Skip to main content
Speclore

Boiler Blowdown

Reference data and engineering information about boiler blowdown for steam and condensate applications.

boilerblowdown

Overview

Engineering reference data for Boiler Blowdown in steam condensate.

Key Formulas

Steam Quality

x=mvmtotalx = \frac{m_v}{m_{total}}

Mass fraction of vapor in two-phase mixture.

Enthalpy of Wet Steam

h=hf+x⋅hfgh = h_f + x \cdot h_{fg}

Specific enthalpy of wet steam.

Flash Steam

mflash=mliquidhf−hf2hfg2m_{flash} = m_{liquid} \frac{h_f - h_{f2}}{h_{fg2}}

Steam generated when condensate flashes to lower pressure.

Condensate Load

mc=Qhfgm_c = \frac{Q}{h_{fg}}

Condensate generated by heat transfer.

Variables

SymbolDescriptionUnit
xxSteam quality—
hfh_fEnthalpy of saturated liquidkJ/kg
hfgh_{fg}Latent heat of vaporizationkJ/kg
hhSpecific enthalpykJ/kg
QQHeat transfer ratekW

References

ASME Guidelines for Watertube Boiler Water Quality

5 rows
Maximum allowable impurities in watertube boiler water per ASME guidelines. All values are in parts per million (ppm) unless noted. Conductivity measured in μS/cm (1 S/m = 10⁴ μS/cm).
pressure
0 - 300
300 - 450
450 - 600
600 - 750
750 - 900

Source: engineeringtoolbox.com

Typical Water Conductivity Ranges

Water TypeSpecific Conductivity (μS/cm)
Ultrapure water (20°C)0.042
Deionized water0.5 – 5
Soft ground water100 – 300
Sea water45,000 – 55,000
Concentrated acids/lyes> 100,000

Common Problems from Uncontrolled Solids

If boiler solids are not properly purged through blowdown, they can lead to:

  • Scale formation – mineral deposits that insulate heat transfer surfaces
  • Carryover – water and impurities entrained in the steam
  • Corrosion – chemical attack on boiler metals
  • Embrittlement – weakening of boiler metal due to caustic conditions
Source: engineeringtoolbox.com