Exam Prep Pt 2 Flashcards
When a discharge valve Is
opened to the atmosphere, the pressure on the upstream side of
the valve will:
decrease, and the pressure on the
downstream side will remain the same.
When comparing a globe valve
and a gate valve in the same
application, the gate valve has a
________pressure drop when
fully opened and is the
_________choice for throttling.
lower: poorer
Which of the following is not a
function of a non-return valve?
opens automatically if the boiler operating pressure drops below the header pressure
Which one of the following
statements is the generally
accepted method to verify at the
local level that a manual valve is
fully closed on a static piping system that is in the depressurized condition?
As an operator you would attempt to turn the handwheel in the closed direction and verify no movement.
Which of the following types of
similarly sized valves in an
operating water system produces
the least frictional head loss
when fully open?
Ball valve
After an adjustment of the
packing gland on a valve that had
a minor packing leak, the operator attempts to operate the
valve but finds it stuck. What is the most probable cause?
The operator overtightened the packing, causing the stem to bind.
What would the valve
position be if the valve actuator
experiences a reduction in air
pressure caused by a leaking air connection?
More Closed
Which of the following types of
similarly sized valves requires the
most manual valve stem rotation
to move the valve from fully open
to fully closed? (Assume that
each valve has a non-rising stem.)
Gate valve
What pressure must be exceeded
in order for a high-pressure valve
to open
125 psi
The ASME Code states that
before bringing a high-pressure boiler online, it must be warmed-up. Assuming all conditions are
normal, what is common practice regarding closing of the vent
valve?
close the vent when the
pressure gauge reads 25 psi
Which of the following is a
generally accepted method for
locally verifying that a manual
valve is fully closed in a
depressurized static piping system?
Attempt to turn the valve hand wheel in the fully closed direction and verify no movement.
The purpose of backseating a
manual valve in an operating
system is to:
isolate system pressure from the packing stuffing box to minimize packing leakage.
In a cooling water system when
comparing a 3-inch gate valve to
a 3-inch globe valve used for the
same application in the process, which statement below is correct
if both valves were fully open?
The globe valve produces the larger head loss and the smaller flow
rate.
The voltage of an ignition transformer is created and travels to
electrodes. What holds and protects the electrodes in place?
the electrodes are held in
place by the porcelains.
What are the two elements in
fuel oil that produce most of its
heat?
carbon and hydrogen
What would a high pressure
differential across a fuel oil
strainer set indicate?
a dirty fuel oil strainer
What is the Btu content of natural
gas?
100,000 Btu/therm
You are installing a boiler
according to the boiler rules and regulations. Where must the filter
and strainers for oil fired boilers
be installed?
Upstream from the safety
shut off valve
Which of the following, best defines the ratio of the total heat
supplied by the fuel to the total
heat absorbed by the boiler
water?
thermal efficiency
The term viscosity can best be
defined as:
the point at which oil starts to flow
Which formula would you use to
calculate the Btu/lb heat content
of fuel oil?
17,687 + 577 x API @ 60
degrees F
The viscosity of fuel oil is lowered by
reducing its temperature. True or False
False
What type of oil burner provides
atomization without the use of
steam or air?
the pressure-type burner
In the ignition system on an oil
burner, what causes the spark to jump the gap and ignite the fuel?
a high voltage spark of 10,000 VDC produced from the transformer, jumps the gap between the electrode tips.
In boiler operation what is
necessary for complete
combustion?
atomization, time, mixture, and temperature
What device is used to maintain the
fuel to air ratio?
Air Damper, butterfly Valve, & modulating motor and linkage
Atomization of the fuel occurs in a
horizontal rotary cup burner by the:
rotary cup and high velocity air
In modern stationary engineering,
a flue gas analysis is done to:
determine combustion efficiency
The most readily discernible indication
of firing with insufficient secondary air
would be:
black smoke coming from the stack
The ignition system on a burner
must be able to generate enough
volts so that it lights the fuel in the burner. What is the line voltage being used?
the line voltage could
vary but is typically 120 V AC.
When making adjustments to the
firing rate of a power boiler, why should the air be increased to the
burner before the fuel?
to prevent incomplete combustion
On boilers equipped with an air
preheater, what is the purpose of the by-pass damper?
to control the temperature of the combustion air
Which of the following auxiliaries
would most improve boiler
efficiency?
an economizer
In a steam generating plant, what purpose does the economizer
serve?
to heat the feedwater
using stack gases
Which of the following stack gas readings would indicate fair to
good combustion taking place?
low oxygen and carbon
monoxide, high carbon dioxide
What must take place in order for
combustion air to flow open
automatically during equipment
operation?
There must be an adequate opening for the flow of fuel gas into the confines of the boiler room to ensure proper combustion
A gradual increase in the stack temperature could indicate what
condition in a boiler?
heating surface fouling
Boilers are equipped with a
combination natural gas/fuel oil burner for:
more flexible operation
Which of the following can cause a furnace explosion?
an accumulation of combustible gases
To eliminate the danger of a furnace explosion during start-up, the firing sequence must first allow for:
a pre-purge period
Furnace explosions can best be avoided by:
purging the furnace after any flame interruption
Before burner ignition, what is the minimum number of furnace volume air changes that should be provided by the purge cycle?
Four
On a heating boiler, where would the flame-sensing device be located?
On the front of the furnace
What control device found on low pressure heating boilers provides for the proper burner control sequence during boiler start-up and shut-down?
programming control
After establishing the proper boiler water level, the burner on a properly operating system is allowed to start the light off sequence when:
after purging the furnace
When a draft fan is located between
the boiler and the chimney, what type
of draft system is it?
Induced Draft
A draft system that maintains a
constant pressure on a boiler is
called a/an:
balanced draft system
How is natural draft produced in a
boiler system?
by the difference in temperature of the gas in the chimney to that of the air outside the chimney
A manometer is calibrated in
what units of measurement?
inches of water
Which of the following could be
used to control a fan’s output?
adjusting the pitch of the
fan blades, adjusting the inlet dampers ,increasing or decreasing
Which of the following best
defines the term “balanced
draft”?
the forced draft and induced draft fans are regulated to keep the furnace below atmospheric pressure
What type of draft system is used
to overcome resistance on power
boilers equipped with an economizer?
an induced draft system
A low pressure boiler with a natural
draft furnace, the amount of draft, will
not be affected by the height of the
stack.
False
What are the three types of draft
used in power plants?
natural, forced, and
induced
Natural draft is produced by a
mechanical fan.
False
Why are staybolts used in the construction of HRT power boilers?
to strengthen and support flat plates on a fire-tube boiler
Why are baffles used in the steam drums of water-tube boilers?
to prevent the carry-over of water
In a fire-tube boiler, how are the tubes usually attached to the tube sheet?
by rolling the tubes and beading the ends
Where would you find downcomer tubes?
in water-tube boilers
How are the tube sheets supported in a fire-tube boiler?
by the shell, stays, and tubes
