Flash Steam Generation - Imperial Units (psig)

When condensate passes steam traps - flash steam is generated

The amount of flash steam generated depends on steam pressure - the pressure in the condensate before it leaves the condensate trap - and the condensate pressure after the trap - the pressure in the condensate return pipe lines.

The diagram and table below indicates the ratio of flash steam generated at different pressures before and after condensate traps:

condensate flash steam generation diagram psig

Flash Steam generated from Condensate (%)
Steam Pressure before the Steam Trap
(psig)
Condensate Pressure after the Trap (psig)
01) 2 5 10 15 20 30 40 60 80 100
5 1.7 1
10 2.9 2.2 1.4
15 4 3.2 2.4 1.1
20 4.9 4.2 3.4 2.1 1.1
30 6.5 5.8 5 3.8 2.6 1.7
40 7.8 7.1 6.4 5.1 4 3.1 1.3
60 10 9.3 8.6 7.3 6.3 5.4 3.6 2.2
80 11.7 11.1 10.3 9 8.1 7.1 5.5 4 1.9
100 13.3 12.6 11.8 10.6 9.7 8.8 7 5.7 3.5 1.7
125 14.8 14.2 13.4 12.2 11.3 10.3 8.6 7.7 5.2 3.4 1.8
160 16.8 16.2 15.4 14.1 13.2 12.4 10.6 9.5 7.4 5.6 4
200 18.6 18 17.3 16.1 15.2 14.3 12.8 11.5 9.3 7.5 5.9
250 20.6 20 19.3 18.1 17.2 16.3 17.7 13.6 11.2 9.8 8.2
300 22.7 21.8 21.1 19.9 19 18.2 16.7 15.4 13.4 11.8 10.1
350 24 23.3 22.6 21.6 20.5 19.8 18.3 17.2 15.1 13.5 11.9
400 25.3 24.7 24 22.9 22 21.1 19.7 18.5 16.5 15 13.4

1) It is common to vent the condensate system to the atmosphere - where the gauge pressure is 0 psig.

  • 1 psi (lb/in2) = 6,894.8 Pa (N/m2) = 6.895x10-3 N/mm2 = 6.895x10-2 bar

Example - Generated Flash Steam

A condensate system is vented to the surroundings and the pressure in the condensate return system after the steam traps is therefore 0 psig (atmospheric pressure).  The steam pressure before the steam traps is 160 psig.

According the table above 16.8% of the condensate evaporates as flash steam passing the traps.

Note! Without any flash recovery system the energy in the flash steam will be lost to the surroundings.

If you prefer SI units - go here!

Related Topics

  • Steam and Condensate - Steam & condensate properties - capacities, pipe sizing, systems configuration and more
  • Flash Steam - Flash steam generation - thermodynamic fundamentals, heat loss, energy recovery and more

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