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The amount of flash steam generated depend on the 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 the condensate trap.

| Percent Flash Steam of 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.
A condensate system is vented to the surroundings and the pressure in the condensate system after the condensate traps is 0 psig. The steam pressure before the condensate trap is 160 psig.
According the table above 16.8% of the condensate will evaporate as flash steam after the trap.
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!
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