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Polaris Engineering Standard 500.1 Rev.: 8 Page: 1 of 25 Date: 04/01/05 PRESSURE VESSELS CARBON AND LOW ALLOY STEEL TABLE OF CONTENTS PAGE I. SCOPE 2 II. REFERENCES 2 III. GENERAL REQUIREMENTS 3 IV. PROPOSAL INSTRUCTIONS 4 V. DESIGN 5 A. General 5 B. Shells and Heads 9 C. Supports 10 D. Internals 11 E. External Connections 12 F. Manways 15 G. Insulation and Fireproofing Supports 15 VI. MATERIALS 15 VII. SHOP DRAWINGS AND DATA 16 VIII. FABRICATION AND WELDING 18 IX. INSPECTION AND TESTING 20 X. DIMENSIONAL TOLERANCES 21 XI. CLEANING AND PAINTING 22 XII. NAMEPLATE 22 XIII. DAVITS 23 XIV. PREPARATION FOR SHIPMENT 23
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PRESSURE VESSELS CARBON AND LOW ALLOY STEEL

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Page 1: PRESSURE VESSELS CARBON AND LOW ALLOY STEEL

Polaris Engineering

Standard

500.1 Rev.: 8 Page: 1 of 25

Date: 04/01/05

PRESSURE VESSELS CARBON AND LOW ALLOY STEEL

TABLE OF CONTENTS PAGE

I. SCOPE 2 II. REFERENCES 2 III. GENERAL REQUIREMENTS 3 IV. PROPOSAL INSTRUCTIONS 4 V. DESIGN 5

A. General 5 B. Shells and Heads 9 C. Supports 10 D. Internals 11 E. External Connections 12 F. Manways 15

G. Insulation and Fireproofing Supports 15 VI. MATERIALS 15 VII. SHOP DRAWINGS AND DATA 16 VIII. FABRICATION AND WELDING 18 IX. INSPECTION AND TESTING 20 X. DIMENSIONAL TOLERANCES 21 XI. CLEANING AND PAINTING 22 XII. NAMEPLATE 22 XIII. DAVITS 23 XIV. PREPARATION FOR SHIPMENT 23

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PRESSURE VESSELS CARBON AND LOW ALLOY STEEL I. SCOPE

A. This Standard covers general requirements for design and fabrication of carbon and low alloy steel (less than 12% Cr) pressure vessels.

B. This Standard is supplemental to design drawings, standard details and instructions

in the purchase order. Should conflict occur, the order of precedence is: design drawings, standard details, and instructions in the purchase order. No variations from these requirements are permitted unless approved in writing by the client and/or Polaris.

C. All codes, standards and specifications (local and national) referred to herein are

meant to be the latest edition and to include latest addenda issued prior to date of purchase.

D. All conflicts between requirements of this Standard, related specifications,

standards, codes, purchase orders or drawings shall be clarified with the client and/or Polaris prior to proceeding with the fabrication of the affected parts.

II. REFERENCES

The following Standards and codes are to be used as applicable with this Standard.

A. Polaris Engineering Standards 1. 140.10 General Welding, Fabrication and Inspection 2. 591.2.1 External Dimensional Tolerances 3. 591.2.2 Internal Dimensional and Installation Tolerances 4. 1400.1 Painting Process Equipment and Piping

B. American Society of Mechanical Engineer (ASME) Standards 1. A58.1 Minimum Design Loads For Buildings and Other Structures

2. B16.5 Pipe Flanges and Flanged Fittings 3. B16.47 Large Diameter Steel Flanges NPS 26 through NPS 60

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4. B31.3 Petroleum Refinery Piping C. ASME Boiler and Pressure Vessel Code

1. Section VIII Pressure Vessels Division 1 Rules For Construction Of Pressure Vessels

D. National Board Inspection Code

E. Uniform Building Code

F. Local, State or Federal Codes

III. GENERAL REQUIREMENTS

A.

1. All pressure vessels, as a minimum, shall be designed, fabricated, inspected, tested and stamped in accordance with the ASME Unfired Pressure Vessel Code, Section VIII, Division 1, unless otherwise noted. Vessel Fabricator is responsible for conformity to ASME Code requirements as well as any state or local requirements. Unless noted otherwise, all vessels shall be registered with the National Board.

2. Prior to beginning of fabrication, the Vessel Fabricator shall submit general

assembly, detail and standard drawings for approval, as called for in the Project Specifications.

B. The Vessel Fabricator is to furnish and install the following in accordance with

design data unless designated to be furnished by others:

1. Vessel internals (see paragraph V.D)

2. Bolts

3. Gaskets and spares as required

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4. Ladder and platform clips (bolting is by others)

5. Pipe support and guide clips (bolting is by others) 6. Column davit brackets and sleeve 7. Manway davits and hinges 8. Insulation rings and stiffening rings 9. Insulation and fireproofing studs and nuts 10. Grounding lugs 11. Lifting and tailing attachments 12. Attachments welded to vessel for removable internals, trays, downcomers,

support beams, etc. 13. All surface preparation and painting shown on design drawings and in

specifications IV. PROPOSAL INSTRUCTIONS A. The Vessel Fabricator shall submit a base proposal for vessels complying strictly

with design data furnished. Conflicting requirements in these documents shall be referred to Polaris Engineering for resolution prior to submission of the proposals. Fabricators are invited to submit an alternate proposal on material and/or construction in cases where a more economical vessel may be manufactured. All alternates and exceptions to specifications, drawings, requisitions and commercial documents shall be clearly noted in the proposal.

B. At the time of quotation the Vessel Fabricator shall furnish a schedule of charges

and credits for nozzles (sizes 1-1/2 inches through 24 inches) for use in estimating future additions, deletions and revisions.

C. Pricing shall include the Vessel Fabricator furnishing and installing the clips, in the

quantity indicated on Polaris Engineering Standard 596.1.8 when it is indicated as an attachment to the requisition. In addition, unit prices are to be submitted with the original quotation for each different style of clip.

D. Pricing shall include the protection and preparation of the vessels for whatever

mode of transportation is to be employed in shipping the vessels to the designated receiving point.

E. Transportation and all related costs, permits and clearances of the vessels to the

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designated receiving point are the responsibility of the Vessel Fabricator. Freight shall be quoted as a separate item.

F. In the case of trayed towers, extra charges will not be allowed for slanted

downcomer bolting bars as opposed to those parallel to the centerline of the vessel.

G. Use of any foreign materials requires prior approval of Polaris Engineering. The Fabricator's proposal shall clearly state if any foreign material is quoted and indicate names of foreign manufacturers.

H. It will be necessary to ship some components separate and apart from the vessels.

The crating and protection of these parts is the responsibility of the Vessel Fabricator.

Parts, which will be fit-in with other vessel components in the field, are to be trial fit in the shop and match marked. Should this for any reason not be practical, a deviation must be obtained from the client and/or Polaris in writing.

I. The Vessel Fabricator shall furnish a detailed schedule with his proposal, including

as a minimum the following information:

1. Fabricator's drawings for approval

2. Time allowed for the client and/or Polaris to check approval drawings

3. Material receipt time for major materials

4. Materials receipt time for internals

5. Shop start-up date

6. Shop fab completion time

7. Hydrotest, PWHT

8. Shipping date

9. Shipping duration and mode 10. Assuming all factors, including drawing preparation and Client's Engineer

approval time, a specific delivery date from purchase award date V. DESIGN

A. General

1. The design pressure for vessels subject to internal pressure shall not be less

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than 110% of the maximum anticipated operating pressure, or the maximum operating pressure plus 25 psig, whichever is greater, unless otherwise specified.

2. All pressure vessels shall be designed to withstand a 14.7 external pressure

at 300oF unless specified to the contrary in the purchase specifications. No internal vacuum stiffeners will be allowed without Polaris Engineering's approval.

3. Maximum allowable working pressure (MAWP) shall be based on total

actual metal thickness, less corrosion allowance.

4. All vessels shall be shop hydrotested at 1.3 times the maximum allowable working pressure based on the new and cold condition.

5. The MAWP shall be limited only by the shell or heads. Flanges or

reinforcing shall not be the limiting component.

6. Unless noted otherwise, all vessels shall be designed to permit full hydrostatic testing, fully corroded condition, in the final erected position with all dead loads at operating condition (includes vessel, insulation, internals, platforms, ladders, external piping, etc., but excludes operating liquid, catalyst, packing, etc.) and 25% of design winds. To compensate for the test medium static head resulting in higher test pressure in the lower area of vessels while maintaining minimum test pressure at the top, allowable stress in the lower area may be increased to a maximum of 90% of the code yield stress at 100o times applicable joint efficiency of the material. The Fabricator shall furnish calculations verifying adherence to this criteria.

7. The design metal temperature of vessels shall not be less than maximum

operating temperature plus 50oF minimum unless specified otherwise. In no case shall vessel design metal temperature be less than the maximum operating temperature of the fluid in the vessel.

The minimum design metal temperature (MDMT) for all vessels shall be as specified on design drawings. Vendor shall calculate actual MDMT based on final design and fabrication drawings. After approved by the client and/or Polaris, the vessel shall be stamped for this revised MDMT.

8. Detailed calculations, for approval and record, are required for the design of

all components and appurtenances of the vessel. These shall include:

a. Weight calculation: fabricated, erection, test and shipping. b. Thickness of shell, head, skirt, etc.

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c. Compliance with charpy test requirements per ASME code based on material, thickness and minimum design metal temperature (MDMT)

d. Reinforcement requirements for nozzles, handholes, manways,

inspection openings, etc.

e. Saddle supports based on Zick analysis

f. Baseplates, anchor bolt chairs, bolt rings, support lugs, etc.

g. Wind and earthquake analysis

h. Local stress analysis for external loads on nozzles and attachments when specified on Project Specifications.

i. Lifting and tailing devices including their effects on the vessel

j. PWHT and hydrotest support system for large, tall vertical vessels

k. Shop support system to be used during hydrotest of large vertical

vessels

Calculations shall be submitted with the first approval issue of Fabricator's detail drawings.

9. Where design calculations are computer generated, input data shall be

included along with necessary explanatory notes for interpretation. Output data shall include the applicable formulas with the proper values shown as a part of those formulas along with the results. The Vessel Fabricator is responsible for the accuracy of all computer programs used for the analysis.

10. It is the Vessel Fabricator's responsibility to design the lifting and tailing

devices for the vessel. Design shall be based on full weight of vessel plus 50% impact loading. Polaris' standards for lifting and tailing devices shall be used only as a guide. Vessel shell, head and skirt shall be checked for added reinforcement and bracing requirements. Weight of vessel shall include, unless noted otherwise, vessel, vessel internals, insulation, ladders and platforms.

Shackles and bolting for lifting and tailing devices shall protrude through insulation to allow vessel erection without damaging the insulation. Lifting and tailing devices will be removed by others after vessel erection. All such devices shall be seal welded with proper venting.

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Date: 04/01/05 11. External loads due to wind and earthquake shall be determined in

accordance with the procedures of the governing code and/or the data specified on the design drawings and Polaris Engineering Standard 415.1.

Vertical vessels with a length over diameter ratio greater than or equal to 15 shall be checked for aerodynamic vibration due to vortex shedding from wind to ensure their structural safety.

Effective vessel diameter for wind shall include the thickness of the shell and insulation. In addition to this, a minimum wind multiplication factor shall also be applied according to vessel diameter in accordance with the following:

Vessel Diameter Factor

less than 36" 1.5 36" - 54" 1.37 55" - 78" 1.28 over 79" 1.18

In addition, wind loads on access platforms shall be considered additive to the basic projected area wind force on the vessel. Effective platform area for wind application shall be at least 50% of the actual floor area of the platform at the specified height.

12. Maximum vertical vessel deflection based on corroded thicknesses shall not

exceed 8 inches per 100 feet of height. 13. For design temperatures of 800oF and higher, the design details for nozzles,

supports and other attachments to the vessel shell shall be free of high local stress concentrations. Design details using fillet welds shall be avoided unless welds are ground to a smooth radius.

14. For unlined carbon steel vessels in services not subject to corrosive

conditions, a minimum corrosion allowance of 1/8 inch shall be provided unless specifically changed and agreed to by the client and/or Polaris. Even in such cases, unlined nozzles shall retain a minimum of 1/8 inch corrosion allowance in any event.

Corrosion allowance, specified on design drawings, shall be provided on all internal surfaces of the shells, heads, nozzles and manways. Internals welded to the shell, tray support rings and downcomer bolting bars shall have 1-1/2 times the specified corrosion allowance on one side only.

Corrosion allowance of alloy clad vessels shall be considered equal to alloy clad thickness of shells and heads.

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Sleeve lined nozzle necks shall have a 1/16 inch corrosion allowance. Strip lining shall not be used for corrosion protection without prior approval from the client and/or Polaris. Vessel support skirts shall have a minimum corrosion allowance of 1/16 inch. Corrosion allowance for anchor bolting shall be 1/8 inch.

15. Unless otherwise noted, the minimum corroded thickness of internal

attachments welded to shell, tray support rings and downcomer bolting bars shall be 3/16 inch.

16. In hydrogen service, all spaces fully closed by welds, (for example,

continuous fillet weld attachments) shall be vented or shall be full penetration welds.

17. Specified thicknesses are minimum, unless otherwise noted. 18. Load bearing welds attaching non-pressure retaining parts to pressure

retaining parts shall be designed according to the same allowable stress basis for primary membrane tensile (compressive) and shear stresses as required for pressure retaining components of like material.

19. All welded vessels, regardless of whether or not they are ASME Code

stamped, shall be (as a minimum) examined by 100% radiography in accordance with paragraph UW-52 of the ASME Code for Unfired Pressure Vessels.

20. All flanges shall protrude through access platforms. Bolting on flanges shall

clear vessel platforms by no less than the distance required to insert and operate a box wrench.

21. Bolting for all external attachments such as platforms, ladders, pipe

supports, pipe guides, lifting lugs, etc., shall be located outside the vessel insulation and jacket.

22. Level instrument nozzles on vertical vessels shall be provided with baffles at

the top nozzle of each set as a minimum. Special attention shall be given to the orientation of level instrument nozzles, in particular, level instrument nozzles shall be located as far away as possible from inlet nozzles.

B. Shells and Heads

1. Minimum design thickness excluding corrosion allowance shall not be less

than 1/4 inch or (I.D. in inches + 100) 1/1000).

2. On vertical vessels with varying wall thicknesses the plate thicknesses indicated on design drawings must be maintained except that the thicker

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sections may be increased in length in order to use standard-length plates. As an example, the lower course of plate may be called out as 3/4 inch plate for 18’-0” up from the tangent line. This could be 19’-0” or 20’-0” if the Fabricator chooses to use a standard length plate.

3. The Vessel Fabricator shall locate all welded joints on shop drawings

submitted for approval. Longitudinal joints in adjacent shell courses shall be offset. No longitudinal welded joints will be allowed within the downcomer area or behind any other obstruction, which may prevent inspection. Circumferential welded joints shall be located so that proper internal inspection can be made and shall clear tray support ring welds by at least 1 inch. Minimum straight flange on heads shall be 1-1/2 inches.

4. Unless otherwise noted on design drawings, heads shall be ellipsoidal with a

ratio of the inside major axis to the inside minor axis of 2 to 1.

Thicknesses specified on design drawings are the minimum thicknesses, including corrosion allowance, after forming the heads.

5. For large diameter, low pressure vessels, the maximum compressive stresses

in the knuckle region of toriconical heads, torispherical heads, and conical reducers with a transition knuckle shall be evaluated for the adequacy of the knuckle radius and thickness for the prevention of buckling of the knuckle under internal pressure and external loads.

6. Wherever possible, nozzles, reinforcing pads for nozzles and other

attachments shall not be located over longitudinal and circumferential weld joints. If this is unavoidable, approval must be obtained from the client and/or Polaris and the welded joint shall be ground smooth and radiographed for its entire covered length, plus 1 inch on each side.

C. Supports

1. Vertical drums 24 inches in diameter and smaller shall be supported on legs.

2. All towers and vertical drums 30 inches and over in diameter shall be skirt-

supported.

3. Drums supported on steel saddles shall be supported in accordance with Polaris Engineering Standard 594.2.1 and the detailed design drawing. Saddles shall not be placed over vessel girth seams and shall be continuously welded to the shell.

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4. Vertical vessel skirts shall be provided with 4 inch Sch. 40 pipe vents as follows:

a. Two vents for vessels under 36 inches in diameter

b. Four vents for vessels 36 inches in diameter and larger

5. Access openings shall be 24 inches outside diameter where possible;

however, a minimum diameter of 20 inches shall be maintained. Minimum wall thickness shall be 1.5 times the skirt thickness. Access openings shall be provided as follows:

a. One required for vessels 48 inches in diameter and smaller

b. Two required for vessels over 48 inches in diameter

Access openings shall be provided with a removable wire cover in accordance with Polaris Engineering Standard 597.1.1.

6. Anchor bolting shall be designed to an allowable stress of 15,000 psi for

carbon steel bolts up to and including 2-1/4 inches diameter and 35,000 psi for alloy bolts larger than 2-1/4 inches diameter. These stresses shall be based on tensile stress area unless otherwise specifically noted on design drawings. The minimum anchor bolt size shall be 1 inch in diameter.

7. Design of vertical vessel base ring shown on Client's vessel design drawings

is based on Brownell and Young method, outlined in "Process Equipment Design" by L.F. Brownell and E.H. Young.

8. Allowable concrete bearing stresses for base design may be taken as 1050

psi.

9. Appendix G "Suggested good practice regarding piping reactions and design of supports and attachments" of the ASME Section VIII, Div. 1 Boiler and Pressure Code shall be considered mandatory.

10. Minimum skirt thickness shall be 1/4 inch excluding corrosion allowance.

11. The attachment of a supporting skirt to a vessel subject to cyclic temperature

change (e.g., coker drums) shall be adequately designed to accommodate flexing at the skirt to vessel joint.

D. Internals

1. Unless otherwise noted on design drawings, the Vessel Fabricator shall

furnish all vessel internals except trays, catalyst, packed beds, etc. The Vessel Fabricator will furnish the tray support rings, downcomer bolting

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bars, temporary tray support clips and beams and all other vessel attachments necessary for tray and other internals installation. The Vessel Fabricator shall also install the trays unless specifically instructed otherwise.

2. All internal piping, which can be flanged to pass through manways, shall be

flanged near the vessel wall. All removable internals shall be fabricated to pass through vessel manways. All internal piping shall be self-venting and draining.

3. Unless otherwise specified on design drawings, all carbon steel internal

piping shall be extra strong or heavier. Low alloy internal piping shall be standard weight or heavier. The use of mitered joints requires prior approval of the client and/or Polaris.

4. Internal flanges may be either ASME 150 lb. forged slip-on welding type or

fabricated from suitable plate and machine faced. They shall be in the same quality material as specified for the internal pipe. All bolting, and gaskets if required, shall conform to ASME Standards. Bolt heads and nuts shall be semi-finished heavy hex type. Stud-bolts with two hex nuts each may be substituted in place of hex head bolts.

5. Carbon steel and ferritic alloy steel internal flanges shall have ASME SA-

193-B6 bolting with ASME SA-194-6 nuts.

6. Austenitic alloy steel internal flanges shall have austenitic alloy steel bolts conforming to ASME SA-193-B8 with ASME SA-194-8 nuts for vessel design temperatures 500oF and under. For temperatures over 500oF, ASME SA-193-B8C bolting shall be used with ASME SA-194-8C nuts.

7. Alloy internal flange bolting shall be securely tightened and the bolt heads

and nuts shall be tack welded.

8. All pipe or tubing for heating or cooling coils shall be seamless.

9. Internal piping shall be supported, as required, by chairs welded to the vessel shell or heads. Distributors shall not be supported from trays.

E. External Connections

1. Unless noted on design drawings:

a. All connections to vessel shall be flanged raised face, unless

specified otherwise

b. Minimum nozzle size shall be 1-1/2 inches for vessel design temperatures up to 750oF

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c. Minimum nozzle size shall be 2 inches for vessel design temper-atures exceeding 750oF

d. With the exception of hill side or long projection nozzles, nozzle

sizes 2 inches and under shall be long welding necks

e. The minimum vessel nozzle rating for sizes 2 inches and less shall be 300 lbs.

2. Flanges for pressure connections, manholes, handholes and enclosures 24

inches nominal size and smaller shall be in accordance with the dimensions and ratings of ASME B16.5. Unless approved by the client and/or Polaris, flanges nominal sizes 26” to 60” inclusive, shall be in accordance with the dimensions and ratings of ASME B16.47 Series B(formerly API 605). Contractor shall verify that ASME B16.47 Series B flanges are suitable for the intended application. Other flange sizes shall be calculated in accordance with the applicable code and shall be approved by the client and/or Polaris.

3. Lap-joint flanges require the client and/or Polaris approval. If allowed, the

stub end shall be equipped with stops to prevent falling when bolting is loosened.

4. Slip-on flanges and couplings are not allowed.

5. Bolting on flanges shall clear vessel insulation by not less than the distance

required to insert and operate a box wrench.

6. The inner edge of all manways and nozzles shall be rounded to 1/8 inch radius. All nozzles including manways shall be flush with the inside surface of the vessel unless noted otherwise.

7. Nozzle necks larger than 10 inches may be made of built-up construction

using formed plate necks and welding neck flanges when seamless pipe is not readily available and such construction is approved by the client and/or Polaris. Nozzle necks 10 inches and smaller shall be made with seamless pipe and welding neck flanges. In any sizes, long welding necks are preferred.

8. The corrosion allowance for nozzles and manways shall be at least equal to

the corrosion allowance specified for the vessel section in which they are located.

9. The minimum neck thickness for all nozzles including manholes (unless

design conditions dictate a heavier wall) shall be schedule 80 up to and including 8 inches size, and 1/2 inch wall for 10 inches and larger. Three inches and smaller connections shall be a minimum of schedule 160.

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Date: 04/01/05 10. Each nozzle shall be adequately reinforced for new and cold as well as

corroded condition in accordance with code requirements. Nozzle reinforcement shall not limit maximum new and cold maximum allowable working pressure. Reinforcement for 2 inch nozzles shall be checked for corroded condition.

Each reinforcing pad or section thereof shall have at least one test hole tapped 1/4 inch IPS. The weld of each pad shall be given an air and soap solution test (5 psig minimum), in the presence of the client's Inspector before post weld heat treatment. After the test, the hole shall be filled with corrosion inhibiting grease and the hole not welded or plugged. If the pad is fabricated in two parts the weld shall be oriented in the circumferential direction. All rectangular and square reinforcing pads shall have rounded corners with 3 inches minimum radius.

11. All bolt holes shall straddle the North, South, East, West, vertical or horizontal centerlines.

12. Flange facings shall be machine finish as noted below for spiral-wound

gaskets, and a fine serrated finish for smooth metal gaskets. The Vessel Fabricator shall specify the type of finish to be furnished. Welding neck flanges shall have the same bore as the nozzle necks to which they are attached.

Where spiral wound gaskets are specified, the flange surface finish range for acceptance shall be 125 Ra minimum to 250 Ra maximum. Finishes shall be judged by visual comparison with surface finish roughness standards conforming to ASME B46.1. It is the Vendor's responsibility both to comply with the above finish requirements and to assure that such flange finishes be protected from damage during shipping, storage and installation.

13. External bolting shall be supplied by the Vessel Fabricator and shall be a

minimum of ASTM A-193 Gr. B7 stud-bolts, complete with two ASTM A-194 Gr. 2H semi-finished oil-quenched heavy hex nuts each. For bolt metal temperatures over 800oF, bolting shall conform to ASTM A-193 Gr. B16 stud-bolts with ASTM A-194 Gr.4 nuts.

14. Gaskets shall be furnished as specified on the design drawings. Dimensions

of raised face gaskets shall be in accordance with ASME B16.5, Appendix E. Flexitallic type "CG" (type "CGI" for flanges over 24 inches diameter) or equal shall be used for all hydrocarbon services. All gasketing and packing, including test gaskets, shall be commercial quality fabricated from asbestos-free material suitable for the process environment. The Fabricator shall ship additional gaskets, shipped separately with proper protection and identification, as follows:

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a. For nozzles sizes up to and including 24 inches diameter, ship one gasket new and unused for each nozzle having a cover.

b. For nozzle sizes larger than 24 inches diameter, ship two gaskets,

new and unused, for each nozzle having a cover.

15. On horizontal vessels: level control, level glass, alarm and shutdown device connections may be individual 1-1/2 inches (2 inches for over 750�F design temperature) nozzles or on a bridle arrangement with 2 inch nozzles (the bridle arrangement is preferred); however, alarm and shutdown device connections shall not be combined on the same bridle with level and gauge glasses.

16. On vertical vessels: level glass, level control, alarm and shutdown device

connections shall have their own individual connections. 17. All level instrument connections shall be jig set. 18. Steam out connections shall be provided on all hydrocarbon processing

vessels.

F. Manways

1. All manways shall be a minimum of 24 inches (nominal) unless especially specified larger for specific purposes or necessarily smaller because of code requirements or the physical construction of the vessel.

2. All manways on vessels shall be hinged except sidemounted manways,

which shall be provided with davits in accordance with Polaris Engineering Standard 593.2.2.

3. Trayed towers shall be provided with top and bottom manways and with

intermediate manways at approximately 10 tray intervals. However, consideration shall be given for providing access to internal pipe distributors in determining the number and location of intermediate manways.

Large towers requiring frequent cleaning or the removal of internal manways each turnaround shall have intermediate manways approximately every 10 trays to facilitate maintenance.

G. Insulation and Fireproofing Supports

1. Insulation and fireproofing supports shall be shown and detailed on the

Fabricator's outline drawings in accordance with applicable Polaris Engineering Standards per applicable Project Specifications.

2. When vacuum stiffeners are used as insulation support rings, sizes must be

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shown on the Vessel Fabricator's drawings. All vacuum stiffener rings shall be seal welded on top side, stitch welded on bottom side and be in accordance with ASME Code. Vacuum stiffeners may be used as insulation supports as long as the maximum distance between them is less than or equal to the Polaris Engineering Standard insulation ring spacing.

VI. MATERIALS

A. Materials shall be as specified on design drawings and data sheets. The material thicknesses specified on vessel drawings are minimum nominal dimensions including corrosion allowance and are based on design analysis. (The analysis considers all applicable loading to which the pressure vessel will be subjected). Specific material thicknesses shall not be reduced without the written approval of the client and/or Polaris. Additional material must be added to the specified thickness of any component subject to thinning due to forming.

B. A request by the Vessel Fabricator for material substitution must be accompanied

by complete information including corrected thickness, and must state the complete ASME (or ASTM) designation, including grade and quality. In cases where the material has no standard designation the entire chemical and physical properties, including amount of cladding or lining, shall be submitted; it shall be the responsibility of the Fabricator to obtain ASME Code approval. The substitution request requires approval by the client and/or Polaris.

C. Substitution of material used for pressure and nonpressure parts of a strength grade

other than that specified shall not be made without the client and/or Polaris approval.

D. Each plate or forging shall be legibly stamped or stenciled showing grade number

and plate or forging number. When metal stamping is done it shall preferably be on the long edge of each component as it leaves the mill. Metal stamping on rolled surfaces shall be done with a "low stress" stamp.

E. As a minimum, materials and consumables subject to post weld heat treatment

(PWHT) shall be purchased with mill test reports indicating time necessary to allow for the greater of the sum of all planned shop PWHT cycles, one field repair cycle, and one extra cycle, or a total of four (4) full PWHT cycles.

F. Reinforcing pads shall be the same quality of steel as specified on the design

drawings for the shell and heads of lined vessels and/or the base metal for integrally clad vessels.

G. Unless noted otherwise, all materials for internal and external attachments,

including vessel TRIM, shall be the same as the shell and heads to which they are attached. In the event of a discrepancy with the Piping Material Specifications at the mating flange, the more stringent requirement governs.

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Date: 04/01/05 VII. SHOP DRAWINGS AND DATA

A. Prior to beginning fabrication, the Vessel Fabricator shall submit "FOR REVIEW" general assembly, detail and standard drawings, as called for in the purchase order and Polaris Engineering Standard 150.1. The general arrangement, assembly, or outline drawing shall show the following minimum information:

1. ASME Code edition and addenda applicable to the pressure vessel

2. Design pressure and temperature. Also allowable external pressure,

MDMT, MAWP, etc.

3. Hydrostatic test pressure and water temperature

4. Basis for calculated hydrostatic test pressure and the limiting part

5. Corrosion allowances

6. Joint efficiencies 7. Applicable code cases

8. Fabricator's and Polaris's standards, specifications and drawings

9. Welding procedures

10. Details of all weld preparations, and the location of all circumferential and

longitudinal weld seams 11. Requirements for radiograph examination, specified by ASME code,

Section VIII, designations for Division 1 vessels 12. Requirements for nondestructive examination, postweld heat treatment and

pressure testing 13. Cleaning, surface preparation, painting and marking requirements 14. Center of gravity (C.G.) net fabricated weights, shipping weights and weight

full of water shall be indicated on Fabricator's drawings. In addition, weight of all removable internals and weight of largest piece of internal to be lifted shall be indicated separately

B. In addition to the Fabricator's drawings, the following is required:

1. The Fabricator shall submit engineering data for review by the client and/or

Polaris as noted below:

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a. All drawings required for the fabrication of the purchased vessel, including those of subsuppliers

b. Welding procedures

c. Heat treatment procedures

d. Nondestructive examination and testing procedures

e. Fabricator's design calculations

2. All documents shall be in reproducible form and the quality shall allow for

microfilming without loss of clarity. All documents shall indicate that they have been checked or reviewed prior to submittal. The Fabricator shall not proceed with fabrication until notified by the client and/or Polaris.

C. Fabrication shall be in accordance with certified final drawings approved by the

client and/or Polaris.

D. Shop drawings shall have the same numbers and letters to identify trays and nozzles as shown on the design drawings.

E. Shop drawings detailing tray support rings and downcomer bolting bars shall be

furnished by the Tray Fabricator. After approval by the client and/or Polaris, they will be forwarded to the Vessel Fabricator.

F. Upon completion of fabrication, the Manufacturer shall supply the following:

1. Mill test reports of plates used for shells, heads, reinforcing pads, forgings

and supports. 2. Hydrostatic test charts

3. Post-weld heat treatment charts if applicable

4. Manufacturer's Data Report

5. Nameplate rubbing or photograph

6. Other nondestructive test reports if applicable

7. As-built drawings if different in any respect from drawings submitted for

approval VIII. FABRICATION AND WELDING

A. Unless otherwise stated on design drawings, all welding shall conform to ASME

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Code requirements regardless of whether or not the vessel carries a Code Stamp.

B. All shell and head joints and skirt seams shall be full penetration, double-welded butt joints. Connections between skirts and vessel head shall be made with a smooth flat faced fillet weld. Skirt attachment weld shall be equal to skirt thickness and height to be at least twice the width.

Single-welded, full penetration joints utilizing permanent back-up strips or consumable inserts are permitted only at closing circumferential joint of vessels which are not provided with a manway, except that vessels less than 24 inches in diameter may have two closing circumferential joints with permanent back-up strips.

C. All welds for nozzles and manways attaching to shell or heads shall be full penetration through the vessel wall, preferably double welded. In certain cases involving very heavy walls, the Fabricator may submit an alternate method for approval. Strength calculations of the attachment shall be submitted for the client and/or Polaris approval.

When access for back welding is not possible, temporary back-up strips may be used but shall be removed after completion of welding.

D. Except in hydrogen (H2) service, tray support rings shall be welded to the vessel

shell with continuous welds, both top and bottom. In hydrogen service the bottom weld shall have a 1/2 inch skip every 8 inches. The top weld shall be designed as the strength weld and the bottom weld shall be a seal weld. All welding must have sufficient metal to provide for the specified corrosion allowance.

E. Vessels in the following services shall have all welds exposed to service

environment ground smooth and wet fluorescent magnetic particle examined. 1. H2S 2. Amine

3. Deaerators 4. Hydrogen 5. Flash Drums

F. Openings in a vessel shall be located to clear both the circumferential and longitudinal seams by at least 6 inches.

G. Reference marks shall not be center-punched on the inside or outside of any vessel

constructed of materials requiring an impact test. Corrosion resistant lining or cladding shall not be center-punched.

H. Fabrication involving welding shall not be sublet to others without prior approval of

the client and/or Polaris.

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I. External attachments for structural elements, manhole davits, etc., shall be welded in place before the vessel is postweld heat treated.

J. Lifting lugs, where required, shall be seal welded at top to prevent corrosion of

shell behind lugs. K. PWHT is required for all pressure vessels unless noted otherwise on design

drawings or inquiry documents. Vessel design drawings will state if it is required due to:

1. Applicable codes (thickness, special service and/or material considerations)

2. Process considerations (note on inquiry documents) 3. By specifications. L. The Vessel Fabricator shall establish the master reference line of Polaris

Engineering Standard 591.2.2 parallel to the root land of the bottom shell course, and perpendicular to the longitudinal axis of the vessel and clearly mark inside and outside of the vessel.

M. Stitch welded attachments are not permitted. All attachments shall be seal welded

and vented.

N. Polaris Engineering Standard 140.10, General Welding, Fabrication and Inspection

requirements shall be followed. IX. INSPECTION AND TESTING

A. In addition to any inspection required by local authorities having jurisdiction, all materials, workmanship, welding procedures, results of operator's qualification tests, as well as any required Code examination shall be subject to witness and/or inspection in the Vendor's shop by the client's Inspector. Records of radiographic examination, certificates of magnetic particle, liquid dye penetrant or other examination shall also be made available, when applicable. Waiver of inspection(s) must be obtained in writing in accordance with Polaris Engineering Standard 140.3. client's Inspector shall be furnished with documentation proving the Fabricator's quality control personnel have the required level of competence for non-destructive examination provided by the shop.

B. Prior to final inspection, all slag, scale, dirt, weld, spatter, paint, oil and other

foreign matter shall be removed in order that the inspection shall be conducted.

C. Inspection by the client and/or Polaris shall in no way relieve the Fabricator of his responsibility to meet the requirements of the purchase documents.

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D. Client's Inspectors shall have free entry to the Fabricator's shop at all times when the work is being performed. The Fabricator shall afford the Inspectors all reasonable facilities to satisfy themselves that the vessels are being furnished in accordance with the purchase documents.

E. Complete radiography is required, regardless of material, thickness or service, of

any welded seam that has been subjected to severe working (as defined in the Code Para. UG-79) after welding. Radiography shall be carried out after postweld heat treatment.

F. Vessels having a design pressure of 500 psig or greater shall have all external

attachment welds to pressure containing parts examined by the magnetic particle (DC prod. contact) or liquid penetrant method. This type examination shall be performed after any required postweld heat treatment and hydrostatic testing.

G. Clean fresh water shall be the primary hydrostatic test medium unless use of a

different medium is approved by the client or his representative. Hydrostatic testing of vessels with austenitic stainless steel internals shall be done with potable quality water having a chloride content of not more than 50 ppm (parts per million). If chloride content is greater than 50 ppm, up to a maximum of 250 ppm, a sufficient quantity of sodium nitrate shall be added to provide a test medium of 0.5% by weight sodium nitrate solution. Water with a chloride content of greater than 250 ppm shall not be used for hydrotesting. Vessel(s) shall be dried thoroughly, imme-diately after draining, to prevent the possibility of evaporation and concentration of chlorides.

H. Field hydrostatic test pressure shall be at 1.3 times the maximum allowable working

pressure at design temperature based on corroded conditions.

I. Vessels and testing medium shall not be less than 70oF during hydrostatic tests. Where the ductile to brittle transition temperature of the steel is known to be, or suspected of being 40oF or higher, it is the Fabricator's responsibility to raise the temperature of the vessel and testing medium to at least 30oF higher than the transition temperature.

J. The test pressure shall be maintained for a period of at least one-half hour per inch

of thickness but not less than one hour. The thickness of the head or shell, whichever is greater, shall be used to determine the length of the test period.

K. A pressure of not less than 2/3 of the test pressure (100% of design) shall be

maintained for sufficient time to determine if there are any leaks, but not less than one hour following the application of the hydrostatic test pressure per UG-99 of the code.

L. The pneumatic test shall be used only when the hydrostatic test is impractical, such

as for vessels so designed and/or supported that filling with water is unsafe, or for vessels in services where a testing liquid cannot be tolerated. Pneumatic testing

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shall not be permitted without the prior written approval of the client and/or Polaris, and only after a detailed test procedure is written which addresses the hazards involved.

M. All pressure boundary forging, except standard ASME flanges, shall be

ultrasonically examined in accordance with the ASME code, Section II, SA-388.

N. Unless noted otherwise, all pressure retaining butt welds, including nozzle welds, shall be fully radiographed.

O. Prior to welding, the cut edges of all openings for nozzles shall be magnetic particle

(liquid penetrant for austenitic and non-ferrous materials) examined for detection of lamination in base metal.

If any objectionable defects and/or lamination are found in plate material, then the repairs will be made per Client's directions and at Client's expense.

P. All non-butt nozzle-to-shell welds shall be ultrasonically examined in accordance

with Appendix 12 of the ASME Section VIII, Div. 1. This examination shall consist of at least two angles - 45o and 60o. If post weld heat treatment is required, this examination shall be done after the final post weld heat treatment.

Q. Requirements of Polaris Engineering Standard 140.10, General Welding,

Fabrication and Inspection Specifications, shall be followed. X. DIMENSIONAL TOLERANCES

Tolerances shall be held as indicated in Polaris Engineering Standards 591.2.1 and 591.2.2.

XI. CLEANING AND PAINTING

A. Each vessel shall be thoroughly cleaned inside and outside and shall be free from grease, weld spatter, scale, slag, rust and any other foreign material.

B. All uninsulated as well as insulated external surfaces of carbon steel and low alloy

vessels including inside/outside of support skirt shall be sandblasted and primed in accordance with Polaris Engineering Standard 1400.1, unless noted otherwise. All nozzle faces shall be adequately protected from damage during sandblasting.

C. Vessels or sections of vessels shall be clearly identified by painting or dye

stenciling with the Client's purchase order number, project number and the vessel equipment number in a conspicuous location on the shell, head or support.

D. Vertical vessels shall be marked on the base and first foot of skirt, indicating the

north, south, east and west coordinates. The coordinates shall be indicated with a painted line and letter for each, according to the orientation shown on the vessel

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drawings. The markings shall be near the bottom tangent line if the vessel does not have a skirt. The Fabricator's drawings shall show this requirement.

E. Horizontal vessels shall have one end head marked north, south, east or west as

shown on the design drawing. The Fabricator's drawings shall show this requirement.

F. The center of gravity shall be marked on all vertical vessels by painting a

continuous 3 inches wide circumferential strip. The letters "C.G." and shipping weight in thousands of pounds and metric tons shall be painted at two locations diametrically opposite and adjacent to the strip. The location of the center of gravity specified on vessel drawings is that of the vessel as fabricated; the Fabricator shall make suitable adjustment for shipping supports, etc., if they cause the center of gravity position to move more than 6 inches. The Fabricator's drawing shall show this requirement.

G. The color of paint for marking and lettering shall conspicuously contrast with the

vessel surface. XII. NAMEPLATE

Each complete vessel shall be provided with austenitic stainless steel or monel nameplate seal welded to the nameplate bracket. The bracket shall be in accordance with Polaris Engineering Standard 592.2.1 and so located that it is easily accessible from grade or platform after installation.

The nameplate shall contain as a minimum, the following data:

A. Code symbol showing if vessel is radiographed and stress relieved

B. Fabricator's name

C. Fabricator's serial number and "National Board" number

D. Date tested

E. Maximum allowable working pressure at design temperature with specified

corrosion allowance

F. Shell and head thicknesses

G. Corrosion allowance

H. Client's item number and description

I. Client's purchase order number

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J. Test pressures both shop and field

K. Minimum design metal temperature XIII. DAVITS

Davits shall be designed for maximum anticipated load plus impact, but not less than 1000 lbs.

XIV. PREPARATION FOR SHIPMENT

A. The Vessel Fabricator shall prepare each vessel for shipment.

B. All internal parts that may become damaged in shipment shall be suitably supported and made fast. Signs indicating that "VESSEL CONTAINS SHIPPING BRACING WHICH MUST BE REMOVED" shall be conspicuously located.

C. Suitable temporary supports, marked and tagged for removal after vessel

installation, shall be provided to prevent damage during shipment.

D. Welding stub-ins shall be provided with adequate weld bevel protectors.

E. All flanged openings shall be protected with 1/2 inch thick one piece plywood covers.

A minimum of four 3/8 inch bolts shall be used for flange sizes 12 inches and smaller and eight 3/8 inch bolts for larger flange sizes.

F. Machined surfaces and flange faces shall be covered with an acceptable rust

preventive.

G. Spare gaskets shall be enclosed in a plywood container marked with the Client's purchase order number and equipment number and shipped with the vessel.

H. All vessels shall be provided with sufficient desiccant during shipment. All

desiccant shall be removed by others at the jobsite.

I. The following shall be applied to vessels prepared for water shipment:

1. All vessel openings shall be made watertight.

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2. All flanged connections which are not furnished with permanent blinds shall be covered with 1/4 inch minimum thickness, full diameter, steel plate covers. The covers shall be installed with 1/8 inch thick cloth inserted neoprene gasket, and secured with full bolting. Covers need not be drilled for bolting larger than 3/4 inch diameter bolts and suitable cut washers if a seal can be maintained.

3. Special vessel openings shall be provided with suitable closures designed by

the Fabricator and approved by the Client.

4. Loose items shipped apart from the vessels shall be crated for protection against physical damage and sealed in sheet plastic against water damage.

5. Protective measures shall be subject to inspection and rejection. All costs

occasioned by any rejection shall be for the account of Fabricator.

6. When vessel has internals or vessel surfaces made from austenitic materials the Vessel Fabricator shall provide a positive nitrogen pressure of 3 psig minimum in the vessel to provide protection against possible chloride attack by the seawater. Protection of outside surface is required also. Fabricator is invited to submit alternate methods for consideration. Vessels shall be assumed to be deck cargo. All manway blinds shall be marked "NITROGEN PURGED - DO NOT OPEN".

7. Desiccant shall be provided in accordance with paragraph XIV.H. above.

J. The vessel internals not installed in the vessel by the Fabricator shall be crated, boxed, and loaded in a manner such as to protect all parts from damage or loss in transit and shall be shipped so that they arrive at the erection site prior to or with the vessel.

K. Shipping Saddles

1. Details of shipping supports, saddles, bracings, tiedowns, loading and unloading methods, etc., are required for approval by the client and/or Polaris.

2. Unless noted otherwise, all vessels requiring shipping saddles shall be

provided with wooden shipping saddles securely strapped to the vessel. 3. For large and/or heavy vessels requiring special shipping saddles, inquiry

and/or purchase order will specify these requirements. 4. It is Vendor's responsibility to design all shipping saddles and vessel for

loads imposed during transportation, loading and unloading of vessel.