Published: May 9, 2018 - by Ray Wohlfarth

Categories: Rules of Thumb

Every effort was made to verify the validity of the formulas but we are not responsible for errors and omissions. These do not take the place of engineering calculations. These are rules of thumb. Please consult with the equipment manufacturer for actual requirements. 

 

Pipe Sizing to Assure Steam Velocities Below 40 FPS

Pipe Size

Pounds / Hr

Btu/ Hr

2”

140

134,400

2 ½”

199

191,200

3”

307

295,600

4”

530

509,200

5”

833

799,600

6”

1,204

1,155,600

8”

2,131

2,046,000

10”

3,397

3,262,000

12”

4,783

4,592,000

 

Pipe Sizing to Assure Steam Velocities Below 50 FPS

Pipe Size

Pounds / Hr

Btu/ Hr

2”

175.00

168,000

2 ½”

248.96

239,000

3”

384.90

369,500

4”

663.02

636,500

5”

1,041.15

999,500

6”

1,504.69

1,444,500

8”

2,664.06

2,557,500

10”

4,247.40

4,077,500

12”

5,979.17

5,740,000

 

How to calculate steam velocity

Lbs/Hr x Cubic Volume of Steam divided by 25 x Internal area of pipe = Steam Velocity

Steam Velocity = Lbs Hour x Cubic Volume of Steam/25 x Internal Area of Pipe

Lbs. Steam/Hr = Btuh/960 Lbs. Steam/Hr = Boiler HP x 34.5 Another formula to calculate steam velocity is:

Steam Velocity = 2.4 x Lbs Hour x Specific Volume of Steam Internal Area of Pipe

 

Volume of Steam in Cubic Feet per Hour

PSIG Steam

Cubic Feet per pound

0

27

1

25

2

24

3

22

4

21

5

20

 

Internal Volume of Schedule 40 Pipe

Pipe Size

Internal Square Inches

2”

3.36”

2 ½”

4.78”

3”

7.39”

4”

12.73”

5”

19.99”

6”

28.89”

8”

51.15”

10”

81.55”

12”

114.80”

 

How Fast is Fast?

One foot per second = 0.6818 miles per hour

The following is a chart to help you to compare the steam velocities.

Feet per Second to Miles per Hour

FPS

MPH

 

FPS

MPH

15

10.2

 

50

34.09

20

13.6

 

55

37.5

25

17

 

60

40.9

30

20.4

 

65

44.31

35

23.86

 

70

47.72

40

27.27

 

75

51.13

45

30.68

 

80

54.54