Often it is necessary to convert a measure of capacity from one term to another.  The conversion table will allow you to quickly convert various measures of capacity.  The table and formulas can help you size and pick out components such as condensate pumps and boiler feed pumps.  Some additional conversion factors that may prove helpful are shown below.

Conversion Factors

                      Multiply                                              By                                            To Get                           

BHP (Boiler Horsepower)                 34.5                                        Lbs/Hr of Steam at 212°F

BHP (Boiler Horsepower)                 0.069                                      GPM Water

BHP (Boiler Horsepower)                 33,479                                    BTU/Hr

Lbs/Hr Steam                                  0.002                                      GPM Water

Lbs/Sq In                                        2.307                                       Feet of Water

Feet of Water (Head)                      0.4335                                     Lbs/Sq In

Cubic Feet of Water                        7.48                                        Gallons of Water

Cubic Feet per Minute                    62.43                                      Lbs of Water/Minute

Cubic Feet per Minute                    448.8                                      Gallons per Hour

Heating Water with Steam

Example:

How many lbs per hour of steam is need to heat 40 gallons per minute flow rate of water from 60°F to 180°F?

Sizing a Boiler Feed Pump Receiver

The receiver tank should be able to hold five minutes worth of condensate for boilers up to 200 BHP and 10 minutes of condensate for boilers over 200 BHP.

An additional 33 percent should be added as a safety factor.  One BHP (Boiler Horsepower) will produce 0.069 gallons per minute of condensate.

Developing a formula results in:

BHP x 0.069 x minutes of storage x 1.33 = Receiver size, in gallons

Examples:

150 BHP Boiler

150(BHP) x 0.069 (gpm/BHP) x 10 (min) x 1.33(SF) = 137.66

Select an available receiver tank equal to or larger than 68.8 gallons.  (Probably a 70-gallon tank will be the standard commercially available tank.)

250 BHP Boiler

250(BHP) x 0.069 (gpm/BHP) x 10 (min) x 1.33(SF) = 229.425

Because of the 10 minute multiplier used in calculating a boiler feed pump receiver for boilers 200 BHP and over, a very fast sizing estimate can be done by simply stating that 1 BHP = 1 gallon of gross receiver capacity.  In other words, the 400 BHP boiler needs about a 400-gallon receiver.

For Boilers under 200 BHP, a fast estimate would be to take half the BHP rating to arrive at the receiver size in gallons.  For the 200 BHP and over boilers, this fast estimating results in receivers slightly larger than a calculated one.  For smaller boilers under 200 BHP, a slightly receiver size results than if calculated.

The difference between the calculated and estimated size will probably be insignificant when selecting from the available receivers, since it would be cost prohibitive to get a special receiver made.

Table 1.

Other Useful Information:

1 SQ.FT. E.D.R. = 240 BTUH @215°F

1 Boiler H.P. = 33493 BTU/Hr

Where             SpGr = Specific Gravity (Water is 1.0)

Condensate Pump Sizing:

A:         Pump Capacity = 2 x Actual GPM Condensate

B:         Minimum Receiver Size in Gallons = 1 minute x GPM found in part A

C:        Pump Head  (In Feet) = Static Lift in Feet + Friction Losses in Feet + Pressure In Vessel That’s Being    

                                                   Pumped To In PSIG x 2.31

Capacity Of A Cylindrical Tank In U.S. Gallons:

Capacity (In Gallons) = Diameter in Feet Squared x Height in Feet x 5.875