DC Boiler Exam Prep (Formulas and
constants used for the DC 3rd class
boiler exam) with Complete Solutions
Area of a rectangle - ANSWER-Length x Width
Area of a Circle - ANSWER-.7854 x Diameter²
Volume of a Box - ANSWER-Length x Width x Height
Volume of a Cylinder - ANSWER-.7854 x Diameter² x Length
Circumference of a Circle - ANSWER-π x Diameter
Unit of Force - ANSWER-Pound (lb)
Formula for Force - ANSWER-Pressure ÷ Area
Unit of Work - ANSWER-in-lb or ft-lb
Formula for Work - ANSWER-Force x Distance
Unit of Power - ANSWER-ft-lb/min
Formula for Power - ANSWER-= Work ÷ Time
or (Force x Distance) ÷ Time
Formula for Mechanical Horsepower - ANSWER-= Power ÷ 33,000 ft-lb/min
,Fahrenheit to Celsius - ANSWER-°C = (°F - 32) ÷ 1.8
Celsius to Fahrenheit - ANSWER-°F = (1.8 x °C) - 32
Fahrenheit to Rankine - ANSWER-°R = °F + 460
Celsius to Kelvin - ANSWER-K = °C +273.15
Charles' First Law - ANSWER-Volume1 / Pressure1 = Volume2 / Pressure2
Charles' Second Law - ANSWER-Pressure1 / Temperature1 = Pressure2 / Temperature2
Boyle's Law - ANSWER-Pressure1 x Volume1 = Pressure2 x Volume2
General Gas Law - ANSWER-(Pres1 x Vol1)/ Temp1 = (Pres2 x Vol2)/Temp2
Formula for Levers - ANSWER-Resistance x DistanceR = Effort x DistanceE
Formula for Inclined Planes - ANSWER-Force x Length = Resistance x Height
Formula for Wheel & Axel - ANSWER-Force x DistanceF = Resistance x DistanceR
Torque - ANSWER-Force x Radius
Safe Working Pressure of a Riveted Boiler (SWP) - ANSWER-(Area of Staybolt x Stress
Constant of Staybolt) ÷ Area Covered by Staybolt or = (a x C) ÷ A
Area Covered by Staybolt - ANSWER-= Pitch x Pitch
, Specific Gravity of Mercury (Hg) - ANSWER-13.57
equivalent psi of water of 1" of Mercury - ANSWER-.491 psi
Atmospheric pressure in psi - ANSWER-14.7 psi
Atmospheric pressure in in.Hg. - ANSWER-29.29 in.HG
Lbs of air required to burn 1 lb of fuel - ANSWER-15 lbs
% of oxygen in air - ANSWER-21%
Lbs of air required to burn 1 lb of carbon - ANSWER-11.53 lbs
Percentage of condensate return (Rc) - ANSWER-= [Mc-Fc)/(Mc - CC)] x 100
Mc = Make-up conductivity
Fc = Feedwater conductivity
Cc = Condensate conductivity
Conversion factor for grains per gallon to parts per million - ANSWER-17.1
Weight of column of mercury in psi = - ANSWER-= 13.57 x .433 x Height
Formula for the horsepower requirement for a pump = - ANSWER-(Q x 8.33 x H x sp.gr. ) /
33,000 x n
Q = flow rate in gpm
H = total head
sp.gr. = specific gravity of fluid being pumped
n = Pump efficiency
constants used for the DC 3rd class
boiler exam) with Complete Solutions
Area of a rectangle - ANSWER-Length x Width
Area of a Circle - ANSWER-.7854 x Diameter²
Volume of a Box - ANSWER-Length x Width x Height
Volume of a Cylinder - ANSWER-.7854 x Diameter² x Length
Circumference of a Circle - ANSWER-π x Diameter
Unit of Force - ANSWER-Pound (lb)
Formula for Force - ANSWER-Pressure ÷ Area
Unit of Work - ANSWER-in-lb or ft-lb
Formula for Work - ANSWER-Force x Distance
Unit of Power - ANSWER-ft-lb/min
Formula for Power - ANSWER-= Work ÷ Time
or (Force x Distance) ÷ Time
Formula for Mechanical Horsepower - ANSWER-= Power ÷ 33,000 ft-lb/min
,Fahrenheit to Celsius - ANSWER-°C = (°F - 32) ÷ 1.8
Celsius to Fahrenheit - ANSWER-°F = (1.8 x °C) - 32
Fahrenheit to Rankine - ANSWER-°R = °F + 460
Celsius to Kelvin - ANSWER-K = °C +273.15
Charles' First Law - ANSWER-Volume1 / Pressure1 = Volume2 / Pressure2
Charles' Second Law - ANSWER-Pressure1 / Temperature1 = Pressure2 / Temperature2
Boyle's Law - ANSWER-Pressure1 x Volume1 = Pressure2 x Volume2
General Gas Law - ANSWER-(Pres1 x Vol1)/ Temp1 = (Pres2 x Vol2)/Temp2
Formula for Levers - ANSWER-Resistance x DistanceR = Effort x DistanceE
Formula for Inclined Planes - ANSWER-Force x Length = Resistance x Height
Formula for Wheel & Axel - ANSWER-Force x DistanceF = Resistance x DistanceR
Torque - ANSWER-Force x Radius
Safe Working Pressure of a Riveted Boiler (SWP) - ANSWER-(Area of Staybolt x Stress
Constant of Staybolt) ÷ Area Covered by Staybolt or = (a x C) ÷ A
Area Covered by Staybolt - ANSWER-= Pitch x Pitch
, Specific Gravity of Mercury (Hg) - ANSWER-13.57
equivalent psi of water of 1" of Mercury - ANSWER-.491 psi
Atmospheric pressure in psi - ANSWER-14.7 psi
Atmospheric pressure in in.Hg. - ANSWER-29.29 in.HG
Lbs of air required to burn 1 lb of fuel - ANSWER-15 lbs
% of oxygen in air - ANSWER-21%
Lbs of air required to burn 1 lb of carbon - ANSWER-11.53 lbs
Percentage of condensate return (Rc) - ANSWER-= [Mc-Fc)/(Mc - CC)] x 100
Mc = Make-up conductivity
Fc = Feedwater conductivity
Cc = Condensate conductivity
Conversion factor for grains per gallon to parts per million - ANSWER-17.1
Weight of column of mercury in psi = - ANSWER-= 13.57 x .433 x Height
Formula for the horsepower requirement for a pump = - ANSWER-(Q x 8.33 x H x sp.gr. ) /
33,000 x n
Q = flow rate in gpm
H = total head
sp.gr. = specific gravity of fluid being pumped
n = Pump efficiency
