DC Boiler Exam Prep 2024 (Formulas And
Constants Used For The Dc 3rd Class Boiler Exam)
– Q&A
Area of a rectangle - ✔️ Length x Width
Area of a Circle - ✔️ .7854 x Diameter²
Volume of a Box - ✔️ Length x Width x Height
Volume of a Cylinder - ✔️ .7854 x Diameter² x Length
Circumference of a Circle - ✔️ π x Diameter
Unit of Force - ✔️ Pound (lb)
Formula for Force - ✔️ Pressure ÷ Area
Unit of Work - ✔️ in-lb or ft-lb
Formula for Work - ✔️ Force x Distance
Unit of Power - ✔️ ft-lb/min
Formula for Power - ✔️ = Work ÷ Time
or (Force x Distance) ÷ Time
Formula for Mechanical Horsepower - ✔️ = Power ÷ 33,000
ft-lb/min
Fahrenheit to Celsius - ✔️ °C = (°F - 32) ÷ 1.8
Celsius to Fahrenheit - ✔️ °F = (1.8 x °C) - 32
Fahrenheit to Rankine - ✔️ °R = °F + 460
Celsius to Kelvin - ✔️ K = °C +273.15
,Charles' First Law - ✔️ Volume1 / Pressure1 = Volume2 / Pressure2
Charles' Second Law - ✔️ Pressure1 / Temperature1 = Pressure2 /
Temperature2
Boyle's Law - ✔️ Pressure1 x Volume1 = Pressure2 x Volume2
General Gas Law - ✔️ (Pres1 x Vol1)/ Temp1 = (Pres2 x
Vol2)/Temp2
Formula for Levers - ✔️ Resistance x DistanceR = Effort x DistanceE
Formula for Inclined Planes - ✔️ Force x Length = Resistance x
Height
Formula for Wheel & Axel - ✔️ Force x DistanceF = Resistance x
DistanceR
Torque - ✔️ Force x Radius
Safe Working Pressure of a Riveted Boiler (SWP) - ✔️ (Area of
Staybolt x Stress Constant of Staybolt) ÷ Area Covered by Staybolt or = (a x C)
÷A
Area Covered by Staybolt - ✔️ = Pitch x Pitch
Longitudinal Stress - ✔️ (P x D x L) / 2t
P = Pressure
D = Diameter
L = Length
t = thickness of steel
Boiler Heating Surface (tubes) = - ✔️ = C x L x #
C = Circumference of tubes
L = Length of tubes
# = Number of tubes
HS = π x Diameter x Length x Number of Tubes
, Watts per Boiler Horsepower - ✔️ 746 Watts
Horsepower formula - ✔️ = ft-lb/min ÷ 33000 ft-lb/min
ft-lb formula for a pump - ✔️ = gpm x 8.33 x head (ft)
Factor of Evaporation (FE) = - ✔️ = [Hs - (tfw-32)] ÷ 970.3
Hs = Enthalpy of steam
tfw = temperature of feed water
Latent Heat of Vaporization for Water - ✔️ 970.3 Btu/lb
Latent Heat of Fusion for Water - ✔️ 144 Btu/lb
1 Boiler Horsepower = x lbs of steam generator per hour - ✔️ 34.5
lbs/hr
1 Boiler Horsepower = x Btu/hr - ✔️ 33,475 Btu/hr
1 BHP = x ft² of heating surface (general) - ✔️ 10 ft² heating surface
Volume of water increases by x percent when it flashes to steam - ✔️
x 1600
Thermal Efficiency (TE) = - ✔️ = 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
Developed Boiler Horsepower (DBHP) = - ✔️ = (Pounds of Steam per
hour (Ws) x FE) ÷ 34.5
Ws = Lbs of steam per hour
FE = Factor of Evaporation
Maximum Allowable Working Pressure (MAWP) - ✔️ = (TS x t x E) /
FS x r
TS = Tensile Strength of steel
t = thickness of steel
E = Efficiency of joint
Constants Used For The Dc 3rd Class Boiler Exam)
– Q&A
Area of a rectangle - ✔️ Length x Width
Area of a Circle - ✔️ .7854 x Diameter²
Volume of a Box - ✔️ Length x Width x Height
Volume of a Cylinder - ✔️ .7854 x Diameter² x Length
Circumference of a Circle - ✔️ π x Diameter
Unit of Force - ✔️ Pound (lb)
Formula for Force - ✔️ Pressure ÷ Area
Unit of Work - ✔️ in-lb or ft-lb
Formula for Work - ✔️ Force x Distance
Unit of Power - ✔️ ft-lb/min
Formula for Power - ✔️ = Work ÷ Time
or (Force x Distance) ÷ Time
Formula for Mechanical Horsepower - ✔️ = Power ÷ 33,000
ft-lb/min
Fahrenheit to Celsius - ✔️ °C = (°F - 32) ÷ 1.8
Celsius to Fahrenheit - ✔️ °F = (1.8 x °C) - 32
Fahrenheit to Rankine - ✔️ °R = °F + 460
Celsius to Kelvin - ✔️ K = °C +273.15
,Charles' First Law - ✔️ Volume1 / Pressure1 = Volume2 / Pressure2
Charles' Second Law - ✔️ Pressure1 / Temperature1 = Pressure2 /
Temperature2
Boyle's Law - ✔️ Pressure1 x Volume1 = Pressure2 x Volume2
General Gas Law - ✔️ (Pres1 x Vol1)/ Temp1 = (Pres2 x
Vol2)/Temp2
Formula for Levers - ✔️ Resistance x DistanceR = Effort x DistanceE
Formula for Inclined Planes - ✔️ Force x Length = Resistance x
Height
Formula for Wheel & Axel - ✔️ Force x DistanceF = Resistance x
DistanceR
Torque - ✔️ Force x Radius
Safe Working Pressure of a Riveted Boiler (SWP) - ✔️ (Area of
Staybolt x Stress Constant of Staybolt) ÷ Area Covered by Staybolt or = (a x C)
÷A
Area Covered by Staybolt - ✔️ = Pitch x Pitch
Longitudinal Stress - ✔️ (P x D x L) / 2t
P = Pressure
D = Diameter
L = Length
t = thickness of steel
Boiler Heating Surface (tubes) = - ✔️ = C x L x #
C = Circumference of tubes
L = Length of tubes
# = Number of tubes
HS = π x Diameter x Length x Number of Tubes
, Watts per Boiler Horsepower - ✔️ 746 Watts
Horsepower formula - ✔️ = ft-lb/min ÷ 33000 ft-lb/min
ft-lb formula for a pump - ✔️ = gpm x 8.33 x head (ft)
Factor of Evaporation (FE) = - ✔️ = [Hs - (tfw-32)] ÷ 970.3
Hs = Enthalpy of steam
tfw = temperature of feed water
Latent Heat of Vaporization for Water - ✔️ 970.3 Btu/lb
Latent Heat of Fusion for Water - ✔️ 144 Btu/lb
1 Boiler Horsepower = x lbs of steam generator per hour - ✔️ 34.5
lbs/hr
1 Boiler Horsepower = x Btu/hr - ✔️ 33,475 Btu/hr
1 BHP = x ft² of heating surface (general) - ✔️ 10 ft² heating surface
Volume of water increases by x percent when it flashes to steam - ✔️
x 1600
Thermal Efficiency (TE) = - ✔️ = 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
Developed Boiler Horsepower (DBHP) = - ✔️ = (Pounds of Steam per
hour (Ws) x FE) ÷ 34.5
Ws = Lbs of steam per hour
FE = Factor of Evaporation
Maximum Allowable Working Pressure (MAWP) - ✔️ = (TS x t x E) /
FS x r
TS = Tensile Strength of steel
t = thickness of steel
E = Efficiency of joint
