Previous Issue: 15 January 2012 Next Planned Update: 23 February 2016
Revised paragraphs are indicated in the right margin Page 1 of 55 Primary contact: Naffaa, Mahmoud Youniss on 966-3-8809614
Materials System Specification
32-SAMSS-004
15 April 2012
Manufacture of Pressure Vessels
Document Responsibility: Vessels Standards Committee
Saudi Aramco DeskTop Standards
Table of Contents
1 Scope... 2
2 Conflicts and Deviations... 3
3 References... 3
4 Definitions... 6
5 Responsibilities... 8
6 Proposals... 8
7 Mechanical Design... 8
8 Nozzles and Manways... 16
9 Internals... 20
10 Vessel Support... 20
11 Clips and Attachments... 23
12 Materials... 24
13 Fabrication... 30
14 Nondestructive Examination... 38
15 Postweld Heat Treatment... 43
16 Examination, Inspection, Pressure Tests and Repairs... 43
17 Nameplates and Stampings... 48
18 Coatings and Painting... 49
19 Shipping Requirements... 49
20 Drawings, Calculations and Data... 53
Table 1 – Nondestructive Examination Requirements………..………. 55
1 Scope
1.1 This specification covers the minimum mandatory requirements for the manufacture of pressure vessels (referred to hereinafter also as vessels). The requirements are in addition to and supplement the requirements of the ASME Boiler and Pressure Vessel Codes.
1.2 Vessels under the scope of this specification are purchased on a stand-alone basis or as an integral part of a skid-mounted packaged equipment unit.
Note: This is applicable irrespective of the party responsible for placing the relevant purchase order (Saudi Aramco facility, LSTK contractor, sub-contractor, etc.). 1.3 This specification does not cover the following:
1) “UM” stamped pressure vessels per ASME SEC VIII D1. 2) In-service pressure vessels.
3) Devices used as an integral part of piping systems, made of what are recognized as piping components (piping, fittings, etc.) and serve purposes such as straining, filtering, mixing, separating, distributing, metering and controlling flow.
4) Pressure vessels used as part of heating, ventilation and air conditioning (HVAC) systems.
5) Compressed gas cylinders.
1.4 Pressure vessels under scope of this specification, having partial or complete cladding, shall also conform to 32-SAMSS-031 in addition to the requirements of this specification.
1.5 Low alloy steels for vessels intended for services within the scope of
API RP 934-A, API RP 934-C or API RP 934-E, shall meet all requirements of the respective document of the aforementioned documents and this specification. 1.6 1 Cr- ½ Mo and 1 ¼ Cr- ½ Mo steels used for vessels not in hydrogen service
with design temperature below 440°C, shall meet all requirements of API RP 934-C and this specification.
1.7 Where a requirement of a licensor’s or a relevant industry standard/specification is more stringent than that of this specification, the most stringent requirement will govern.
1.8 A vessel that is an integral part of a skid-mounted packaged equipment unit shall be designed and manufactured by a manufacturer of such unit per the relevant SAP database.
2 Conflicts and Deviations
2.1 Any conflicts between this Specification and other applicable Saudi Aramco Materials System Specifications (SAMSSs), Standard Drawings (SASDs), or industry standards, codes, and forms shall be in writing by the Company or Buyer Representative through the Manager, Consulting Services Department of Saudi Aramco, Dhahran.
2.2 Direct all requests to deviate from this specification in writing to the Company or Buyer Representative, who shall follow internal company procedure SAEP-302
and forward such requests to the Manager, Consulting Services Department of Saudi Aramco, Dhahran.
3 References
Materials or equipment supplied to this specification shall comply with the latest edition of the references listed below, unless otherwise noted.
3.1 Saudi Aramco References
Saudi Aramco Engineering Procedures
SAEP-302 Instructions for Obtaining a Waiver of a Mandatory
Saudi Aramco Engineering Requirement
SAEP-347 Supplying Material from Stockists
Saudi Aramco Materials System Specifications
01-SAMSS-016 Qualification of Storage Tanks and Pressured
Equipment for Resistance to Hydrogen-Induced Cracking
32-SAMSS-020 Manufacture of Trays and Packing
32-SAMSS-031 Manufacture of Clad Vessels and Heat Exchangers
32-SAMSS-036 Manufacture of Small Pressure Vessels
Saudi Aramco Engineering Standards
SAES-A-007 Hydrostatic Testing Fluids and Lay-Up Procedures
SAES-A-112 Meteorological and Seismic Design Data
SAES-A-206 Positive Materials Identification
SAES-H-001 Coating Selection and Application Requirements for
Industrial Plants and Equipment
Piping and Process Equipment
SAES-M-001 Structural Design Criteria for Non-Building
Structures
SAES-N-001 Industrial Insulation
SAES-W-010 Welding Requirements for Pressure Vessels
Saudi Aramco Standard Drawing
AA-036322 Anchor Bolt Details
Saudi Aramco Inspection Requirements
Form 175-321900 Manufacture of Pressure Vessels
Saudi Aramco Forms and Data Sheets
NMR-7919-1 Nonmaterial Requirements for Pressure Vessels
9527-ENG Pressure Vessel Data Sheet (herein referred to as
data sheet)
3.2 Industry Codes and Standards
American Institute of Steel Construction
AISC M011 Manual of Steel Construction
American Petroleum Institute
API RP 520 Part I - Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
API RP 582 Recommended Practice and Supplementary Welding
Guidelines for the Chemical, Oil, and Gas Industries
API RP 934-A Materials and Fabrication of 2 1Mo, 2 ¼Cr-1Mo-¼V, 3Cr-1Mo, and 3Cr-1Mo- ¼V Steel Heavy Wall Pressure Vessels for
High-temperature, High-pressure Hydrogen Service API RP 934-C Materials and Fabrication of 1 ¼ Cr-½ Mo Steel
Heavy Wall Pressure Vessels for High-pressure Hydrogen Service Operating at or Below 825°F (440°C)
API RP 934-E Materials and Fabrication of 1 ¼ Cr-½ Mo Steel Pressure Vessels for Service above 825°F (440°C)
American Society of Civil Engineers
ASCE 7 Minimum Design Loads for Buildings and Other
Structures
American Society of Mechanical Engineers (Boiler and Pressure Vessel Codes)
ASME SA-20 Specification for General Requirements for Steel Plates for pressure Vessels
ASME SA-388 Ultrasonic Examination of Heavy Steel Forgings ASME SA-578 Specification for Straight-Beam Ultrasonic
Examination of Rolled Steel Plates for Special Applications
ASME SEC V Nondestructive Examination
ASME SEC VIII D1 Rules for Construction of Pressure Vessels ASME SEC VIII D2 Rules for Construction of Pressure Vessels,
Alternative Rules
ASME B16.5 Pipe Flanges and Flanged Fittings NPS ½ through
NPS 24
ASME B16.25 Butt-welding Ends
ASME B16.47 Large Diameter Steel Flanges NPS 26 through NPS 60
ASME PCC-1 Guidelines for Pressure Boundary Bolted Flange
Joint Assembly
American Society for Testing and Materials
ASTM A380 Practice of Cleaning, Discleaning and Passivation of Stainless Steel Part Equipment and System
ASTM E381 Standard Method of Macrotech Testing Steel Bars,
Billets, Blooms, and Forgings American Society for Nondestructive Testing
American Society for Non-destructive Testing
ASNT CP-189 Standard for Qualification and Certification of Nondestructive Testing Personnel
International Standards Organization
ISO 15156 Petroleum and Natural Gas Industries - Materials
for Use in H2S Containing Environments in Oil and Gas Production
National Association of Corrosion Engineers
NACE RP0472 Methods of Control to Prevent In-Service Cracking of Carbon Steel Welds in P-1 Materials in Corrosive Petrochemical Refining Environments NACE RP0590 Recommended Practice for Prevention, Detection
and Correction of Deaerator Cracking
NACE TM0208 Laboratory Test to Evaluate the Vapor-Inhibiting Ability of Volatile Corrosion Inhibitor Materials for Temporary Protection of Ferrous Metal Surfaces
Process Industry Practices
VEFV1100 Vessel/S&T Heat Exchanger Standard Details
Welding Research Council
WRC 107 Welding Research Council Bulletin
WRC 297 Welding Research Council Bulletin
4 Definitions
AARH: Average arithmetic roughness height, which is a measure of surface texture. Cyclic Service: Services that require fatigue analysis according to screening criteria
per 5.5.2 of ASME SEC VIII D2. This applies to Division 1 and Division 2 of ASME SEC VIII.
Design Engineer: The Engineering Company responsible for specifying on the data
sheet the mechanical design requirements for pressure vessels.
Design Thickness: Sum of thickness required to withstand all primary loads and an
allowance for corrosion.
High - Alloy Steels: Steels with a total alloying content more than 5%.
Hot Forming: Forming operations carried out at an elevated temperature such that
re-crystallization occurs simultaneously with deformation.
Hydrogen Induced Cracking (HIC) Environment: Process streams that introduce
HIC according to SAES-L-133.
Hydrogen Service: Process streams containing relatively pure hydrogen and process
streams containing hydrogen as a component with an absolute partial pressure of 350 kPa (50 psi) and higher.
Lethal Services: Process streams containing a concentration of hydrogen sulfide in
excess of 20% volume per total volume of vessel shall be considered as lethal service. Other services as determined by the project design may also be designated as lethal services.
Low - Alloy Steels: Steels with a total alloying content of less than 5% but more than
specified for carbon steels.
MDMT: Minimum design metal temperature determined by the Design Engineer and
specified in the data sheet.
Nominal Thickness: Thickness selected as commercially available, and supplied to the
Manufacturer. For plate material, the nominal thickness is the measured thickness of the plate at the joint or location under consideration after forming.
Pressure Vessel and Vessel: As defined in the ASME Boiler and Pressure Vessel
Codes.
Saudi Aramco Buyer: The person or company authorized by Saudi Aramco to procure
pressure vessels to the requirements of this specification.
Saudi Aramco Engineer: The chairman of the Vessels Standards Committee. Saudi Aramco Inspector: The person or company authorized by the Saudi Aramco
Inspection Department to inspect pressure vessels to the requirements of this specification.
Skid-mounted packaged equipment unit: Self-contained units for process and utility
applications (e.g., air dryers, portable air compressors, filtering unit, nitrogen
generation, dehydration, etc.) fabricated and skid-mounted in one section. Such unit consists of equipment (pressure vessels, compressors, pumps, storage tank, etc.), interconnecting piping, electrical and/ or instrument components, and support structures.
Sulfide Stress Cracking (SSC) Environment: Process streams that introduce SSC
according to SAES-L-133.
Thick Wall: Nominal thickness of a pressure-retaining vessel’s component (shell,
head, nozzle, etc.) greater than 50 mm.
Unfired Steam Drums: As defined in ASME SEC VIII D1, paragraph U-1 (g) (2). Utility Services: Water, air and nitrogen services.
Vessel Manufacturer: The Company responsible for the manufacture of new pressure
5 Responsibilities
5.1 The Vessel Manufacturer is responsible for the manufacture of pressure vessels, which includes complete mechanical design, Code and structural calculations, supply of all materials, fabrication, nondestructive examination, inspection, testing, surface preparation, and preparation for shipment in accordance with the completed data sheet and the requirements of this specification.
5.2 The vessel manufacturer shall neither prepare nor certify a User’s Design Specification.
6 Proposals
6.1 The Vessel Manufacturer's proposal shall be based on details for individual vessels and the requirements of this specification.
6.2 The Vessel Manufacturer may offer an alternative design, but must quote on the base inquiry documents.
6.3 The proposal shall include a detailed description of any exception to the requirements of this specification.
7 Mechanical Design
7.1 General
7.1.1 All pressure vessels shall be designed in accordance with the rules of the Boiler and Pressure Vessel Codes, ASME SEC VIII D1 or ASME SEC VIII D2 (herein referred to as the Codes), and the requirements of this specification.
7.1.2 The ASME SEC VIII D1 or ASME SEC VIII D2, to which a vessel is to be manufactured, shall be in accordance with the data sheet.
7.1.3 Should the Vessel Manufacturer have any part of a stress analysis executed by a third party, the Vessel Manufacturer shall advise the Saudi Aramco Engineer.
7.1.4 No proof testing shall be permitted unless specifically approved by the Saudi Aramco Engineer.
7.1.5 No credit shall be given to thickness of integrally-bonded or weld metal overlay cladding in calculating material thickness, required to sustain all primary loads.
7.1.6 Application of ASME Code Cases to the manufacturing of pressure vessels requires approval of the Saudi Aramco Engineer.
7.1.7 Unfired steam drums shall be manufactured and stamped in accordance with the requirements of this specification.
7.1.8 All welded joints of category A, B, C and D shall be complete fusion full penetration welds, except for joint welds of slip-on flanges specified per paragraph 8.1.3(d) of this specification.
7.2 Design Pressure
The value of design pressure(s) shall be in accordance with the data sheet. Commentary Note:
Design pressure is the maximum difference in pressure between the inside and the outside of a vessel, or between the chambers of a combination unit. The term internal design pressure is used when the internal pressure is greater than the external pressure. However, the term external design pressure is used when the internal pressure is less than the external pressure.
7.2.1 Unless otherwise specified on the data sheet the design pressure will be assumed to be at the top of the vessel in the operating position.
7.2.2 Design pressure(s) acting at the bottom of vessels shall take into account pressure heads, both static and dynamic, due to the maximum liquid levels.
7.2.3 Design pressure differential for the partition(s) separating the
compartment(s) of multi-compartment vessels shall be as specified on the data sheet.
7.2.4 The external design pressure and corresponding temperature shall be as specified on the data sheet.
7.2.5 Requirements for the design of packing bed supports for vessels that contains packing shall be as specified on the data sheet.
7.3 Maximum Allowable Working Pressure
7.3.1 The Vessel Manufacturer shall calculate the maximum allowable working pressure (MAWP) acting on the top of a vessel, in the hot and corroded condition in accordance with the applicable Code.
7.4 Design Temperature
7.4.1 The value of design temperature(s) shall be as specified on the data sheet.
7.4.2 Where there are differences in the design temperatures for different zones in a vessel, the extremities of these zones will be shown on the data sheet.
7.5 Minimum Design Metal Temperature (MDMT)
The value(s) of the minimum design metal temperature (MDMT) shall be as specified on the data sheet.
7.6 Service and Description
7.6.1 The service of a vessel; hydrocarbon, hydrogen, caustic, amine, wet sour, steam or utility and whether the service is cyclic and/or lethal shall be as specified on the data sheet.
7.6.2 The process description of a vessel (for examples: Amine Regenerator, Air Receiver) shall be specified on the data sheet.
7.7 Joint Efficiency
7.7.1 The joint efficiency shall be as specified on the data sheet.
7.7.2 A joint efficiency of 85% or higher shall be specified for the design of all pressure containing components of ASME SEC VIII D1 pressure vessels.
7.8 Corrosion Resistance
7.8.1 Corrosion allowance shall be as specified on the data sheet. 7.8.2 The corrosion allowances required for tray assemblies, except for
attachments welded to pressure boundary components and intended to support internals, e.g., tray support rings, brackets, etc., shall be in accordance with the requirements of 32-SAMSS-020.
7.8.3 Cladding shall be applied according to the boundaries as specified on the data sheet.
7.9 Nominal Thickness
a) Carbon steels, 6 mm.
b) Low chrome alloy steels, 5 mm. 7.10 Head Types
7.10.1 Refer to the data Sheet for the type of head.
7.10.2 The type of heads to be used shall be ASME 2:1-ellipsoidal or ASME hemispherical.
7.10.3 ASME flanged flat heads and ASME torispherical heads can be used only for air and water services up to a design pressure of 690 kPa (100 psi). 7.10.4 One piece construction (made from one-piece or welded multi-piece
blanks) shall be used for heads with nominal thickness greater than 50 mm and vessels in cyclic, hydrogen or lethal services. Other types of head construction shall require prior approval of Saudi Aramco Engineer as defined in this specification.
Note: Following shall be submitted to support review of the proposed multi-segment construction head:
a) Layout of head.
b) Nondestructive examination. c) Forming procedure and,
d) Heat treatment procedure, as applicable.
7.10.5 Heads in vessels with design thickness greater than 50 mm shall be hemispherical unless 2:1 ellipsoidal heads are deemed more
economical.
7.10.6 Minimum inside radius of knuckles for conical transition sections or torispherical heads shall be as follows:
a) Not be less than 15% of the outside diameter of the adjoining cylindrical section with conical section of thickness more than 50 mm.
b) Not be less than 10% of the outside diameter of the adjoining cylindrical section with conical section of transition sections or torispherical heads with thickness more than 19 mm or less than 50 mm.
c) Not be less than 6% of the outside diameter of the adjoining cylindrical section with conical section of transition sections or torispherical heads with thickness 19 mm and less.
7.10.7 Reinforcing for conical transition sections in vessels with design thickness greater than 50 mm shall be provided by increased plate thickness. Use of reinforcing rings is prohibited.
7.10.8 Shell-to-internal head joint shall be only any of the following details: a) Forged junction ring according to ASME SEC VIII D2,
Table 4.2.5 - Detail 7.
b) Weld build-up construction connecting shell to internal head. This is not applicable to vessels in cyclic service.
7.10.9 Joint details in paragraph 7.10.8 shall provide a smooth transition, minimizing peak stress concentration effects. The inner radius of the weld build-up and forged detail shall be minimum 1 inch. Backing strips used in fabricating the junction shall be removed after
completion of welding. All welds shall be ground smooth flush contour of the joined parts.
7.11 Loads
7.11.1 Wind and Earthquake Loads
a) The Vessel Manufacturer shall calculate the static effects of loads due to wind and the effects due to earthquake loads acting on the vessel in the operating position accordance with the requirements of this specification.
b) Wind and seismic loads shall be calculated for the vessel in its erected position in accordance with ASCE 7, using Occupancy Category IV and based on design data corresponding to the site location per SAES-A-112.
c) Wind pressures shall be assumed to act on the projected surface area of the pressure vessel and shall include due allowances for platforms, ladders, piping, insulation, and equipment supported from the pressure vessel as specified on the data sheet.
d) Seismic loads shall include due allowances for platforms, ladders, piping, insulation, and equipment supported from the pressure vessel as specified on the data sheet.
e) The maximum allowable deflection in the corroded condition at the top tangent line of a vessel shall not exceed 150 mm / 30 m of height.
7.11.2 Wind-induced Vibration
1) Vertical vessels shall be checked for wind-induced vibration by the Vessel Manufacturer for the following cases:
a) H > 30 m with H/D ratio > 15 b) W/HD² < 400
Where:
H is the height of the vessel in meters, including the
supports.
D is the diameter of vessel in meters.
(For multi-diameter vessels the diameter shall equal the weighted diameter of the top third).
W is the weight of the vessel in kilograms in both the erected empty and operating conditions.
2) The use of vortex breakers or guying devices in order to maintain stresses, due to wind-induced vibration within allowable limits, is prohibited.
3) The fatigue life of those vessels susceptible to wind induced vibration shall be a minimum of one million cycles. The fatigue curves in ASME SEC VIII D2 shall be used for the materials at the specified design temperature.
7.11.3 Dead Weights of a Vessel
Design of vessels shall consider the following dead loads:
a) Weight of vessel including internals, supports (e.g., skirts, lugs, saddles and legs), and appurtenances (e.g., platforms, ladders, etc.).
b) Weight of vessel contents under operating and testing conditions. c) Weight of refractory linings, insulation.
d) Weight of attached equipment such as motors machinery, valves, other vessels, and piping.
7.11.4 Piping, Equipment and External Loads
a) The Vessel Manufacturer shall ensure that local stresses imposed on a vessel due to piping (other than the dead load), equipment,
lifting, supports and other external loads do not exceed the allowable limits in accordance with the applicable Code. b) Refer to the data sheet for piping and equipment loads imposed
on a vessel. 7.11.5 Dynamic Loads
Dynamic loads caused by the action of vibratory equipment (e.g., agitators), liquid sloshing, sub-liquid surface jets, etc.
7.11.6 Thermal Loads
Thermal Loads are loads caused by thermal transients and restraining thermal expansion/ interaction of the vessel and/ or its support(s). 7.12 Load Combinations
7.12.1 All components of a vessel, including its support(s), shall be designed to withstand stresses resulting from load combinations in accordance with, but not be limited to, those shown in Table 4.1.2 of
ASME SEC VIII D2.
7.12.2 Anchor bolts shall be designed for load combinations, based on the allowable stress design method (Service Loads) in accordance with
SAES-M-001.
7.12.3 All pressure vessel components whether shop or field fabricated shall be designed to withstand a full hydrostatic test in the erected position. 7.12.4 Combined stresses due to full hydrostatic test and the greater of wind
and earthquake loads shall be within the allowable limits per
ASME SEC VIII D2, paragraph 4.1.6.2, based on the lowest Specified Minimum Yield Strength (SMYS) of the materials of construction at test temperature. However, wind and earthquake design loads can be reduced to 50% of its values.
7.12.5 In cases where it is desirable to pressure test a vessel partially filled with liquid, the requirements of paragraph 7.12.4 shall be met, except the pneumatic pressure applied above the liquid level shall at no point result in a total pressure that causes the general membrane stress to exceed 80% of the specified minimum yield strength of the material at test temperature.
7.12.6 Loads (moments or forces) acting on a vessel due to external piping that will affect the overall integrity of the vessel shall be added to
moments and forces due to other external primary loads (weight, wind or earthquake loads). Addition of piping loads shall be based on performing stress analysis.
7.13 Stress Analysis
7.13.1 Where applicable, the requirements for thermal stress and fatigue stress analyses shall be as specified in the data sheet. Analysis methods and stress combination limits presented in Division 2, Section 5, shall be used for vessels under scope of Division 1 and Division 2. However, allowable stresses shall be taken from the respective tables of
ASME SEC II for each division for the corresponding material and temperature.
7.13.2 The Design Engineer is responsible for specifying the heat transfer coefficients to be used for all thermal stress analysis.
7.13.3 Thermal Analysis
1) A thermal stress analysis is required for a vessel, if a thermal gradient (calculated under steady state operating conditions and, if applicable, transient operating conditions) across any vessel section exceeds 65°C (150°F), in a distance equal to the square root of R times T, where:
- R is the radius of the vessel component under consideration and, - T is the thickness of the component under consideration
- R and T have the same units.
2) As a minimum, the scope of the stress analysis shall include the following junctures, as applicable:
- Head-to-shell - Support-to-vessel
- Nozzle-to-shell, considering external piping loads - Tray supports to vessel wall
3) Thermal analysis shall be based on gradients under steady state design conditions and also, if applicable, transient design conditions.
4) Thermal gradients may be reduced to within allowable limits with the provision of:
a) Thermal sleeves in pressure-retaining components b) Hot-box design at the to-vessel junction in
skirt-supported vessels with design temperatures greater than 260°C (500°F).
7.13.4 Fatigue Analysis
1) Scope of the required stress analysis shall be as specified in the data sheet, in accordance with the rules of Division 2, by the Design Engineer.
2) As a minimum, the scope of the stress analysis shall include the following junctures, as applicable:
- Head-to-shell - Support-to-vessel
- Nozzle-to-shell, considering external piping loads - Tray supports to vessel wall
3) Analysis shall be based on the calculated number of cycles for a minimum 20 year service life, as determined in accordance with the rules of Division 2, paragraph 5.5.2.
4) The number of cycles shall include the number of start-ups, shut-downs, emergency shut-shut-downs, and upset conditions.
7.13.5 Local Stress Analysis
Stress analysis due to piping, equipment, lifting, supports and other external loads shall be completed in accordance with the procedures as detailed in WRC 107, WRC 297 or a finite element analysis.
8 Nozzles and Manways
8.1 General
8.1.1 The quantities, sizes, ratings, (ASME pressure classes), facings, elevations, and orientations of nozzles and manways shall be as specified on the data sheet.
8.1.2 Unless otherwise specified on the data sheet, the minimum projections for nozzles and manway necks, as measured from the outside surface of the shell or head to the face of a flange, shall meet the following requirements:
a) 6 inches for NPS 6 nozzles and smaller.
b) 8 inches for NPS 8 nozzles and larger and manways necks. c) For insulated vessels, projection shall be sufficient to allow
bolting of studs without interference with the insulation. d) For vessel drain connections and other connections, where a
process stream is likely to be stagnant, the projection shall not exceed three times the connection nominal diameter.
8.1.3 Permissible types of flanges for nozzles and manways are according to the following:
a) Forged steel long welding neck flange.
b) Forged steel welding neck flange. Such type of flange is welded to seamless pipe, rolled plate with 100% radiography or an integrally reinforced contour shaped forged nozzle or manway. The bore of flange shall match the bore of nozzle and manway, as applicable.
c) Studded nozzles and proprietary designs may be offered as alternatives provided their design is in accordance with the applicable Code and approved by the Saudi Aramco Engineer. d) Slip-on type flange with seamless pipe nozzle necks or rolled
plate with 100% radiography is permissible for vessels, which are integral parts of skid-mounted packaged equipment units, in only non-cyclic air and water services with design temperature and design pressure not exceeding 121C (250F) and 1.7 MPA (245 psi), respectively. Slip-on flange shall be welded on the front or face and at the back of the hub.
8.1.4 A body flange shall be constructed of a single-piece forging. 8.1.5 Nozzles less than 2-inch NPS are not permissible.
8.1.6 Only flanged nozzles shall be used.
8.1.7 Vessels in services other than air and water shall be provided with a minimum 2-inch NPS flanged steam-out connection.
8.1.8 The ends of butt-welded connections shall be in accordance with ASME B16.25.
8.1.9 The Vessel Manufacturer shall design nozzles that are required for the supporting of mechanical mixers and shall include the additional loads and dimensional tolerances as specified on the data sheet.
8.1.10 Minimum four gusset plates for the reinforcement of nozzles supporting mixers shall be provided.
8.1.11 Minimum inside corner radius of integrally reinforced contour nozzles and manways shall be 13 mm.
8.1.12 Design of flanged connections with stud bolts of diameter 1½ inch and above shall be such as to provide clearance to permit use of a stud and bolt-tensioning device.
8.2 Reinforcement of Openings
8.2.1 Reinforcement of vessel openings shall be in accordance with the applicable Code and this specification.
8.2.2 The thickness of reinforcing pads shall not exceed the shell or head thickness of a vessel.
8.2.3 Use of internal reinforcing elements is not permitted. 8.3 Flange Ratings, (ASME Pressure Classes) and Facings
8.3.1 The ASME pressure classes and facings shall be as specified on the data sheet.
8.3.2 Bolted joints specified with non-ASME flanges shall be designed to meet all anticipated loading conditions of the vessel.
8.3.3 Pressure ratings for standard flanges shall be in accordance with the following:
a) ASME B16.5 for flanges NPS 24 and smaller.
b) ASME B16.47, Series A for flanges larger than NPS 24. 8.3.4 Gasket seating surfaces shall comply with the following:
a) For spiral wound gaskets, 125 to 250 AARH, in all services, except hydrogen.
b) For spiral wound gaskets in hydrogen service, 125 to 150 AARH. c) The side-walls of rings joint flanges in all services, 63 AARH. d) For Nonmetallic gaskets, 250 to 500 AARH.
8.3.5 Machined surfaces other than gasket contact faces shall not exceed 500 AARH.
8.4 Manways
8.4.1 The number, nominal inside diameter and locations of manways shall be as specified in the data sheet.
8.4.2 All manways shall be circular. The manway covers shall be hinged or provided with handling davits as specified on the data sheet, according to PIP VEFV1100.
8.5 Attachment Details for Nozzles, Manways and their Connections
8.5.1 All nozzles and manway necks shall be attached by welding completely through the total thickness of the vessel shell, head or nozzle wall, including any reinforcement. Backing rings used in attaching nozzles and manways to vessels shall be removed after welding.
8.5.2 Permissible types of nozzles, manways and their connections shall be according to the table below.
Design Conditions / Services Group Attachment
Figure Reference from Indicated ASME Code Section VIII
Division 1 Vessels Division 2 Vessels
Group I
a. Pressure-retaining vessel’s component (shell, head, nozzle or manway) with design thickness greater than 50 mm
b. Unfired steam boilers with design pressure exceeding 50 psi
c. Lethal, hydrogen and cyclic services d. Openings larger than 900 mm (Note 1) e. Design temperature greater than 400°C (Note 1) f. Low alloy steel vessels with design thickness greater
than 25 mm (Note 1)
g. Vessels that will undergo PWHT (Note 1)
All nozzle sizes and manway necks
Connections attached to nozzles and manways
Figure UW-16.1, details: (f-1), (f-2), (f-3) or (f-4)
Table 4.2.13, details: (1), (2), (3), (4), (5) or (6)
Group II
Design conditions and service other than those in Group I of this table
NPS 4 and smaller nozzles
Figure UW-16.1, details: (a), (a-1), (b), (c), (d), (e), (f-1), (f-2), (f-3), (f-4) or (g). - Table 4.2.10, details: (1), (2), (3), (4), (6), (7) or (9) - Table 4.2.11, detail (2) - Table 4.2.13, details: (1), (2), (3), (4), (5) or (6)
Nozzles larger than NPS
4 and manway necks Figure UW-16.1, details: (c), (d), (e), (f-1), (f-2), (f-3), (f-4) or (g) Connections attached to
nozzles and manways
Note 1: Alternatively, detail per Figure UW-16.1(g) may be used for Division 1 vessels provided that design conditions/ services per a, b and/or c of group I are not applicable.
8.5.3 Integrally reinforced contour shaped attachments made partially or completely of weld build up are prohibited.
9 Internals
9.1 All fixed and removable internals, including trays, packing, distributors, screens, etc. shall be specified on the data sheet.
9.2 Tray rings and tray supports that are welded to vessels shall be designed by the tray manufacturer and supplied and installed by the Vessel Manufacturer in accordance with the requirements of 32-SAMSS-020.
9.3 The Vessel Manufacture shall design, supply and install all other internals, except for trays, as specified on the data sheet.
9.4 All removable internals are to be designed so that they may be passed through tray and vessel manways.
9.5 Internal ladder rungs shall be provided by the Vessel Manufacturer according to PIP document VEFV1100.
10 Vessel Support
10.1 General
10.1.1 Refer to the data sheet for the type of support.
10.1.2 Supports shall be designed to prevent excessive localized stresses due to deformations produced by the internal pressure, primary loads and, if applicable, thermal gradients in the vessel and support system. 10.1.3 Each vessel shall be designed as a self-supporting unit in accordance
with the requirements of the applicable Code and AISC. 10.1.4 All supports shall be continuously welded to the vessel. 10.1.5 The material of anchor bolts shall be in accordance with this
specification.
10.1.6 Base plates shall be designed by the Vessel Manufacturer for all loading conditions in accordance with this specification.
10.1.7 The allowable concrete bearing stress to be used for the design of base plates shall be 5170 kPa.
10.2 Supports for Vertical Vessels
10.2.1 The data sheet shall specify the type, location and overall dimensions required for the design of supports for vertical vessels.
10.2.2 The Vessel Manufacturer shall design all supports required, including skirts, legs, lugs, base plates, number of anchor bolts in accordance with the data sheet.
10.2.3 Skirts shall have a minimum thickness of 6 mm.
10.2.4 The mean corroded diameter of the shell and the mean diameter of the skirt shall coincide [rounded off to the nearest 3 mm], and shall be symmetrical about the vessel centerline. Exceeding this offset limit shall require prior approval of the Saudi Aramco Engineer, as defined in this specification, supported by stress analysis.
10.2.5 Hot-box design when specified for skirt-supported vessels with design temperatures greater than 205°C (400°F) shall be in accordance with PIP VEFV1100 and dimensions that meet the intent of reducing the thermal gradient at the skirt-to-vessel junction.
10.2.6 One minimum 500 mm diameter skirt access opening shall be provided for vessels with diameters equal to and larger than 1200 mm.
For vessels with diameters less than 1200 mm, skirt access opening diameter shall be minimum one half of the vessel diameter.
Skirt access opening diameters smaller than the above specified shall require prior approval of the Saudi Aramco Engineer. It is the vessel manufacturer's responsibility to determine the need for reinforcing the opening, according to the applicable Code.
10.2.7 Piping passing through skirt openings shall be adequately supported to prevent damage during shipment.
10.2.8 The Vessel Manufacturer shall provide skirt bracing to prevent buckling during shipping and lifting in the field.
10.2.9 Skirt-to-vessel juncture details for vessels with design thickness greater than 50 mm and vessels in cyclic, hydrogen or lethal services shall be only any of the following details:
a) Forged junction ring: according to ASME SEC VIII D2, Figure 4.2.4(e).
b) Weld build-up construction (connecting skirt to head): according to ASME SEC VIII D2, Figure 4.2.4(b). (Exception: This is not
applicable to vessels in cyclic service.)
c) Weld build-up construction (connecting skirt to shell): according to ASME SEC VIII D2, Figure 4.2.4(f). (Exception: This is not applicable to vessels in cyclic service.)
d) Forged skirt-to-shell junction ring: similar to ASME SEC VIII, D2, Table 4.2.5 - Detail 7.
10.2.10 Joint details in paragraph 10.2.9 shall provide a smooth transition, minimizing peak stress concentration effects. The inner radius of the weld build-up and forged detail shall be minimum 1 inch.
Backing strips used in fabricating the junction shall be removed after completion of welding. All welds shall be ground smooth flush contour of the joined parts.
10.2.11 Skirt-to-vessel juncture in vessels other those specified in paragraph 10.2.9 shall be according to ASME SEC VIII D2, Figure 4.2.4, detail (a), (b) or (c) and shall meet the following weld spacing requirements: 1. Adjacent edges of the head-to-shell and skirt-to-head welds shall
not be closer than the head thickness or 1 inch, whichever is greater.
2. Adjacent edges of the skirt-to-shell weld and any category B weld joint shall not be closer than the shell thickness or 1 inch,
whichever is greater. 10.3 Supports for Horizontal Vessels
10.3.1 Two saddles with anchor bolts shall be used to support horizontal pressure vessels. The vessel shall be fixed at one saddle support and free to slide at the other saddle. Saddle base plates shall be in full direct contact with the foundation.
10.3.2 The data sheet shall specify locations of the fixed and sliding saddles and dimension from vessel centerline to underside of saddle base plate. 10.3.3 The shell shall be analyzed in accordance with the “LP Zick” method.
Saddle supports and the vessel shell shall be analyzed for operating and hydrotest loads including any piping, wind or other external loads. 10.3.4 Minimum of 10 mm thick reinforcing pad is required at the junction of
the saddle and the vessel with all corners rounded to a minimum radius of 50 mm.
facilitate thermal expansion/ contraction along the longitudinal axis of the vessel.
10.4 Anchor Bolts
10.4.1 The Vessel Manufacturer shall determine the size and number of anchor bolts required.
10.4.2 Anchor bolts shall straddle vessel centerlines on the north-south, east- west axes.
10.4.3 Anchor bolts shall not be less than 19 mm minimum nominal diameter. 10.4.4 Design of anchor bolts shall be based on the following allowable stresses:
a) 104 MPa (tension). b) 69 MPa (shear).
10.4.5 Vessels supported on skirts, lugs or legs shall be provided with an even number of anchor bolts with a minimum of four anchor bolts.
10.4.6 Vessels supported on saddles shall be provided with an even number of anchor bolts with a minimum of two anchor bolts per saddle.
11 Clips and Attachments
11.1 General
The Vessel Manufacturer shall supply and install all clips and attachments as specified on the data sheet.
11.2 Insulation Supports
11.2.1 Support for insulation system shall be according to the data sheet. 11.2.2 The Vessel Manufacturer shall supply and install supports required for
insulation.
11.2.3 The bottom heads of vertical vessels that are externally insulated shall be provided with 12 mm blank nuts. Blank nuts shall be welded on edge and located on 300 mm square centers.
11.3 Refractory Supporting System
11.3.1 Anchoring system of refractory lining shall be according to the data sheet.
11.3.2 The Vessel Manufacturer shall supply and install anchoring system required for refractory.
11.4 Fireproofing Supports
11.4.1 Support for fireproofing system shall be according to the data sheet. 11.4.2 The Vessel Manufacturer shall supply and install supports required for
fireproofing materials.
11.4.3 Vertical vessels, which are not externally insulated, shall be provided with a 5 mm thick steel weather cap on the skirt to provide a flashing for fireproofing.
11.5 Grounding Lugs
All pressure vessels shall be provided with a grounding lug connection welded to the vessel support in accordance with PIP VEFV1100.
11.6 Equipment Davit
11.6.1 A davit for the lifting of equipment shall be supplied when specified on the data sheet.
11.6.2 The davit shall be in accordance with PIP VEFV1100. 11.7 Reinforcing Pads
Reinforcing pads for all internal and external welded attachments shall be sized to meet requirements of paragraph 7.11.4 of this specification. Pads shall be a minimum of 10 mm (3/8") thick, but shall not exceed the shell thickness; with all of their corners rounded to a minimum radius of 50 mm. Distance from any edge of the attachment to the closest edge of the reinforcing pad shall not be less than 50 mm.
12 Materials
12.1 General
12.1.1 All carbon, low alloy and high alloy steels required for pressure and non-pressure components shall be as specified on the data sheet. 12.1.2 Prior approval by the Saudi Aramco Engineer is required for use of
alternative materials of construction for carbon and low alloy steels pressure vessels. Alternative materials must comply with all the requirements of the applicable Code and this specification.
12.1.3 Material specifications and tests procedures for base metal and weldments materials for 1 Cr- ½ Mo, 1 ¼ Cr- ½ Mo, 2 ¼ Cr-1 Mo, 2 ¼ Cr-1 Mo- ¼ V, 3 Cr-1 Mo and 3 Cr-1 Mo- ¼ V shall be submitted to Saudi Aramco Engineer for review and approval prior to ordering the materials from the mill.
12.1.4 All materials must be clearly identified and provided with legible original or certified true copies of Mill Test Certificates. Lack of adequate identification and certification shall be cause for rejection. 12.1.5 1 Cr- ½ Mo and 1 ¼ Cr- ½ Mo steels with thickness exceeding 100 mm
can be used for components (shell, head, integrally reinforced nozzles, flanges, etc.) of vessels within scope of API RP 934-C, API RP 934-E and paragraph 1.6 of this specification, provided that fracture toughness requirements of the respective document of the aforementioned
documents and this specification can be met.
12.1.6 Use of high alloy steels, including austenitic stainless steels, shall be on a case-by-case basis, with prior approval of the Saudi Aramco Engineer as defined in this specification. Material selection shall be based on the design temperature, minimum design metal temperature and intended service.
12.1.7 All materials, except carbon steels, shall be alloy-verified by the Vessel Manufacturer in accordance with SAES-A-206.
12.1.8 The use of C-½ Mo steels in hydrogen services is prohibited.
12.1.9 Material of construction (pressure-retaining and attachments used for supporting or lifting the vessel) shall be tested, as applicable, to verify that their mechanical properties will be retained considering all of the following thermal treatments that could affect the material:
a) All heat treatment cycles that will be required for the fabrication of the vessel, including as applicable: normalizing, normalizing and tempering, quenching and tempering, intermediate stress relief (ISR), and final postweld heat treatment (PWHT), b) Two PWHT cycles to account for future repairs and/or
alterations.
12.1.10 As an alternative to material qualification requirements per paragraph 12.1.9 of this specification for carbon steel nozzles and standard flanges according to ASME B16.5 and B16.47 that do not require impact testing, materials of construction shall have minimum 70 MPa
(10 ksi) over their specified minimum yield strength and ultimate tensile strength values.
12.1.11 Forgings shall meet a material cleanliness C2/R2/S2 rating, as described in ASTM E381.
12.1.12 Specimens for material testing shall be taken per the following: a) Plates
Specimens shall be taken from each plate transverse to the rolling direction in accordance with SA-20 at the standard test locations and at a depth of ½T (T = maximum heat-treated thickness) location. If required, ½T specimens should be used for hot tensile and step cooling tests.
b) Plate-like forgings (forged rings, tubesheets, blind flanges, etc.) Specimens shall be taken from each heat transverse to the major working direction in accordance with the material specification, and at a depth of ½T of a prolongation or of a representative separate test block.
c) Standard flanges according to ASME B16.5 and B16.47. 1. For flanges with T equal to or less than 50 mm, specimens
shall be removed in accordance with the material specification. 2. For flanges with T greater than 50 mm, specimens shall be
removed in accordance with the material specification from a production forging or a representative separate test block that are machined to essentially the finished product configuration prior to heat treatment. The center axis of the specimen shall be at a depth of ½T and the mid-length of the test specimen shall be at a depth at least equal to T from any second heat-treated surface.
d) Other forgings that are contour shaped or machined to essentially the finished product configuration prior to heat treatment, test specimens shall be removed in accordance with the material specification of a production forging or a representative separate test block. The center axis of the specimen shall be at a depth of ½T and the mid-length of the test specimen shall be at a depth at least equal to T from any second heat-treated surface.
e) Pipe
Specimens shall be taken from each heat and lot of pipe, transverse to the major working direction in accordance with used material specification except that test specimens should be taken from a depth of ½T.
f) A separate test block, if used, should be made from the same heat and should receive substantially the same reduction and type of hot working as the production forgings that it represents. It should be of the same nominal thickness as the production forgings and shall be machined to essentially the finished product configuration prior to heat treatment. The separate test forgings should be heat-treated in the same furnace charge and under the same conditions as the production forgings.
12.1.13 Layered constructions are prohibited for all vessels.
12.1.14 Materials for pressure vessels for de-aeration service shall be in accordance with NACE RP0590.
12.1.15 Materials for vessels exposed to SSC environments shall be in accordance with the following:
a) Forged flanges and forged fittings are restricted to: SA-350 LF1 or LF2 or SA-266 Grade 4.
b) Flanges above 24-inch diameter shall be SA-266 Grade 4. c) Studs are restricted to: SA-193 B7M or SA-320 L7M. d) Nuts are restricted to: SA-194 Grade 2HM.
e) It shall satisfy the requirements of ISO 15156 and NACE RP0472. 12.1.16 Low alloy steels shall not be mixed. For example, a vessel requiring
1 Cr-½ Mo materials shall have all components manufactured from 1 Cr-½ Mo.
12.1.17 Low alloy steels shall be specified in the normalized and tempered heat-treated or quenched and tempered conditions. Material of construction shall be tested, as applicable, to verify that their
mechanical properties will be retained considering thermal treatments specified in paragraph 12.1.9 of this specification.
12.1.18 Material for nameplate mounting brackets shall be of the same type and material grade as the shell material.
12.1.19 SA-36 and SA-285 materials may be used only for pressure retaining components of vessels in water and air services with plate thickness not exceeding 19 mm.
12.1.20 Materials of supports shall be as follows:
1) Legs and lugs: same material as vessel wall base material. Supports of vessels described in paragraph 12.1.19 of this
specification may be of the same ASME material P No. as that of the vessel wall base material.
2) Skirts: same material as the vessel wall base material for a
minimum distance of 300 mm measured below the vessel-to-skirt connection line, unless thermal calculations require additional length. Remaining section of skirt shall be of the same material or same ASME material P No.
3) Saddles: same material as the vessel wall base material. 12.1.21 External attachments, other than those in paragraph 12.1.20 of this
specification, and internal attachments welded to the vessel shall be of the same material as the vessel wall base material. With prior approval of Saudi Aramco Engineer as defined in this specification, Stainless Steel (SS) internal attachments can be welded to carbon steel pressure-retaining parts of vessels in non-sour services.
12.1.22 Internal attachments to clad vessels shall be of the same material as that of the cladding. SS 321 and SS 347 can be used interchangeably. 12.1.23 Material of construction for anchor bolts shall be ASTM A193 /
A193M, ASTM F1554 Grade 36 or ASTM F1554 Grade 105 with the corresponding material of construction for nuts according to SASD
AA-036322.
12.1.24 One temper embrittlement test block shall be installed in hydrotreating or hydrocracking reactors made of 2 ¼ Cr-1Mo, 2 ¼ Cr-1Mo- ¼ V, 3Cr-1Mo or 3Cr-1Mo- ¼ V. Test block shall be made from
prolongation of a shell ring or a shell plate used for constructing the reactor shell. Test block shall be 300 mm long, 300 mm wide, and have thickness same as the shell. Test block shall be weld overlaid from 5 sides with the same welding procedures used to fabricate the reactors. After weld overlay, test block shall be exposed to the minimum post weld heat treatment cycle before attaching to a bottom structure of the reactor. Fabricator shall provide the test block
12.1.25 One manual UT test block and one TOFD UT test block shall be provided by the fabricator of hydrotreating or hydrocracking reactors made of 2 ¼ Cr-1Mo, 2 ¼ Cr-1Mo- ¼ V, 3Cr-1Mo or 3Cr-1Mo- ¼ V with shell thickness greater than 150 mm. Test blocks shall be made from prolongation of a shell ring or a shell plate used for constructing the reactor. Test blocks shall be prepared in such a way that they can be used to meet all fabricator’s UT calibration procedures and that inspection according to API RP 934A, Appendix A can be performed on site in a later date, if deemed necessary.
12.2 HIC Resistant Materials
Hydrogen Induced Cracking (HIC) resistant steel shall be qualified in accordance with 01-SAMSS-016. HIC resistant steel shall be procured from Saudi Aramco approved manufacturers within a list available by the Saudi Aramco buyer, as defined in this specification.
12.3 Gasket Materials
Types and material specifications of gaskets shall be as specified on the data sheet.
12.4 Impact Testing
12.4.1 The Vessel Manufacturer is responsible of determining the required Charpy impact energy value(s) based on the test temperature specified on the data sheet and the purchased vessel’s component thickness. 12.4.2 Impact test temperature for a component of a vessel shall be as
specified on the data sheet.
12.4.3 Minimum acceptable Charpy impact energy values for all materials of construction (base and weld metals) shall not be less than the highest of the following applicable values:
1) 40/32 Joules for carbon steels thicker than 50 mm 2) As specified by ASME SEC VIII D2, but not less than
34/27 Joules
3) As specified by the licensor’s specification, but not less than 34/27 Joules
4) 55/47 Joules for 1 Cr- ½ Mo, 1 ¼ Cr- ½ Mo, 2 ¼ Cr- 1 Mo, 2 ¼ Cr- 1 Mo- ¼ V, 3 Cr- 1 Mo and 3 Cr- 1 Mo- ¼ V steels.
Commentary Notes:
a) The first number of required energy values is the minimum average energy of three specimens and the second number is the minimum for one specimen of the impact test results. The second number shall not be less than 80% of the average value.
b) Minimum acceptable Charpy impact energy values are applicable to Div. 1 and Div.2 vessels.
12.4.4 For Div. 1 vessels the impact testing exemptions of UG-20 (f),
UCS-66 (b) (1) and (3), UCS-68(c), UG-84 (b) (2) and by reference to Table UG-84.4 are not permitted. For Div. 2 vessels the exemptions of 3.11.2.3, 3.11.2.4, 3.11.2.5, 3.11.2.6, 3.11.2.8, 3.11.2.10, 3.11.3.1 and 3.11.4 are not permitted.
12.4.5 Impact testing is required, with no exception, for pressure vessels made of low alloy steels.
12.4.6 Impact testing of materials and welding procedures are required when test temperature is lower than -28°C.
12.5 All forgings shall be forged as close as practicable to finished shape and size to develop metal flow in a direction most favorable for resisting the stresses encountered in service.
12.6 All flanges, fittings and piping for use as integral parts of pressure vessels shall be purchased from Saudi Aramco approved manufacturers, either directly or through approved stockists. Procurement of these items from stockists shall be in accordance with SAEP-347.
13 Fabrication
13.1 Fabrication Tolerances
13.1.1 Fabrication tolerances shall be in accordance with the more stringent of the applicable Code and PIP document VEFV1100, with the following exceptions to tolerances on page 1 of drawing VEFV1102:
Tolerance 1: Height from base line to face of top nozzle shall be the smaller of 4 mm per 3000 mm of height or 19 mm. Tolerance 2: Flange face of nozzle with agitator shall be aligned within ±¼ degree of indicated plan in any direction. Tolerance 7: Unless more stringent tolerances are specified by the
without an agitator shall be within ±½ degree of specified plan, but not to exceed 5 mm across the diameter.
Tolerance 12: Bottom of vessel support to base line 0 mm, -6 mm. Tolerance 13: For supports located above baseline, tolerances shall be
0 mm, + 6 mm.
Tolerance 14: Maximum difference in peak deviations from straight, applied to the shell at any location along the
circumference clear of openings, shall be: 3 mm in any 3000 mm of length, 12 mm in any 15000 mm of length, and shall not exceed 19 mm over the overall length of shell. In addition, distortion caused by welding of longitudinal or circumferential joints shall not exceed 6 mm maximum depth in a 900 mm length of shell centered on the weld.
Tolerance 20: Deviation from average I.D. (as determined by strapping) from nominal I.D. shall be as follows: a) ±3 mm for I.D. ≤ 1200 mm
b) ±6 mm for I.D. > 1200 mm
Out-of- roundness tolerances shall be according to applicable ASME SEC VIII.
Tolerance 26: Supports out of level shall be within ±3 mm. Deviation from flatness of support base plate is not acceptable, i.e., support base plates shall be in full direct contact with the foundation.
Tolerance 28: Delete.
Tolerance 31: Distance between centerlines of support bolt holes shall be within ±6 mm and maximum diagonal measurements shall be within ±6 mm.
13.1.2 Use of fitness-for-service assessment methodology to qualify the design of components that do not satisfy the fabrication tolerances according to this specification is prohibited.
13.1.3 Dished heads shall achieve at least the minimum required thickness in all areas after forming.
13.2 Forming and Assembly
13.2.1 Tapered transitions shall be made only on the external surface of the vessel, according to the rules of the applicable Code, in the following conditions:
a) There will be an interference with the removal of a vessel's internals.
b) Vessels that have strict requirements regarding smooth internal profiles for flow or cyclic loading conditions or internal volume constraints.
13.2.2 The beveled edges of weld preparations for carbon steel plates with thickness 25 mm and thicker and all ferrous alloy plates shall be
magnetic particle examined for linear discontinuities. Defects shall not exceed limits as per ASME SA-20.
13.2.3 Plate edge laminations revealed by magnetic particle examination shall be completely removed and repaired.
13.2.4 Each shell section shall be completely welded longitudinally and corrected for out of roundness and peaking of the weld seam prior to welding to adjoining shell or head.
13.2.5 All re-rolling or forming of the shell sections is to be completed prior to radiography.
13.2.6 Welds Encroachment
13.2.6.1 It is the responsibility of the manufacturer to ensure that the outer edge of welds attaching manways, nozzles (with and without reinforced pads) and other structural attachments (with and without reinforced pads), except those in paragraph 10.2.11, to pressure-retaining components shall not be closer than 1 inch from the adjacent edge of any other weld. It is the responsibility of the manufacturer to ensure that requirements of paragraph 7.11.4 of this specification are met in the vicinity of the welds.
Commentary Note:
Weld spacing requirements for skirt-to-vessel junctures shall be according to paragraph 10.2.11 of this specification.
13.2.6.2 Where the optimized fabrication layout and/ or process design requirements do not absolutely allow meeting the spacing requirement in paragraph 13.2.6.1 of this specification, NDE per paragraph 14.6 shall be performed.
13.2.6.3 It is prohibited to cover butt welds in wall of vessels that will undergo PWHT by structural attachments (with or without reinforcing pads).
13.2.7 Telltale Holes in Reinforcing Pads
13.2.7.1 ¼ - inch telltale vent holes drilled and tapped for ⅛ -inch NPT shall be provided in reinforcing pads for welded attachments, including nozzles and manways, per the following:
1) One hole in single piece reinforcing pad.
2) Where a pad is split, each segment shall have at least one hole.
13.2.7.2 Telltale holes shall be located at the lowest position accessible for inspection with center of the hole 25 mm from edge of the pad. This is applicable to each segment of a split reinforcing pad.
Commentary Note:
In case of reinforcing pads for attachments, other than nozzles and manways, center of telltale hole shall be 25 mm from the closest edge of the pad.
13.2.7.3 Telltale holes in reinforcing pads for external welded attachments shall be plugged with grease or other materials adequate for the operating temperature but not capable of retaining pressure, to prevent moisture ingress between the pad and the vessel pressure-retaining component. Telltale holes in internal attachment pads shall be seal welded. 13.2.8 Segments of split reinforcing pad shall be welded together without
using a backing strip.
13.2.9 All internal and external attachments, including clips, welded directly to pressure-retaining parts, shall be fully seal welded, except for blank square nuts used for external insulation where tack welding is allowed. 13.2.10 No tack welding is permitted between heads and skirts on the inside of
13.2.11 Vessels with large diameter and/ or overall length which fabrication cannot be completely done in shop shall be designed to minimize the amount of field welding, radiography and heat treatment. Where adjacent sections are of such a size that shop fabrication and field assembly is required, the sections shall be match marked to ensure proper field fit up.
13.2.12 Forming
13.2.12.1 General
a) Cold forming is performed at temperatures within the range of above 20°C (68°F) and below 120°C (248°F). b) Hot forming is any forming performed above the
austenite phase start temperature of 740°C (1364°F). c) All tempering heat treatments must be at least 25°C
(45°F) above the nominal PWHT temperature as given in the applicable ASME code for the respective material.
13.2.12.2 Hot Forming
1) All quenched and tempered materials must be completely heat-treated after hot forming to achieve the original material properties.
2) All hot forming procedures require approval of the Saudi Aramco Engineer as defined in this
specification prior to commencement of any of forming activities. Hot forming procedure shall describe all heat treatment operations and tests to be performed. The tests shall include, but not limited to, all of the mechanical tests required by the original material specification.
3) Normalized materials that are hot formed need to be heat treated unless the below rules are followed: a) Normalized materials that are hot formed in the
range of 750°C (1382°F) to 950°C (1742°F) and still air-cooled.
b) Normalized materials that are hot formed in a multi-step sequence must be cooled to below 200°C (392°F) prior to the last step. The material will then
be re-heated within the range of 750°C (1382°F) to 950°C (1742°F) for forming in the last step.
c) Normalized and tempered materials that are formed in accordance with either 13.2.14.2(3)(a) or
13.2.14.2(3)(b) of this specification need only receive a tempering heat treatment. The tempering temperature must not exceed the temperature stated in the steel manufacturers Material Test Certificate. 13.2.12.3 Cold Forming
a) Heat treatment requirements for Carbon Steels (P-1) and Low Alloy Steels (P-3, 4, 5, 9A and 9B) that undergo cold forming (by pressing or cold spinning) shall be as follows:
Material Fiber Elongation Strain εf (%) Heat Treatment Requirement
Carbon Steels P-1
Less than or equal to 5
None
(Exception: PWHT per the applicable Code shall be performed for cold spun heads)
Greater than 5 and
equal to or less than 10 PWHT per the applicable Code
Greater than 10
Normalizing, Normalizing and tempering or quenching and tempering, as required to maintain original material properties.
Low Alloy Steels P-3, P-4, P-5, P-9A & P9B
Less than or equal to 3
None
(Exception: PWHT per the applicable Code shall be performed for cold spun heads)
Greater than 3 and
equal to or less than 10 PWHT per the applicable Code
Greater than 10
Normalizing, normalizing and tempering or quenching and tempering, as required to maintain original material properties. High Alloy Materials Table 6.2 of ASME Section VIII,
Division 2 Table 6.2 of ASME Section VIII, Division 2 Non-ferrous Materials Table 6.3 of ASME Section VIII,
b) Calculation of forming fiber elongation strain εf (%) shall be according to the following:
Type of Part Being Formed Fiber Elongation Strain εf (%)
For double curvature heads that are formed from one-piece or welded multi-piece blanks by any process that includes dishing or cold spinning (e.g., dished heads or cold spun heads)
εf = 100 ln[Db/(Df -2ta)]
For heads that are assembled from formed segments (e.g., spherical dished shell plates or dished segments of ellipsoidal or torispherical heads)
εf = 100 tb / Rfd
Cylinders and cones formed from plate εf = (50 tb / Rfc) [1-(Rfc / Ro)] Where:
ln is the natural logarithm
Db is the diameter of unformed blank plate or diameter of intermediate product Df is original outside diameter
Rfd is the smallest mean radius of curvature of formed segment (mean radius of spherical
segment, mean knuckle radius of knuckle segment of multi sectional semi-ellipsoidal or torispherical heads)
Rfc is the mean radius of curvature of finished product (mean radius of cylinder, mean
radius of the smaller diameter of cone)
Ro is the mean radius of initial product (flat plate) or the intermediate product (in case of
unformed initial product equals to infinity)
ta is the nominal thickness of the plate before forming or intermediate product tb is the nominal thickness of the plate before forming
Commentary Notes:
i) Cold spun heads with nominal thickness exceeding 50 mm shall be heat treated by normalizing, normalizing and tempering or quenching and tempering, as required to maintain original material properties), irrespective of the calculated fiber elongation strain.
ii) For semi-ellipsoidal and torispherical heads formed from one-piece or welded multi-piece blanks, maximum calculated extreme fiber elongation strain among all head’s zones shall be used to determine the need of heat treatment. Separate calculation for each zone (spherical crown, knuckle area, etc.) shall be made, using the greatest measured thickness and smallest radius of curvature of the zone after forming.
iii) Separate calculation of extreme fiber elongation shall be made for each formed segment (e.g., spherical dished shell plates or dished segments of ellipsoidal or torispherical heads).
Need for heat treatment shall be determined for each segment individually using the greatest measured thickness and smallest radius of curvature after forming.
iv) In case of different forming steps without intermediate heat treatment are employed, extreme fiber elongation is the total amount of elongation of the individual forming steps. In case of intermediate heat treatment, the deformation is that elongation achieved after the last previous heat treatment. This is applicable for all types of formed part.
v) Filler metal used in items subjected to hot forming temperatures, or normalized, shall satisfy the weld joint design requirements after such heat treatment. This is considering that such welds will generally suffer significant strength reduction.
13.2.13 Bolt tensioning device shall be used for bolting up flanged connections with stud bolts of diameter 1-½ inch and above. Bolt up of flanges, irrespective of bolt diameter shall be according to ASME PCC-1 requirements.
13.2.14 Correction of fit-up offsets of the closing longitudinal butt joint in a rolled shell ring shall be achieved by only employing rolling machine operation until the deviations are within the specified Code tolerances. 13.2.15 Alignment of pre-formed sections of multi-piece vessel head at butt
joints, with fit-up deviations exceeding the Code tolerances, shall be achieved by only reforming (employing pressing machine) the head segments until the deviations are within the specified limits.
13.2.16 Alignment of completely fabricated sections at girth joints (shell ring-to-shell ring and head-to-ring-to-shell ring), with fit-up deviations exceeding the Code tolerances, shall be achieved by only reforming the shell (using rolling machine) or head (employing pressing machine), whichever is out-of-true, until the deviations are within the specified limits.
13.3 Welding
13.3.1 All welding shall be in accordance with the requirements of
SAES-W-010.
13.3.2 Dissimilar metal welds (DMW) are not permitted in sulfide stress cracking environment as defined in this specification. Welds in clad systems are acceptable if the DMW interface with the ferritic steel is not in contact with the sour fluid.
13.3.3 Following maximum allowable carbon equivalent, based on thickness (t) shall be met for pressure vessels intended for sulfide stress cracking environment.
