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up Stationary Grade 3 Engineering License Exam Questions and Answers
Typology: Exams
1 / 53
how can you loose your license? - Answer- 1) drinking on the job
name 4 types - Answer- those in which the grate and combustion chamber are enclosed within the boiler shell.
name 4 types - Answer- the setting, including the furnace and grates is separate and distinct from the boiler shell.
what is a tube sheet and its purpose? - Answer- in a vertical firetube boiler holds the tubes and is thicker because it is exposed to the fire.
holds the tubes and does not see the fire what is a waterleg on a boiler? - Answer- space between the outer shell and the furnace containing boiler water. it absorbs heat that would be wasted and increases the capacity of the boiler. the surfaces are flat and must be stayed. is an HRT Boiler set level or inclined and why?
are HRT Boiler tubes set level or inclined and why? - Answer- INCLINED 1-3" front to rear to permit drainage and removal of water impurities
INCLINED with the boiler Name 2 way to support and take care of expansion of an HRT Boiler
Which way is best? - Answer- 1) Suspended from hangars and supported by overhead beams
Suspended from hangars and supported by overhead beams is best because it works no hardship on the furnace walls
what is a circumferential joint? - Answer- LONGITUDINAL JOINT = seam running the length of the shell and is butt strap construction or fusion welded. it is above the fireline to avoid overheating.
CIRCUMFERENTIAL JOINT = lap joint running the circumference of the drum what is the difference between a flue and a tube? - Answer- 1) Flue - 4" or more in diameter measured internally
how it is fired - Answer- it is an internally fired self contained horizontal return firetube boiler.
it is a cylindrical shell containing the combustion chamber and tubes that are surrounded by water. how is a Stirling Boiler suspended? - Answer- lugs on the ends of the upper drums rest on the beams of its structure. the lower (MUD) drum is suspended from the tubes and is free to move by expansion. describe the circulation of water within the Stirling Boiler - Answer- feed water enters the top rear drum, passes down the rear tubes to the mud drum. steam and boiler water go up the front and center tubes to the front and center drums. CIRCULATING TUBES allow boiler water to pass between the drums. what does not go out as steam, goes back down the rear tubes. what provisions are made for tube removal on water boilers? - Answer- 1) some tubes are left out
list 5 disadvantages
name 4 types - Answer- in a water tube boiler, products of combustion pass around tubes containing boiler water
ADVANTAGES:
DISADVANTAGES:
TYPES:
name 4 types - Answer- in a fire tube boiler, products of combustion pass through tubes or flues surrounded by water.
ADVANTAGES:
DISADVANTAGES:
what are the advantages of a superheater? - Answer- a super heater is a device used to raise the temperature of steam without raising its pressure.
what is the third type of superheater? - Answer- A radiant superheater is set over the fire to absorb radiant heat from the furnace by direct radiation
a convection superheater is placed in the gas passage of the furnace, usually between the first and second pass. little to no radiation will reach this type
the third type is a combination of radiant and convection what is an economizer?
what is a air pre-heater? - Answer- an economizer is a heat exchanger designed to recover waste heat from the products of combustion by pre-heating the feedwater. It's located in the breaching between the boiler and stack. NOTE: there is great economy in heating feedwater.
the air pre-heater consists of a series of tubes or plates that have hot gasses on one side and incoming air on the other. heat in the hot gasses leaving the boiler is recovering by the incoming air.
(both reduce stack temperatures and increase boiler efficiency) what is a water wall? - Answer- a set of tubes containing boiler water set in the refractory. they absorb heat that would otherwise be lost to the refractory and they increase the capacity of the boiler what is A.S.M.E. and its purpose?
where are the code markings found on a boiler? - Answer- American Society of Mechanical Engineers has written a set of minimum standards for the safe construction of pressure vessels.
stamped on the boiler shell or a plate attached to the shell will be:
fire tube boiler - it may be located by the water column near the front right side water tube boiler - it will be located next to the manhole on the steam drum what is the cross section of a 1" bolt? - Answer- DxDx.7854(1/4pi) 1x1x.7854=.7854 sq.in. show your work and label everything! what is an alloy?
what is a butt-strap joint? - Answer- LAP JOINT = when one plate overlaps the other and is joined
BUTT-STRAP JOINT = when two ends of the plate meet end to end and are joined by a plate. (one plate is a single butt strap joint / two plates are a double butt strap joint) is the longitudinal joint the strongest part of the boiler - Answer- NO! it is the strongest type joint, but any joint is the weakest part of a boiler two boilers are make of the same grade of steel, same thickness of plate and same type of joints. one is 30" in diameter the other is 60" diameter. which will withstand the greatest pressure and demonstrate your answer - Answer- the 30" boiler-it has less total pressure on the shell. DxDx.7854(1/4pi)xpsi 30x30x.7854x120 psi = 84,823 lbs. total pressure 60x60x.7854x120 psi = 339,292 lbs. total pressure show your work on everything! what are tube ligaments? - Answer- the area between the tube holes on the tube sheet what type stays are used in the heads of water tube boilers?
the head of the boiler drum is shaped with a die, which dishes and forms them in to the shape they would take as a result of the pressure to which they will be subjected why is a row of tubes sometimes left out of an HRT boiler? - Answer- to improve circulation reducing carryover in a firetube boiler how are the tubes secured in a tube sheet and why?
in a water tube boiler why are only some of the tube ends beaded? - Answer- fire tube boiler - they are rolled then beaded to keep them from pulling out and to prevent heat damage
for drainage of the top drums and to prevent air pockets in the lower drums. is it necessary to brace or stay a flat surface?
name 3 types of stays - Answer- YES, to overcome the force on heads and flat surfaces. Where there are no tubes, braces and stays must be provided to prevent bulging of the boilerplate.
why are hollow through bolts used on water legs? - Answer- a through stay is a rod threaded on both ends, held in place with nuts on the inside tightened against nuts on the outside of the plates. it runs from one tube sheet or flat surface to the other.
a small hole is drilled into the stay bolt so if it failed a leak will develop and be detected at once describe a diagonal stay
where would each be used? - Answer- DIAGONAL STAY = made of flat materials similar to the boiler shell and is attached directly to the boiler shell and head or tube sheet
GUSSET STAY = made of boilerplate riveted to the shell and head or tube sheet by means of angle iron. MORE RIGID
both are used to brace right angle surfaces why are hand-holes and man-holes made oval instead of round?
what are the minimum sizes for man-hole and hand-hole openings? - Answer- so they can be inserted into and removed from their respective openings in the boiler
man-hole = 10x16 or 11x hand-hole = 2-3/4 x 3-1/ what is thermal efficiency?
what is considered a good percentage? - Answer- the ratio of heat absorbed by the water (TO) the heat provided by the fuel
a good percentage is 85%, some boilers made today can reach 95% how do you determine boiler capacity?
BOILER HEATING SURFACE = any area that has hot gases on one side - boiler water on the other. MEASURED FROM THE FIRE SIDE. what is furnace volume?
is furnace volume measured in square feet or cubic feet? - Answer- FURNACE VOLUME = the space available for complete combustion of the fuel before the products of combustion enter the heat absorbing sections of the boiler. varies with the type of fuel used
cubic feet what is superheated steam?
does its temperature rise? - Answer- SUPERHEATED STEAM = steam that has been heated to a higher temperature, but its pressure remains the same
YES define flash point
define ignition point
define pour point - Answer- 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 open flame
POUR POINT = the lowest temperature at which liquid will flow define combustion - Answer- a CHEMICAL REACTION between oxygen and combustibles. it is the process of rapid OXIDATION by which the heat stored in fuel is released what is rate of combustion?
does air and fuel have any relationship in figuring the rate of combustion? - Answer- the rate at which the heat stored in fuel is released
YES, when oxygen and combustibles are mixed in definite proportion at an elevated temperature, given proper time, will combine completely define primary air
is secondary air necessary in a boiler and why? - Answer- PRIMARY AIR = enters the furnace with the fuel and determines the rate of combustion
SECONDARY AIR = creates turbulence around the fuel to complete the burning process
YES, secondary air is introduced above the fuel bed to burn combustible gasses what are the three "T's" of combustion? - Answer- 1) time
POUNDS PER SQUARE INCH ABSOLUTE = gauge readings plus atmospheric pressure could too much secondary air have a bad effect on the efficiency of a boiler? - Answer- YES, excess secondary air will not enter into the reaction and will pass through the furnace wasting heat out the stack what percent of air is oxygen by volume?
% of oxygen in air by weight is 23% define perfect combustion
define incomplete combustion - Answer- PERFECT COMBUSTION - burning all the fuel using only the theoretical amount of air
COMPLETE COMBUSTION - burning all the fuel using more than the theoretical amount of air
INCOMPLETE COMBUSTION - when a portion of the fuel remains unburned because of insufficient amounts of air in a flue gas analysis, what do you consider a good percent of CO2? - Answer- good = 12% to 15% ideal = 20% (mostly unattainable) how is density of smoke measured?
how do you use a Ringlemann Chart? - Answer- With an opacimeter or Ringlemann chart.
why is it used? - Answer- a flue gas analyzer detecting amounts of CO, CO2 and O2 in flue gasses
to determine combustion efficiency and excess air what is a Fyrite analyzer?
why is it used? - Answer- a flue gas analyzer to determine the amounts of CO2 and O in flue gasses
to determine combustion efficiency what is a pyrometer?
where would it be located on a boiler? - Answer- thermometer for measuring temperatures above the range of mercury
in the hot gas passages and in the refractory what are tuyeres (tweyars)? - Answer- air-admitting grates on stokers what is a waterback? - Answer- a water wall that is behind the grate on a stoker and its purpose is to cool the wall to prevent clinkers from sticking to the back wall define purging
name two types - Answer- purging = the forced removal of combustibles from the firebox.
how would you correct this condition? - Answer- pulsations = when the flame leaves the burner tip and then returns. this may become so severe that the combustion consists of a series of small explosions.
how to correct: pulverized coal or oil furnace = the proper air-fuel mixture. gas furnace = increase the draft how do you pipe an oil supply line from the tank to the burner? - Answer- 1) oil flows from the storage tank through the suction strainer
if you are firing #4 oil and lose oil pressure, what are the first two things you would look for?
when would you change a strainer? - Answer- difficulties may include:
1st two things to look for:
you would valve over to a clean strainer if the delta-P was excessive name three types of nozzles used in oil burners.
explain where secondary air is admitted. - Answer- nozzles:
secondary air is admitted around the tip. under what conditions must fuel oil be heated?
oil should not be heated to more than 10F below its flash point. (rule of thumb is) #4 - 135F #5 - 185*F
parts:
what causes natural draft? - Answer- when the weight of the warm air in the stack is less than the cool air around the stack which causes an upward flow pulling air through the furnace
the heavier, cool air outside the stack gives a push to the warm lighter air in the stack causing air to flow through the furnace how is the flow of natural draft controlled? - Answer- by automatic electric or pneumatic controlled dampers that are mounted in the breeching and/or the burner does the diameter or height of a stack have an effect on the draft? - Answer- yes diameter = determines the volume height = determines the velocity how is draft measured?
a draft gauge is used to measure the pressure difference of the boiler room and inside the setting or firebox
one tube end is connected into the breeching and the other end is open to the boiler room (or atmosphere). Pressure moves the liquid in the tube. the difference is read in tenths of an inch. when would you employ forced draft? - Answer- when you fail to have sufficient natural draft through the boiler what is mechanical draft?
name and describe 3 types - Answer- the adding of fans to make up for insufficient natural draft
why is it not desirable on large boilers? - Answer- PRESSURIZED FURNACE = has a fan placed at the point of air entry to maintain the furnace above atmospheric pressure pushing the products of combustion through the furnace and out the stack.
flue gasses can leak into the operating areas and become a health hazard how do you control the dampers on a large fan from a remote location? - Answer- the control panel sends a signal to electric or pneumatic actuators that move the damper linkages if maintenance was done on your boiler, put back in operation, and the stack temperature was higher than normal, what would you look for as the cause? - Answer- water tube boiler = most likely defective or missing baffles fire tube boiler = could be missing turbulators or blocked tubes where are turbulators used and what is their purpose? - Answer- used in the tubes of a fire tube boiler to increase heat transfer to the tubes how often should you test the low water cutoffs and fully describe 3 ways of safely doing this. - Answer- 1) at least once a shift furiously blow down the water column and insure that the water returns rapidly and smoothly into the glass
what would you do if the glass broke while the boiler was operating? - Answer- the start of each shift
what style fittings are used to pipe a water column and why? - Answer- 1" made of brass, extra heavy iron or steel
crosses and tees for cleaning and inspection describe how to pipe a water column on an H.R.T. boiler - Answer- 1) the top of the column is connected to the top of the steam shell
How can you determine if a water gauge glass is properly set on a fire tube boiler? - Answer- by filling the boiler with water to normal operating level and measuring the depth of the water to the top row of tubes how high above the top row of tubes in an HRT boiler must the lower gauge cock be set to have a safe amount of water at this point? - Answer- at least 3" above the top row of tubes name 3 appliances that can warn you of low water - Answer- 1) water sight glass
what is a modulating control? - Answer- it proves that the forced fan damper has fully opened prior to starting the pre-purge period to insure adequate purge air flow.
it adjusts the firing rate of the burner to maintain the boiler steam pressure is an automatic shutoff allowed between the boiler and the water column? - Answer- NO, only between the water column and gauge glass what type valves are allowed between the boiler and the water column? - Answer- only O.S. and Y valves or stopcocks which are locked or sealed open. (outside screw & yolk) name 2 types of fusible plugs - Answer- 1) fire side
how do you properly mount a steam gauge to a boiler? - Answer- mounted on top of the water column or the the top of the steam drum.
gauge is mounted with:
how does it operate? - Answer- a device to EXPEL ALL EXCESS steam pressure from a boiler
the huddling chamber causes the valve to open fully and quickly causing a definite drop in pressure before closing a safety valve is limited to how many square feet of heating surface? - Answer- any boiler with more than 500 square feet of heating surface must have 2 or more safety valves if a safety valve lifts at 100 psi, what pressure should it close?
safety valves shall operate without chattering with a blow down of not more than 4% of the set pressure and in no case less than 2 lbs. (100x4%=4 so 100-4=96) how do you determine if a boiler has sufficient safety valve capacity? - Answer- accumulation test = determines if the valves will discharge all the steam generated by the boiler without allowing the pressure to rise more than 6% above where the valve is set and in no case by more than 6% above the maximum allowable working pressure of the boiler
how must a safety valve be connected to the boiler? (pic thumb and fingers) - Answer-
I'm not certified to make adjustments what is a surface blow-off?
why is it used? - Answer- removal of oil and contaminants from the surface of boiler water
It controls the total dissolved solids (TDS) what is a continuous blow down system?
where is it installed? - Answer- based on water analysis the surface blow down is metered for a continuous flow.
the take-off is located just below the normal operating water level (NOWL) in the steam and water drum how should a continuous blow-down be piped as it leaves the boiler and why? - Answer- piped through:
to recover heat when is the best time to blow down a boiler?
what important safety procedure is observed when using a bottom blow down? - Answer- during light loads because more of the sludge has settled to the bottom.
do not take your hand off valve once opened until you have closed it! where is the bottom blow down pipe connected to an HRT boiler?
what size piping is used in the blow down line? - Answer- rear of the boiler drum, on underside of the shell.
the piping must be at least 1" and not greater than 2 1/2" in diameter. 3/4" is allowed on boilers of less than 100 sq ft heating surface what is a slow opening valve? - Answer- a screw type valve that requires at least 5 full turns from closed to open position what is a plug valve?
why is it used on blow down lines? - Answer- a circular, tapered plug ground down to fit into the valve body. when open - a hole through the plug aligns with the hole in the valve body. when closed - the holes are out of line.
its shearing action cuts through scale and it will not fail open how is a blow down tank piped?
why isn't any blow down connected directly to the sewer? - Answer- 1) blow down enters the tank above the water line and maintained in the tank against a splash guard.
the discharge line is opposite the inlet, resulting in the cooler water being discharged first.
flash steam and hot water directly into the sewer:
why does it have a drain? - Answer- automatic stop check valve to prevent a back-flow of steam when the boiler pressure falls below that of the header
to remove condensate make a drawing of 3 boilers in battery showing the steam header, valves and piping - Answer- (pic) 3 boilers 3 non-return valves w/condensate drain valves 3 header valves w/condensate drain valves steam header isolation valve/strainer/isolation valve what is a soot blower?
name 2 types - Answer- a device using jets of steam, compressed air or both to remove the ash and slag from the fire side of the tubes.
a revolving blow-arm equipped with properly spaced nozzles that is operated by a chain and wheel while the boiler is in service.
what happens if the condensate isn't drained from the soot-blower steam supply prior to using the soot-blower? - Answer- 1) always with the boiler on high fire.
name 6 places for a bypass - Answer- it consists of a plug or disk that is forced into a tapered hole called a seat. it can be plugged or damaged easily and has more resistance to flow, therefore it is not used as a steam stop valve.
common around:
where it is used most often? - Answer- a valve with a wedge shaped gate which is raised or lowered into a passageway. the wedge-shape tightens against the sides of the slot when closed. it offers little resistance to flow when fully open and should not be used to throttle.
for isolating devices for repair or to shut off the flow to the boiler what are rising stem valves?
what are non-rising stem valves? - Answer- rising = has a stem that rises as the valve opens
non-rising = has a stem that stays stationary explain the letters SWP and WOG found on the side of a valve? - Answer- SWP = maximum Steam Working Pressure rating WOG = maximum Water, Oil or Gas pressure the valve may be used for (ie. 140 SWP & 40 WOG) describe a balanced (double seated) feed water valve?
why is it used? - Answer- a valve with two disks and two seats. one disk opens with the pressure and one against
with forces balanced, it opens easily what is a pressure-reducing valve (PRV)?
where is it used? - Answer- PRV automatically reduces high pressure and maintains a lower delivery pressure
used for: