Boiler Capacity
It is common to express the output of steam boilers in Boiler Horsepower, BTU or in Pounds of Steam delivered per hour
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Boiler loads, or the capacity of steam boilers, are often rated in boiler horsepowers, lbs of steam delivered per hour, or BTU.
Lbs Steam delivered per Hour
Large boiler capacities are often given in lbs of steam evaporated per hour under specified steam conditions.
BTU - British Thermal Units
Since the amount of steam delivered varies with temperature and pressure, a common expression of the boiler capacity is the heat transferred over time expressed as British Thermal Units per hour. A boilers capacity is usually expressed as kBtu/hour (1000 Btu/hour) and can be calculated as
W = (hg - hf) m (1)
where
W = boiler capacity (Btu/h)
hg = enthalpy steam (Btu/lb)
hf = enthalpy condensate (Btu/lb)
m = steam evaporated (lb/h)
Boiler Horsepower - BHP
The Boiler Horsepower (BHP) is
- the amount of energy required to produce 34.5 pounds of steam per hour at a pressure and temperature of 0 Psig and 212 oF, with feedwater at 0 Psig and 212 oF.
An BHP is equivalent to 33,475 BTU/Hr or 8430 Kcal/Hr and it should be noted that a boiler horsepower is 13.1547 times a normal horsepower.
- 1 horsepower (boiler) = 33445.6 Btu (mean)/hr = 140671.6 calorie/min (thermo) = 140469.4 calorie (mean)/min = 140742.3 calorie (20oC)/min 9.8095x1010 erg/sec = 434107 foot-pound-force/min = 13.1548 horsepower (mech) = 13.1495 horsepower (electric) = 13.3372 horsepower (metric) = 13.1487 horsepower (water) = 9809.5 joule/sec = 9.8095 kilowatt
Horsepower (hp) can be converted into lbs of steam by multiplying hp with 34.5.
Example - Boiler Horsepower to lbs of Steam Conversion
200 hp x 34.5 = 6900 lbs of steam per hour
Lbs of steam can be converted to hp by dividing lbs steam per hour by 34.5
Example - Lbs of Steam to Boiler Horsepower Conversion
5000 lbs of steam / 34.5 = 145 hp boiler
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Related Topics
- Thermodynamics - Thermodynamics of steam and condensate applications
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Related Documents
- ASME - International Boiler and Pressure Vessel Code - The International Boiler and Pressure Vessel Code establishes rules of safety governing the design, fabrication, and inspection of boilers and pressure vessels, and nuclear power plant components during construction
- Boiler Blowdown - Suspended solids entering boilers through feed water will remain behind when steam is generated. After a while the concentration of solids makes the operation of the boiler unsatisfactory
- Boiler Blowdown Rate - Calculating boiler blowdown rate
- Boiler Efficiency - Boiler efficiency - combustion gross and net calorific value
- Safety Valve Standards - An survey of international safety valve standards. The most common used standards in Germany, UK, USA, France, Japan, Australia and Europe





