iron fittings permitted? - ANS-15 psi or 250 degrees
F not to exceed either one
Could too much secondary air have a bad effect on the efficiency of a boiler? -
ANS-YES
Excess secondary air will not enter into the reaction, but will pass through the furnace
wasting heat out the stack
Define combustion - ANS-Combustion is a chemical combination of oxygen with the
combustible elements of fuel, such as carbon and hydrogen, and this results in the
production of heat.
Define flash point, ignition point, and pour point. - ANS-Flash point - the lowest
temperature at which vapors of a substance will make a flash of flame but not continue
to burn when exposed to open flame.
Ignition point - the lowest temperature at which vapors of a substance will ignite and
burn continuously when exposed to an open flame.
Pour point - the lowest temperature at which liquid will flow.
Define Perfect, Complete and Incomplete combustion. - ANS-Perfect - burning all the
fuel using only the theoretical amount of air
Complete - Burning all the fuel using more than the theoretical amount of air
Incomplete - when a portion of the fuel remains unburned because of insufficient
amounts of air
Define primary air, secondary air and excess air. Is secondary air necessary in a hand
fired boiler and why? - ANS-Primary air enters the furnace with the fuel and determines
the rate of combustion.
Secondary air creates a turbulence around the fuel to complete the burning process.
Excess air is more than what is theoretically needed to complete combustion.
Yes - Secondary air is introduced above the fuel bed to burn combustible gases.
, Define PSI, PSIG, and PSIA - ANS-PSI- pressure exerted on a surface
PSIG- pressure read on a gauge
PSIA- gauge reading plus atmosphere
Define purging and name two types. - ANS-Purging is the forced removal of
combustibles from the firebox.
Pre-purge is purging the firebox before the pilot is lit.
Post-purge is purging the firebox after the combustion cycle.
Describe a diagonal and a gusset stay. Where would each be used? - ANS-A diagonal
stay is made of a flat material similar to the boiler shell and is attached directly to the
boiler shell and head or tube sheet.
A gusset stay consists of boiler plate riveted to the shell and head or tube sheet by
means of angle iron. They are more rigid.
Both are used to brace right angle surfaces.
Describe a scotch marine boiler and how it is fired? - ANS-A scotch marine boiler is an
internally fired self contained horizontal return fire tube boiler. It is a cylindrical shell
containing the combustion chamber and tubes that are surrounded by water.
Describe a sectional Boiler. - ANS-The sectional headers are built up of vertical sections
or units. A sufficient number of sections are clamped together to form the desired size of
a boiler. These boilers can be erected in an existing building by carrying them in piece
by piece and clamping the pieces together. This boiler is also called a pork chop boiler.
Describe a through stay. Why are hollow stay bolts used on water legs? - ANS-A
through stay runs from one tube sheet to the other or one flat surface to another. A rod
threaded on both ends is held in place with nuts on the inside tightened against nuts on
the outside of the plates.
A small hole is drilled into the stay bolt so if it was to fail, it would develop a leak and be
detected at once.
Describe the circulation of water within the sterling boiler. - ANS-Feedwater enters the
top rear drum, passes down the rear tubes to the mud drum. Steam and boiler water go
up the front banks of tubes to the front and center drums. Circulator tubes allow the
boiler water to pass between drums. What does not go out as steam goes back down
the rear tubes.
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