Steam Boiler Formulas, Condensate and Boiler Feed tank Sizing

Steam Conversion Formulas

Boiler Horsepower (BHP) * 34.5 = Lb of Steam/Water per hour(lb/hr)
Boiler Horsepower * 0.069 = Gallons of Water Per Minute (GPM)
Sq Ft of EDR * 0.000637 = Gallons of Water Per Minute (GPM)
Boiler Horsepower * 33,479 = BTU
Boiler Horsepower * 108 = Equivalent Direct Radiation (EDR)
Lbs per Sq In * 2.31 = Feet of Water
Lbs per Sq In * 2.036 = Inches of Mercury
Feet of Water (Head) * 0.4335 = Pounds per Sq In
Inches of Mercury * 13.6 = Inches of Water Column
Gallons of Water * 8.34 = Pounds of Water
Cubic Feet of Water * 7.48 = Gallons of Water
Cubic Feet per Minute * 62.43 Pounds of Water per Minutes
Cubic Feet per mInute * 448.8 = Gallons per Hour
Pounds of Condensate x 4 = Sq Ft EDR
EDR/ 1000 * 0.5 = Evaporation Rate Gallons per minute (GPM)
Pounds of Steam/hr / 500 = Evaporation Rate Gallons per minute (GPM)

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Condensate Pump Sizing

Evaporation Rate * 3 = Pump GPM Required
Pump GPM * 1 = Receiver Tank Size (Gallons Storage)
Example; 4,500,000 Output boiler / 240 = 18,750
18,750 EDR / 1000 x .5 = 9.37
9.37 GPM * 3 = 28 GPM Pump Capacity
Pump GPM * 1 = 28 Gallon Tank

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Boiler Feed Tank Sizing

Evaporation Rate * 1.85 = Pump GPM Required
Evaporation Rate * 20 = Receiver Tank Size (Gallon Storage at 20 Minutes)
Example; 4,500,000 BTU Output / 33.479 = 134.5 BHP
134.5 BHP * .069 = 9.28 GPM
9.28 GPM * 1.85 = 17.1 Pump GPM Required
17.1 * 20 = 342 Gallons Storage

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What is A Condensate Pump

Operation of a condensate pump is like a sump pump. It works off of a float mechanism. When the condensate tanks gets enough water in it to lift the float it makes a switch. This turns the pump on and pumps water back into the boiler. The problem is the boiler may not need water at that time and it overfills the boiler. This will create wet steam. Wet steam moves slower and turns back into condensate long before it should. You lose the heating capability of steam and must run the boiler to make more steam.

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Boiler Feed Tank Operation

The boiler feed unit is larger and holds more water than a condensate pump and does not work off of a float. The boiler feed tank will get a signal from a boiler pump controller to start and stop the pump. The boiler only gets water when it is needed. The boiler does not overfill. If the near boiler piping is correct we get drier steam. The other difference is the make-up water for the boiler is fed into the tank not the boiler. The feed water is controlled by a float. The benefit of this is as the boiler feed tank is hot due to returning condensate it helps remove the damaging oxygen before getting to the boiler. It also give a place for dissolved solids to drop out before getting to the boiler.