DC 3rd Class Boiler Exam Prep:
Essential Formulas and Constants for
Success
Length x Width - Area of a rectangle
.7854 x Diameter² - Area of a Circle
Length x Width x Height - Volume of a Box
.7854 x Diameter² x Length - Volume of a Cylinder
π x Diameter - Circumference of a Circle
Pound...
DC 3rd Class Boiler Exam Prep:
Essential Formulas and Constants for
Success
Length x Width - ✔✔Area of a rectangle
.7854 x Diameter² - ✔✔Area of a Circle
Length x Width x Height - ✔✔Volume of a Box
.7854 x Diameter² x Length - ✔✔Volume of a Cylinder
π x Diameter - ✔✔Circumference of a Circle
Pound (lb) - ✔✔Unit of Force
Pressure ÷ Area - ✔✔Formula for Force
in-lb or ft-lb - ✔✔Unit of Work
Force x Distance - ✔✔Formula for Work
ft-lb/min - ✔✔Unit of Power
= Work ÷ Time
or (Force x Distance) ÷ Time - ✔✔Formula for Power
= Power ÷ 33,000 ft-lb/min - ✔✔Formula for Mechanical Horsepower
°C = (°F - 32) ÷ 1.8 - ✔✔Fahrenheit to Celsius
°F = (1.8 x °C) - 32 - ✔✔Celsius to Fahrenheit
°R = °F + 460 - ✔✔Fahrenheit to Rankine
,K = °C +273.15 - ✔✔Celsius to Kelvin
Volume1 / Pressure1 = Volume2 / Pressure2 - ✔✔Charles' First Law
Pressure1 / Temperature1 = Pressure2 / Temperature2 - ✔✔Charles' Second
Law
Pressure1 x Volume1 = Pressure2 x Volume2 - ✔✔Boyle's Law
(Pres1 x Vol1)/ Temp1 = (Pres2 x Vol2)/Temp2 - ✔✔General Gas Law
Resistance x DistanceR = Effort x DistanceE - ✔✔Formula for Levers
Force x Length = Resistance x Height - ✔✔Formula for Inclined Planes
Force x DistanceF = Resistance x DistanceR - ✔✔Formula for Wheel & Axel
Force x Radius - ✔✔Torque
(Area of Staybolt x Stress Constant of Staybolt) ÷ Area Covered by Staybolt or =
(a x C) ÷ A - ✔✔Safe Working Pressure of a Riveted Boiler (SWP)
= Pitch x Pitch - ✔✔Area Covered by Staybolt
(P x D x L) / 2t
P = Pressure
D = Diameter
L = Length
t = thickness of steel - ✔✔Longitudinal Stress
=CxLx#
C = Circumference of tubes
L = Length of tubes
# = Number of tubes
HS = π x Diameter x Length x Number of Tubes - ✔✔Boiler Heating Surface
(tubes) =
, 746 Watts - ✔✔Watts per Boiler Horsepower
= ft-lb/min ÷ 33000 ft-lb/min - ✔✔Horsepower formula
= gpm x 8.33 x head (ft) - ✔✔ft-lb formula for a pump
= [Hs - (tfw-32)] ÷ 970.3
Hs = Enthalpy of steam
tfw = temperature of feed water - ✔✔Factor of Evaporation (FE) =
970.3 Btu/lb - ✔✔Latent Heat of Vaporization for Water
144 Btu/lb - ✔✔Latent Heat of Fusion for Water
34.5 lbs/hr - ✔✔1 Boiler Horsepower = x lbs of steam generator per hour
33,475 Btu/hr - ✔✔1 Boiler Horsepower = x Btu/hr
10 ft² heating surface - ✔✔1 BHP = x ft² of heating surface (general)
x 1600 - ✔✔Volume of water increases by x percent when it flashes to steam
= Lbs Steam per hour [Hs -(fwt° -32)] ÷ Units of Fuel per hour x Btu content per
unit of fuel
Hs = Btu content of steam
fwt = feed water temperature - ✔✔Thermal Efficiency (TE) =
= (Pounds of Steam per hour (Ws) x FE) ÷ 34.5
Ws = Lbs of steam per hour
FE = Factor of Evaporation - ✔✔Developed Boiler Horsepower (DBHP) =
= (TS x t x E) / FS x r
TS = Tensile Strength of steel
t = thickness of steel
E = Efficiency of joint
FS = Factor of Safety
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