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APPENDIX C

FUNDAMENTALS OF PIPELINE HYDRAULICS

Section I. Physical Properties of Petroleum

TYPES OF PROPERTIES

Petroleum products have both chemical and physical properties or qualities. This manual is mainly concerned with kerosene, automotive gasoline, jet fuel, and diesel fuel. Both physical and chemical properties are of concern to the scheduler and dispatcher. However, only physical properties as they affect product storage and movement in pipelines are covered in this appendix. They include density, gravity, viscosity, compressibility, effect of temperature, and vapor pressure.

Density

All substances have weight. Their weight depends on the number and arrangement of molecules of which they are composed. Weight is a measure of the force of gravity. The weight of a definite mass of a substance varies slightly in different parts of the country because gravity varies. For this reason, weight and mass are not identical. Mass stays constant, but weight may not stay constant. The weight density or specific weight of a substance is its weight per unit volume. The term specific refers to a unit quantity. In the metric system of measurement, the mass of 1 cubic centimeter of water is 1 gram. Therefore, the density or specific weight of water is 1 gram per cubic centimeter. In the English system of measurement, the density or specific weight of water is expressed as 62.3 pounds per cubic foot. Specific volume is the space occupied by a unit quantity. In the metric system, 1 gram of water occupies 1 cubic centimeter. In the English system, 62.3 pounds of water occupies 1 cubic foot.

Gravity

Gravity is the attraction between matter and the earth's center. It is properly referred to as acceleration due to gravity, which is the change in speed of a body falling freely toward the earth. This change in speed is 32.2 feet per second. This means that during each second of fall, the speed increases 32.2 feet per second. Gravity is measured by weight. Petroleum operations are concerned with specific gravity and API gravity. Specific gravity and API gravity and formulas for converting one to the other are described below.

  • Specific Gravity. Specific gravity is a means of comparing weights of substances. This is independent of the actual numerical value of the pull of gravity in any locality. Specific gravity is the ratio between the weight of a quantity or volume of a substance and the weight of an equal quantity of water. It is a relative measure of weight density compared with water. Solids and liquids are usually compared with water at its maximum density at 4° C. The specific gravity of water is 1. A substance of specific gravity 0.5 weighs half as much as water. A substance of specific gravity 5.0 weighs five times as much as water. Petroleum products moved by pipeline are lighter than water. Therefore, their specific gravities are fractions in a narrow numerical range. Specific gravity is measured with a hydrometer.
  • API Gravity. The petroleum industry uses the API gravity scale almost exclusively to designate gravities of products. API gravities are based on reciprocals of specific gravities. They are whole numbers with a greater numerical spread. The API scale has a range of 0° to 100° . Water has a gravity of 10° API. This leaves a spread of 90° API between the heaviest and lightest petroleum products. API gravity is inversely proportionate to specific gravity. In other words, the higher the specific gravity, the heavier the product and the lower the API gravity. The lightest products have the highest API gravities.
  • Formulas and Conversion Table. Formulas for converting specific gravity to API gravity and vice versa are given below. Table C-1 lists API gravity and corresponding specific gravity and weights at 60° F.

      Degrees API gravity =

                     141.5              

      -131.5

      specific gravity (60/60° F)

      Specific gravity (60/60° F) =

                     141.5              

       

      131.5 + degrees API

Table C-1. API gravity equivalents at 60° F

   

POUNDS PER

BARRELS PER

API SPECIFIC

SPECIFIC
GRAVITY

US
GALLON

IMPERIAL
GALLON

BARREL

LONG
TON

METRIC
TON

SHORT
TON

1........

1.0679

8.895

10.683

373.59

5.996

5.901

5.353

2........

1.0599

8.828

10.602

370.78

6.041

5.946

5.394

3........

1.0520

8/762

10.523

368.00

6.087

5.991

5.435

4........

1.0443

8.697

10.446

365.32

6.132

6.035

5.475

5........

1.0368

8.634

10.369

362.63

6.177

6.080

5.516

6........

1.0291

8.571

10.294

359.98

6.223

6.124

5.556

7........

1.0217

8.509

10.219

357.38

6.268

6.169

5.596

8........

1.0143

8.448

10.146

354.82

6.313

6.213

5.637

9........

1.0071

8.388

10.074

352.30

6.359

6.258

5.677

10a.......

1.0000

8.328

10.002

349.78

6.404

6.303

5.718

11.........

0.9930

8.270

9.932

347.34

6.449

6.347

5.799

12.........

0.9861

8.212

9.863

344.90

6.495

6.392

5.799

13.........

0.9792

8.155

9.794

342.51

6.540

6.437

5.839

14.........

0.9725

8.099

9.727

340.16

6.585

6.481

5.880

15.........

0.9659

8.044

9.661

337.85

6.630

6.525

5.920

16.........

0.9593

7.989

9.595

335.54

6.676

6.570

5.961

17.........

0.9529

7.935

9.530

333.27

6.721

6.615

6.001

18.........

0.9465

7.882

9.466

331.04

6.766

6.660

6.042

19.........

0.9402

7.830

9.404

328.86

6.812

6.704

6.082

20.........

0.9340

7.778

9.341

326.68

6.857

6.749

6.122

21.........

0.9279

7.727

9.280

324.53

6.902

6.793

6.163

22.........

0.9218

7.676

9.219

322.39

6.948

6.838

6.204

23.........

0.9159

7.627

9.160

320.33

6.993

6.882

6.244

24.........

0.9100

7.578

9.101

318.28

7.038

6.927

6.284

25.........

0.9042

7.529

9.042

316.22

7.084

6.972

6.325

26.........

0.8984

7.481

8.985

314.20

7.129

7.017

6.365

27......

0.8927

7.434

8.928

312.23

7.174

7.061

6.406

28......

0.8871

7.387

8.872

310.25

7.220

7.106

6.446

29......

0.8816

7.341

8.817

308.32

7.265

7.150

6.487

30......

0.8762

7.296

8.762

306.43

7.310

7.194

6.527

31......

0.8708

7.251

8.708

304.54

7.356

7.239

6.568

32......

0.8654

7.206

8.654

302.65

7.401

7.284

6.603

33......

0.8602

7.162

8.603

300.85

7.446

7.328

6.648

34......

0.8550

7.119

8.550

299.00

7.492

7.373

6.689

35......

0.8499

7.076

8.498

297.19

7.537

7.418

6.730

36......

0.8448

7.034

8.448

295.43

7.582

7.462

6.770

37......

0.8398

6.992

8.399

293.71

7.628

7.506

6.810

38......

0.8348

6.951

8.348

291.94

7.673

7.552

6.851

39......

0.8299

6.910

8.299

290.22

7.718

7.597

6.891

40......

0.8251

6.870

8.251

288.54

7.764

7.641

6.931

41......

0.8203

6.830

8.203

286.86

7.809

7.686

6.972

42......

0.8156

6.790

8.155

285.18

7.854

7.731

7.013

43......

0.8109

6.751

8.109

283.58

7.900

7.774

7.053

44......

0.8063

6.713

8.062

281.95

7.945

7.819

7.093

45......

0.0817

6.675

8.017

280.35

7.990

7.864

7.134

46......

0.7972

6.637

7.971

278.75

8.036

7.909

7.175

47......

0.7927

6.600

7.927

277.20

8.081

7.953

7.215

48......

0.7883

6.563

7.882

275.65

8.126

7.998

7.256

49......

0.7839

6.527

7.838

274.09

8.172

8.043

7.297

50......

0.7796

6.491

7.794

272.58

8.217

8.088

7.337

51......

0.7753

6.455

7.752

271.11

8.262

8.132

7.377

52......

0.7711

6.420

7.710

269.64

8.308

8.176

7.417

53......

0.7669

6.385

7.668

268.17

8.353

8.221

7.458

54......

0.7628

6.350

7.626

266.70

8.398

8.266

7.499

55......

0.7587

6.316

7.586

265.27

8.444

8.130

7.539

56......

0.7547

6.283

7.546

263.89

8.489

8.354

7.579

57......

0.7507

6.249

7.505

262.46

8.534

8.400

7.620

58......

0.7467

6.216

7.465

261.07

8.850

8.444

7.661

59......

0.7428

6.183

7.427

259.73

8.625

8.488

7.700

60......

0.7389

6.151

7.387

258.34

7.670

8.534

7.742

61......

0.7351

6.119

7.349

257.00

8.716

8.578

7.782

62......

0.7313

6.087

7.310

255.65

8.761

8.623

7.823

63......

0.7275

6.056

7.273

254.35

8.807

8.668

7.863

64......

0.7238

6.025

7.236

253.05

8.852

8.712

7.904

65......

0.7201

5.994

7.199

251.75

8.897

8.757

7.944

66......

0.7165

5.964

7.163

250.49

8.943

8.801

7.984

67......

0.7128

5.934

7.127

249.23

8.988

8.846

8.025

68......

0.7093

5.904

7.091

247.97

9.033

8.891

8.065

69......

0.7057

5.875

7.055

246.71

9.079

8.936

8.107

70......

0.7022

5.845

7.020

245.49

9.125

8.980

8.147

71......

0.6988

5.816

6.986

244.31

9.169

9.024

8.187

72......

0.6953

5.788

6.951

243.10

9.215

9.069

8.227

73......

0.6919

5.759

6.917

241.88

9.260

9.114

8.269

74......

0.6886

5.731

6.883

240.70

9.305

9.159

8.309

75......

0.6852

5.704

6.849

239.53

9.351

9.204

8.350

76......

0.6819

5.676

6.817

238.39

9.396

9.248

8.390

77......

0.6787

5.649

6.784

237.26

9.442

9.292

8.430

78......

0.6754

5.622

6.752

236.12

9.487

9.337

8.470

79......

0.6722

5.595

6.720

234.99

9.532

9.382

8.511

80......

0.6690

5.569

6.687

238.86

9.578

9.427

8.552

81......

0.6659

5.542

6.656

232.76

9.623

9.472

8.593

82......

0.6628

5.516

6.624

231.67

9.668

9.516

8.633

83......

0.6597

5.490

6.595

230.62

9.714

9.559

8.672

84......

0.6566

5.465

6.563

229.53

9.759

9.605

8.713

85......

0.6536

5.440

6.533

228.48

9.805

9.649

8.754

86......

0.6506

5.415

6.503

227.43

9.850

9.694

8.794

87......

0.7476

5.390

6.473

226.38

9.895

9.738

8.835

88......

0.6446

5.365

6.443

225.33

9.941

9.784

8.876

89......

0.6417

5.341

6.415

224.32

9.986

9.828

8.916

90......

0.6388

5.317

6.385

223.27

10.031

9.874

8.957

91......

0.6360

5.293

6.357

222.31

10.077

9.917

8.996

92......

0.6331

5.269

6.328

221.30

10.122

9.962

9.038

93......

0.6303

5.245

6.300

220.33

10.168

10.006

9.077

94......

0.6275

5.222

6.273

219.37

10.213

10.050

9.117

aWater (H2O AT 60oF)

VISCOSITY

Viscosity is the internal resistance of a liquid to flow. A liquid is said to be viscous if it is sluggish or thick. Lubricating oil must be viscous enough to maintain a lubricating film under all operating conditions. However, it must not be so viscous that it becomes a drag or causes a power loss. Absolute viscosity is a measure of the force required to produce motion. The unit of force in the metric system is called the poise. One poise is equal to 100 centipoises. Viscosity is measured by noting the time in seconds for a standard amount of product to flow through a viscosimeter. The Saybolt Universal instrument is the type of viscosimeter commonly used for such measurements. A more accurate instrument for measuring viscosity is the Ubbelohde viscosimeter. Conversions from kinematic to Saybolt viscosity can be taken from the ASTM table (Table C-2).

Table C-2. Kinematic viscosity converted to Saybolt Universal viscosity

KINEMATAIC
VISCOSITY
cSt

EQUIVALENT SAYBOLT
UNIVERSAL VISCOSITY, SECONDS

KINEMATAIC
VISCOSITY
cSt

EQUIVALENT SAYBOLT
UNIVERSAL VISCOSITY, SECONDS

AT 100F
BASIC VALUES

AT 210F

AT 100F
BASIC VALUES

AT 210F

2........

32.6

32.9

27

128.1

129.0

2.5.......

34.4

34.7

28

132.5

133.4

3........

36.0

36.3

29

136.9

137.9

3.5.......

37.6

37.9

30

141.3

142.3

4........

39.1

39.4

31

145.7

146.8

4.5.......

40.8

41.0

32

150.2

151.2

5........

42.4

42.7

33

154.7

155.8

6.......

45.6

45.9

34

159.2

160.3

7........

48.8

49.1

35

163.7

164.9

8........

52.1

52.5

36

168.2

169.4

9........

55.5

55.9

37

172.7

173.9

10......

58.9

59.3

38

177.3

178.5

11.......

62.4

62.9

39

181.8

183.0

12.......

66.0

66.5

40

186.3

187.6

13.......

69.8

70.3

41

190.8

192.1

14.......

73.6

74.1

42

195.3

196.7

15.......

77.4

77.9

43

199.8

201.2

16.......

81.3

81.9

44

204.4

205.9

17.......

85.3

85.9

45

209.1

210.5

18.......

89.4

90.1

46

213.7

215.2

19.......

93.6

94.2

47

218.3

219.8

20.......

97.8

98.5

48

222.9

224.5

21.......

102.0

102.8

49

227.5

229.1

22.......

106.4

107.1

50

232.1

233.8

23.......

110.7

111.4

55

255.2

257.0

24.......

115.0

115.8

60

278.3

280.2

25.......

119.3

120.1

65

301.4

303.5

26.......

123.7

124.5

70

324.4

326.7

     

Over 70.....

Saybolt
seconds =
centistokes x
4.635

Saybolt
seconds =
centistokes x
4.667

Note: To obtain the Saybolt Universal viscosity equivalent to a kinematic viscosity determined at tF, multiply the equivalent Saybolt Universal viscosity at 100F by 1+(t - 100) 0.000034: for example, 10cSt at 210F are equivalent to 58.9 x 1.0070 or 59.3 seconds Saybolt Universal at 210F.

Compressibility

All fluids are compressible to an extent. That is, they can be made to occupy less space by increasing the pressure or decreasing the temperature. Liquids have perfect elasticity. They return to their original volume when the pressure is lowered or the temperature is increased. Products of the highest API gravity have the greatest compressibility. They can generate the highest surge pressure, known as hydraulic shock or water hammer. Products of high API gravity can also be transferred at the highest rate of flow. This also increases the possibility of surge pressure. Surge pressure must be avoided. Apart from surge pressure, compressibility has little significance in military dispatching of petroleum products.

TEMPERATURE

The effects of product temperature and its measurement and correction are described below.

Effects

Product temperature affects all of the properties discussed above. Volume, API gravity, compressibility, and volatility increase with temperature. Density, specific gravity, and viscosity decrease when the temperature increases. Pipeline throughput is higher in summer than in winter and requires less power. A pipeline heated by the sun delivers a greater volume. The API gravity is also higher in a pipeline than in the cool interior of a storage tank. Lubricating oil may be too thick to lubricate an engine properly when the engine is started on a cold morning. The same engine oil may thin out under operating temperatures. The change in viscosity with temperature is called viscosity index. It varies from product to product.

Measurements

Product is measured and tested many times between manufacture and consumption. Input stations report to the dispatcher temperatures and quantities pumped every hour. Takeoff stations report temperatures and quantities received every hour. Quantities are determined by gaging as shown in Tables C-3 and C-4, page C-6. Because of the effects of temperature on volume and gravity, all measurements are corrected to 60° F.

Table C-3. Gage data for military bolted tanks (capacities shown in barrels of 42 gallons)

DEPTH

100 bbla

250 bbla

500 bbla

1,000 bbla
or
3,000 bblb

10,000 bblb

in

0.24

0.69

1.35

2.57

8.81

in

.49

1.38

2.70

5.15

17.62

in

.73

2.07

4.06

7.72

26.43

1 in

.98

2.76

5.41

10.30

35.23

2 in

1.97

5.52

10.82

20.59

70.47

3 in

2.96

8.28

16.23

30.89

105.70

4 in

3.95

11.04

21.64

41.18

140.94

5 in

4.94

13.80

27.05

51.48

176.17

6 in

5.93

16.56

32.46

61.77

211.41

7 in

6.92

19.32

37.87

72.07

246.64

8 in

7.91

22.07

43.28

82.36

281.88

9 in

8.90

24.83

46.68

92.66

317.11

10 in

9.89

27.59

54.09

102.96

352.35

11 in

10.88

30.35

59.50

113.25

387.58

1 ft 0 in

11.87

33.11

64.91

123.56

422.82

2 ft 0 in

23.76

66.22

129.83

247.09

845.64

3 ft 0 in

35.66

99.34

194.74

370.64

1,268.46

4 ft 0 in

47.54

132.45

259.65

494.19

1,691.28

5 ft 0 in

59.43

165.56

324.56

617.74

2,114.09

6 ft 0 in

71.32

198.67

389.48

741.28

2,536.91

7 ft 0 in

83.21

231.79

454.39

864.38

2,959.73

8 ft 0 in

95.10

c264.90

c519.30

988.38

3,382.55

9 ft 0 in

106.99

c298.01

584.22

c1,111.93

3,805.37

10 ft 0 in

118.88

331.12

649.13

1,235.47

4,228.19

11 ft 0 in

130.77

364.24

714.04

1,359.02

4,651.01

12 ft 0 in

142.66

397.35

778.96

1,482.57

5,073.83

13 ft 0 in

154.55

430.46

843,87

1,606.12

5,496.64

14 ft 0 in

166.44

463.57

908.78

1,729.66

5,919.46

15 ft 0 in

178.33

496.69

973.69

1,853.29

6,342.28

16 ft 0 in

190.22

529.80

1,038.61

1,976.76

6,765.10

17 ft 0 in

.....

....

....

2,100.30

7,187.92

18 ft 0 in

.....

....

....

2,223.85

7,610.74

19 ft 0 in

.....

....

....

2,347.40

8,033.56

20 ft 0 in

.....

....

....

2,470.95

8,456.38

21 ft 0 in

.....

....

....

2,594.49

8,879.19

22 ft 0 in

.....

....

....

2,718.04

9,302.01

23 ft 0 in

.....

....

....

2,841.59

9,724.83

24 ft 0 in

.....

....

....

2,965.13

10,147.65

           

a One-ring tank.
b
More than n-ring tank.
c
Capacities greater than nominal size are produced by adding one additional ring. No more than one is permitted.

Table C-4. Deadwood for military bolted tanks (capacities are in barrels of 42 gallons)

DEPTH

100 bbla

250 bbla

500 bbla

1,000 bbla
or
3,000 bblb

10,000 bblb

1 ft 0 in

0.007

0.008

0.010

0.030

0.055

2 ft 0 in

.013

.016

.020

.060

.110

3 ft 0 in

.019

.024

.030

.089

.164

4 ft 0 in

.026

.032

.40

.119

.217

5 ft 0 in

.031

.039

.048

.145

.279

6 ft 0 in

.036

.046

.057

.169

.340

7 ft 0 in

.042

.053

.065

.195

.405

8 ft 0 in

.047

.058

.073

.219

.467

9 ft 0 in

.052

.066

.081

.243

.508

10 ft 0 in

.058

.073

.089

.268

.548

11 ft 0 in

.063

.079

.098

.292

.586

12 ft 0 in

.069

.086

.105

.317

.624

13 ft 0 in

.074

.093

.113

.340

.665

14 ft 0 in

.079

.100

.122

.366

.700

15 ft 0 in

.084

.106

.129

.390

.740

16 ft 0 in

.090

.113

.137

.416

.779

17 ft 0 in

.....

....

....

.441

.817

18 ft 0 in

.....

....

....

.464

.855

19 ft 0 in

.....

....

....

.490

.893

20 ft 0 in

.....

....

....

.521

.933

21 ft 0 in

.....

....

....

.538

.972

22 ft 0 in

.....

....

....

.562

1.006

23 ft 0 in

.....

....

....

.586

1.100

24 ft 0 in

.....

....

....

.690

1.368

a One-ring tank.
b
More than one-ring tank.
C
Capacities greater than nominal size are produced by adding one additional ring. No more than one is permitted.

Corrections

Volume correction to 60° F requires observation of both gravity and temperature. They should be taken as close to the same time as possible. Combination hydrometers and thermometers make this easier. If specific gravity is taken, it must be converted to API gravity. Gravity at the observed temperature is corrected to 60° F. Volume correction factors are based on true or corrected gravity. Corrections are made according to the API/ASTM-IP Petroleum Measurement Table (Tables 5B and 6B) and DA Pam 710-2-2. Table 5B gives factors for correcting observed API gravity to true gravity at 60° F. Table 6B gives correction factors for each degree or half degree of API gravity and each degree or half degree of temperature. Gravity must be corrected to 60° F to ensure that the multiplier is selected from the proper group. This is most important near the ends of the eight gravity ranges. The multiplier is a ratio volume at 60° F to volume at the observed temperature. If the observed temperature is higher than 60° F, the multiplier is less than 1 and the corrected volume will be smaller. If observed temperature is less than 60° F, the multiplier is less than 1 and the corrected volume will be larger.

Section II. Flow in Pipelines

HYDRAULICS

The principles of hydraulics govern flow in pipelines. Hydraulics is the branch of science that deals with the behavior of liquids. It also deals with the equipment required to raise liquids to higher elevations and to transfer them from place to place. The broad subject includes the pressure and the equilibrium of liquids at rest (hydrokinetics), as in an operating pipeline, and forces exerted on liquids by objects in motion (hydrodynamics), as in pumping equipment.

PRESSURE

Pressure is the main element in pipeline hydraulics. All forces producing pipeline flow and those opposing it can be measured in terms of pressure or head. Coupled military pipelines are low-pressure systems that operate at pressures of not more than 600 PSI. The low pressure requires closer pump station spacing than in commercial pipeline. Pump stations are spaced about 12 to16 miles apart in military systems on level terrain. Welded lines constructed for the military operate at higher pressures. The two types of pressure in a pipeline are static and dynamic.

Static Pressure

Static pressure is a measure of pressure in liquids at rest. At any level in any size or shape of container, static pressure depends solely upon the vertical height of liquid above that level. Unit pressure at the bottom of all containers shown in Figure C-1, is the same, 1 PSI. A column of water 1 inch square and about 27 inches high weighs 1 pound. The force of 1 pound acts on an area of 1 square inch in the first container. The second container holds 4 pounds of water distributed over 4 square inches. The third container holds 16 pounds distributed over 16 square inches. The fourth holds 64 pounds distributed over 64 square inches. Total pressure varies at the bottom of all containers in Figure C-1, and Figure C-2, but unit pressure is the same, 1 PSI. The height of water in all the containers, 27 inches or 2.31 feet, is the head required to produce a pressure of 1 PSI. Static pressure in any column of water is the head in feet divided by 2.31 or multiplied by 0.433 (Table C-5, page C-9). Static pressure is proportionally less in a petroleum product because of its lower specific gravity. The formulas for converting head to pressure and vice versa are as follows:

    Pressure (PSI) =

    head (in feet) x specific gravity

     
    2.31
    or
    Pressure (PSI) = 0.433 x head (in feet) x specific gravity
    or

    Head (in feet) =

                  PSI              

     
    0.433 x specific gravity

Figure C-1. Pressure in containers of different dimensions

Figure C-2. Pressure in irregularly shaped containers

Table C-5. API gravity, corresponding specific gravity, weights, and pressure at 60F

API GRAVITY

SPECIFIC
GRAVITY

POUNDS PER
CU FT

FEET PER PSI

PSI PER FOOT

10

1.0000

62.30

2.31

0.433

15

.9659

60.17

2.39

.418

20

.9340

58.18

2.48

.404

25

.9042

56.32

2.56

.391

26

.8984

55.96

2.57

.389

27

.8927

55.61

2.59

.386

28

.8871

55.26

2.61

.384

29

.8816

54.92

2.62

.381

30

.8762

54.58

2.64

.379

31

.8708

54.24

2.66

.377

32

.8654

53.90

2.67

.374

33

.8602

53.58

2.69

.372

34

.8550

53.25

2.70

.370

35

.8498

52.93

2.72

.368

36

.8448

52.62

2.74

.365

37

.8398

52.31

2.75

.363

38

.8348

52.00

2.77

.361

39

.8299

51.69

2.79

.359

40

.8251

51.39

2.80

.357

41

.8203

51.09

2.82

.355

42

.8155

50.79

2.84

.353

43

.8109

50.51

2.85

.351

44

.8063

50.22

2.87

.349

45

.8017

49.93

2.88

.347

46

.7972

49.65

2.90

.345

47

.7927

49.37

2.92

.343

48

.7883

49.10

2.93

.341

49

.7839

48.82

2.95

.339

50

.7796

48.55

2.97

.337

51

.7753

48.29

2.98

.335

52

.7711

48.02

3.00

.334

53

.7669

47.76

3.02

.332

54

.7628

47.50

3.03

.330

55

.7587

47.25

3.05

.328

56

.7547

47.00

3.06

.326

57

.7507

46.75

3.08

.325

58

.7467

46.50

3.10

.323

59

.7428

46.26

3.11

.321

60

.7389

46.01

3.13

.320

61

.7351

45.77

3.15

.318

62

.7313

45.53

3.16

.316

63

.7275

45.30

3.18

.315

64

.7238

45.07

3.19

.313

65

.7201

44.84

3.21

.311

66

.7165

44.61

3.22

.210

67

.7128

44.39

3.24

.308

68

.7093

44.16

3.26

.307

69

.7057

43.94

3.27

.305

70

.7022

43.72

3.29

.304

71

,6988

43.51

3.30

.302

72

.6953

43.30

3.32

.301

73

.6919

43.08

3.34

.299

74

.6886

42.87

3.35

.298

75

.6852

42.66

3.37

.296

Dynamic Pressure

Dynamic pressure or head is a measure of pressure in liquids in motion. Dynamic head is also a measure of potential energy or energy of position. Figure C-3, shows the relationship between static head and dynamic head. Static head at ground level behind the nozzle is measured by the vertical height of liquid in the tank above the ground. When liquid starts to flow down the pipe, it loses static head, but it gains in dynamic head. Potential energy becomes kinetic energy or energy in motion. Dynamic head or velocity is greatest at ground level where the stream changes direction and starts to rise. Dynamic head decreases after that until all velocity is lost. Meanwhile, the stream regains some portion of its initial static head and final static head is the head loss because of friction and change in direction. In other words, dynamic head is the static head required to accelerate the stream to its flowing velocity. It is the elevation to which a pump can push a column of liquid.

Figure C-3. Relationship between static head and dynamic head

Pascal's Law

Pascal's law states that pressure, applied to the surface of a liquid, is transmitted equally in all directions through the liquid. It adds that, at any point, pressure acts at right angles to the confining container with undiminished intensity. Figure C-4, shows Pascal's law and the effect of total pressure. Unit pressure is the same on both pistons, 10 PSI. This pressure is transmitted throughout the liquid. Therefore, a total pressure of 30 pounds on one piston can exert a total pressure of 1,000 pounds on the other. This principle is used in hydraulic presses, jacks, and brakes.

Atmospheric Pressure

Atmospheric pressure is caused by the weight of air above the earth. It is the same everywhere at any given elevation. Atmospheric pressure is similar to static pressure in liquids. The height of a column of air depends upon the height of the column. It is measured by the height in inches it raises a column of mercury in a barometer. Atmospheric pressure is 14.695 PSI at sea level and proportionally less at higher altitudes. Maximum suction lift of centrifugal pumps at sea level is 33(+) feet of water (14.695 PSI x 2.31). Pump engines are affected at elevations greater than 3,000 feet because of thinner air. This same condition lowers atmospheric pressure. Design loads on pumps are usually reduced by 4 percent for each 1,000 feet of elevation above 3,000 feet. Normal suction pressure of 20 PSI is based on a design fuel of 0.725 specific gravity. This pressure should be increased to 30 PSI for elevations over 5,000 feet.

Figure C-4. Illustration of Pascal's law

Vacuum

A vacuum is created when pressure is reduced below atmospheric level. The theoretical limit of pressure reduction is absolute zero or perfect vacuum. Vacuums are measured as absolute pressure in inches of mercury. Pump suction reduces atmospheric pressure at the point of intake. This allows atmospheric pressure on the source of supply to push liquids into the pump. Figure C-5 shows the relationship between atmospheric pressure, gage pressure, vacuum, and absolute pressure.

Figure C-5. Interrelationship of atmospheric pressure, gage pressure, vacuum, and absolute pressure

Vapor Pressure

All liquids, especially light petroleum products, tend to vaporize. This results from motion of the molecules of which they are composed. Motion of molecules near the surface causes some to escape into the air. The tendency to vaporize is called volatility. Volatility increases with temperature and decreases with pressure. Vapor pressure is formed when a vaporizing liquid is confined in a closed container like that used in the Reid vapor pressure test. The temperature at which vapor pressure is the boiling point of the liquid. For this reason, liquids boil at lower temperatures at high elevations than at sea level. Vapor pressure reduces the effect of atmospheric pressure acting on the liquid. Maximum net suction lift is reduced accordingly. For this reason, pump suction pressure always must be greater than the vapor pressure of the product. Normal suction pressure of 20 PSI should be increased to 30 PSI for operating temperatures over 100° F.

NATURE OF FLOW

The two types of flow are laminar and turbulent. They are covered in Chapter 9. Liquids flow in pipelines because of gravity or pump action. In both cases, they flow because of pressure. Pressure is supplied by weight of the liquid in gravity flow and by pump action in discharge flow. While pressure and head are almost synonymous, they are actually proportional to each other.

RESISTANCE OF FLOW

Flow in a pipeline continues until the head producing it has been lost. The loss of head or the difference between pressure at the source and at any point downstream is caused by factors that resist flow. The main factors that resist flow are friction of the pipe walls and viscosity of the liquid. Friction loss calculations are covered in detail in FM 5-482, Chapter 4. To calculate friction loss for JP-8, use Table C-6, and Figure C-6. Less important factors in flow resistance include:

  • Entrance to the pipe.
  • Sudden changes in cross-sectional area or direction of flow.
  • Resistance of valves and fittings.
  • Passage through equipment, such as meters and traps.
  • Corrosion or deposits in the line.

RATE OF FLOW

The rate of flow depends on pump pressure and differences in elevation. It also depends on gravity and viscosity of the product, diameter and length of the pipe, and roughness of the pipe.

Pressure

There is friction between the liquid and the pipe walls. The pressure needed to overcome this resistance is expressed as pressure drop or loss in pounds per square inch per mile of pipe as shown in Figure C-7. The pressure needed to overcome the resistance of valves and fittings is similarly expressed in equivalent lengths of pipe as shown in Figure C-8, and Table C-6. The total pressure needed to overcome all resistance in the line is pressure drop per mile times length of the line in miles. There is a direct relationship between pressure and rate of flow. This is shown by the fact that about double the pressure is needed to increase throughput by one half as shown in Table C-8, page C-16.

Figure C-6. Kinematic viscosities for common military fuels

Table C-6. Pipe lengths equivalent to lubricated plug valves

Nominal Size
(inches)

125-POUND CAST IRON AND 150-POUND NONFERROUS METAL

250-POUND CAST IRON

150-POUND STEEL

300-POUND STEEL

Regular
(feet)

Short
Pattern
Wedge Gate (feet)

Venturi
(feet)

Regular
(feet)

Venturi
(feet)

Regular

Short
Pattern
(feet)

Venturi
(feet)

Regular
(feet)

Short
Pattern
(feet)

Venturi
(feet)

6

12

44

36

12

36

9.6

14.4

36

...

42

...

8

18

54

54

18

54

12.0

48.0

54

9.6

54

54

10

24

60

60

24

60

....

54.0

60

...

66

60

12

30

72

78

...

78

...

72.0

84

...

...

77

Table C-7. Relationship of pressure and quantity with length and diameter constant

RELATIVE
PRESSURE

INCREASE
IN
PRESSURE
(percent)

RELATIVE
QUANTITY
(percent)

INCREASE IN QUANTITY
(percent)

RELATIVE
PRESSURE

DECREASE IN
PRESSURE
(percent)

RELATIVE
QUANTITY

DECREASE IN QUANTITY
(percent)

1.00

.....

1.00

......

1.00

......

1.00

......

1.02

2

1.01

1

.98

2

.99

1

1.04

4

1.02

2

.96

4

.98

2

1.06

6

1.03

3

.94

6

.96

4

1.08

8

1.05

5

.92

8

.95

5

1.10

10

1.06

6

.90

10

.94

6

1.12

12

1.07

7

.88

12

.93

7

1.15

15

1.08

8

.85

15

.91

9

1.20

20

1.11

11

.80

20

.88

12

1.25

25

1.14

14

.75

25

.85

15

1.30

30

1.16

16

.70

30

.81

19

1.40

40

1.22

22

.60

40

.74

26

1.50

50

1.26

26

50

50

.67

33

1.75

75

1.38

38

.40

60

.58

42

2.00

100

1.49

49

.30

70

.49

51

Figure C-7. Pressure loss due to friction in pipe

Figure C-8. Pipe lengths equivalent to valves and fittings

Elevation

Pressure needed to overcome friction is not the total pressure supplied if the product is to be pumped over a hill higher than the pump. The pressure equivalent of the difference in elevation in feet must be added to the pressure needed to overcome friction. If the liquid is to flow downhill from the pump, the difference in elevation can be subtracted. Otherwise, the liquid will flow proportionally farther at the same pump pressure. Elevation or static pressure acts at all times on a filled line whether the liquid is flowing or not.

Gravity

Specific gravity of the product is important because the liquid being moved has weight. The greater the specific gravity, or the lower the API gravity, the greater must be the pump pressure to move it. As heavier products are pumped in the line, pressure must be increased to keep the same flow rate. At the same pressure, flow rate falls off to suit the heaviest product being pumped. Observed gravity should be used in rate-of-flow computations instead of true gravity. This is because the computation will be concerned with an actual, not theoretical, condition. Changing from 40 API gravity to 60 API gravity lessens pressure requirements 10 percent. At the same pressure, changing from 40 API gravity to 60 API gravity increases rate of flow about 7 percent.

Viscosity

Viscosity and specific gravity of product affect pump pressure in the same way. As more viscous products are pumped, pressure must be increased to keep the same rate of flow as shown in Table C-8. Both gravity and viscosity vary with temperature. Therefore, locations with temperature differences of about 50° F require 10 to 20 percent higher pumping pressures in winter.

Table C-8. Relationship of viscosity, quantity, and pressure

VISCOSITYa

RELATIVE QUANTITY WITH
PRESSURE CONSTANT

VISCOSITYa

RELATIVE PRESSURE WITH
QUANTITY CONSTANT

Ab
 

Bc

Ab
 

Bc

35

120

100

35

73

100

40

110

91

40

85

117

45

104

86

45

90

128

50

100

83

50

100

137

55

97

81

55

105

144

60

95

79

60

109

150

70

91

76

70

117

161

80

89

74

80

123

168

90

87

72

90

128

175

100

85

71

100

132

182

125

82

68

125

142

194

150

79

66

150

150

205

200

75

63

200

162

222

300

71

59

300

182

249

a Viscosity in Saybolt Universal seconds.
b
Quantity or pressure relative to 50 seconds.
c
Quantity or pressure relative to 35 seconds.

Diameter of Pipe

The pressure needed to pump at a given flow rate decreases rapidly as pipe diameter increases. It requires about 85 feet of pressure drop per mile to pump gasoline at the rate of 550 GPM through a 6.407-inch pipeline. Only about 22 feet of pressure drop are needed to pump at the same rate through 8.407-inch pipeline as shown in Figure C-6. The decrease is about 74 percent. The same rate of flow requires about 600 feet of pressure drop for 4.344-inch pipeline. This is an increase of more than 500 percent. At any given pressure, throughput may be increased about threefold by increasing the pipe diameter 50 percent.

Length of pipe

Required pumping pressure increases directly with distance pumped. In other words, pressure drop per mile is proportional to distance pumped. If distance is doubled, pressure must be doubled. If pressure stays constant, rate of flow varies inversely as the approximate square root of length. For example, if station spacing is decreased by one half, flow rate will increase by about one half.

Roughness of pipe

Required pumping pressure increases directly with roughness of pipe For this reason, scrapers and corrosion inhibitors must be used to keep the pipeline in good operating condition.

Section III. Examples of Flow

HYDRAULIC GRADIENT

Figure C-9 shows what is meant by hydraulic gradient. The figure shows a tank with a pipeline of uniform size and grade connected at point A and discharging into the atmosphere at point B. Vertical pipes that open to the atmosphere have been connected at points X, Y, and Z. The tank is filled with product to a height of 10 feet above A and B. The hydraulic gradient exists only under conditions of flow. It is assumed that the level of product in the tank stays the same when flow begins. Product rises in each of the vertical pipes to a height (D, E, and F) that represents the remaining feet of head at X, Y, and Z. The head that has been lost at each point is proportional to the length of pipe through which product has flowed. Pressure head is lost uniformly from A to B. This uniform loss of head is the hydraulic gradient. It is shown by the line connecting points C, D, E, F, and B.

Figure C-9. Hydraulic gradient

DOWNHILL FLOW

Figure C-10, shows a situation in which the product flows downhill. Conditions are the same as in Figure C-8, except that point B is 10 feet below the tank connection A. This change increases the head to 20 feet. The new C to B line is the hydraulic gradient. This gradient is steeper than in Figure C-8. The rate of flow or velocity is also greater.

Figure C-10. Downhill flow

UPHILL FLOW

Figure C-11, shows a situation in which product flows uphill. The point of discharge B is 5 feet above the tank outlet A. Effective head has been reduced to 5 feet. The hydraulic gradient is not as steep as that in Figure C-9. The rate of flow is also less. The tank could not be emptied by gravity below point D.

Figure C-11. Uphill flow

SIZE OF PIPE

Figure C-12, shows a situation in which size of the line is increased at point X. Pressure lost because of friction is greater in smaller pipe than in the larger pipe. Therefore, the hydraulic gradient is not a straight line from A to B. Instead, it has a steeper slope from A to X and a lesser slope from X to B.

Figure C-12. Varying size of pipe



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