2000 Hook-up Book

Flash Steam

Example Size a 20 psig flash recovery ves sel utilizing condensate from a 160 psig steam trap discharging 3000 lb/h. 1. Determine percent flash steam produced using Table 12. With a steam pressure of 160 psig and a flash tank pressure of 20 psig, read a value of 12.4%. 2. Next, multiply the condensate load by the percent flash from Step #1 to determine the

flowrate, of flash steam pro duced. 3,000 lb/h x .124 = 372 lb/h. 3. Using the calculated flash steam quantity of 372 lb/h enter Fig. 51 at “A” and move horizontally to the right to the flash tank pressure of 20 psig “B”. Rise vertically to the flash tank diameter line (600 ft/min) at “D”. Read tank diameter of 5”. If schedule 80 pipe is to be installed, the table within the body of the

chart can be used to deter mine whether the velocity will exceed the recommended limit of 600 ft/min. 4. From point “D” continue to rise vertically to “E” to deter mine the size of vent pipe to give a velocity between 3000 and 4000 ft/min. In this case 2” schedule 40 pipe. As before, use the table within the body of chart for schedule 80 pipe.

SYSTEM DESIGN

Figure 51: Condensate Line, Flash Tank, and Vent Line Sizing

Velocity (ft/min)

Velocity (ft/sec)

Pipe Size (schedule 40)

Recommended Service Condensate Return Line Sizing Vent Pipe Sizing

6000

100

C

3000 4000

66 50

E

2000

33

28"

1-1/4"

1-1/2"

2-1/2"

12"

3/4"

1/2"

16"

14"

24"

18"

20"

26"

10"

1"

30"

3"

5"

2"

6"

4"

8"

1000

17

D

Flash Tank Diameter Sizing

600

10

50,000

Multiply chart velocity by factor below to get velocity in schedule 80 pipe Pipe Size 1/2" 3/4" & 1" 1-1/4" & 1-1/2" 2" & 3" 4" to 24" 26" to 30" Factor 1.30 1.23 1.15 1.12 1.1 1.0

100

80

30,000

60

40

30

20

20,000

10

5

0

10,000 8000

5000

100

80

3000

60

40

30

20

2000

10

5

0

800 1000

500

B

A

300

200

Flash Steam Flowrate (lb/h)

100

80

60

30 40 50 60 80 100

40

30

20

10

5

0

Pressure in condensate line or flash tank (psig)

20

10

43