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Steam Formulas

JStarJStar Member Posts: 2,668
So, I'm sitting in the office on a Saturday, thinking about steam like usual. Came up with a few quick reference guides for header and vent sizing. This will be a growing list, I'm sure. Feel free to improve my numbers or add to them.

Steam Formulas and Capacities

****Header Size per Maximum BTUH DOE Output****

(Based on Velocity of 15 ft/sec. to 20 ft/sec. and 1 PSI of pressure)

2" Header    = 48,384 - 64,512

2.5" Header = 68,832 - 91,776

3" Header    = 106,416 - 141,888

4" Header    = 183,312 - 244,416

5" Header    = 287,856 - 383,808

6" Header    = 416,016 - 544,688

3&4 Section Boilers = 3" Header

5&6 Section Boilers = 4" Header


****Steam Venting Practical Capacities****


1-1/2"    @ 25 feet

2"           @ 15 feet

2-1/2"    @ 10 feet

3"          @ 6 feet


1-1/2"    @ 80 feet

2"           @ 50 feet

2-1/2"    @ 35 feet

3"          @  20 feet
- Joe Starosielec
[email protected]


  • jumperjumper Member Posts: 864
    steam drums

    Bigger boilers sometimes had drums. When I think about it now, I wonder how thermal expansion was accommodated.
  • JStarJStar Member Posts: 2,668

    I used the formulas in TLAOSH and the venting charts. I don't have it on hand right now. I'll post my notes later in the week.

    The only numbers I couldn't calculate were header sizing for lower pressures than 1 psi. Your system at 1 oz could probably work with a 1" header!
    - Joe Starosielec
    [email protected]
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