SPC-0804.02-20.06 Rev D2 Field-Erected Low Pressure Storage Tank

PREPARED BY CHECKED BY APPROVED BY CERTIFIED (PTT) REV. DATE NO. 18-FebD1 08 11-JunD2 08

NA

PTT PUBLIC COMPANY LIMITED ONSHORE COMPRESSOR STATION 4 PROJECT

NA REVISED BY

APPROVED BY NA NA

DESCRIPTION ISSUED FOR ITB ISSUED FOR ITB

FIELD-ERECTED LOW PRESSURE STORAGE TANK SPC-0804.02-20.06 REV.D2 TOTAL 14 PAGES

AREA CODE OF SITE LOCATION GENERAL AREA: 010 PTT PLC. CONTRACT NO.

.

PTT PLC. PROJECT NO. 0804.02

FIELD-ERECTED LOW-PRESSURE STORAGE TANKS

PTT PUBLIC COMPANY LIMITED ENGINEERING STANDARD

SPC-0804.02-20.06 PAGE: 2 OF 14 REV: D2

CONTENTS SECTION 1.0

SCOPE ..........................................................................................3

2.0

APPLICABLE CODES AND STANDARDS ............................................3

3.0

BASIS OF DESIGN ..........................................................................3

4.0

MATERIALS OF CONSTRUCTION .....................................................5

5.0

DETAIL DESIGN..............................................................................6

6.0

FABRICATION ..............................................................................10

7.0

INSPECTION AND TESTING ...........................................................12

8.0

CODE STAMP, NAMEPLATE ..........................................................13

9.0

SUPPLIER'S DATA REQUIREMENTS ................................................13

10.0 PAINTING, SHIPMENT ...................................................................14 11.0 GUARANTEES AND WARRANTIES..................................................14

FIELD-ERECTED LOW-PRESSURE STORAGE TANKS 1.0


SPC-0804.02-20.06 PAGE: 3 OF 14 REV: D2

SCOPE

1.1

This standard covers the design and construction of storage tanks in API standards.

1.2

Specific information given on PTT drawings, data sheets content in project specification shall have precedence over this standard, but any conflicting requirements must be referred to PTT/ CONSULTANT for resolution before proceeding.

2.0 2.1

APPLICABLE CODES AND STANDARDS The following Codes and Standards are applicable as required by this standard. API Standard 650,

Welded Steel Tanks for Oil Storage

API Standard 620,

Recommended Rules for Design and Construction of Large Welded Low Pressure Storage Tanks

API RP 2000,

Venting Atmospheric and Low Pressure Storage Tanks

ANSI B16.47 Series B

Large diameter Carbon Steel Flanges

ANSI B16.5,

Steel Pipe Flanges and Flanged Fittings

ASCE 7-95

Minimum Design Loads for Building and Other Structures

2.2

The latest editions and addenda of all Codes and Standards at date of contract shall be employed.

2.3

Tankage and appurtenances shall meet all applicable requirements of local and national regulations, ordinances statutes or codes, including approval of design & manufacturing.

3.0

BASIS OF DESIGN

3.1

Standard

3.1.1 Atmospheric pressure non-refrigerated tanks shall be designed to API 650. Closed Top subject to low pressure shall additionally satisfy Appendix F. Higher pressure tanks up to 15 psig shall comply with API 620 and shall include any API 650 requirements for materials and examinations.



SPC-0804.02-20.06 PAGE: 4 OF 14 REV: D2

3.1.2 API 650 tanks with wall thickness up to and including 0.5 inch shall be to Appendix A except that Group I materials of Table 4.3 shall not be used below -20 C. °

3.1.3 Shop assembled API 650 tanks shall comply with Appendix J except that a minimum of spot radiography shall be applied with joint efficiency of 0.85.

3.2

Design Temperature

3.2.1 API 650 is used for operating temps up to 90 C. Appendix M allow design temperature up to 260 C. °

Conditions detailed in

°

3.3

Design Loading

3.3.1 Wind load shall be to ASCE 7-95 and PTT Specification, SPC-0804.02-40.05 3.3.2 For design of API 650 top and intermediate wind girders the maximum gust velocity shall be used if greater than 100 mph. 3.3.3 The need for intermediate wind girders shall be assessed for API 650. 3.3.4 Earthquake load is not applicable to this project. 3.3.5 The CONTRACTOR shall also consider the following in addition to standard design loads 1. 2. 3. 4.

3.4

Platforms, ladders and piping loads Loads imposed during transport Support column lateral loads Heat treatment effects

Foundations and Settlement

3.4.1 API recommended practice shall be followed by CONTRACTOR to produce the tank foundation. 3.4.2 Facilities for monitoring settlement shall be provided. This shall include for monitoring settlement of the bottom relative to the tank wall. 3.4.3 This shall include clips welded to the shell wall near the annular plate and extended legs or probes to monitor floor settlement.

3.5

Allowable Stress

3.5.1 Maximum allowable stress values shall be in accordance with the API Standard, section 5.6.2 Table 5.2. 3.5.2 For austenitic stainless steel tanks the allowable stress shall be to the rules of API 620 Appendix Q.

FIELD-ERECTED LOW-PRESSURE STORAGE TANKS 3.6


SPC-0804.02-20.06 PAGE: 5 OF 14 REV: D2

Corrosion Allowance

3.6.1 Corrosion allowance is specified in tank data sheet. CA on removable internal part shall be ½ of tank corrosion allowance applied to all exposed surfaces. 3.6.2 CA on fixed internal parts shall be same as the vessel corrosion allowance applied to all exposed surfaces.

4.0

MATERIALS OF CONSTRUCTION

4.1

Material specifications shall be as permitted by the API Standard.

4.2

CONTRACTOR shall identify the material specification to be used.

4.3

When plate impact tests are required by API 650 they shall be to the procedure of paragraph 4.2.10.1.

4.4

Annular bottom plates shall be to the same material specification and grade as the bottom shell course.

4.5

Plate material used for reinforcement and for nozzle or manhole necks shall be to the same material specification as the shell and shall meet the same notch toughness requirements.

4.6

If forgings are used for shell reinforcement or nozzle or manhole necks, they shall meet the same notch toughness requirements as specified for the shell plate.

4.7

Cast fittings shall not be used in the shell or bottom of the tank.

4.8

Bolting for carbon or low alloy steel flanges shall both be to ASTM A193 grade B7 with A194 grade 2H nuts. Structural steel bolting shall be to ASTM A307 grade A or B.

4.9

For stainless steel tanks to API rules use the material specifications and allowable stress rules of API 620 Appendix Q.

4.10

All attachments to the tank shall be of the same material type as the tank and meet all applicable carbon/carbon equivalent and impact test requirements.

4.11 Structural steel for platforms, ladders, stairways etc., shall be to ASTM A36 or equivalent. 4.12

4.12.1

Corrosion allowance shall be a minimum of 1.5 mm unless stated in project specification. All structures such as ladders, platforms, stairs and handrails shall be hot dipped galvanized.



SPC-0804.02-20.06 PAGE: 6 OF 14 REV: D2

4.12.2

Carbon steel floating roof guides, support bags and sleeves, vents, roof drain piping, gauge wells, emergency drain piping shall be hot dipped galvanized after fabrication.

4.12.3

Floating roof seal metal parts shall be hot dipped galvanized or stainless steel. Flexible shoes and all fastenings and pins shall be stainless steel type 430.

4.13

Gaskets shall be as noted in the project specification.

4.14

Flexible seal material flame spread rating shall not exceed 35% to ASTM E162.

4.15

Notch toughness requirements for API 620 tank materials shall not be less than those required by API 650 and this standard.

5.0

DETAIL DESIGN

5.1

Minimum Thickness and Corrosion Allowance

5.1.1 Minimum thickness shall be as required by the API Standard except that the minimum installed shell thickness up to 15 meter diameter shall be increased to 6mm and over 15 meter diameter shall be 11mm. 5.1.2 Corrosion allowance shall be added to the minimum annular plate thickness of API 650 Table 5-1. 5.1.3 If settlement at the tank wall is expected to exceed 4 inches during testing and service then annular plates shall be strengthened. The minimum thickness from Table 5-1 shall be selected from only the 33000 or 36000 psi columns. 5.1.4 Minimum thickness of internal structural members shall be 6mm plus corrosion allowance. 5.1.5 The CONTRACTOR shall specify the corrosion allowance required of each tank but shall be not less than 1.5mm. 5.1.6 Minimum nozzle wall thickness required by the API Standard shall be checked for suitability against the specified corrosion allowance.

5.2

Shell, Bottom and Wind Girders

5.2.1 Shell thicknesses for API 650 tanks shall be calculated by the One-Foot Method, unless otherwise agreed. 5.2.2 The thickness provided at any shell course shall not be less than the course above.



SPC-0804.02-20.06 PAGE: 7 OF 14 REV: D2

5.2.3 For cone roof tanks the height specified shall be from the bottom of the shell to the top of the top angle. For floating roof tanks the height specified shall be from the bottom of the shell to the maximum filling height. 5.2.4 Fixed roof API 650 tanks shall have a frangible joint between the top angle and the roof plates. 5.2.5 For austenitic stainless steel tanks the API 650 area formula in 5.10.2.5 shall be multiplied by 24000 / S where S is the stainless steel design stress (psi). 5.2.6 For fixed roof pressurized design to API 650 Appendix F the F.S. shall also be multiplied by 24000 / S for stainless steel design. 5.2.7 The top angle for fixed roof tanks shall be turned inwards unless required externally to assist insulation support. 5.2.8 Anchorage for pressurized tanks shall follow API recommendations. 5.2.9 For stainless steel tanks the wind girder section modules of API 650 shall be multiplied by 21000 / S, where S is the stainless steel design stress. 5.2.10

Annular plates shall be butt-welded. Annular plates radial minimum width shall be 915 for tank diameters 36 meter and over. This shall be reviewed where high levels of settlement are expected. If tank wall settlement is expected to exceed 100 mm then bottom plate filler welds shall be 2-pass. If tank wall settlement is expected to exceed 200 mm then increased strength of annular plates and bottom plate welds must be considered.

5.2.11

5.3

Tank bottoms shall be sloped as required by the tank data sheet in project specification.

Fixed Roof

5.3.1 Fixed roofs shall be self supporting at least up to 12 meter diameter and support columns shall be avoided up to the largest possible diameter. 5.3.2 Supporting structures shall be braced to provide a stable design. 5.3.3 Columns shall be of pipe or structural sections. Base and cap plates shall be continuously welded. Pipe sections shall be sealed.

5.4

Floating Roof

5.4.1 The low leg position shall not lower than 1300 mm above the bottom. If necessary the pontoons shall be notched to accommodate internals. The high leg position shall be 6 feet 6 inches above the bottom. 5.4.2 The low leg elevation shall be stated in tank data sheet.



SPC-0804.02-20.06 PAGE: 8 OF 14 REV: D2

5.4.3 Bearing plates 10 mm thick shall be provided under each support leg. 5.4.4 Thickness of the outer rim shall be 6 mm plus corrosion allowance minimum. 5.4.5 Design shall minimize vapor space. 5.4.6 CONTRACTOR shall demonstrate the adequacy of his design to resist distortion under the design loads. 5.4.7 Roof decks shall be continuously welded from the top side and pontoon bulkheads shall be welded at the top to be vapor tight. 5.4.8 Roof shall have two anti-rotation devices approximately 180 apart. 5.4.9 A continuous foam dam shall be provided on tanks 304 meter diameter and over. The dam shall be of 5 mm plate and shall be to NFPA No. 11 Appendix A-311. 5.4.10

Floating roofs and seals shall be grounded to the shell using stainless steel shunts.

5.4.11

Roof seals design shall 1.

Be sufficiently flexible and have sufficient range of movement to accommodate roof movements and flexing of the roof and tank wall.

2.

Remain stable in sunlight, tank liquid, tank vapor etc.

3.

Prevent contact between organic materials and the tank contents.

4.

Have metallic components galvanized unless otherwise agreed.

5.

Ensure contact between seal and shell above liquid level. Shoe type seals to have 90% minimum contact and flexible seal type 100% minimum contact. No gap shall exceed 6 mm or be circumferentially longer than 1200 mm.

6.

Include primary and secondary seals unless otherwise agreed.

7.

Include rim seal vents.

5.4.12

Sleeves for leg supports shall remain above liquid level when the deck is fully deflected.

5.4.13

Internal floating roofs shall comply with API 650 Appendix H except that minimum thickness shall be 6mm for aluminium and stainless steel. Pan type floating roofs shall not be used.



SPC-0804.02-20.06 PAGE: 9 OF 14 REV: D2

5.4.14

Internal floating roofs shall be designed to self drain or to float when flooded.

5.4.15

A corrosion gauge comprising a strip of roof skin material shall be provided local to the ladder access. The strip shall be suspended into the liquid and easily removed for inspection.

5.5

Manholes and Nozzles

5.5.1 The number of manholes that shall be provided are shown in the table below: TANK NOMINAL DIA. (FT)

MANWAY S IN SHELL

MANWAYS FIXED ROOF

IN ROOF FLOATING ROOF DECK

Up to 20

1 inch

24

1 - 24 inch

1 - 30 inch

Over 20 to 60

2 inch

24

1 - 24 inch

1 - 30 inch

Over 60 to 120

3 inch

24

1 - 24 inch

2 - 30 inch

Over 120

2 inch

24

2 - 24 inch

2 - 30 inch

1 inch

30

In addition 1 - 20 inch manway shall be provided in each floating roof pontoon compartment, covers shall be secured against wind and entry of rain. Multiple manways shall be approximately equally spaced and a manway shall be positioned adjacent to the water draw-off.

5.5.2 One 8 inch gauge hatch, self closing and non-sparking shall be provided on each API 650 tank. The hatch shall be located adjacent to the gauging platform. 5.5.3 For gas blanketed fixed roof tanks the gauge hatch shall be flanged to an 8 inch gauge pipe extending to 12 inches from the tank bottom. The gauge pipe shall be slotted to allow liquid movement. 5.5.4 All API 650 tanks shall have a water draw-off connection constructed of Sch. 80 pipe minimum. A sump shall be provided. 5.5.5 All API 650 fixed roof tanks shall have a scaffold cable support. 5.5.6 Roof vapor vents for normal and emergency conditions shall be sized to API-RP2000 by the tank Supplier. Emergency vents shall be provided on fixed roof tanks except for designs with an API 650 roof to top angle weld. Vents shall be provided with weather shields.



SPC-0804.02-20.06 PAGE: 10 OF 14 REV: D2

The need for flame arrestor shall be defined in the requisition or data sheet. 5.5.7 Nozzles shall be flanged to ANSI B16.5 Class 150. Flanges 30 inch and over shall be ANSI B16.47 Class 150. Manhole shall be per API 650. Nozzles shall be attached with welds that fully penetrate the shell. 5.5.8 The minimum size for any nozzle connection onto a shell shall be 2” NB

5.6

Structural Steelwork

5.6.1 Gauge or sampling hatches shall have an access platform. Tanks shall have a vertical ladder or spiral stairway as specified on data sheets. 5.6.2 Platforms/access shall also be provided at all roof accessories such as vents, operating valves and instruments. 5.6.4 Handrail shall be provided for all platform and stairways. For fixed roof tanks the handrail shall be extended around the entire edge of the roof.

6.0

FABRICATION

6.1

Welds

6.1.1 Welding shall conform to the API standard. 6.1.2 Welding procedures shall be approved by CONTRACTOR before commencement of welding. Welding procedures of the major weld seams shall be subject to approval before order placement for tank construction. 6.1.3 All main seams and annular plate welds shall be butt welds with full penetration and full fusion. Main seams shall be welded from both sides. 6.1.4 Nozzles and manways shall be welded through the shell with full penetration and full fusion. 6.1.5 Electroslag welding and stud welding are not permitted. 6.1.6 The Brinell hardness of any weld or heat affected zone shall not exceed 225 BHN. 6.1.7 Vertical joints in each course shall be complete before the horizontal joints are welded. 6.1.8 All nozzle welds and reinforcement welds shall be positioned to clear main seams by at least ten times shell thickness or 150mm whichever is the least. 6.1.9 API 620 tanks shall not use single fillet lap joints.



SPC-0804.02-20.06 PAGE: 11 OF 14 REV: D2

6.1.10

All components welded to the shell shall be welded all round to avoid corrosion.

6.1.11

Galvanized components shall not be welded to the tank shell or roof.

6.1.12

All weldments shall meet the notch toughness requirements of the base material.

Each weld procedure qualification test piece shall be impact tested on the weld metal and HAZ at the lower design temperature for notch toughness (paragraph 3.2.1). A change of brand of consumables requires re-qualification. Production weld test pieces are not required for circumferential seams unless specifically noted in the project specification.

6.2

General

6.2.1 The design shall maximize shop fabrication. 6.2.2 The tank erector shall inspect and accept the foundation as accurate and acceptable for tank construction prior commencing of erection. 6.2.3 Tank plates shall not be misused or mishandled; for example by being used for a roadway or by being dragged. 6.2.4 Plates shall not have holes cut in them for handling. 6.2.5 Reinforcing pads shall be vented by a 1/4 inch BSP drilled and tapped hole, which shall be located at low point on the pad and shall be left unplugged and packed with grease. 6.2.6 All parts that must be welded to the tank shall be installed before the hydrostatic test. 6.2.7 Bottom plates shall be thoroughly cleaned on the underside before being positioned.

6.3

Tolerances

6.3.1 Shell plates shall be cut to within

a

1/16 inch on length, width and diagonals.

6.3.2 Peaking and banding shall "average" less than 0.25 inches with occasional values reaching 0.5 inches maximum. 6.3.3 The maximum out-of-plumbness of the top of the tank shell relative to the bottom of the shell shall not exceed 1/300 of the tank height.



7.0

INSPECTION AND TESTING

7.1

Pressure and Vacuum Testing

SPC-0804.02-20.06 PAGE: 12 OF 14 REV: D2

7.1.1 All tanks shall be tested full of water. The CONTRACTOR shall include for corrosion allowance during hydrostatic test of the total filling/holding/ emptying time exceeds 30 days. 7.1.2 Floating roofs shall be demonstrated to move freely through their full range during the tests. 7.1.3 Staged filling may be required for tanks on soils subject to settlement. 7.1.4 Settlement shall be monitored during the testing period and recorded in the tank inspection and testing records. Minimum 8 points of measurement shall be performed equally spaced over circumference. The position of measuring point shall be recorded by drawing. 7.1.5 For hydrostatic test water, all drain piping, pumps, valve etc. shall be provided by the CONTRACTOR. 7.1.6 Any repairs shall CONSULTANT.

require

re-test

unless

otherwise

agreed

with

PTT/

7.1.7 Water used for stainless steel tanks shall contain no more than 10 ppm of Chlorides. 7.1.8 All tank bottom welds and roof welds shall be tested by the vacuum box method. This includes the inner fillet weld between the annular plate and the bottom course. Vacuum of 3 psig minimum shall be used. 7.1.9 Shell nozzle and manway reinforcing pads shall be pneumatically tested to 1 bar(g). 7.1.10

Tanks shall not be painted or internally coated until hydrostatic test is completed.

7.1.11

After test the tank shall be thoroughly cleaned out.

7.2

Examinations

7.2.1 Radiography shall be to the API Standard. Each radiograph shall be not less than 10 inches long. Eastman Kodak Industrial Film Type AA or equal shall be used. 7.2.2 Vertical joints in steels of yield strength over 43000 psi shall be 100% radiographed. 7.2.3 Annular plate butt welds shall be 100% radiographed or magnetic particle inspected after the root pass and final pass.



SPC-0804.02-20.06 PAGE: 13 OF 14 REV: D2

7.2.4 Annular plate to bottom course inner shell weld shall be tested by magnetic particle or liquid penetrant method. 7.2.5 Nozzle to shell welds, reinforcing pad welds and attachment welds to materials in API 650 Classes IV, IVA, V and VI shall receive magnetic particle examination. This shall include temporary attachment welds and the ground surface where temporary attachments have been removed. 7.3

The CONTRACTOR shall carry out the following as a minimum:

7.3.1 Review the identification of all materials and check that all contract requirements have been met. 7.3.2 Verify and approved welding procedures are used and that any special qualification requirements have been met. 7.3.3 Select spots for radiography. Review radiographs. 7.3.4 Visually examine the tank and all welds and appurtenances. 7.3.5 Witness hydrostatic test. 7.3.6 Witness dimensional checks. 7.3.7 Ensure completeness of tank and appurtenances. 7.3.8 Ensure shop built tank is suitably protected for transport. 7.3.9 Check nameplate and Manufacturer's Certification. 7.3.10 Review compilation of data books

8.0

CODE STAMP, NAMEPLATE

8.1

The CONTRACTOR shall provide a corrosion resistant nameplate permanently fixed to the tank at a suitable location.

8.2

The nameplate shall contain at least the information required by the API Standard and shall include tank number and the Manufacturers General Arrangement drawing number.

8.3

For insulated tanks the nameplate shall be mounted on a bracket so that it is outside the insulation.

9.0

SUPPLIER'S DATA REQUIREMENTS

9.1

The CONTRACTOR shall provide all documentation as required by the project specification.



10.0

PAINTING, SHIPMENT

10.1

Painting

SPC-0804.02-20.06 PAGE: 14 OF 14 REV: D2

10.1.1

The tank shall not be painted until after mechanical acceptance by the PTT /CONSULTANT.

10.1.2

Surface preparation and painting shall be carried out in accordance with SPC-0804.02-93.06.

10.1.3

Machined surfaces shall not be painted but shall be protected with a rust preventative.

11.0

GUARANTEES AND WARRANTIES

11.1

CONTRACTOR shall take fully responsible for the design and manufacture of the tank and its suitability for the defined duty.

11.2

CONTRACTOR is responsible for the correctness of any computer programs used in the design of the tank. He shall be prepared to justify the programs to the PTT / CONSULTANT if requested; this shall include sample problems calculated by hand or other suitable means.

SPC-0804.02-20.06 Rev D2 Field-Erected Low Pressure Storage Tank

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