DC 3rd Class Test, 3rd class
stationary steam engineer
license prep, Stationary Engineer,
Station engineer exam, DC 1st
Class Boiler Complete Exam Guide
Latest Update 2026
The component in which liquid vapor by absorbing heat is called? - ANSWER-
evaporator
the best ANSWER for an electrical grounding method? - ANSWER-Metal stake drive 8
foot into the ground.
A _____ valve should be used for throttling purposes? - ANSWER-Globe
What is the acceptable range for residual sodium sulfite in the boiler maintain? -
ANSWER-30-70
What is the BTU content of a gallon of #4 fuel oil? - ANSWER-146,000
What does a zeolite water softener system use as a means of regeneration? -
ANSWER-brine
What are the 4 steps for a Zeolite Rejuvenation water softener process? - ANSWER-
Backwash, Brine, Rinse, Service
Where medium temperature liquid found? - ANSWER-Condenser
Where is high temperature vapor found? - ANSWER-At the discharge of the
compressor or condenser
What stays are used to support the burner chamber in a scotch marine boiler? -
ANSWER-Diagonal Stays
What type of safety valve is this? - ANSWER-( Full) Crosby nozzle-type safety valve.
Page 365 BOG
Where do you get superheat reading? - ANSWER-Take suction line pressure
,Name the wire that connects all component of a system to a physical ground or water
pipe? - ANSWER-Grounding electrode conductor
Where do you get sub-cooling reading? - ANSWER-Take liquid line pressure
Cross reference to temperature using a P/T Chart
Get liquid line temperature
Subtract actual temperature from cross referenced temperature
Result is Sub cooling
On the boilers that have both Quick opening and Screw type blow down valves, the
Quick opening valve must be located? - ANSWER-closest to the boiler and followed by
the screw-type valve
High pressure boilers equipped with Quick opening and Screw type valves are blown
down how? - ANSWER-By opening the Quick opening valve first and closing it Last.
ASME Code defines a slow opening valve as what? - ANSWER-One requiring at least 5
full 360 degree turns between full open and close position.
A 300 Horsepower boiler operating at 100psi has an average load of 75% with 80%
condensate return and 5% blow down. The treatment provides a chemical which costs
$8.75 per gallon, and will treat 600 gallon. Find the amount of the chemical needed for
the day period, and the cost of the chemical for a 30 days period? - ANSWER-Water In
= Water Out
Makeup + Condensate Return = Evaporator + Blow Down
Average Evaporator Rate = 300 x 34.5 pph x .75% load = 7762, 50 pph
1 Month + .8( 7762.50 pph) = 7762.50 pph + 0500 m
1 Month + 6210 pph = 7762.50 pph + .0500 m
-6210 -6210
1 Month = 1552.5 pph + .0500
.9500 m = 1552.5 pph
.9500m .9500
1Month = 1,634.21 pph
Gallons per Month = 1634..33 x 24 x 30 = 141, 252.24 gallons per month
Chemical needed = 141,252.24 gallon / 600 gallon = 235, 40 gallon
Cost per month = 235, 40 gallon x 8.75 = $2,059.75
,During a 24 hours operation how often should you check the water level? - ANSWER-
once per shift
How often do you check the high limit switch? - ANSWER-Annually
What is the recommended time for a complete external inspection of a boiler? -
ANSWER-once per shift
What is the first thing to do when shutting down a boiler? - ANSWER-To turn off the fire
A flow control should be blown down when? - ANSWER-once per shift
How often should you check the Low Water Fuel Cut off? - ANSWER-once per shift
Why is oil added to the refrigerant? - ANSWER-lubrication of the compressor
Keep refrigerant migrating
Recycled and filtered refrigerant can be used where? - ANSWER-By the same owner in
the same type of equipment
Data printed on the equipment nameplate would include manufacturer, model, and
serial number and________________? - ANSWER-Stamp of approval from
commissioning authority
How many BTU's does it take to raise 10 lbs of steam from 40 to 41 degrees? -
ANSWER-1 BTU
When working on a boiler, permits should be required? - ANSWER-For every shift
How many things do safety controls protect against? - ANSWER-Over pressure
Over Heating
Fire side explosions
What chemical compounds in water cause permanent hardness? - ANSWER-Calcium
Sulfate and Magnesium Silicate
What chemicals are used to combat corrosion? - ANSWER-sodium sulfite and
hydrazine
You have boiler water that is found to have a PH of 5. What compound do you add to
neutralize? - ANSWER-bases
What produces soft scale? - ANSWER-calcium carbonate and magnesium carbonate
With normal oxygen and low alkalinity, what is added to boiler water? - ANSWER-
Neutralizing Amines
, What is hard forming scale? - ANSWER-silica
Which chemicals are used to combat scale? - ANSWER-Combined Phosphate
Treatment
Which compound is not heat produce? - ANSWER-Nitrogen
What takes no actual action in combustion? - ANSWER-Nitrogen
With hydroxide present & normal oxygen levels; which chemical will cause problems? -
ANSWER-Chlorine
What mechanical device is used to remove scale from Fire Tubes? - ANSWER-A Tube
Rattler or Vibrator is used
Who can make Adjustments or repairs on a Safety Valve? - ANSWER-Qualify person
from Manufacturer or Representative
What mechanical device is used to remove scale from water Tubes? - ANSWER-A
Tube Turbine is used
In a duct air handling system, space thermostat control building temperatures by? -
ANSWER-Mixing the air from hot & cold duct in a mixing box serving the space
The removal of moisture from air using a cooling coil is called _________
dehumidification? - ANSWER-Passive
In a multi-zone air handler unit, the zone thermostat controls the zone temperature by? -
ANSWER-Dampers that control the air flow from the hot & cold duct
An air handler unit that has hot & cold air ducts connected to (molding boxes?) located
in each building space is called a __________air handler unit? - ANSWER-dual duct
An air handler unit supplies a constant supply air temperature of 55 degree F to building
spaces and includes a coil called _____air handler unit? - ANSWER-terminal reheat
An air handler unit that provides heating, cooling, ventilation, and air conditioning to
more than one building or area and has its cooling & heating Coil in separate side-by
side ducts is called a _______air handling unit? - ANSWER-multi-zone
In a dual duct air handling system space thermostatic controls building temperature by?
- ANSWER-Moving the air from the hot & cold duct in a molding box serving the space.
A boiler is rated at (86,250 lbs, 88,250 lbs, 96,250 lbs) of steam per hour. What is the
equivalent boiler horsepower? - ANSWER-2500 HP = 86,.5 = 2500 lbs
stationary steam engineer
license prep, Stationary Engineer,
Station engineer exam, DC 1st
Class Boiler Complete Exam Guide
Latest Update 2026
The component in which liquid vapor by absorbing heat is called? - ANSWER-
evaporator
the best ANSWER for an electrical grounding method? - ANSWER-Metal stake drive 8
foot into the ground.
A _____ valve should be used for throttling purposes? - ANSWER-Globe
What is the acceptable range for residual sodium sulfite in the boiler maintain? -
ANSWER-30-70
What is the BTU content of a gallon of #4 fuel oil? - ANSWER-146,000
What does a zeolite water softener system use as a means of regeneration? -
ANSWER-brine
What are the 4 steps for a Zeolite Rejuvenation water softener process? - ANSWER-
Backwash, Brine, Rinse, Service
Where medium temperature liquid found? - ANSWER-Condenser
Where is high temperature vapor found? - ANSWER-At the discharge of the
compressor or condenser
What stays are used to support the burner chamber in a scotch marine boiler? -
ANSWER-Diagonal Stays
What type of safety valve is this? - ANSWER-( Full) Crosby nozzle-type safety valve.
Page 365 BOG
Where do you get superheat reading? - ANSWER-Take suction line pressure
,Name the wire that connects all component of a system to a physical ground or water
pipe? - ANSWER-Grounding electrode conductor
Where do you get sub-cooling reading? - ANSWER-Take liquid line pressure
Cross reference to temperature using a P/T Chart
Get liquid line temperature
Subtract actual temperature from cross referenced temperature
Result is Sub cooling
On the boilers that have both Quick opening and Screw type blow down valves, the
Quick opening valve must be located? - ANSWER-closest to the boiler and followed by
the screw-type valve
High pressure boilers equipped with Quick opening and Screw type valves are blown
down how? - ANSWER-By opening the Quick opening valve first and closing it Last.
ASME Code defines a slow opening valve as what? - ANSWER-One requiring at least 5
full 360 degree turns between full open and close position.
A 300 Horsepower boiler operating at 100psi has an average load of 75% with 80%
condensate return and 5% blow down. The treatment provides a chemical which costs
$8.75 per gallon, and will treat 600 gallon. Find the amount of the chemical needed for
the day period, and the cost of the chemical for a 30 days period? - ANSWER-Water In
= Water Out
Makeup + Condensate Return = Evaporator + Blow Down
Average Evaporator Rate = 300 x 34.5 pph x .75% load = 7762, 50 pph
1 Month + .8( 7762.50 pph) = 7762.50 pph + 0500 m
1 Month + 6210 pph = 7762.50 pph + .0500 m
-6210 -6210
1 Month = 1552.5 pph + .0500
.9500 m = 1552.5 pph
.9500m .9500
1Month = 1,634.21 pph
Gallons per Month = 1634..33 x 24 x 30 = 141, 252.24 gallons per month
Chemical needed = 141,252.24 gallon / 600 gallon = 235, 40 gallon
Cost per month = 235, 40 gallon x 8.75 = $2,059.75
,During a 24 hours operation how often should you check the water level? - ANSWER-
once per shift
How often do you check the high limit switch? - ANSWER-Annually
What is the recommended time for a complete external inspection of a boiler? -
ANSWER-once per shift
What is the first thing to do when shutting down a boiler? - ANSWER-To turn off the fire
A flow control should be blown down when? - ANSWER-once per shift
How often should you check the Low Water Fuel Cut off? - ANSWER-once per shift
Why is oil added to the refrigerant? - ANSWER-lubrication of the compressor
Keep refrigerant migrating
Recycled and filtered refrigerant can be used where? - ANSWER-By the same owner in
the same type of equipment
Data printed on the equipment nameplate would include manufacturer, model, and
serial number and________________? - ANSWER-Stamp of approval from
commissioning authority
How many BTU's does it take to raise 10 lbs of steam from 40 to 41 degrees? -
ANSWER-1 BTU
When working on a boiler, permits should be required? - ANSWER-For every shift
How many things do safety controls protect against? - ANSWER-Over pressure
Over Heating
Fire side explosions
What chemical compounds in water cause permanent hardness? - ANSWER-Calcium
Sulfate and Magnesium Silicate
What chemicals are used to combat corrosion? - ANSWER-sodium sulfite and
hydrazine
You have boiler water that is found to have a PH of 5. What compound do you add to
neutralize? - ANSWER-bases
What produces soft scale? - ANSWER-calcium carbonate and magnesium carbonate
With normal oxygen and low alkalinity, what is added to boiler water? - ANSWER-
Neutralizing Amines
, What is hard forming scale? - ANSWER-silica
Which chemicals are used to combat scale? - ANSWER-Combined Phosphate
Treatment
Which compound is not heat produce? - ANSWER-Nitrogen
What takes no actual action in combustion? - ANSWER-Nitrogen
With hydroxide present & normal oxygen levels; which chemical will cause problems? -
ANSWER-Chlorine
What mechanical device is used to remove scale from Fire Tubes? - ANSWER-A Tube
Rattler or Vibrator is used
Who can make Adjustments or repairs on a Safety Valve? - ANSWER-Qualify person
from Manufacturer or Representative
What mechanical device is used to remove scale from water Tubes? - ANSWER-A
Tube Turbine is used
In a duct air handling system, space thermostat control building temperatures by? -
ANSWER-Mixing the air from hot & cold duct in a mixing box serving the space
The removal of moisture from air using a cooling coil is called _________
dehumidification? - ANSWER-Passive
In a multi-zone air handler unit, the zone thermostat controls the zone temperature by? -
ANSWER-Dampers that control the air flow from the hot & cold duct
An air handler unit that has hot & cold air ducts connected to (molding boxes?) located
in each building space is called a __________air handler unit? - ANSWER-dual duct
An air handler unit supplies a constant supply air temperature of 55 degree F to building
spaces and includes a coil called _____air handler unit? - ANSWER-terminal reheat
An air handler unit that provides heating, cooling, ventilation, and air conditioning to
more than one building or area and has its cooling & heating Coil in separate side-by
side ducts is called a _______air handling unit? - ANSWER-multi-zone
In a dual duct air handling system space thermostatic controls building temperature by?
- ANSWER-Moving the air from the hot & cold duct in a molding box serving the space.
A boiler is rated at (86,250 lbs, 88,250 lbs, 96,250 lbs) of steam per hour. What is the
equivalent boiler horsepower? - ANSWER-2500 HP = 86,.5 = 2500 lbs
