Friction loss

 

Pipe friction is the resistance to flow created by the interior

surface of the pipe through which a liquid is moving. The

smaller the diameter of the pipe, or greater the rate of flow,

the greater the amount of friction (friction loss).

Friction loss is expressed as feet of head in 100 feet of pipe and will vary depending upon the material of which the pipe

is made. The following charts show friction losses in steel,

copper, and plastic pipe, Pipe size should be sufficiently large

so that not more than 10% of the total dynamic head is in

friction loss.

Equivalent Number of Feet Straight Pipe for Different Fittings

 

Size of fittings, Inches

90° EII

45° EII

Long sweep EII

Close return bend

Tee-straight run

Tee-side inlet or outlet

Globe valve open

Angle valve open

Gate valve - fully open

Check valve (Swing)

Chcek valve (Spring)

 

 

1/2"

1.5

0.8

1.0

3.6

1.0

3.3

17.0

8.4

0.4

4.0

4.0

 

 

3/4"

2.0

1.0

1.4

5.0

2.0

4.5

22.0

12.0

0.5

5.0

6.0

 

1"

2.7

1.3

1.7

6.0

2.0

5.7

27.0

15.0

0.6

7.0

8.0

 

 

1-1/4"

3.5

1.7

2.3

8.3

3.0

7.6

36.0

18.0

0.8

9.0

12.0

 

1-1/2"

4.3

2.0

2.7

10.0

3.0

9.0

43.0

22.0

1.0

11.0

14.0

 

 

2"

5.5

2.5

3.5

13.0

4.0

12.0

55.0

28.0

1.2

13.0

19.0

 

 

2-1/2"

6.5

3.0

4.2

15.0

5.0

14.0

67.0

33.0

1.4

16.0

23.0

 

 

3"

8.0

3.8

5.2

18.0

 

17.0

82.0

42.0

1.7

20.0

32.0

 

 

4"

10.0

5.0

7.0

24.0

 

22.0

110.0

58.0

2.3

26.0

43.0

 

 

5"

14.0

6.3

9.0

31.0

 

27.0

140.0

70.0

2.9

33.0

58.0

 

 

6"

15.0

7.1

11.0

37.0

 

31.0

160.0

83.0

3.5

39.0

 

Pipe Friction Tables - by Nelsen Corporation

Figure friction loss for 118.5 ft. of pipe

 

(B) Assume flow to be 80 GPM through 2" plastic pipe.

  1. Friction loss table shows 10.9 ft. loss per 100 ft. of pipe.
  2. In step (A) we have determined total feet of pipe to be 118.5 ft.
  3. Convert 118.5 ft. to percentage 118.5 ÷ 100 = 1.185.
  4. Multiply 10.9 x 1.185 = 12.9165 or 12.92 ft. = Total friction loss in this system

Example

(A) 100 ft. of 2" plastic pipe with one (1) 90° elbow and one

(1) swing check valve.

 

 

90° elbow — Equivalent to

Swing Check — Equivalent to

100 ft. of pipe — Equivalent to

 

 

 

5.5 ft. of straight pipe

13.0 ft. of straight pipe

100.0 ft. of straight pipe

118.5 ft. = Total equivalent pipe

 

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George Hogg

WTC

 

Email:

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Lloydminster, AB T9V 0Y4