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Grade 3 Engineering Omaha exam prep by NAPE
Grade 3 Engineering Omaha exam prep by NAPE
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Grade 3 Engineering Omaha exam prep byNAPE
# 112 Why is a boiler feed pump used on some boilers and not others? - ANS-you will
not need a pump if the operating pressure of the boiler is below city water pressure
# 89 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? -
ANS-water tube boiler: most likely defective or missing baffles
fire tube boiler: could be missing turbulators or blocked tubes
#1 How can you loose your license? - ANS-drinking on the job, sleeping on the job,
negligence unsafe work, signing a falsified license application for someone, failing to
renew your license annually
#10 What is a crown sheet and its purpose?
-----
what is a tube sheet and its purpose? - ANS-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
#100 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? - ANS-at least 3" above the top row
of tubes
#101 Name 3 appliances that can warn you of low water - ANS-1) water sight glass
2) low water alarm
3) fusible plug
#102 If your boiler has only one low water cutoff, what is the ASME code requirement? -
ANS-it must be a manual reset.
Side note: the City of Omaha requires one to be a manual reset even if you have 2
cutoffs. if there is repair work done on the boiler there must be a manual reset added.
#103 What is the purpose of a high fire limit control on a boiler?
,-----
what is a modulating control? - ANS-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
#104 Is an automatic shutoff allowed between the boiler and the water column? -
ANS-NO, only between the water column and gauge glass
#105 What type valves are allowed between the boiler and the water column? -
ANS-only O.S.&Y. valves or stopcocks which are locked or sealed open. (outside screw
& yolk)
#106 Name 2 types of fusible plugs - ANS-1) fire side
2) water side
refers to the side where they are installed
#107 What is a bourdon tube? - ANS-A curved tube with an oval cross-section. One end
is attached to the frame and pressure connection. The other end is attached to a pointer
by linkage and gears. An increase in pressure tends to straighten the tube; its motion is
transmitted to the pointer.
#108 What is a siphon tube and what is it used for? - ANS-a siphon tube or pigtail loop
protects the mechanism of a gauge from live steam.
#109 What pressure range should the steam gauge be when used on a boiler? - ANS-it
should be a compound gauge at least 1 1/2 times the maximum allowable working
pressure
#11 What is a water leg on a boiler? - ANS-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.
#110 Where is the steam gauge connected to the boiler?
-----
how do you properly mount a steam gauge to a boiler? - ANS-mounted on top of the
water column or the the top of the steam drum.
-----
gauge is mounted with:
1) a siphon tube
,2) a isolation valve
3) a test connection
#111 Name 3 types of feed-water regulator systems - ANS-1) On-off such as float or
probe
2) Modulating such as thermodynamic or thermohydrolic
3) Metering such as a two or three ement
#113 What is the most important valve on a boiler? - ANS-SAFETY VALVE!
#114 What is a safety valve?
-----
how does it operate? - ANS-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
#115 A safety valve is limited to how many square feet of heating surface? - ANS-any
boiler with more than 500 square feet of heating surface must have 2 or more safety
valves
#116 If a safety valve lifts at 100 psi, what pressure should it close?
-----
what are the requirements governing safety valve blow down? - ANS-96 to 98 psi
-----
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)
#117 How do you determine if a boiler has sufficient safety valve capacity? - ANS-The
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
#118 How must a safety valve be connected to the boiler? (pic thumb and fingers) -
ANS-1) independent of any other steam connection
2) close as possible without any unnecessary piping
3) screwed into the boiler shell or fastened to a flange welded to the shell
4) connected to stand upright
, 5) vents must be fastened to the building and not connected to the valve!!!
#119 At what temperature does a safety valve on a superheater have to be protected
with heat resisting materials? - ANS-450*F
#12 Is an HRT Boiler set level or inclined and why?
-----
are HRT Boiler tubes set level or inclined and why? - ANS-INCLINED 1-3" front to rear
to permit drainage and removal of impurities
-----
INCLINED with the boiler
#120 How do you regulate the blow down of a safety valve? - ANS-the blow down is
regulated by adjusting the blow back ring, the spring or both (about 10%). ONLY
TRAINED AND LICENSED PERSONNEL SHOULD ADJUST SAFETY VALVES!
#121 How often is it recommended to test your safety valves manually and how often
under pressure? - ANS-manually: every 30 days
under pressure: annually
#122 How is a superheater protected? - ANS-each superheater must have one or more
safety valves near their outlet with the pressure set below those on the boiler insuring a
constant flow of steam through the superheater
#123 A boiler designed to operate at 125 psi is now operating at 15 psi, what changes
will be made to the safety valve? - ANS-if change is permanent, install a safety valve
with:
1) a larger disk
2) lower pressure rating
#124 On an Ashton type safety valve, a screw adjustment is labeled O and S. What do
these letters stand for?
-----
What adjustments can you make? - ANS-Open & Shut
-----
I'm not certified to make adjustments
#125 What is a surface blow-off?
-----
where is it employed?
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