CO2 Safety Manual

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CO2 Safety and Operations Manual

Halliburton Energy Services, Inc.Part No. 101273169


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Table of Contents

Preface

Section 1Using CO2 Safely

Introduction .............................................................................. 1

Respiratory Hazards ................................................................ 1Background ......................................................................... 1

Precautions .......................................................................... 1

Frozen Flesh ............................................................................ 2

Background ......................................................................... 2

Precautions .......................................................................... 2

The Cannonball Effect ............................................................. 2

Background ......................................................................... 2

Precautions .......................................................................... 2Cracked Cylinder-Head Threads ............................................. 3

Background ......................................................................... 3

Precautions .......................................................................... 3

Protective Front Covers ........................................................... 3

Improperly Secured Lines ........................................................ 3

Hammer Unions ....................................................................... 3

Open Valves ............................................................................ 4

Notes on Figure 1.2 ............................................................. 4

Example ......................................................................... 4

Notes on Figure 1.3 ............................................................. 4

Example ......................................................................... 5


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Section 2CO2 Properties

Differences Between CO2 and Water ...................................... 1

CO2 Heat Capacities ............................................................... 6

Delivering CO2 to the Job ........................................................ 7

Section 3CO2 Pumping Equipment

Boost Pumps ........................................................................... 1

Liquid-Gas Separator ............................................................... 4

Suction Y Header ..................................................................... 5

HT-400 Pumps .................................................................... 5

HQ-2000 Pumps .................................................................. 5

HT-2000 Pumps .................................................................. 5

HT-400 Fluid-End Cover Gasket ............................................. 5

HT-400 Header Ring ................................................................ 6

Pumping Liquid CO2 with a Positive-Displacement Pump ...... 6

Performance Curves ........................................................... 6

Determining the Correct Plunger Size ................................. 6

Problem ......................................................................... 6

Answer ........................................................................... 6

Extending the Maximum Operating Pressure ...................... 7

Example ......................................................................... 7

Appendix ADetermining CO2Discharge Temperatures

Numerical Approach ................................................................ 1

Graphical Approach ................................................................. 1

Example .............................................................................. 3

Appendix BModifying the Fluid Ends of HT-400 Pumpsfor CO2 Jobs

Tie-Bolt Arrangement ............................................................... 1

Part Numbers ........................................................................... 2

Modifying Fluid Ends ............................................................... 2


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Appendix CCO2 Job Procedures

Preparing the Equipment ......................................................... 1

Determining Available CO2 Product for Job ............................ 1

Downstream CO2 Turbine Meterwith Temperature Probe .......................................................... 3

Setting up the Job .................................................................... 4

Pretreatment Safety Meeting ................................................... 5

Pressure-Testing and Cooling Down ....................................... 5

Vapor-Testing CO2 Lines .................................................... 5

Testing CO2 Lines with Glycol ............................................ 5

Liquid CO2 Pumping Procedure .............................................. 8

Shutting Down ......................................................................... 9Disassembling Equipment ....................................................... 9


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CO2 Safety Manual

Section 1 2 of 6 September 2001

Frozen Flesh

Background

Solid CO2, commonly known as dry ice, has a temper-

ature of -109F. At this temperature, CO2 will freeze

flesh upon contact.

Precautions

To prevent injury from solid CO2, follow these

guidelines:

Never pick up solid CO2 with your bare hands.

Never let solid CO2 come into contact with any

exposed skin.

Never ingest solid CO2.

When working near CO2 equipment and lines,

wear standard protective gear, as well as the

following:

face shield

noncotton work gloves

long pants not tucked into boots

ear protection

The Cannonball Effect

Background

The cannonball effect occurs when slugs of solid CO2shoot out of the hoses like cannonballs. Liquid CO2

will flash-set to dry ice slugs when you disconnect the

hoses after a job. The slugs will lodge in the low areas

of the hoses and hose ends. When the temperature inand around the hoses increases, the slugs will release

gas, building pressure behind the slugs and forcing

them to shoot out of the hoses.

Precautions

To prevent the cannonball effect, follow these

guidelines:

Keep low spots out of hoses, as shown in Figure 1.1

(Page 3).

Carefully drain and clear hose lines after each job.

Do not look into hoses or lines unless they have

been properly drained.

When using high-pressure pumps, never point

cylinder-head covers toward personnel or other

equipment.

Table 1.1Effects of Exposure to CO2

CO2 in Air

(ppm)Effect

0.1 to 1.0 Slight, unnoticeable increase in

respiration rate

2.0 50% increase in respiration rate



10.0 Unconsciousness after a few

minutes of exposure

12.0 to 15.0 Unconsciousness immediatelyupon exposure

25.0 Possible death after several hoursof exposure


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CO2 Safety Manual

Figure 1.1CO2suction hose with minimal low spots

Cracked Cylinder-Head Threads

Background

At normal temperatures, the threads of cylinder-head

cover retainers crack slowly. At the temperature of

liquid CO2, cracking occurs more rapidly. Cracked

cylinder-head threads can spontaneously fail, causing

the cylinder heads to blow off.

Precautions

To avoid injury resulting from cracked cylinder-head

threads, follow these guidelines:

When possible, position pump cylinder heads away

from personnel and other equipment.

Regularly perform magnetic particle inspections

on equipment.

Use a cutting torch to destroy all parts that are

cracked or otherwise damaged so that they will not

be used by mistake.

Protective Front Covers

HT-400s and GrizzlyWhen pumping CO2, protec-

tive covers should be taken out of any HT-400s or Griz-

zlies and replaced with standard end caps. Protective

front covers have been developed to protect HT-400

and Grizzly fluid ends from becoming damaged by

proppant packed in front of the plunger. This is not a

problem on the pumps which will be pumping CO2 and

can cause a serious safety hazard due to a sudden

release of liquid CO2 at the end of the CO2 pump.

HT-2000Protective covers used in the HT-2000

pumps are hydraulically preloaded and do not pose asafety hazard in CO2 services.

Improperly Secured Lines

Improperly secured CO2 discharge lines can break or

whip if the well kicks or if a closed valve is pumped

into the line. To avoid such occurrences, follow current

best practices for securing discharge irons. Prior to

beginning the job, unhook the glycol return line and

any other prime up lines that are not necessary when

pumping downwell.

Hammer Unions

Hammer unions can become very brittle at the extreme

temperature of dry ice and will easily break or chip. Rig

down with caution.


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Open Valves

A temperature increase will cause any trapped liquid

CO2 to expand and increase in pressure, possibly

causing equipment damage or failure. To prevent trap-

ping liquid CO2, ensure that one valve is always open

before opening or closing other valves to change fromthe cool-down loop to the wellhead.

Figure 1.2 (Page 5), and Figure 1.3 (Page 5), show the

effect of temperature on a closed system. Pressures can

be increased above the working pressure of the iron,

hoses, and equipment.

NoteTypical CO2 hoses used on the suction side of

positive-displacement pumps have a working pressure

of 500 psi. Therefore, you should confirm that all trans-

ports, receivers, suction hoses, suction manifolding,

and boost pumps are properly rated and have working

relief valves.

Notes on Figure 1.2

Figure 1.2 shows the effects of temperature increases

on lines and equipment between the CO2 storage vessel

and the positive-displacement pumps. Pressure-relief

valves should be installed on CO2 transports, suction

hoses, and booster pumps. Ensure that these valves are

in place and working properly.

Example

The pumps have been cooled downs, but the job is

delayed. The transport or receiver valves are shut, and

no downstream release is open. The initial pressure in

the transport tank was 220 psi; therefore the tempera-

ture of the liquid CO2

was -15F. On a hot day, the

temperature of the liquid CO2 in the transport tank

reaches 10F, and the line pressure increases to 2,500

psi

Notes on Figure 1.3

Figure 1.3 (Page 5) shows the effects of temperature

between the positive-displacement pump and the well-

head. Extra care must be taken to prevent a closed-

stop situation in which pressure cannot be released

and consequently reaches a dangerous level.

The pressure increase shown in Figure 1.3 depends onthe initial pressure in the CO2 receiver/supplier tanks.

This chart is based on a tank pressure of 200 psi. When

lines are being tested, if the tank pressure is greater than

200 psi, then the pressure increase will be smaller. If

the pressure is less than 200 psi, then the pressure

increase will be greater.


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CO2 Safety Manual

Example

Lines containing liquid CO2 are tested to 5,000 psi.

One line is left full of CO2 with no release open. On a

hot day, the liquid CO2 temperature reaches 100F, and

the line pressure increases to 15,000 psi.

.

Figure 1.2Potential pressure buildup on lines and equipment between the CO2storage vessels and positive-

displacement pumps if CO2warms to 10and 20F.

Figure 1.3Potential pressure buildup downstream of positive-displacement CO2pumps during pressure test

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

200 210 220 230 240 250 260 270 280 290 300

Receiver or StorageTank Original Pressure (psi)

HosePressureIfTemperatureIncreases

A

gainstClosedStops(psi)

20F

10F

0

5,000

10,000

15,000

20,000

25,000

30,000

1,000 2000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,00011,00012,00013,00014,00015,000

InitialTest Pressure (psi)

60F

80F

100F

120F

Lin

ePressureIfDischarge

LineTemperatureIncreases(psi)

,


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CO2 Safety Manual



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Section

2CO2 Properties

Differences Between CO2 and Water

Like water, CO2 can exist as a liquid, a solid, or a

vapor. Table 2.1 describes the similarities and differ-

ences between CO2 and water. As shown in Figure 2.1(Page 2), the form of CO2 is primarily affected by

temperature, but pressure and energy levels also affect

its form. When handling CO2, remember the following:

At its triple point (-69.9F), CO2 can be a liquid, a

solid, or a vapor. At temperatures below the triple

point, CO2 can be either a solid or a vapor.

At temperatures between the triple point and the

critical temperature (87.8F), CO2 can be a liquid

or a vapor, depending on pressure and energylevels.

At temperatures above the critical temperature,

CO2 is a vapor, and no amount of pressure will

transform it into a liquid.

Table 2.2 (Page 3) lists values for different properties

of CO2 at temperatures ranging from -147F to 87.8F.

Table 2.1Similarities and Differences between CO2 and Water

Form Similarities Differences

Vapor Both are clear and odorless. CO2 is heavier than air; water is not.Neither will burn or explode.

Neither is poisonous.

Liquid Both are clear and have a

similar weight.The viscosity of liquid CO2 is

1/10th

that of water.

Solid Both are white and have a

temperature of approxi-mately -109F.

Unlike water, CO2 expands when it

changes from a solid to a liquidform.

Transitional States Both can turn directly into a

vapor from a solid state.

The triple point for CO2 is -69.9F.

The triple point for water is 32F.


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Figure 2.1CO2equilibrium curve

0.1

0.2

0.3

0.4

0.50.6

0.81.0

2.0

3.0

4.0

5.0

6.0

10

8.0

20

30

50

40

80

60

100

200

300

500

800

600

1,000

400

2,000

Temperature (F)

Pressure

(psig)

-180 100806040200-20-40-60-80-100-120-140-160

Critical point

Triple point

Vapor region(superheated)

Solid region

Liquid region

Solid

bound

ary

Vap

or

bound

ar

y

8.0 lb/g

al

8.5

lb/ga

l

9.5

lb/g

al

9.0

lb/ga

l

7.0

lb/g

al7.5

lb/gal


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Table 2.2Properties of CO2

Temp

(F)

Pressure

Volume

ft3/lb

Density

lb/ft3Enthalpy (1)

BTU/lb

Entropy

BTU (lb) (R)

Viscosity

cp

Vapor Liquid Vapor Liquid Vapor Liquid Vapor LiquidVapor Liquid

psia psig Vg Vf I/Vg I/Vf hg hf Sg Sf

-147 2.14 35.80 0.0100 0.0279 99.60 128.2 -123.3 0.4832 -0.3214

-140 3.19 24.50 0.0100 0.0408 99.30 129.3 -121.4 0.4691 -0.3153

-130 5.39 14.74 0.0101 0.0678 98.81 130.7 -118.7 0.4500 -0.3068

-120 8.85 9.13 0.0101 0.1095 98.23 132.1 -116.0 0.4318 -0.2986

-110 14.22 5.85 0.0102 0.1709 97.66 133.3 -113.1 0.4145 -0.2904

-109.4 -Boiling point at 1 atmosphere (sublimes)

-109.4 14.70 0.03 5.69 0.0102 0.1757 97.56 133.4 -112.9 0.4134 -0.2898

-105 17.80 3.13 4.72 0.0102 0.2118 97.28 133.9 -111.5 0.4062 -0.2860

-100 22.34 7.67 3.80 0.0103 0.2631 96.90 134.4 -110.0 0.3981 -0.2815

-95 27.60 12.96 3.09 0.0103 0.3236 96.53 134.9 -108.3 0.03902 -0.2768

-90 34.05 19.38 2.52 0.0104 0.3968 96.15 135.3 -106.5 0.3822 -0.2720

-85 41.67 27.00 2.07 0.0104 0.4830 95.78 135.6 -104.5 0.3742 -0.2667

-80 50.70 36.03 1.70 0.0104 0.5882 95.33 135.8 -102.3 0.3665 -0.2610

-75 61.75 47.08 1.40 0.0105 0.7142 94.88 135.9 -100.1 0.3585 -0.2551

-70 74.90 60.23 1.17 0.0105 0.8547 94.43 136.0 -98.0 0.3508 -0.2494

-69.9 75.1 60.43 1.16 0.0105 0.8620 94.43 136.0 -97.8 0.3506 -0.2493

-69.9 Freezing point - tripple point (At this temperature, CO2 can be gas, liquid, or solid.)

-69.9 75.1 60.43 1.1570 0.0135 0.8643 73.53 136.0 -13.7 0.3506 -0.0333

-68 78.59 63.92 1.1095 0.136 0.9013 73.37 136.2 -12.8 0.3491 -0.0312

-66 82.42 67.75 1.0590 0.0136 0.9442 73.05 136.3 -11.9 0.3475 -0.0290

-64 86.39 71.72 1.0100 0.0137 0.9900 72.83 136.4 -10.9 0.3460 -00266

-62 90.49 75.82 0.9650 0.0137 1.0362 72.57 136.6 -10.1 0.3444 -0.0243

-60 94.75 80.08 0.9250 0.0138 1.0810 72.25 136.7 -9.1 0.3428 -0.0221

-58 99.15 84.48 0.8875 0.0138 1.1267 71.99 136.8 -8.2 0.3413 -0.0198

-56 103.69 89.02 0.8520 0.0139 1.1737 71.79 137.0 -7.3 0.3398 -0.0175

-54 108.40 93.73 0.8180 0.0139 1.2224 71.53 137.1 -6.4 0.3383 -0.0153

-52 113.25 98.58 0.7840 0.0140 1.2755 71.28 137.2 -5.5 0.3368 -0.0131

-50 118.27 103.60 0.7500 0.0140 1.3333 70.97 137.3 -4.6 0.3354 -0.0109

-48 123.45 108.78 0.7200 0.0141 1.3888 70.72 137.5 -3.6 0.3339 -0.0087

-46 128.80 114.13 0.6930 0.0141 1.4430 70.47 137.6 -2.7 0.3325 -0.0065

-44 134.31 119.64 0.6660 0.0142 1.5015 70.18 137.7 -1.8 0.3311 -0.0048

-42 140.00 125.33 0.6380 0.0143 1.5673 69.93 137.8 -0.9 0.3297 -0.0021

-40 145.87 131.20 0.6113 0.0143 1.6358 69.59 137.9 0.0 0.3285 0.0000

-38 152.01 137.34 0.5881 0.0144 1.7003 69.35 138.0 0.95 0.3271 0.0021

-36 158.15 143.48 0.5650 0.0144 1.7699 69.11 138.1 +1.9 0.3258 0.0043

Solid

orVapor

Triple

Point

Liquid

orVapor


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Temp.

(F)

Pressure

Volume

ft3/lb

Density

lb/ft3

Enthalpy (1)

BTU/lb

Entropy

BTU (lb) (R)

Viscosity

cp



-34 164.66 149.99 0.5430 0.0145 1.8416 68.84 138.2 2.85 0.3245 0.0054

-32 171.17 156.50 0.5210 0.0145 1.9193 68.58 138.3 3.8 0.3232 0.0085

-30 178.07 163.40 0.5027 0.0146 1.9892 68.25 138.35 4.7 0.3218 0.0105

-28 184.97 170.30 0.4845 0.0147 2.0639 67.93 138.4 5.6 0.3205 0.0126

-26 192.27 177.60 0.4672 0.0147 2.1404 67.63 138.5 6.5 0.3217 0.0147

-24 199.57 184.90 0.4500 0.0148 2.2222 67.34 138.6 7.4 0.3180 0.0168

-22 207.29 192.62 0.4332 0.0149 2.3084 67.05 138.65 8.3 0.3167 0.0179

-20 215.02 200.35 0.4165 0.0149 2.4009 66.76 138.7 9.2 0.3155 0.0210

-18 223.17 208.50 0.4015 0.0150 2.4906 66.47 138.75 10.7 0.3142 0.0231

-16 231.32 216.65 0.3865 0.0151 2.5873 66.18 138.8 11.2 0.3130 0.252

-14 239.92 225.25 0.3727 0.0151 2.6831 65.87 138.8 12.05 0.3117 0.0272

-12 248.52 233.85 0.3590 0.0152 2.7855 65.57 138.8 12.9 0.3104 0.0293

-10 257.57 242.90 0.3467 0.0153 2.8843 65.25 138.85 13.95 0.3104 0.314

-8 266.63 251.96 0.3345 0.0153 2.9895 64.94 138.9 15.0 0.3079 0.0335

-6 276.16 261.49 0.3231 0.0154 3.0950 64.62 138.9 15.95 0.3079 0.0355

-4 284.70 271.03 0.3118 0.0155 3.2071 64.31 138.9 16.9 0.3054 0.0376

-2 295.73 281.06 0.3011 0.0156 3.3211 63.98 139.9 17.85 0.3037 0.0397

0 305.76 291.09 0.2905 0.0157 3.4423 63.65 138.9 18.8 0.3030 0.0419

2 316.28 301.61 0.2806 0.0157 3.5637 63.33 138.9 19.8 0.3018 0.0440

4 326.8 312.1 0.2708 0.0158 3.6927 63.01 138.9 20.8 0.3006 0.0462 0.0132a 0.115

6 337.8 323.13 0.2614 0.0159 3.8255 62.66 138.85 21.85 0.2994 0.0482

8 348.9 334.2 0.2520 0.0160 3.9682 62.31 138.8 22.9 0.2982 0.0503

10 360.5 345.8 0.2435 0.0161 4.1067 61.96 138.75 23.95 0.2970 0.525

12 372.1 357.4 0.2350 0.0162 4.2553 61.61 138.7 25.0 0.2958 0.0547

14 384.2 369.5 0.2272 0.0163 4.4014 61.25 138.65 26.15 0.2945 0.0569

16 396.4 381.7 0.2195 0.0164 4.5558 60.90 138.6 27.3 0.2933 0.0591

18 409.1 394.4 0.2121 0.0165 4.7147 60.53 138.55 28.45 0.2921 0.0613

20 421.8 407.1 0.2048 0.0166 4.8828 60.17 138.5 29.6 0.2909 0.0636 0.0135a 0.0110

22 435.1 420.4 0.1979 0.167 5.0530 59.77 138.4 30.7 0.2897 0.0660

24 448.4 433.7 0.1910 0.0168 5.2356 59.38 138.3 31.8 0.2885 0.0684

26 462.3 447.6 0.1846 0.0169 5.5171 58.98 138.15 33.05 0.2873 0.0707

28 476.3 461.6 0.1782 0.0170 5.6116 58.58 138.0 34.3 0.2861 0.0730

30 490.8 476.1 0.1722 0.0171 5.8072 58.17 137.85 35.55 0.2859 0.0754

32 505.3 490.6 0.1663 0.0173 6.0132 57.77 137.7 36.8 0.2837 0.0778

34 520.5 505.8 0.1606 0.0714 6.2266 57.34 137.5 38.05 0.2882 0.0800

36 535.7 521.0 0.1550 0.0175 6.4516 56.92 137.3 39.3 0.2807 0.0823

38 551.5 536.7 0.1496 0.0177 6.6844 56.45 137.05 40.55 0.2791 0.0847


Liquid

orVapor


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Temp.

(F)

Pressure

Volume

ft3/lb

Density

lb/ft3Enthalpy (1)

BTU/lb

Entropy

BTU (lb) (R)

Viscosity

cp



40 567.3 552.6 0.1442 0.0178 6.9348 55.99 136.8 41.8 0.2775 0.0872 0.0140a 0.095

42 583.8 569.1 0.1392 0.0180 7.1839 55.51 136.5 42.6 0.2760 0.0897

44 600.4 585.7 0.1342 0.0181 7.4515 55.04 136.2 44.4 0.2745 0.0922

48 634.9 620.2 0.1250 0.0185 8.0000 54.00 135.5 47.1 0.2715 0.0972

50 652.8 638.1 0.1206 0.0186 8.2918 53.49 135.05 48.5 0.2698 0.0999

52 670.8 656.1 0.1163 0.0188 8.5984 52.99 134.6 49.9 0.2681 0.1026

54 689.5 674.8 0.1121 0.0190 8.9206 52.45 134.0 51.85 0.2663 0.1053

56 708.3 693.6 0.1080 0.0192 9.2592 51.92 133.4 52.8 0.2645 0.1080

58 727.8 713.1 0.1037 0.0194 9.6432 51.34 132.8 54.25 0.2625 0.1108

60 747.7 732.7 0.0995 0.0197 10.050 50.76 132.2 55.7 0.2606 0.1136

62 767.7 753.0 0.0957 0.0199 10.449 50.11 131.45 57.25 0.2584 0.1164

64 788.1 773.4 0.0920 0.0202 10.869 49.46 130.7 58.8 0.2563 0.1192

66 809.3 794.6 0.0881 0.0205 11.351 48.78 129.8 59.4 0.2539 0.1221

68 830.6 815.9 0.0842 0.0207 11.876 48.10 128.9 62.0 0.2516 0.1250

70 852.7 838.0 0.0801 0.0211 12.484 47.35 127.7 63.8 0.2480 0.1283

72 874.9 860.2 0.0760 0.0214 13.158 46.60 126.5 65.6 0.2455 0.1316

74 898.0 883.3 0.0720 0.0219 13.889 45.62 124.7 67.85 0.2420 0.1353

76 921.1 906.4 0.0680 0.0224 14.706 44.64 122.9 69.9 0.2386 0.1390

78 945.2 930.5 0.0640 0.0230 15.625 43.41 120.95 70.95 0.2345 0.1429

80 969.3 954.6 0.0600 0.0237 16.667 42.19 119.0 74.0 0.2305 0.1469 0.064

82 995.0 980.3 0.0537 0.0258 18.622 38.69 113.5 79.8 0.2199 0.1571

84 1020.7 1006.0 0.0474 0.0284 21.097 35.19 108.0 85.5 0.2093 0.1673

86 1046.4 1031.7 0.0411 0.0315 24.331 31.69 102.6 91.3 0.1987 0.1775

87.8 1072.1 1057.4 0.0345 0.0345 28.96 28.96 97.1 97.1 0.1880 0.1880

87.8 - Critical temperature

aAt one atmosphere pressure


Liq

uid

orVapor

Vapor


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CO2 Safety Manual


CO2 Heat Capacities

The thermal conductivity for CO2 vapor at 1 atm and

32F is 0.0085 Btu/hr/ft2/F/ft. Table 2.3 lists the char-

acteristics of CO2 vapor. Table 2.4 lists the heat capac-

ities of CO2 vapor at various temperatures. Table 2.5

lists the heat capacities of CO2 liquid at various

temperatures.

Table 2.3Characteristics of CO2

Vapor

Property Value

Molecular weight (M) = 44.01 lb/mol

Specific volume (v) at 14.7 psia and

68F= 8.755 ft3/lb

Gas constant

(R = pv/T)a=

35.11 ft-lb/lb R0.04512 Btu/lb R

CO2 gas constant (R0) = 1,545.3 ft-lb (lb-mol, R) 1.986 Btu/(lb-mol, R)

p Vm/R0Tb = 1.000

ap = psia, T = RbVm = volume per mole

Table 2.4Heat Capacity ofCO2 Vapor at 1 atm

Temperature(F)

Btu/lb/F

Cpa Cp Cv

b = Kc

32 0.205 59 1.304

212 0.215

aCp = specific heat at constant pressurebCv = specific heat at constant volumecK = specific heat ratio

Table 2.5Heat Capacity of Liquid CO2

Temperature

(F)Btu/lb/F

-30 0.45

0 0.48

30 0.62

60 0.75


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CO2 Safety Manual

Delivering CO2 to the Job

In a tanker, liquid CO2 boils slowly because it absorbs

the heat that is outside the tank (Figure 2.2 ). Liquid

CO2 behaves like water in a car radiator when the car

engine is at operating temperature and the radiators

pressure cap is on. If the cap is removed slowly, thedecrease in pressure will cause the water in the radiator

to boil. Similarly, when liquid CO2 is removed from the

tanker, pressure decreases in the tank and causes the

CO2 to boil more rapidly (Figure 2.3 ). Boiling will

continue until enough vapor has formed, or until the

liquid is cool enough to satisfy conditions in the satu-

rated liquid line.

CautionSlowly remove liquid CO2

from the tanker.

If liquid CO2 is released too quickly, boiling will

become extremely violent, possibly causing injury.

The circles in Figures 2.2 and 2.3 represent vapor

bubbles.

Figure 2.2Liquid CO2in sealed tank (boiling caused by tank absorbing outside heat)

Figure 2.3Liquid CO2during the emptying process

Liquid slowly boiling

Vapor

Liquid increased boiling

Vapor


22/51

CO2 Safety Manual



23/51


Section

3CO2 Pumping Equipment

This section provides information about CO2 pumping

equipment and includes performance charts for various

sizes of HT-400, HT-2000, and Grizzly pumps.

Boost Pumps

Boost pumps prevent CO2 from boiling in the suction

manifold by increasing pressure. This pressure increase

changes CO2 vapor into liquid, which reduces vapor

locking in the high-pressure pump.

Although the boost pump prevents liquid CO2 from

boiling while it is in the suction manifold, the CO2 will

still boil during the suction stroke because of the rapid

acceleration of the plunger, as shown in Figure 3.1.

Boiling will increase because of heat left in the

unswept volume of the fluid section. This heat is a

result of friction, engine horsepower, and atmosphere.

The most efficient pump for boosting CO2 pressure is

a centrifugal pump. A centrifugal boost pump can

pump a liquid containing some vapor and can run dry

for short periods. If the pump is powered by a hydraulic

drive, operators do not have to heat the CO2 by

pumping it through a bypass valve. Figure 3.2 (Page 2)

shows a centrifugal pump with a hydraulic drive.

Figure 3.3 (Page 2) and Figure 3.4 (Page 3) demon-

strate dimensions and a pressure-volume curve for a

centrifugal boost pump with a 10.19-in. impeller.

CO2 can be pumped without a boost pump when the

pump rate is low (typically below 1 bbl/min). The

maximum rates without a booster will vary depending

on the suppliers equipment and the tanks starting

pressures. Figure 3.5 (Page 3) depicts an arrangement

for pumping CO2 without a boost pump.

Figure 3.1HT-400 plunger in discharge and suction

strokes

Plunger onsuction stroke

Plunger ondischarge stroke


24/51

CO2 Safety Manual


Figure 3.2CO2 centrifugal boost pump with hydraulic drive

Figure 3.3Dimensions of centrifugal boost pump with 10.19-in. impeller

Treating fluid

To wellhead

Flowmeter

Injection-pumpfluid end

Liquid-gas separator

Relief valve

COtransport

2

Check-valve

Tricooiler

1.625-in. Shaft dia.w/0.375-in. Keywayy

Suction

Boost pump

24.69-in.10.00-in.

Gas purge valve

Temperature

recorder

Pressuretransducer

CO2 Pump vent

Check-valve

Trico Oiler 1.625-in. Shaft dia.w/ 0.375-in. keyway

Suction

24.69 in.10.00 in.

10.75 in.

7.50 in.Discharge

8-in., 300-lbANSI Flange

7/8-in. dia.-12 holeson 13-in. dia. B.C.

15-in. dia.


3/4-in. dia.-8 holeson 7.88-in. dia. B.C.

10.00-in. dia.



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CO2 Safety Manual

Figure 3.4Pressure-volume curve for centrifugal boost pump with 10.19-in. impeller

Figure 3.5Arrangement for pumping CO2without a booster

266

213

160

107

0

TotalHead

(ft)

U.S. gal/min

146 292 438 584 730 876 1,022

16

10.6

5.5

NPSH(

ft)

NPSH

55 6273

7678%

7673

59 bhp

49 bhp

39 bhp29 bhp

9-in. Dia.

10-in. Dia.

8-in. Dia.

45 69

Check-valve

Flowmeter

To wellhead

Treating fluidCO2 Pump vent

COtransport

2

Injection-pumpfluid end

Gas purge valve

Temperaturerecorder

Presssuretransducer

Check-valve


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CO2 Safety Manual


Liquid-Gas Separator

If the liquid-gas separator is used correctly, it will save

some CO2 and cool the standby pump. Separators are

used on most boost-pump units.

Figure 3.6 shows the separator with liquid CO2

at the

proper operating level. The liquid level should be kept

between the high and low tubes connected to the 1/4-in.

indicator valves. Table 3.1 lists some problems and

solutions related to the presence of liquid in the liquid-

gas separator.

ImportantNever allow the vent valve on the sepa-

rator to release dry ice. If this condition occurs, theseparator cannot function properly because it is

completely full of CO2, and CO2 is being wasted.

Figure 3.6Liquid-gas separator

Table 3.1Liquid CO2 in the Liquid-Gas Separator

Condition Problem Solution

Liquid CO2 comes out of both

indicator valves.

The level of liquid CO2 in the

separator is too high.

Slightly close the vent valve.

CO2

vapor comes out of both

indicator valves.

The level of liquid CO2

in the

separator is too low.

Slightly open the vent valve.

CO2 vapor comes out of one

indicator valve, and liquid CO2comes out of the other.

The liquid level is correct. No adjustment is necessary. Con-tinue pumping the job.

Liquid CO2 isdrawn off here.


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CO2 Safety Manual

Suction Y Header

HT-400 Pumps

A new suction Y header is available from the Duncanwarehouse. It is specifically designed for use with CO2,

but it can also be used with sand and other stimulationfluids. Use the new header for all CO2 pumpingservices. Standard suction Y headers (Part Nos.100054527 and 280.00668) cannot withstand the lowfluid temperatures and high boost pressures associatedwith pumping CO2.

The new suction Y header is designed according to theANSI B31.3 piping code and can withstand a workingpressure of 500 psi. Special materials and weldingtechniques give the header exceptional low-tempera-ture impact resistance and an operating temperaturerange of -75 to +300F.

The new suction Y header uses a 4-in. low-temperaturehammer union connection, allowing the header to beused in standard stimulation service. Table 3.2 listsavailable parts for the suction Y header. These partsare available in a kit (Part No. 100058529).

NoteFor short pumping interruptions, the boostpumps and the HT-400 pumps can be placed in neutral,but long delays may require pumps to be reprimed. Thetime after which a pump must be reprimed depends onfactors such as ambient temperatures and the pressure

in the treatment line.

When working with the CO2 suction header, use

ASTM 320-L7 screws rather than standard cap screws.ASTM 320-L7 screws have superior low-temperatureimpact strength.

CautionSuction Y headers must be welded by

personnel certified to weld ASME P9B, Group Imaterials.

HQ-2000 Pumps

Three suction headers are available for the HQ-2000

pump, all of which are designed for pumping CO2.

HT-2000 Pumps

Available suction headers for HT-2000 pumps are

designed for pumping CO2.

ImportantUse nuts and studs only as outlined in

bulletin SEQ-01-001, which is available at the

following address: http://halworld.halnet.com/hes/

hesps/hespspe/hespspe_content/fracacid/equip/

bulletin/seq01001.pdf

HT-400 Fluid-End Cover Gasket

NoteSee Appendix B of this manual for instructions

on modifying the fluid ends of HT-400 pumps.

New fluid-end cover gaskets for the HT-400 pump

have been tested successfully in all pumping services.

These gaskets are harder than standard rubber gaskets

and are more difficult to install, but they will provide

longer service and can be used for all pumping

services. See Table 3.3 for part numbers.

Table 3.2Part Numbers forthe Suction Y Header

Part Number Description

100011736 Suction Y header for CO2 service

100002455 Hex cap screw,5/8-in.,

11 UNC 1 3/4-in

100015419a O-ring, 90d, 53/8 4

7/8

1/4

aO-ring 100001979 can be substituted.

Table 3.3Fluid-End Cover Gaskets for CO2Service with HT-400 Pumps

Part Number Description

100002857 No. 3 cover gasket



http://localhost/var/www/apps/conversion/tmp/scratch_10/hes/hesps/hespspe/hespspe_content/fracacid/equip/bulletin/seq01001.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_10/hes/hesps/hespspe/hespspe_content/fracacid/equip/bulletin/seq01001.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_10/hes/hesps/hespspe/hespspe_content/fracacid/equip/bulletin/seq01001.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_10/hes/hesps/hespspe/hespspe_content/fracacid/equip/bulletin/seq01001.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_10/hes/hesps/hespspe/hespspe_content/fracacid/equip/bulletin/seq01001.pdf


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CO2 Safety Manual


HT-400 Header Ring

Another improvement in CO2 service is a new urethaneheader ring. When used in CO2 and Xylene services,the standard header ring swells and blisters, signifi-cantly decreasing its working life. A urethane headerring suitable for use in CO

2

, Xylene, and standardservices has been tested and is now available forgeneral use. Table 3.4 lists part numbers.

To install the new header ring, follow the installation

instructions in the HT-400 Repair and Overhaul

Manual (Part No. 100002809). Tighten the packing to

a 30-lb pull with a standard (short) packing wrench.

CautionOvertightening will cause the ring to get

too hot and melt.

NoteSet the plunger lube system to 15 to 20 psi. Use

a low-temperature rock-drill oil with a pour point of

-40F or less, or use C-3 hydraulic fluid.

ImportantPumping systems that use recirculating oil

are not recommended for CO2 services. The CO2 can

impregnate the oil, causing the reservoir tank to expand

and rupture.

Pumping Liquid CO2 with a Positive-

Displacement PumpThe following factors influence the performance of a

crankshaft pump during operations with liquid CO2:

differential boost pressure (pressure rise across

boost pump)

discharge pressure

pump speed (flow rate)

ambient temperature

plunger size

suction-hose diameter and length

packing lubrication

Performance Curves

Figure 3.7 (Page 7) through Figure 3.19 (Page 13)

show theoretical performance curves for various

plunger sizes used with Halliburton pumps. For a given

plunger size, each chart shows the maximum pressure

at which a pump can operate without vapor-locking,

depending on flow rate and ambient temperature.

These performance curves are based on the following

assumptions:

The differential boost pressure is 60 psi (4 bar).

The suction hose has a 4-in. ID and is 10 ft long.

The plunger packing is poorly lubricated.

NoteUsing a differential boost pressure lower than

60 psi (4 bar) or a suction hose longer than 10 ft would

invalidate the charts; however, a higher differential

boost pressure or a shorter suction hose would be bene-

ficial. Pumps will cavitate when used outside their

performance ranges for pumping CO2.

Determining the Correct Plunger Size

Problem

You want to use an HT-400 pump to pump liquid CO2.

The job pressure is 7,397 psi (510 bar), the flow rate is

63 gal/min, and the ambient temperature is 100F.

What is the correct plunger size for the job?

Answer

The answer is based on a 60-psi differential boost pres-

sure provided by a Halliburton boost trailer. Figure 3.7

(Page 7) through Figure 3.8 (Page 8) show that

3 3/8-in. and 4-in. plungers are unsatisfactory for this

job. Under the pumping conditions described in the

problem above, these plunger sizes cause vapor

locking.

Figure 3.9 (Page 8) shows that the 4 1/2-in. plunger can

operate at a maximum pressure of 8,000 psi, making it

suitable for this job.

Table 3.4Urethane Header Rings for CO2Service with HT-400 Pumps

Part Number Size

100058346 3 3/8 in.

100002897 4 5 in.

100002949 4 1/2 in.

100058486 5 in.

100058613 6 in.


29/51


CO2 Safety Manual

Extending the Maximum OperatingPressure

To extend the maximum operating pressure of a pump

beyond the values listed in the performance charts,

perform the following:

1. Increase the differential boost pressure above

60 psi.

2. Thermally insulate the suction hose and the fluid

end of the pump.

3. Lubricate the fluid-end packing with Dexron II or

an equivalent low-viscosity oil.

Example

Theoretically, the 3 3/8-in. plunger can operate at

15,000 psi (with a flow rate between 1.2 and 1.5 bbl/min

and an ambient temperature of 120F). You can ensure

that the plunger operates correctly at this pressure by

using a 100-psi differential boost pressure, a 2-in. ID

suction hose, thermal insulation, and packing lubrica-

tion.

See Appendix C of this manual for information about

modifying the fluid end of the HT-400 pump for use with

CO2.

Figure 3.7Minimum flow rate for liquid CO2in an HT-400 pump with a 33/8-in. plunger at a differential boost pres-

sure of 60 psi

0F 20

F 40

F

60F

80F

100F

120F

1 10Rate (bbl/min)

1,000

10,000

100,000

0.1

Pressure

(psi)

5,000

50,000

pressure = 20,000 psiMaximum operating

0.5 5


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CO2 Safety Manual


Figure 3.8Minimum flow rate for liquid CO2in an HT-400 pump with a 4-in. plunger at a differential boost pres-sure of 60 psi

Figure 3.9Minimum flow rate for liquid CO2in an HT-400 pump with a 4 1/2-in. plunger at a differential boostpressure of 60 psi

1,000

10,000

100,000

0F 20F 40F60F

80F100F

120F

0.1 1 10Rate (bbl/min)

Pressure(psi)

5,000

50,000

0.5 5

Maximum operatingpressure = 14,000 psi

10,000

100,000



1,000

5,000

50,000

0F 20F

40F

60F

80F

100F

120F

0.5 5

Pressure

(psi)


31/51


CO2 Safety Manual

Figure 3.10Minimum flow rate for liquid CO2in an HT-400 pump with a 5-in. plunger at a differential boost pres-sure of 60 psi

Figure 3.11Minimum flow rate for liquid CO2in an HT-400 pump with a 6-in. plunger at a differential boost pres-

sure of 60 psi

1,000

10,000

100,000

0.1 1 10

Rate (bbl/min)

Maximum operatingPressure = 9,000 psi5,000

50,000

0.5 5

Pressure(psi)

0F 20F40F

60F80F

100F120F

1,000

10,000

100,000


Maximum OperatingPressure = 6,250 psi

5,000

50,000

0.5 5

0F 20F

40F

60F

80F

100F

120F

Pressure

(psi)


32/51

CO2 Safety Manual


Figure 3.12Minimum flow rate for liquid CO2in an HQ-2000 (Grizzly) pump with a 33/8-in. plunger at a differ-

ential boost pressure of 60 psi

Figure 3.13Minimum flow rate for liquid CO in an HQ-2000 (Grizzly) pump with a 4-in. plunger at a differentialboost pressure of 60 psi

1,000

10,000

100,000


Maximum operatingPressure = 20,000 psi

0F 20F40F

60F

80F100F

120F

0.5 5

5,000

50,000

Pressure(psi)

1,000

10,000

100,000


Maximum operating

Pressure = 14,000 psi5,000

50,000

0.5 5

0F 20F

40F

60F

80F

100F

120F

Pressure(psi)


33/51


CO2 Safety Manual

Figure 3.14Minimum flow rate for liquid CO2in an HQ-2000 (Grizzly) pump with a 41/2-in. plunger at a differ-

ential boost pressure of 60 psi

Figure 3.15Minimum flow rate for liquid CO2in an HQ-2000 (Grizzly) pump with a 5-in. plunger at a differential

boost pressure of 60 psi

0F

1,000

10,000

100,000

0.1 1 10

Rate (bbl/min)


0.5 5

50,000

5,000Pressure

(psi)

20F 40F 80F 120F60F 100F

1,000

10,000

100,000


0F


120F80F

20F

40F

60F 100F

Pressure

(ps

i)

5,000

50,000

0.5 5


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CO2 Safety Manual


Figure 3.16Minimum flow rate for liquid CO2in an HQ-2000 (Grizzly) pump with a 6-in. plunger at a differentialboost pressure of 60 psi

Figure 3.17Minimum flow rate for liquid CO2in an HT-2000 pump with a 41/2-in. plunger at a differential boost

pressure of 60 psi

1,000

10,000


0F 20F

40F

60F

80F

100F

120F


Pressure(psi)

5,000

0.5 5

1,000

10,000

100,000

0.1 1 10 100Rate (bbl/min)

0F 20F

40F

60F

80F

100F

120F

Pressure(psi)

50,000

5,000

0.5 5 50

Maximum operating

pressure = 20,000 psi


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CO2 Safety Manual

Figure 3.18Minimum flow rate for liquid CO2in an HT-2000 pump with a 5-in. plunger at a differential boost

pressure of 60 psi

Figure 3.19Minimum flow rate for liquid CO2in an HT-2000 pump with a 6-in. plunger at a differential boostpressure of 60 psi

1,000

10,000

100,000

0.1 1 10 100Rate (bbl/min)

0F 20F

40F

60F

80F100F

120FPr essure(psi)

50,000

5,000

0.5 5 50


1,000

10,000

100,000


0F 20F 40F

60F

80F

100F

120F

Pressure(psi)

5,000

50,000

0.5 5



36/51

CO2 Safety Manual



37/51

September 2001 1 of 4 Appendix A

Appendix

AAppendix ADetermining CO2

Discharge Temperatures

The temperature of the CO2 entering the wellhead

determines the amount of tubing contraction that will

occur during a job. Therefore, people who use CO2 for

oilfield operations must be able to determine CO2

discharge temperatures.

After the CO2 discharge temperature has been deter-

mined, software programs can be used for determining

the temperature of the mixture containing CO2 and

water or hydrocarbon-based stimulation fluid. The

soft-ware program CO2 Calcs, which is available in

HalWins StimWin package, can be used for deter-

mining the temperature of the mixture entering the

wellhead, and StimWins TMP program is used for

determining tubing contraction.

Numerical Approach

Use Equation 1 to calculate the discharge temperature

of liquid CO2as a function of the discharge pressure:

Td= TtEa..............................................................Eq. 1

Where

Td= absolute temperature of CO2at discharge, R

Ts= absolute temperature of CO2 in the tank, R

a = [1.257 10-5 - 2.2147 10-10 (Pd- Pt)][Pd- Pt]

Pd= discharge pressure, psi

Pt= suction pressure (pressure in the CO2 tank), psi

Equation 1 is based on the assumption of adiabatic

compression, and it predicts the discharge temperature

within 2F of available experimental data. Use Equa-

tion 2 to calculate the absolute temperature for a given

tank pressure (in psi):

Tt= 402.65 + 0.19056 Pt.......................................Eq. 2

Generally, tank pressure varies from 280 psi to approx-

imately 220 psi as the liquid level decreases. The

reduced pressure causes the suction-fluid temperature

to vary between -4 and -15.4F, resulting in a CO2discharge-temperature fluctuation of approximately11.4F.

Graphical Approach

Table A.1 (Page 2) shows the discharge temperature of

CO2 as a function of discharge and tank pressures. You

can accurately determine discharge temperatures from

Table A.1 (Page 2), but interpolation is required for

intermediate values.


38/51

CO2 Safety Manual

Appendix A 2 of 4 September 2001

Table A.1Discharge Temperature of Liquid CO2 as aFunction of Discharge and Tank Pressures

Discharge

Pressure(psi)

Tank Pressure (psi)

200 220 240 260 280 300

1,000 -14.88 -11.14 -7.41 -3.68 0.05 3.79

2,000 -9.55 -5.77 -1.99 1.79 5.56 9.34

3,000 -4.36 -0.53 3.29 7.11 10.93 14.76

4,000 0.69 4.56 8.42 12.29 16.15 20.02

5,000 5.59 9.50 13.40 17.31 21.21 25.12

6,000 10.33 14.28 18.23 22.17 26.11 30.06

7,000 14.91 18.90 22.88 26.87 30.85 34.83

8,000 19.33 23.35 27.37 31.39 35.41 39.43

9,000 23.56 27.62 31.68 35.73 39.79 43.85

10,000 27.63 31.72 35.81 39.90 43.98 48.0811,000 31.50 35.63 39.75 43.87 47.99 52.12

12,000 35.19 39.35 43.50 47.65 51.80 55.96

13,000 38.69 42.87 47.05 51.24 55.41 59.60

14,000 41.98 46.20 50.41 54.62 58.82 63.04

15,000 45.08 49.32 53.55 57.79 62.02 66.26


39/51

September 2001 3 of 4 Appendix A

CO2 Safety Manual

Example

Figure A.1 provides curves for various CO2 discharge

temperatures. To determine the discharge temperature

for a particular discharge pressure, follow the line for

the appropriate discharge pressure upward until you

reach the appropriate curve for tank pressure. Then,

follow that line to the left. For example, if the discharge

pressure is 5,000 psi and the tank pressure is 280 psi,

the discharge temperature would be 21F.

Figure A.1CO2discharge temperatures

5,000 10,000

Discharge Pressure (psi)15,0000

-20

-10

0

10

20

30

40

50

60

70

Disc

hargeTemperature(F)

+21F

Tank

Pressure

=300

psi

280

psi

260

psi

240

psi

220

psi

200

psi


40/51

CO2 Safety Manual

Appendix A 4 of 4 September 2001


41/51

September 2001 1 of 2 Appendix B

Appendix

BAppendix BModifying the Fluid Endsof HT-400 Pumps for CO2 Jobs

Tie-Bolt ArrangementTo pump CO2 with HT-400 pumps fitted with true

4-in., 4 4 1/2-in., or 41/2-in. fluid ends, you must

modify the tie-bolt arrangement.

The left side ofFigure B.1 depicts the current fluid-end

arrangement, which includes a 1 3/8-in. diameter top

tie-bolt and a single 3/4-in. diameter bottom tie-bolt.

The right side of the figure depicts the new, modified

arrangement, which eliminates the bottom 3/4-in. tie-

bolt and inserts two 1-in. diameter tie-bolts through the

fluid-end sections. This new arrangement lowers cyclic

bolt stress and reduces the possibility of CO2 leakage at

the discharge-passage seals.

Use the improved top tie-bolt (Part No. 100002993,

1- 32 1/2-in.) for all fluid-end assemblies. This top

tie-bolt will be standard on new fluid ends and will

replace the old top tie-bolt. In addition, use improved

nuts (Part No. 100002976) with the new top tie-bolts.

Figure B.1Old and new tie-bolt arrangements

Discharge flanges

Top tie bolts

1-in.Washer

New bottomtie bolts1-in. x 32 1/2-in.

Drilledthrough

1 1/16-in.Currentbottomtie bolt

Flange-

attachingstuds

Current design Modified design

1-in. Internalhex head nut

Fluid-end assemblyFluid-end assembly

Discharge passage Discharge passage


42/51

CO2 Safety Manual

Appendix B 2 of 2 September 2001

Part Numbers

Table B.1 lists the sizes and part numbers for drilled,

single fluid-end sections and complete fluid-end

assemblies that are available from the Duncan ware-

house.

Table B.2 lists the part numbers and quantities of tie-

bolts, washers, and hex nuts required for modifying a

complete fluid-end (three-section) assembly in the

field.

Modifying Fluid Ends

To modify a fluid end, perform the following:

1. Disassemble the fluid end:

a. Drill a 1 1/16-in. diameter hole through all three

fluid-end sections at the location of the flange-

attaching studs.

b. Pilot-drill the fluid-end sections with a 5/8- or3/4-in. bit.

NoteDrill slowly from both sides of each section so

that the bit can walk to the centerline.

2. Coat all threads of the tie-bolts with thread lubri-

cant.

3. Place 1 32 1/2-in. flange tie-bolts (Part No.

100002994) through the 1 1/16-in. drilled holes.

4. Place hardened washers (Part No. 100002798)

and hex nuts on each end of the new tie-bolts.

CautionDo not substitute other washers for the

hardened washers. Only hardened washers can

withstand the stresses associated with these tie-

bolts.

5. Adjust the torque of the 1-in. flange tie-bolts to

200 lb-ft.

6. Place the top tie-bolt through the discharge

flanges, and secure the top tie-bolt with nuts.

7. Adjust the torque of the top tie-bolt to 200 lb-ft.

8. While holding one nut fixed, tighten each 1-in.

tie-bolt 11/4 turns.

9. Hold one nut fixed, and tighten the top tie-bolt

one full turn.

Table B.1Drilled, Single Fluid-End Sectionsand Complete Fluid-End Assemblies

Fluid-End

Size(in.)

Part No. of

DrilledSection

Part No. of

CompleteFluid-End

Assemblya

True 4 101240205 316.2291

4 1/2 100058461 316.2391

aEquipped with curved discharge flanges on both

sides and plungers for L-spacers.

Table B.2Tie-Bolt, Washer,and Hex Nut Part Numbers

Tie-Bolt

Part No.aWasherPart No.

Hex NutPart No.

Top 100002993

(one unit)

100002976

(two units)

Bottom 100002994

(two units)100002798b

(four units)

100002811

(four units)

aUse the short top tie-bolt (Part No. 100002893)

with narrow blank flanges.bThis washer is specially hardened.


43/51

September 2001 1 of 9 Appendix C

Appendix

CAppendix CCO2 Job Procedures

Preparing the Equipment

To prepare equipment for use with CO2, perform the

following:

1. Magnetically inspect the HT-400, HT-1000, and

Grizzly pumps or intensifiers.

2. Use a clean rag or methanol to dry out the fluid

ends and flowmeter bearings.

CautionWater left in the fluid ends or flowmeter

bearings will freeze, allowing ice to plug valves and

prevent the turbine from spinning.

3. To prevent valves from becoming plugged with

ice, lubricate the plunger with one of thefollowing materials suitable for low tempera-

tures:

5W motor oil

Automatic transmission fluid

Diesel fuel

Conoco DN-600

Mobil SHC734

ImportantEnsure that all heavier lubricants havebeen flushed from the system

4. Verify that all valves, seats, and inserts are in

excellent condition.

5. Replace seals that leak during acid, cement, or

water pumping.

6. Clean out the boost-trailer strainer.

Determining Available CO2 Product

for JobThe volume of CO2 delivered to location should always

be greater than the necessary volume expected for the

job. When ordering CO2, consider the following:

The first ton of liquid CO2 added into a receiver or

storage device on location will be converted to gas.

This gas cap is necessary for pushing the liquid

CO2 out of the receiver. At least 5% of the product

in the receiver at the beginning of the job will be

converted to CO2 gas. As the job progresses, the

pressure in the receiver will decrease, and addi-

tional liquid CO2 will be converted to gas.

The location of the bottom liquid sump varies on

different receivers. Most sumps are located in the

center of the CO2 receiver, but some sumps are

located in the front or back. See Figure C.1 (Page

2). However, the liquid lines are not always located

adjacent to the sump. Therefore, you should always

have the CO2 supplier verify the location of the

sump as well as whether the tanks are level or

leaning to the front or back. Adjust accordingly for

losses resulting from inaccessible liquids left at the

bottom of the tank. Conditions such as ambient temperatures, wind,

and the length of time the product is left in the

receiver will cause additional losses. These losses

are especially common in the summer when the

receivers or transports can reach the maximum

tank pressure within a few days. Consequently,

CO2 gas will be vented to the atmosphere.


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Appendix C 2 of 9 September 2001

The volume of CO2 necessary for cooling down

each pump varies. The volume of CO2 used in the

field will vary depending on ambient temperature,

wind, and the distance from the suction hose to

other equipment, such as the pump, the suction

manifolding arrangement, and the plunger. Follow

these guidelines for determining the volume of CO2required for cooling an individual pump:

HT-400 pump = 2 to 3 tons per pump

Grizzly pump = 3 to 4 tons per pump

HT-2000 pump = 3 to 4 tons per pump

During job delays, additional CO2 may be neces-

sary for performing vapor tests and cooldowns.

Figure C.1Level CO2receiver with sump in middle


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Downstream CO2 Turbine Meterwith Temperature Probe

To accurately meter CO2, you must consider the effects

of temperature and pressure. A CO2 turbine meter will

be within 1% tolerance if it (1) is properly calibrated,

(2) includes a temperature probe downstream of a posi-tive-displacement pump, (3) and designed to account

for the wellhead treating pressure (WHTP).

Table C.1 shows the limitations of a turbine meter that

is not designed to compensate for the effects of temper-

ature. When a temperature probe is not used, the

expected temperature should be determined and manu-

ally entered into the data-acquisition system (DAS) to

limit the error factor. If a turbine meter is used on both

the booster trailer and downstream of the positive-

displacement pumps, the meters will track each other.

Consequently, both meters will be inaccurate becausedecreasing pressure in the receivers will cause temper-

ature fluctuations during the job.

Appendix A provides guidelines for determining CO2

discharge temperatures.

Table C.1

Storage Receiver

Pressure (psi) WHTP Error Percentageb

When CO2 Temperatureis Not Accounted For

200 2,000 7.2

300 2,000 3.2

200 6,000 10.5

300 6,000 7.3

200 8,000 14.3

300 8,000 11.8

Storage Receiver

Pressure (psi)WHTP

Error Percentage

b

With a Hard-Entered CO2 Discharge Temperature of 30F

200 2,000 8.9

300 2,000 4.8

200 6,000 3.0

300 6,000 0.0

200 8,000 -0.6

300 8,000 -2.8


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Setting up the Job

To set up a CO2 pumping job, perform the following

steps:

1. Connect the vapor lines between the liquid CO2

containers to equalize pressure.

2. Install a vapor line from the CO2 supply to the

CO2 booster separator (Figure C.2).

Figure C.2Vapor line (smaller hose) used to equalizepresure between receivers

3. Ensure that the hoses you will be using have been

approved for CO2 service.

4. To reduce heat absorption by the CO2, ensure that

the suction hoses are the minimum required

lengths.

5. Inspect all external covers and braids for damage.

CautionAlways use 4-in. hose unions for CO2

service; 5-in. unions are not rated for CO2 suction

pressures.

6. Securely chain all hose connections (Figure C.3).

Figure C.3CO2hose with pressure release, secured

with chain

7. Clean all unions, and lubricate them with diesel.

8. Ensure that the flowmeter is a cryogenic flow. Do

not purge through the flowmeter at a high

velocity with vapor. This prevents the turbine

from overspeeding.

9. Secure all discharge lines.

10. Install a check valve or manifold trailer in the

discharge of each HT-400 pump.

11. Install a check valve on the CO2 line upstream of

the master CO2 liquid valve.

12. Install a plug valve and a check valve on the non-

CO2

liquid line upstream of the master CO2

liquid

valve.

13. Install a check valve in the treating line as close to

the well as possible.

14. Use a plug valve and a choke on the release line

at the wellhead, placing the plug valve upstream

of the choke.


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Pretreatment Safety Meeting

To ensure the safety of personnel and equipment, hold

a pretreatment safety meeting before each CO2 job:

1. Inform personnel about the jobs maximum pres-

sure and the pressure-testing procedures used.

2. Discuss job hazards, emergency procedures, fire

fighting equipment, personal safety equipment,

and an emergency meeting place.

3. Ensure that personnel are familiar with universal

hand signals for CO2 in case a verbal communi-

cation breakdown occurs. Figure C.4 shows hand

signals associated with CO2.

Figure C.4Hand signals

4. Supply 5-minute escape packs to all personnel,

and randomly choose one individual to demon-

strate proper pack use.

5. Inform operators that once liquid CO2 has been

admitted into the system, leaking unions in the

CO2 line must not be tightened.

CautionNever tighten CO2 unions after CO2 has

been admitted into the system. The unions could

break.

Pressure-Testing and Cooling Down

A typical line-test procedure is demonstrated in Figure

C.6 (Page 7).

Vapor-Testing CO2Lines

Perform the following low-pressure (< 350 psi) gas test

to identify rank leaks:

1. Using vapor lines and gas from the top of the CO2

product source, vapor-test all lines up to a master

CO2/liquid valve.

2. Release pressure, and repair any leaks.

3. After repairing the leaks, repeat this procedure.

Testing CO2

Lines with Glycol

Figure C.5 (Page 6) shows the glycol tank setup for

testing lines. After vapor-testing the CO2 lines, test

them with glycol as follows:

1. Prepare a -50F mixture containing 11 parts

ethylene glycol (antifreeze) and 8 parts water for

pressure-testing.

2. Hook up the glycol to the suction side of the pump

nearest to the wellhead.

3. Install a release line to the glycol trailer.

ImportantDo not use rubber hoses for the release line.

4. Open the bleeder tee.

5. Start boosting glycol through the suction lines to

ensure good returns.

6. Engage the positive-displacement pump, and

prime the pumps, one at a time, to the glycol trailer.

7. Shut in the plug valve at the bleeder tee.

8. Engage one pump with the engine at idle, and

increase the line pressure up to 20% of the test

pressure.

9. Engage the other pumps (one at a time) in gear to

initially open (bump) the check valves at the

current line pressure and test the lines to the

desired pressure.

10. Monitor the pressure chart for leaks.

11. Open the bleeder tee to the glycol trailer, and

release pressure.

12. Repair any leaks, and retest if leaks were found.

13. If the glycol trailer includes a suction pump,

vaccum fluid out of the suction hose and pumps.

14. Hook up the CO2 suction hose to the pumps.

15. Release pressure from the CO2 units to push out

any excess glycol.

Liquid Vapor


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16. When vapor is present at the trailer, shut off gas

vapor.

17. Before beginning the job, unhook the steel line at

the bleeder tee going to the glycol tank.

ImportantIf the ethylene glycol mixture and the

formation are incompatible, remove as much of the

mixture as possible from the discharge lines and the

pumps by displacing the mixture with CO2 vapor

through the release lines and back into the acid trans-

port. Save this mixture for use during other jobs.

Figure C.5Glycol trailer with suction hose to pump and steel line release back to trailer


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CO2 Safety Manual

Figure C.6Typical line-test procedure

Fractanks

HT-400s pumpingliquid phase

No fluid CO contacts thesehigh-pressure liquid lines.Can use water for pressure-testing.

2

Discharge ironfor CO Liquid2

Wellhead

Securedreleaseline

GlycolTank

CO transports2

HT-400spumping CO2

Blender

Check valve

Antifreeze solutionrequired in thisline for pressure-testing.

Temperature recorder

1-in. Lo-Torcbleeder tee

CO boosttrailer

2

Flowmeter

Low-torque valves

Check valve

Check valve

Master CO liquid valve2

Choke

Unhook line atbleeder teeafter purging

glycol with vapor.

Pressure transducer


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Liquid CO2 Pumping Procedure

To pump CO2, perform the following:

1. Close the release valves on top of the HT-400

pumps, and allow the CO2 vapor pressure to reach

the maximum value.

2. Completely close the CO2 supply valve.

3. Slowly open the main CO2 source liquid-line

valve.

4. Start the boost pumps.

5. Prime each HT-400 pump through the release

valve located on top of the pump (Figure C.7).

6. Open the master CO2 liquid valve tee.

NoteThe pump is primed when a solid, white stream

of gas and dry ice/snow continuously blows from the

discharge (Figure C.8 and Figure C.9).

7. Slowly close the release valve on each HT-400pump and begin pumping CO2.

NoteFor short interruptions in pumping, the boost

pumps and HT-400 pumps can be placed in neutral.

However, long delays may require that the pumps be

reprimed. The point at which pumps must be reprimed

depends on conditions such as ambient temperature,

wind speed, and manifolding.

Figure C.7Positive-displacement pumps with remote and manual valves

Figure C.8Initial CO2gas during pump prime-up Figure C.9CO2pump primed with liquid CO2

CO gas2

CO liquid2


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Shutting Down

To shut down the CO2 job, perform the following steps:

1. Shut down the fracturing pumps.

2. Close all liquid CO2 source supply valves at the

container.

3. Open the vapor supply valves, and admit CO2

vapor into the system.

4. Close the plug valve in the CO2 discharge line at

the master CO2 liquid valve.

5. Slowly open the release valve first at the bleeder

tee and then at each fracturing pump.

CautionDo not allow the manifold pressure to

drop below 100 psi because dry ice will form.

6. Place the fracturing pumps in first gear. Allow the

pumps to purge the system at idle until only vapor

is discharged.

7. Allow the system pressure to bleed off.

Disassembling Equipment

CautionIf the pressure drops below 70 psi when

the job stops, wait 30 minutes before draining the

system to allow vapor pressure and heat from theatmosphere to melt any dry ice. This will prevent

the cannonball effect, which can cause dry-ice slugs

to shoot out of hoses. (See Section 1.)

After venting the discharge lines, ensure that the

boost pump does not contain residual liquids.

Slowly drain the liquid CO2, opening the valves at

the lowest points of the boost pump first. Then,

drain the vent line. Ensure that the boost-pump

pressure is above 100 psi.

To disassemble the equipment after a CO2 job, perform

the following steps:

1. When the job is complete, close all valves and

remove the vapor line.

CautionDo not exceed a pressure of 400 psi. The

hoses cannot withstand pressures above 400 psi.

2. Allow the frost to melt on the outside of the

unions. Then, gently hammer the unions loose.

CautionHammer gently on pipe unions. The

unions can become brittle at the temperature of dry

ice and will easily break or chip.

CautionDo not flex the rubber hoses until the

frost has melted from the outside. The liners in the

hoses are not flexible at the temperature of dry ice.

Documents

CO2 Safety Manual