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STANDARD PRACTICE CONFIDENTIAL

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HIGH - PRESSURE STORAGE TANKS

JGS Rev.0

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JUL.-31-'96

CONTENTS PAGE 1. SCOPE.............................................................................................................................................................. 2 2. WORK PROCEDURE ..................................................................................................................................... 2 2.1 Information for Detailed Design................................................................................................................ 2 2.2 Tank Basic Design Work Flow ................................................................................................................. 2 2.3 JOB Data ................................................................................................................................................... 2 3. DESIGN............................................................................................................................................................ 2 3.1 Type Selection ........................................................................................................................................... 2 3.1.1 Tank Type.......................................................................................................................................... 2 3.1.2 Selection of Tank Type ..................................................................................................................... 2 3.2 Storage Capacity........................................................................................................................................ 2 3.2.1 Definition of Capacity ....................................................................................................................... 2 3.2.2 Liquid Level ...................................................................................................................................... 3 3.2.3 Sphere Maximum Capacity ............................................................................................................... 4 3.3 Operating and Design Conditions.............................................................................................................. 4 3.3.1 Operating Conditions ........................................................................................................................ 4 3.3.2 Design Conditions ............................................................................................................................. 5 3.4 Tank Nozzles ............................................................................................................................................. 6 4. ATTACHMENT............................................................................................................................................... 7 4.1 Instrumentation.......................................................................................................................................... 7 4.1.1 Level.................................................................................................................................................. 7 4.1.2 Temperature....................................................................................................................................... 7 4.1.3 Pressure ............................................................................................................................................. 7 4.1.4 Water Drain ....................................................................................................................................... 7 4.2 Others ........................................................................................................................................................ 8 4.2.1 Insulation and Painting...................................................................................................................... 8 4.2.2 Tank Heaters or Coolers.................................................................................................................... 8 5. CALCULATION EXAMPLE .......................................................................................................................... 8 5.1 Calculation Basis ....................................................................................................................................... 8 6. APPENDIX ...................................................................................................................................................... 9

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1. SCOPE This section covers the basic design of pressurized storage tanks to store liquefied petroleum gas (LPG). Refrigerated storage tanks, gas holders and atmospheric storage tanks are not included.

2. WORK PROCEDURE 2.1 Information for Detailed Design JGC blank form “SKELETON OF VESSEL” for pressure vessels shall be used for information on process requirements. The following sections relate to the preparation procedures of the process requirements.

2.2 Tank Basic Design Work Flow The tank basic design work flow is the same as pressure vessels in process plant. Operating pressure and the equilibrium temperature of the storage vessels vary due to the operating modes and the weather conditions. This point is a difference between the process vessels and the storage vessels. Basic design work flow is shown in APPENDIX-2.

2.3 JOB Data The tank lists in major projects are attached in Appendix-1, for reference.

3. DESIGN 3.1 Type Selection 3.1.1 Tank Type Spherical or horizontal cylindrical type (bullet type) storage tanks are used to store LPG. The horizontal cylindrical type will usually be used for small capacity or underground installations.

3.1.2 Selection of Tank Type A tank type will usually be selected considering the cost or the size for transportation. The spherical type is usually employed for sizes greater than 500 m3. The horizontal cylindrical type is usually used for sizes smaller than 100 m3. Both types will be applicable for volumes ranging from 100 to 500 m3. The type of this capacity range will be decided by the total weight. There is no limitation to the size of the horizontal cylindrical type. Where the tank is installed underground, the horizontal type shall be selected, even if the vessel capacity exceeds 100 m3. The maximum size of tank which JGC has constructed is so far 2,000 m3 as net working volume.

3.2 Storage Capacity 3.2.1 Definition of Capacity Nominal capacity ; All this capacity can be used, defined as below. This capacity is usually used as tank name. Geometrical capacity ; Volume inside a vessel which is called “a water volume” in NFPA. Storage capacity ; The volume from the tank bottom to the maximum design level. This volume varies depending on operating temperature. Net working capacity ; Volume between HLL and LLL or HHLL and LLLL TOP OF SPHERE HHLL (or HLL) Net Working LLLL (or LLL)

Geometrical

Storage

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3.2.2 Liquid Level (1) Maximum liquid level (maximum Storage Capacity) Many countries specify a maximum liquid level (max. storage capacity) in their regulations. In countries that have no such regulations, NFPA or Japanese regulations (High Pressure Gas Control Law) shall be applied. NFPA-58 and 59 specify details of the maximum liquid level including liquid volume correction factors and equations concerning capacity and temperature (Refer to NFPA 58 Para. 4-4 and Appendix-F). The Japanese regulations specify that a vapor space of 10% shall be secured under the severest conditions, thus resulting in the following equation. V = W/0.9d Where V = tank geometrical volume (m3) W ; Storage capacity (kg) d ; Density at the maximum design temperature (kg/m3) NFPA specifies the coefficient of the above equation, i.e. 0.9 as follows. · 0.9 to 0.95 at 100° F · 0.98 to 0.99 at the maximum storage temperature. This maximum liquid level fluctuates according to operation temperatures as below. Example ; The following figures are the results of example calculations according to the physical properties of Pure Propane. NFPA ; Storage at 115°F (46°C) 85°F (29.4°C) 60°F (15.6°C)

Volume % 98.0 92.4 88.6

Height % 93 83 79

Density (kg/m3) 459 487 508

Japanese regulation (High Pressure Gas Control Law) Storage at Volume % Height % Density (kg/m3) 90.0 81 455 48 °C 84.8 75 483 32 °C 81.6 73 502 20 °C From the above, it is not possible to set a fixed level for the highest limit point. Therefore the highest limit of level should be compensated with the storage temperature or a differential pressure type level indicator shall be used. (2) Minimum levels Refer to FIG. 3.2-1 H2 ; 150 mm or 10 minutes from the maximum filling volume H3 ; A height of Dead stock area. The height shall be calculated by the reasonable dead stock volume. The recommended height for spherical tank is shown below. Dead stock volume Tank diameter Recommended height (H3) Less than 12 m 1.0 m More than 2 % 12 and lager but not exceed 19 m 1.5 m 1.8 to 4.5 % 19 m and larger 2.0 m Less than 3 % Relation between the tank size, the volume and the level is shown on attached figures, Fig.-3.2-2 and 3.2-3. The volume is calculated by the following equations. Tank Volume/sphere ; V = π * D3/6 1   Sphere/bottom or top section ; Vb = π aH 2 − H 3   3  D a = 2

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Where ;

D : Diameter of sphere H : Height of level V : Sphere volume Vb : Sectional Volume of the height H H4 ; 300 mm/ minimum 100 mm Note 1 ; High and low level (HLL and LLL) alarm shall be set at the maximum and the minimum operation respectively. If high high and low low level (HHL and LLL) for an emergency shutdown or an automatic diversion system are provided, set points shall be selected at lower than the maximum and higher than the minimum design, but not inside of the maximum and the minimum operation. Figure 3.2-1 TANK LEVELS TOP OF SHELL VAPOR SPACE

MAXIMUM DESIGN

H2 H1

MAXIMUM OPERATION MINIMUM OPERATION MINIMUM DESIGN

H3

H4

BOTTOM OF SHELL

3.2.3 Sphere Maximum Capacity The maximum sphere capacity is limited due to the wall thickness. The wall thickness is limited by the manufacturing and the stress relief requirement. Those limitations are shown in Appendix 3 as a guide line. The limitations will be slightly changed depending on the tank vendor, therefore, the firm figures shall be confirmed with the mechanical design group.

3.3 Operating and Design Conditions 3.3.1 Operating Conditions (1) Operating temperature Operating temperatures are not so important for the design of tanks; they are merely used to design pumps connected to tanks. A maximum operating temperature and a minimum operating temperature as pump design bases shall be determined separately. An operating temperature of a tank shall be determined based on the following conditions. - Temperature of rundown from process units - Ambient air temperature (annual mean or annual highest mean temperature) - Temperature of products when they are received from a tanker. (2) Operating Pressure An operating pressure shall be an equilibrium pressure at an operating temperature. Where the mole fraction of contents of the liquid in the tank fluctuates, the most severe case in normal operation shall be considered.

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3.3.2 Design Conditions (1) Design Temperature A design temperature shall be determined based on the assumed highest temperature, with consideration given to input heat generated by solar radiation. Generally, design temperatures are specified per country based on the ambient air conditions of the district where the plant facilities are to be constructed. Major oil companies may have their own design standard of temperatures selection. Where the country's regulations or the client's design standards do not specify design temperatures, NFPA or Japanese standards shall be applied. Design temperature determination standards are closely connected with design pressures and are set forth in paragraph (2) below. Major oil companies, in some cases, have specified the lowest design temperature as a design standard; they employ the equilibrium temperature of a tank internal at atmospheric pressure as the lowest design temperature. Low-temperature service materials, therefore, shall be used for tanks storing propane or lighter fluids. (2) Design Pressure The equilibrium pressure of a tank internal at the design temperature shall be used as the tank design pressure. Where the country’s regulations or the client’s design standards do not specify a design temperature, NFPA or Japanese regulations shall be applied as per the tables below, Table 3.3-1 for NFPA and Table 3.3-2 for Japanese regulation. Some major oil companies specify a higher temperature e.g. 65° C to be a mechanical design temperature, in their standards. In this case, however, they do not employ the equilibrium pressure of the internal at the specified temperature as a design pressure, but the design pressure will be specified separately or the minimum design pressure specified in NFPA is otherwise used. (a) NFPA NFPA 58, Para. 2-2.2.2 specifies minimum design pressures, which are presented in Table 3.3-1 below. Table 3.3-1 The minimum design pressure of ASME container For Gases with Vapor Pressure in psig (MPa gauge ) at 100°F (37.8°C) Not to Exceed 80 (0.6) 100 (0.7) 125 (0.9) 150 (1.0) 175 (1.2) 215 (1.5) 215 (1.5)

Minimum Design Pressure in psig (MPa gauge) ASME Code, Section VIII,1991 Edition 100 (0.7) 125 (0.9) 156 (1.1) 187 (1.3) 219 (1.5) 250 (1.7) 312.5 (2.2) (Note 1)

Note 1: Refer to NFPA 58, Para. 8-2.2 The NFPA specifies the equilibrium pressure at a design temperature of 41, 46 and 54° C, respectively, to be a design pressure, for each type of vessel as given below. · Vessels up to 4.5 m3 incl. in capacity (54°C) · Vessels over 4.5 m3 in capacity (46°C) · Underground vessels (41°C) (b) Japanese Regulations In Japan, JLPA recommends that pressures given in the table below be used to determine an LPG tank design pressure. Design pressures given in the table 3.3-2 have been established based on the assumed highest temperature during operation under severe climatic conditions in summer. In summer, the Japanese Islands are subjected to conditions more severe than those in tropical countries, including South-east Asian countries. Therefore, if there is no regulation in those countries , the design pressures given in the table below can be applied, with the approval of the client. Table 3.3-2 Design pressure of LPG vessel

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STANDARD PRACTICE CONFIDENTIAL A (55°C) kg/cm2G 21.6 18.0 7.2 6.6 4.5 6.0

Case Contents Propylene Propane Butadiene Iso-Butane N-Butane Butene

JGS B (48°C) kg/cm2G 18.6 15.6 6.0 5.4 3.6 4.8

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C (40°C) kg/cm2G 15.8 12.7 4.8 4.4 2.9 3.6

Design pressures A shall be applied to LPG tanks whose storage capacity is 1,000 m3 or less. Design pressures B shall be applied to LPG tanks whose storage capacity exceeds 1,000 m3. Design pressures C are sometimes used for LPG tanks whose storage capacity exceeds 3,000 m3 or installed in the northern area of Japan. Note that these design pressures are more severe than those specified by NFPA. However, the Japanese guideline is preferable for tanks installed in tropical areas and which have a capacity less than 1,000 m3.

3.4 Tank Nozzles (1) Tank nozzle information to be provided by basic engineering. The following items of nozzle information shall be provided by the basic design group. (a) Size, number and location of inlet and outlet nozzles Note: The pump suction nozzle shall be inserted by 300 mm from the tank bottom.

Water level

300mm/ 100mm Min.

Pump Suction Nozzle

(b) Size, number and location of sampling nozzle(s) and water draw off nozzle, if required (c) Size and number of spare nozzle(s), if required (d) Size and number of vent and drain nozzle Minimum one vent and drain nozzle shall be provided. (e) Size and number of nozzles for safety relief valves Minimum one spare PSV shall be provided. (2) Nozzle for instrumentation Nozzle information for instrumentation will be provided by others. (3) Nozzles to be decided by the detailed engineering group (a) Top and bottom manways

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4. ATTACHMENT 4.1 Instrumentation 4.1.1 Level Generally, two level instruments will be installed to permit mutual calibration to be carried out, because LPG tanks cannot open without the tank shut down. One level instrument may be permitted, if it is possible to remove and calibrate it by installing an isolation valve such as radar type. To use the LPG tank capacity as effectively as possible, it is necessary to compensate the level with temperature instrument or use differential pressure type level instrument, because of the reason described in Para. 3.1.

4.1.2 Temperature Generally, a temperature indicator shall be installed at the bottom crown.

4.1.3 Pressure Generally, two pressure gauges should be provided at the sphere top and bottom. One pressure instrument should be provided and indicated in control room. Two pressure relief valves, each have a 100% capacity shall be provided. This configuration allows the PRV maintenance without sphere shutdown.

4.1.4 Water Drain A Water draw off line shall be installed on each LPG tank. The simplest installation is shown below. Two isolation valves shall be provided on the water draw off line : a distance of more than one meter shall be provided between the valves to prevent freezing the valves as figures below. As an alternate system, a water draw off pot is provided, and the vent line from the water pot is returned to the flare line or the LPG tank.

1m minimum 1m minimum

UNDERGROUND TANK

Alternate Plan

To tank vapor zone

To flare

LG Steam Trace

1m minimum To clean or oily sewer

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4.2 Others 4.2.1 Insulation and Painting For aboveground tanks, in some cases, cold-insulation or fire protection may be provided, according to the client's request. In such a case, it is possible to reduce the safety valve relieving capacity.

4.2.2 Tank Heaters or Coolers A tank heater or cooler shall not be installed in the tank. However an external heater may be required in the coldest areas, i.e. North East of China or Siberia, to avoid a vacuum in the tank.

5. CALCULATION EXAMPLE The following is an example calculation of spherical tank sizing.

5.1 Calculation Basis (1) Basic requirement Net working requirement ; 700 tons Run down temperature ; 40 °C Location ; South East Asia (2) Sizing Basis Code ; Japanese regulation Design Temperature ; 48 °C Tank minimum level ; 1.5 m (3) Physical property of stored fluid Fluid ; Pure Propane Density ; 455 kg/m3 at 48 °C ; 508 kg/m3 at 60 °F(15.4°C) Vap.Press. ; 15.6 kg/cm2 G (4) Calculation V = W/ 0.9 sw -------- from 3.2.2 (1) V = 700,000 / (0.9 * 455) = 1709 m3 D = 14.8 m (tentative size)----------- from Fig 3.2-2 Dead stock 1.5 m = 2.8 % ----------- from Fig. 3.2-2 1,709 * 1.028 = 1760 m3 -- 15.0 m -- from Fig. 3.2-2 Maximum level at 90 volume % ----- 81 % of height, 12.15 m -- from Fig. 3.2-3 (5) Summary of result MAX. LEVEL

90 %

2,850mm

10,650mm

15,000mm

MIN. LEVEL 1,500mm

Pure Propane ; Design pressure ---15.6 kg/cm2G---from table 3.3-2

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(6) Alternate Design The size calculated in accordance with NFPA 700 tons plus dead stock = 700 * 1.03 = 721 tons V = 721 / 0.45 = 1602 m3 (0.45 came from NFPA 58 table 4-4.2.1) D = 14.6 m Density = 457 kg/m3 at 46 °C Liquid maximum volume = 721,000 / 457 = 1577 m3 1577 / 1602 = .984 ---- 98 Volume % ---- 93 % of height from Fig. 3.2-3 MAX. LEVEL

98vol %

1000mm

12,100mm

14,600mm

MIN. LEVEL 1,500mm

Vapor pressure ; 172 lb/ft2 G at 100 °F Design Pressure ; 219 psig (1.5 Mpa G)---from table 3.3-1

6. APPENDIX Appendix 1 Figures for tank sizing Appendix 2 Current Job Tank list Appendix 3 Tank basic Design work Flow Appendix 4 Sphere volume limits

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FIG. 3.2-2

TANK SIZE VS BOTTOM HEIGHT/VOLUME

10000 V=(PI/6)*D3

TANK VOLUME

1000

VOLUME % 4%

VOLUME (m3)

Vb=(PI/3)*H2*(3D/2-H)

3% 2.5 % 2% 1.5 % 1%

HEIGHT H=2.0m

100

1.5m 1.0m 10 0.5m 1 5

7

9

11

13

15

17

TANK DIAMETER (m)

19

21

23

25

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FIG. 3.2-3 CYLINDRICAL TANK HEIGHT % VS VOLUME % 100 90 80

VOLUME %

70 60

Volume % 2:1ELIP/SPH.

50

Volume % cylind.

40 30 20 10 0 0

10

20

30

40

50

60

TANK HEIGHT %

70

80

90

100

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DAYLY (KL) PRODUCTION

LPG Propane Butane LPG Propylene Total

TANKER SIZE (MDWT/MKL)

360 860 700 Lorry 1,070 Ship/ 17000 10000 8500 4500 15000 7500 6500 3500 12000 6000 5000 2600 9500 4500 4000 2200 8000 3500 3200 1700 6500 3000 2600 1500 5500 2500 2200 1200 4500 2000 1700 1000 3700 1600 1500 900 3200 1500 1200 800 2800 1300 1100 650 2500 1200 1000 600 2200 1000 850 500 1700 800 750

MAX. t=57mm C.A.=1.5

>17000 14000 11000 9500 8000 6500 5500 5000 4000 3500 3100 2700

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JIS B 8243 DESIGN

MATERIAL SPV20 PRESSURE SR LIMIT VOL. kg/cm2G

C.A.=0.0 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

5000 3500 2500 1600 1400 1000 900 700 500 450 400 300 270 220 200 150 140

DESIGN SPV46 PRESSURE SR LIMIT VOL. kg/cm2G

C.A.=0.0 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

>17000 12000 9500 7500 6000 4500 3500 3000 2500 2000 1700 1500 1200 1100 1000 900

SPV36 MAX. t=57mm SR LIMIT VOL. C.A.=1.5mm C.A.=1.5 C.A.=0.0 C.A.=1.5mm 4500 >17000 17000 15000 3000 9500 12000 10000 2100 7000 9000 7500 1500 5000 6500 5500 1200 4000 5000 4500 900 3000 4000 3500 720 2500 3000 2500 600 1700 2500 2000 480 1500 2000 1600 400 1200 1600 1500 320 1000 1500 1200 250 900 1200 1000 240 700 1000 900 200 600 900 800 180 500 800 700 150 430 700 600 130 400 600 500 SPV50 MAX. t=57mm SR LIMIT VOL. C.A.=1.5mm C.A.=1.5 C.A.=0.0 C.A.=1.5mm >17000 15000 >17000 >17000 11000 15000 13000 8500 11000 10000 6500 >17000 9000 8000 5000 16000 7000 6000 4000 13000 5500 5000 3000 11000 4500 4000 2500 9000 3500 3000 2200 7500 3000 2500 1800 6500 2500 2100 1500 5500 2000 1800 1200 4500 1700 1500 1000 4000 1500 1300 950 3500 1300 1200 900 3000 1100 1000 800 2700 1000 900

MAX. t=57mm C.A.=1.5

>17000 14000 11000 9500 7500 6000 5000 4500 3700 3000 2500 2400 2000 1700

MAX. t=57mm C.A.=1.5

>17000 16000 13000 11000 9000 7500 6500 5500 5000 4200 3700 3200

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