veslp001-0907

TECHNICAL REVISION September 2007

Process Industry Practices Vessels

PIP VESLP001 Specification for Low-Pressure, Welded, Shop-Fabricated Vessels

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice.

This Practice is subject to revision at any time.

© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas 78759. PIP member companies and subscribers may copy this Practice for their internal use. Changes, overlays, addenda, or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP.

PRINTING HISTORY March 1999 Issued September 2007 Technical Revision

Not printed with State funds


Process Industry Practices Vessels

PIP VESLP001 Specification for Low-Pressure, Welded, Shop-Fabricated Vessels Table of Contents 1. Introduction................................. 3 1.1 1.2 1.3

Purpose .......................................... 3 Scope ............................................. 3 Alternative Design Proposals ......... 3

2. References .................................. 4 2.1 2.2 2.3 2.4

Process Industry Practices............. 4 Industry Codes and Standards....... 4 Government Regulations................ 5 Other References ........................... 5

3. Definitions ................................... 5 4. General Requirements ............... 6 4.1 4.2 4.3 4.4 4.5 4.6

Applicable PIP Documents............. 6 Code ............................................... 6 Jurisdictional Compliance............... 6 Units of Measurement .................... 6 Language ....................................... 7 Documentation to be Provided to the Manufacturer ............................ 7

5. Design Requirements................. 7 5.1 5.2

Design Criteria................................ 7 Miscellaneous Design Requirements ................................. 9

Process Industry Practices

6. Working Drawings and Calculations.............................. 13 6.1 6.2 6.3 6.4

Information Required.................... 13 Special Notes ............................... 14 Purchaser Review ........................ 14 Calculations.................................. 14

7. Materials.................................... 14 7.1 7.2 7.3 7.4

Code Materials Required ............. 14 Unspecified Materials ................... 15 Flange Gaskets ............................ 15 Solution Anneal ............................ 15

8. Fabrication Details ................... 16 8.1 8.2 8.3 8.4 8.5

Weld Metal ................................... 16 Butt Joints Required ..................... 16 Nozzle Attachment Welds ............ 16 Nozzle Location............................ 16 Nozzles for Safety Relief and Drainage....................................... 16 8.6 Flange Drilling .............................. 16 8.7 Seams in Formed Heads ............. 16 8.8 Intermediate Head Weld .............. 16 8.9 Grounding Clip ............................. 16 8.10 Gasket Contact Surfaces ............. 17 8.11 Tolerances.................................... 17 8.12 Welds ........................................... 17

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8.13 Welding and Grinding Restrictions ...................................17 8.14 Welded Pressure Joints that will be Inaccessible after Assembly .........17 8.15 Clearance of Shell Seams ............17 8.16 Radiographic Examination............17 8.17 Postweld Heat Treatment .............18

9. Hydrostatic Testing ..................18 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10

Vertically-Mounted Vessels ..........18 Horizontally-Mounted Vessels ......18 Compartmented Vessels ..............18 Water Quality ................................18 Holding Time.................................18 Metal Temperature........................19 Flange Assembly for Test .............19 Retesting Repaired Vessels .........19 Disassembly of Flanged Joints after Testing ..................................19

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TECHNICAL REVISION Septermber 2007

10. Manufacturer’s Nameplates..... 19 11. Required Information ............... 20 11.1 Reports .........................................20 11.2 Drawings and Calculations ...........20

12. Cleaning, Painting, and Shipping Protection.................................. 20 12.1 Drying and Cleaning .....................20 12.2 Painting .........................................20 12.3 Protection of Machined Surfaces........................................21 12.4 Welded Attachments.....................21 12.5 Loading for Shipment....................21



1.


Introduction 1.1

Purpose This Practice provides requirements for the construction of low-pressure, welded, shop-fabricated vessels that generally meet the philosophy and requirements of Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code, henceforth referred to as the Code. However, Code inspection and stamping are not required.

1.2

1.3

Scope 1.2.1

This Practice describes the general requirements for the design, materials, fabrication, examination, inspection, and testing of aboveground, welded, cylindrical shell, single-wall, shop-fabricated vessels having an internal and external Maximum Allowable Working Pressure (MAWP) not exceeding 15 psig (100 kPa) at the top of the vessel while in normal operating position. An additional Low-Pressure Vessel Specification is required to define options covered herein and other specific requirements considering service (startup, normal operation, upset, shutdown), location, maintenance, etc. The documents listed in Section 2.1 shall be used for a complete purchase specification. See PIP VECV1001, PIP VESV1002, and PIP VEDV1003 for vessels having an MAWP in excess of 15 psig (100 kPa).

1.2.2

This Practice is intended for low-pressure vessels capable of being hydrostatically tested in both shop and operating positions. This Practice is not intended for flat-bottom tanks or API-type field-erected storage tanks. Unless approved by Purchaser, this Practice is not to be used for lowpressure vessels that will contain “Lethal Substances” as defined in Footnote 1 of Code Paragraph UW-2. PIP VECV1001, PIP VESV1002, and PIP VEDV1003 apply for vessels that are classified for “Lethal Service” or other highly hazardous chemical services.

1.2.3

Many recognized and generally accepted good engineering construction practices are included herein. However, in light of the many diverse service applications of low-pressure, shop-fabricated vessels, these practices shall be employed with engineering judgment and supplemented as appropriate with requirements related to specific materials of construction, service fluids, operating environments, and vessel geometries. Accordingly, provisions of this Practice may be overridden or supplemented by an Overlay Specification (see Section 3 for definition).

Alternative Design Proposals The Manufacturer shall provide a base bid in full compliance with the purchase request for quotation. The Manufacturer may submit an alternative design if, in the Manufacturer’s judgment, economy and/or improved schedule can be realized without loss of capability or shortening the anticipated life of the vessel. The Manufacturer shall comply with the following requirements when submitting an alternative bid: a. Alternative design quotations shall be accompanied by the base quotation and shall be clearly noted as an alternative design.


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b. Alternative designs shall be fully and clearly described and substantiated by sketches or drawings. Specific exceptions to the Low-Pressure Vessel Specifications or this Practice shall be identified as such. c. An alternative design shall not be used unless approved in writing by the Purchaser.

2.

References Applicable parts of the following Practices, industry codes and standards, and references shall be considered an integral part of this Practice. The edition in effect on the date of contract award shall be used, except as otherwise noted. Short titles are used herein when appropriate. The documents listed in this Section are only those specifically referenced in this Practice. In applications where there are laws or regulations issued by municipal, state, provincial, or federal authorities covering low-pressure vessels, these laws or regulations shall be reviewed prior to the initiation of design work since the requirements may be different or more restrictive than the specifications covered in this Practice. 2.1

Process Industry Practices (PIP) – PIP VECV1001 – Vessel Design Criteria ASME Code Section VIII, Divisions 1 and 2 – PIP VEDV1003 – Vessel Drawing/Data Sheet and Instructions – PIP VEFV1100/VEFV1100M – Vessel/S&T Heat Exchanger Standard Details PIP VEFV1101 – Vessel Nameplate Bracket PIP VEFV1102 – Vessel Tolerances PIP VEFV1103 – Vessel Grounding Lug PIP VEFV1105 – Vessel Saddles Supported on Concrete PIP VEFV1106 – Vessel Saddles Supported on Structural Steel PIP VEFV1117 – Vessel Manway Vertical Davit PIP VEFV1118 – Vessel Manway Horizontal Davit PIP VEFV1128 – Vessel Skirt Attachment – PIP VESV1002 – Vessel Fabrication Specification ASME Code Section VIII, Divisions 1 and 2

2.2

Industry Codes and Standards For the documents listed in Table U-3 of the Code, the edition listed in Table U-3 shall be used. American Society of Civil Engineers (ASCE) – ASCE 7 – Minimum Design Loads for Buildings and Other Structures • American Society of Mechanical Engineers (ASME) – ASME Boiler and Pressure Vessel Code Section VIII, Division 1 – Pressure Vessels Section IX – Welding and Brazing Qualifications

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– ASME B16.5 – Pipe Flanges and Flanged Fittings NPS 1/2 through NPS 24 – ASME B16.9 – Factory-Made Wrought Steel Buttwelding Fittings – ASME B16.47 – Large Diameter Steel Flanges NPS 26 through NPS 60 – ASME B46.1 – Surface Texture (Surface Roughness, Waviness, and Lay) – ASME SA-193 – Specification for Alloy Steel and Stainless Steel Bolting Materials for High-Temperature Service – ASME SA-194 – Specification for Carbon and Alloy Steel Nuts for Bolts for High-Pressure and High-Temperature Service – ASME SA-480 – Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip – ASME PCC-1 – Guidelines for Pressure Boundary Bolted Flange Joint Assembly • American Welding Society – ANSI/AWS A2.4 – Standard Symbols for Welding, Brazing and Nondestructive Examination 2.3

Government Regulations • US Department of Labor, Occupational Safety and Health Administration (OSHA) – OSHA 29 CFR 1910.119 – Process Safety Management of Highly Hazardous Chemicals

2.4

Other References – “Design Equations for Preventing Buckling in Fabricated Torispherical Shells Subjected to Internal Pressure,” G.D. Galletly, Proceedings, Institution of Mechanical Engineers, London, Vol. 200 No. A2, pp.127-139. – “Stresses in Large Cylindrical Pressure Vessels on Two Saddle Supports,” L.P. Zick, Pressure Vessels and Piping: Design and Analysis, A Decade of Progress, Volume Two, 1972, p. 959.

3.

Definitions For the purposes of this Practice, the following definitions apply: Code: Section VIII, Division 1 ASME Boiler and Pressure Vessel Code Construction: An all-inclusive term comprising materials, design, fabrication, examination, inspection, and testing and pressure relief. Designer: The party responsible for defining and specifying the mechanical design requirements (e.g., Vessel Drawing/Data Sheet) consistent with the Low-Pressure Vessel Specifications or User criteria for use by the Manufacturer. The Designer is frequently an engineering contractor, but could be the User, third party consultant, or the Manufacturer. Low-Pressure Vessel Specification: This term shall be understood to include any drawings, specifications, or service-specific data designated by Purchaser for a particular vessel or


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group of vessels. The Manufacturer is responsible for notifying the Purchaser in writing of any apparent conflicts between the Low-Pressure Vessel Specification and this Practice. See PIP VEDV1003 for Vessel Drawing/Data Sheet and Instructions. Manufacturer (Supplier): The party entering into a contract with the Purchaser to construct a vessel in accordance with the purchase order. In accordance with the Code definition, the Manufacturer is the party that possesses a current and valid Certificate of Authorization to manufacturer pressure vessels with the “U” or “UM” ASME Stamp. The Manufacturer may or may not be the Supplier. Overlay Specification: Technical requirements that supplement or override the provisions of this Practice, such as a Low-Pressure Vessel Specification or a project specification Purchaser: The party actually placing the order for the vessel or vessel components. This may be the User or the User’s designated agent. User: The party responsible for establishing construction criteria consistent with the Code philosophy and service hazards as described in the Purpose and Scope statements. This term refers to the owner and/or operator of the equipment.

4.

General Requirements 4.1

Applicable PIP Documents All vessels shall be designed in accordance with this Practice; PIP VEFV1101, PIP VEFV1102, and PIP VEFV1103; other standard details in PIP VEFV1100 as applicable; and PIP VEDV1003. Sections of PIP VECV1001 (e.g., Appendix B Welded Pressure Joint Requirements Form) and PIP VESV1002 (e.g., Appendix A Quality Overview Plan and Appendix B - Manufacturer’s Data Package) may be used as needed.

4.2

Code Materials, design, welding, and fabrication shall be in accordance with the Code, except as modified herein. Examination, inspection, and testing shall be in accordance with the requirements of this Practice. The Manufacturer shall be a valid ASME Code “U” Symbol stamp holder and shall comply with all aspects of their Code Quality Control System, except that inspection by the Authorized Inspector and Code stamping are not required.

4.3

Jurisdictional Compliance All aspects of the work shall comply with applicable local, county, state, and federal rules and regulations. This includes, but is not limited to, the rules and standards established by EPA and OSHA, if applicable.

4.4

Units of Measurement U.S. customary (English) units shall be regarded as standard; metric (SI) units may be included for reference only and shall not be interpreted as a precise conversion.

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TECHNICAL REVISION


September 2007

4.5

Language The language of all documents shall either be English or include the English translation.

4.6

Documentation to be Provided to the Manufacturer Design requirements to be provided to the Manufacturer shall be in accordance with PIP VEDV1003.

5.

Design Requirements Vessels or parts of vessels shall be in accordance with the following requirements. Any differences between this Practice and laws or regulations issued by regulatory authorities shall be brought to the attention of Purchaser for review and approval of any necessary changes or additions. 5.1

Design Criteria 5.1.1

Design Calculations Low-pressure vessels shall be designed in accordance with the formulas and allowable stresses in the Code, except that use of standard flanged and dished heads shall be permitted if the following conditions are met:

5.1.2

•

The inside crown radius shall not be greater than the OD of the skirt

•

The inside knuckle radius is not less than three times the head thickness

•

The minimum head thickness after forming is computed in accordance with Code rules

Design Pressure Vessels shall be designed to withstand the specified internal design pressure (nameplate pressure rating) plus any additional loadings (e.g., wind and seismic loadings) at both the maximum and minimum design metal temperatures. The internal design pressure applies to the top of the vessel in its operating position and shall be established considering: startup and startup following an emergency shutdown; normal, temporary, and emergency operation; and normal and emergency shutdown. The internal design pressure (e.g., MAWP) shall not exceed 15 psig (100 kPa) at the top of the vessel (see Section 5.1.4).

5.1.3

Hydrostatic Tests All provisions of Code Paragraph UG-99 must be met. UG-99(b), including Footnote 34, shall be considered the standard hydrostatic test. The test pressure or applicable Code paragraph number shall be specified on the LowPressure Vessel Specification. All vertical vessels shall be designed to be capable of a field hydrostatic test in the vertical position.


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5.1.4


Design Temperature Vessels shall have both maximum and minimum design metal temperature ratings. Both of these ratings shall be marked on the vessel nameplate. The maximum design metal temperature shall be 150°F (66°C) or higher. The minimum design metal temperature shall not be warmer than 30°F (-1°C). The MAWP at the maximum and minimum design metal temperatures shall be the same.

5.1.5

Corrosion Allowance The specified corrosion allowance shall be added to all pressure parts in contact with the service fluid. Non-pressure internal parts that are welded in place shall include a corrosion allowance on all wetted surfaces of not less than 75% of that for pressure parts. Non-pressure internal parts that are removable shall not require corrosion allowance unless specified in the LowPressure Vessel Specifications or required by the Manufacturer’s standard practice.

5.1.6

Compartmented Vessels Common components of compartmented vessels shall be designed for the most severe combinations of pressure, vacuum, temperature, and other loadings that may occur during operation and test conditions. Design on the basis of simultaneous loading of internal pressure in adjacent compartments shall not be permitted.

5.1.7

Wind or Earthquake Loads Vessels shall be self-supporting and designed to resist the specified wind pressures or seismic loadings. Do not design as if wind and earthquake loads occur simultaneously. The vessel, vessel supports, and anchor bolting shall be designed to withstand the greater of the wind or seismic moments when acting simultaneously with other loadings imposed upon the vessel. Load combinations shall be in accordance with Section 5.4 of PIP VECV1001. 5.1.7.1 Wind Loads

Design wind loads shall be determined in accordance with design criteria established by the Purchaser. The basic wind speed, exposure category, and topographic factor shall be as specified in the LowPressure Vessel Specifications. For ASCE 7 wind load design all horizontal vessels and for vertical vessels having a height-todiameter ratio (h/D) not greater than 1.0, the force coefficient, Cf, shall be 0.5. For vertical vessels having h/D greater than 1.0, the value shall be 0.7. Apply wind load to the total projected area of the vessel including insulation, ladders, platforms, attached piping, and other appurtenances. 5.1.7.2 Earthquake Loads

Seismic loads shall be determined in accordance with design criteria established by the Purchaser.

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5.1.8

5.1.9


Minimum Thicknesses 5.1.8.1

Material thicknesses for shells and formed heads, exclusive of corrosion allowance, shall not be less than 3/16 inch (5 mm) for high-alloy steel and 1/4 inch (6 mm) for carbon and low-alloy steels.

5.1.8.2

Nozzle neck thicknesses, including those of manways, shall not be less than permitted by Paragraph UG-45 of the Code.

Torispherical Heads To prevent internal pressure-induced buckling of large diameter, thin (ratio of spherical or crown radius-to-required head thickness greater than 300), formed (torispherical) heads, a design check of the Code-required thickness shall be performed. One acceptable method (among several that have been published) is found in G.D. Galletly’s “Design Equations for Preventing Buckling in Fabricated Torispherical Shells Subjected to Internal Pressure” (see Section 2.3). This check may reveal the need for a head thickness greater than the Code-required minimum thickness.

5.2

Miscellaneous Design Requirements 5.2.1

Vessel Connections 5.2.1.1 Nozzle Connections

External nozzle flanges for nozzle sizes NPS 24 (DN 600) and smaller shall be in accordance with ASME B16.5. Larger flanges shall conform to ASME B16.47 Series B. Couplings shall not be less than Class 6000, smaller than NPS ¾ (DN 19), or larger than NPS 2 (DN 50). 5.2.1.2 Lap Joints

Flanged joints for stainless steel and nonferrous components may be of the lap-joint type with carbon or low-alloy steel flanges. Lap joint flanges NPS 24 (DN 600) and smaller shall be furnished in strict accordance with ASME B16.5. Flanges for fabricated laps larger than NPS 24 (DN 600) shall be in strict accordance with ASME B16.47. Flanges for aluminum lap-joint stub ends shall be galvanized. The nominal OD of laps shall correspond to dimensions in ASME B16.9 when used with standard (in accordance with ASME B16.5) flanges. 5.2.2

Nozzles and Manways 5.2.2.1 Projection

For nozzles up to and including NPS 8 (DN 200), the minimum projection from the outside of the vessel wall to the nozzle face shall be 8 inches (200 mm). For nozzles larger than NPS 8 (DN 200), the minimum projection shall be 10 inches (250 mm). 5.2.2.2 Minimum Manway Size

The nominal recommended manway size is NPS 24 (DN 600) with a finished ID not less than 23 inches (584 mm). Manways shall not be


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smaller than NPS 20 (DN 500) or have a finished ID of less than 19 inches (483 mm). Larger diameter manways shall be used to satisfy additional needs such as, but not limited to, installation of internals/catalyst, packing, maintenance requirements, long projection due to thick insulation, etc. 5.2.3

Vessel Supports The type of vessel support (skirt, legs, saddles, lugs) shall be as specified in the Low-Pressure Vessel Specifications (see Section 5.2.4 for anchor bolting). 5.2.3.1 Design Stresses

Allowable design stresses for all vessel support components shall be the same as specified in the Code for pressure parts, except as follows: Stresses resulting from direct bending in anchor ring base plates shall not exceed 1.5 times the Code-allowable tensile stress values. Compressive stresses in anchor ring gussets and other compression members shall not exceed 1.25 times the Code-allowable tensile stress values. 5.2.3.2 Skirt Supports

Support skirts for vertical vessels with bottom head having a knuckle radius < 6% of the head skirt ID shall be continuously welded to the straight flange (cylindrical portion) of the head with the weld sized so as to provide for the maximum imposed loadings. The skirt attachment detail shall be the lapped type (e.g., the skirt is lapped to the straight flange of the head). Skirts shall be attached to bottom heads having a knuckle radius > 6% of the head skirt ID by a continuous weld sized so as to provide for the maximum imposed loadings. The preferred skirt attachment detail shall be butt type (skirt butted to knuckle portion of head such that the centerlines of the skirt plate and the head flange are the same nominal diameter or such that the outside diameters of the shell and skirt coincide). A lapped-type skirt design (skirt lapped to straight flange of head) may also be used. See PIP VEFV1128 for some illustrative weld attachment details and associated minimum weld sizes. All butt weld joints within the skirt shall be Type No. 1 of Code Table UW-12. Alignment tolerance at plate edges to be butt-welded shall be in accordance with Code Paragraph UW-33. The type of skirt attachment detail, the style of anchor ring assembly (e.g., single ring with gussets, single ring with chairs, double ring with gussets, etc.), and the type/degree of nondestructive examination of the skirt assembly welds shall be a matter of agreement between the User and the Designer.

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5.2.3.2.1

Access Openings - Skirt diameter permitting, one or more openings 24 inches (600 mm) in diameter or larger shall be provided to allow free access for inspection and/or maintenance work inside the skirt. Other opening geometries are acceptable and are a matter of agreement between the User and the Designer.

5.2.3.2.2

Vent Openings - Provision shall be made for venting of the skirt with a minimum of two, 2-inch (50 mm) openings, located near the top of the skirt, but below the head insulation or fireproofing.

5.2.3.2.3

Reinforcement of Skirt Openings - All skirt openings shall be provided with rings or collars, sized to provide 100% reinforcement of the opening.

5.2.3.3 Leg Supports

Leg supports shall be limited to vessels that meet the following conditions: 1. Design temperature does not exceed 450°F (232°C) 2. Service is noncyclic and nonpulsating (see Note 1) 3. Vessel h/D does not exceed 5 (see Note 2), where height, h, is defined as the distance from the base of the supports to the top tangent line of the vessel. The diameter, D, is defined as the outside diameter of the vessel, exclusive of any insulation that may be present. Note 1: Vessels having agitators experience transient transverse forces due to dynamic bending moments from the agitator and sloshing of the liquid. Therefore, design of leg-supported vessels with agitators requires the application of experience-based engineering judgment to ensure that displacement stiffness and stress levels essential to satisfactory operation are provided. Note 2: Caution is advised for leg-supported vessels where h/D ≤ 5 but could have excessive axial and/or bending loads on the legs or an overstress condition in the vessel wall at the points of attachment. 5.2.3.4 Saddle Supports

Vessels that will be horizontally installed shall be mounted on two saddle-type supports. Supports shall extend over at least one-third (120 degrees) of the circumference of the vessel shell. Wear plates shall be provided with radiused corners and shall be welded to the shell with a continuous fillet weld (see Section 8.15). Wear plates shall be provided with two telltale holes. The holes shall be plugged with a Room Temperature Vulcanizing (RTV) silicone sealant. The


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bottom of the supports shall extend at least 1 inch below nozzles or other projecting vessel components.

5.2.4

5.2.3.4.1

Slide Plates - One of the two saddles shall be designated as the fixed saddle with holes provided to receive the anchor bolts. The other saddle shall be designated as the sliding saddle and slotted holes of sufficient length to permit the maximum anticipated expansion or contraction shall be provided. Slide plates shall be furnished by Purchaser under all sliding saddles. See PIP VEFV1105 and PIP VEFV1106 for examples of standard saddle details that may be used.

5.2.3.4.2

Saddle Design - The effect of the saddles on the shell shall be analyzed using the method developed by L. P. Zick in “Stresses in Large Cylindrical Pressure Vessels on Two Saddle Supports” (see Section 2.3).

Anchor Bolting 5.2.4.1 Design Stresses

Anchor bolts shall not be smaller than 3/4 inch (19 mm). Allowable design tensile stresses for carbon steel anchor bolts, as calculated using the tensile stress area of the threaded portion, shall be 20000 psi (138 MPa). 5.2.4.2 Spacing and Location

Anchor bolts for vertical vessels shall be selected in multiples of four bolts and shall straddle the natural centerlines of the vessel. Orientation shall be furnished by Purchaser. 5.2.4.3 Supplier

Anchor bolting will be furnished and installed by others. Anchor bolts shall be hot-dipped galvanized. 5.2.5

Lifting Lugs 5.2.5.1 Vessel Lifting Lugs

Vertical vessels shall be furnished with lifting lugs designed to permit erecting the vessel from a horizontal position. A minimum impact factor of 2 shall be applied to the design lift weight. Where two ear-type lugs are spaced 180 degrees apart and welded to the straight flange portion of the top head and shell, the weld across the bottom of the lug shall be omitted to allow drainage. The crevice between the lug and the top head dish surface shall be sealed by a bead of RTV silicone sealant after painting. Another common type is a single lug welded to a blind flange that is bolted to the nozzle in the center of the top head. 5.2.5.2 Lugs for Removable Covers

Removable vessel covers and manway covers shall be provided with suitable lifting lugs (see PIP VEFV1117 and PIP VEFV1118).

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5.2.6


Vessels with Agitators When an agitator is mounted on a nozzle (or studding outlet), in a formed head, the head thickness based on Code formulas for pressure loadings and static local loadings analysis is often not sufficient to provide the rigidity and stress levels acceptable for the dynamic loadings that will be applied. The agitator manufacturer shall be consulted regarding the recommended minimum head thickness and nozzle attachment details for the agitator installation under consideration.

6.

Working Drawings and Calculations 6.1

Information Required Manufacturer shall provide certified fabrication drawings for all low-pressure, shopfabricated vessels. Drawings shall be complete and shall include all relevant design, materials, fabrication, examination, inspection, and testing requirements. All welds shall be either detailed or identified by the standard welding symbols of ANSI/AWS A2.4. In addition, drawings shall include the following information: 1. Purchaser’s item number, purchase order number, and shop order number 2. Reference to all applicable PIP, Manufacturer, and other specifications and standards. When reference is made to Manufacturer’s own standards, copies of such standards shall be included with the drawings. 3. Facsimiles of Manufacturer’s nameplates as stamped by the Manufacturer 4. Design specific gravity, maximum liquid level, and other operating loads 5. Corrosion allowance (Specify as none when applicable.) 6. Service-specific requirements 7. Hydrostatic test pressure (see Section 5.1.3). Show the hydrostatic test pressure in both the operating position and the shop test position, if different. a. Horizontal position (referenced to top of vessel) b. Vertical position (for vertical vessels only, referenced to top of vessel). This may be a shop test or a future test in the operating position. 8. Estimated weight of vessel when empty, maximum operating, and full of water 9. Capacity of vessels or each compartment 10. Surface preparation and painting or other protective coating specifications 11. Designations for nozzles, manways, and skirt openings. These designations shall be the same as those shown on Purchaser’s drawings. For nozzles located normal to a cylindrical shell, the vessel assembly drawings shall include dimensions from the centerline (axis) of the shell to the nozzle faces.


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6.2


Special Notes Manufacturer’s drawings shall also include the following notes as applicable: 1. All vessels - “Chlorides or substances that contain chlorine that will decompose to form chlorides (e.g., coatings to prevent adhesion of weld spatter) shall not be applied to any part of the vessel.” 2. Stainless steel or nickel-alloy vessels - “Zinc-coated (galvanized or painted) components shall not be in contact (welded, bolted, or loose) with any alloy parts of the vessel.” 3. Nickel or nickel-alloy vessels - “Substances containing sulfur (e.g., lubricants to aid machining) shall not be applied to alloy parts of the vessel.” 4. All PWHT vessels shall have the following notice painted on two sides of the shell and insulation covering, if present, in 3-inch (75 mm) high letters visible in the shipping position from grade: POSTWELD HEAT TREATED - DO NOT BURN OR WELD 5. All vessels with nonmetallic linings shall have the following notice painted on two sides of the shell and insulation covering, if present, in 3-inch (75 mm) high letters visible in the shipping position from grade: LINED VESSEL - DO NOT BURN OR WELD

6.3

Purchaser Review Manufacturer’s drawings shall be reviewed by Purchaser prior to the start of fabrication unless a release to proceed is obtained from Purchaser in writing.

6.4

Calculations Calculations are required for each vessel in sufficient detail to demonstrate compliance with the requirements of this Practice and the referenced documents.

7.

Materials 7.1

Code Materials Required Materials for pressure parts, vessel supports, and other nonpressure parts welded to pressure parts shall be materials allowed by the Code (see Code Foreword). 7.1.1

Impact Test Exemptions Impact test exemptions for carbon and low-alloy steels shall be established in accordance with Code requirements. Attachments welded to the pressurecontaining components shall be treated as being essential to the structural integrity of the vessel.

7.1.2

Pressure Bolting Bolting materials for pressure-resisting flanged joints shall be SA-193 Grade B7 bolts with SA-194 Grade 2 or 2H heavy hex nuts. When stainless steel bolting is required, SA-193 Grade B8, Class 2 bolts with SA-194 Grade 8 or 8A heavy hex nuts shall be used.

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TECHNICAL REVISION


September 2007

7.2

Unspecified Materials Materials not completely defined in the Low-Pressure Vessel Specifications shall conform to the requirements of Section 7.1.

7.3

Flange Gaskets Gaskets, except metal gaskets made integral by welding and nonmetallic (e.g., flexible graphite) tape gaskets with abutting ends suitably joined, shall be seamless. Manufacturer shall provide a means for positioning (centering) the gasket during joint make-up. No joint sealing compound or lubricant shall be used unless specified by Purchaser. A light dusting of 3M® 77 or equal spray adhesive may be used if required to hold the gasket in place during assembly. 7.3.1

Service Gaskets When service gaskets are designated to be furnished by the Manufacturer (e.g., for manways and blind flanged nozzles), the gaskets shall be as specified in the Low Pressure Vessel Specifications. When gaskets are cut from sheet stock they shall be 1/16 inch (1.5 mm) thick minimum.

7.3.2

Test Gaskets Any flanged joint for which the service gasket is to be furnished by the Manufacturer and which will not be disassembled after testing shall be tested with the specified service gasket (see Section 7.3.1). If the joint is to be disassembled after testing and employs flanges in accordance with ASME B16.5 or B16.47, the test gasket may be selected by the Manufacturer subject to the approval of the Purchaser and the limitations in Section 7.3.2.1. If the joint is to be disassembled after testing, employs non-standard flanges (e.g., not in accordance with ASME B16.5 or B16.47), and the service gasket is not specified, the test gasket shall be approved by Purchaser. 7.3.2.1 Limitations

Test gaskets shall be the same type as the service gaskets. In no case shall the nominal thickness of sheet or laminate gasketing be greater than 1/8 inch (3 mm). 7.3.2.2 Flanged Joints Disassembled After Testing

Flanged joints specified to be furnished with service gaskets (e.g., manways and blind flanged nozzles) and disassembled following tests shall be reassembled using new service gaskets. If such joints are shipped unassembled, new service gaskets for field installation shall be suitably packaged, marked, and shipped with the vessel. 7.4

Solution Anneal When specified in the Low-Pressure Vessel Specifications, all formed heads fabricated from austenitic (types 304 and 316 only, including low-carbon and stabilized grades) or duplex stainless steel shall be solution annealed after forming in accordance with ASME SA-480.


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8.


Fabrication Details 8.1

Weld Metal Deposited weld metal shall be essentially of the same mechanical, chemical, and toughness properties as the material joined.

8.2

Butt Joints Required Welded joints of Code Categories A, B, and butt-type Category C (when used) shall be Type No. 1 of Code Table UW-12. Butt welds with one plate edge offset [Code Figure UW-13.1(k)] and permanent weld-joint backing strips shall not be permitted.

8.3

Nozzle Attachment Welds Attachment welds connecting nozzles (including manways, couplings, sight glasses, and studding outlets) to the vessel wall shall be full penetration welds extending through the entire thickness of the vessel wall and through the inside edge of reinforcing plates (when used). Nozzles designated to extend beyond the inside surface of the vessel wall shall have a fillet weld at the inside corner.

8.4

Nozzle Location Plate layouts shall be arranged so that, to the maximum extent possible, longitudinal and circumferential weld seams clear all nozzles, manways, and their reinforcing pads by 2 inches (50 mm) minimum, measured from weld edge to weld edge.

8.5

Nozzles for Safety Relief and Drainage Nozzles intended for use with a safety relief device or as vessel drains shall be trimmed flush inside the vessel wall.

8.6

Flange Drilling Bolt holes in all fixed flanges and studding outlets shall straddle the natural centerlines. For nozzles in heads, the bolt holes shall straddle centerlines parallel to or coincident with the natural vessel centerlines. Bolt holes in flanges shall be 1/8 inch (3 mm) larger than the diameter of the bolts.

8.7

Seams in Formed Heads Seamless formed heads are recommended. As a minimum, weld seams in formed heads shall be radiographed in accordance with Code Paragraph UW-51 in the straight flange, knuckle region, and 2 inches (50 mm) into the spherical portion regardless of the joint efficiency used.

8.8

Intermediate Head Weld For compartmented vessels having an intermediate formed head, the end of the intermediate head skirt shall be seal-welded to the shell of the compartment (see Code Figure UW-13.1(f)).

8.9

Grounding Clip Provide each vessel with a grounding clip in accordance with PIP VEFV1103.

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8.10


Gasket Contact Surfaces All gasket seating surfaces shall be plane and true. If necessary, shop-fabricated flanges and lap rings shall be machined after welding, heat treatment, or other fabrication steps that can result in warpage or distortion from a plane and true surface. Surface finish shall have 125 - 250 microinch (3.2-6.4 micrometers) Ra roughness as defined in ASME B46.1 with spiral or concentric circular serrations. Surface finish for flanges in accordance with ASME B16.5 and ASME B16.47 shall be in accordance with the applicable ASME standard.

8.11

Tolerances Dimensional tolerances shall apply to the completed vessel after final pressure test and shall conform to PIP VEFV1102.

8.12

Welds All welds, including those attaching non-pressure parts to pressure parts, shall be made by welders (or welding operators) and welding procedures both qualified under the provisions of Section IX of the ASME Boiler and Pressure Vessel Code. Approval shall be obtained from Purchaser before any welding or preparation for welding is subcontracted to another shop or supplier. Such approval shall require knowledge by Purchaser of the qualifications of the subcontractor performing the work. The Manufacturer retains accountability for the subcontracted fabrication work.

8.13

Welding and Grinding Restrictions Welding on pressure resisting components and grinding (including cosmetic grinding) on pressure-resisting welds shall not be permitted after pressure testing unless approved in writing by Purchaser.

8.14

Welded Pressure Joints that will be Inaccessible after Assembly Finished surfaces of welded pressure joints that will be inaccessible after assembly (e.g., those surfaces between lap joint flanges and associated nozzle necks, shells and lap-ring, or lap joint stub end attachment welds) shall be examined using either the magnetic particle or the liquid penetrant method in accordance with Appendix 6 or Appendix 8, respectively, of the Code. Required repairs shall be completed prior to painting.

8.15

Clearance of Shell Seams The minimum distance from the toe of fillet welds that attach saddle supports or wear plates to the centerline of either a longitudinal or circumferential shell seam shall be

Rt where R = shell inside radius in inches (mm) and t = shell thickness (in inches (mm), exclusive of corrosion allowance). 8.16

Radiographic Examination Radiographic examination of butt-welded seams is not required except as specified in Section 8.7.


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8.17


Postweld Heat Treatment 8.17.1 Alternative PWHT requirements of Code Table UCS-56.1 for carbon and low-alloy steels shall not be employed. 8.17.2 The equipment shall be adequately supported during PWHT to avoid distortion. 8.17.3 If any high nickel alloy equipment must be PWHT, the atmosphere shall be free of sulphur.

9.

Hydrostatic Testing 9.1

Vessels shall not be painted or shot peened prior to the hydrostatic test except as specified in Section 12.2.

9.2

Vertically-Mounted Vessels Vertical vessels shall be tested in their operating position if practicable. If a vertical vessel is shop-tested in the horizontal position, Manufacturer shall be responsible for determining the need for and providing any temporary supports to prevent distortion or other damage to the vessel during the test.

9.3

Horizontally-Mounted Vessels Horizontal vessels shall be tested on their operating supports without additional temporary supports or shoring. All supporting lugs, rings, saddles, legs, and other permanently attached supports shall be attached to the vessel before the test.

9.4

Compartmented Vessels For vessels that consist of two or more compartments, each compartment shall be given a separate and individual test with atmospheric pressure in the adjacent compartments.

9.5

Water Quality Testing of vessels shall be conducted with test water that is clean and free of debris. Brackish or untreated water shall not be used. Potable water as delivered through municipal systems is acceptable for carbon or chrome steel vessels or components. For vessels or components made of austenitic stainless steel materials, testing water shall contain no more than 50 ppm chloride. Water containing more than 50 ppm chloride, but no more than 250 ppm, may be used only if the test procedure is 72 hours or less in duration and includes rinsing with water containing less than 50 ppm chloride.

9.6

Holding Time Test pressure shall be maintained for a minimum of one hour. Following the application of the hydrostatic test pressure, an inspection shall be made of all joints and connections. This inspection shall be made at a pressure not less than two-thirds of the test pressure.

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9.7


Metal Temperature For the entire duration of the test, vessel metal temperature shall not be colder than the Minimum Design Metal Temperature plus 30° F (17°C) (MDMT + 30° F (17°C)) (see Section 5.1.4).

9.8

Flange Assembly for Test The Manufacturer shall furnish all blind flanges, gaskets, and bolting (or other types of blanking covers) necessary for testing. For connections not specified to be furnished with blind flanges, the blind flanges and bolting (or other type covers) may be removed after testing and remain the property of the Manufacturer (see Section 12.3.2 for shipping covers). All flange bolting procedures shall be in accordance with ASME PCC-1.

9.9

Retesting Repaired Vessels Repairs to eliminate leaks revealed during pressure testing shall be tested by reapplying the original pressure test(s).

9.10

Disassembly of Flanged Joints after Testing If practicable, body flanges, manways, and nozzles specified to be furnished with blind flanges shall be left undisturbed and assembled after testing. If disassembly is necessary for shipping, draining, or other purposes, new gaskets shall be furnished as specified in Section 7.3.2.2.

10.

Manufacturer’s Nameplates Each vessel shall be furnished with the Manufacturer’s nameplate made of austenitic stainless steel and attached by an austenitic stainless steel nameplate bracket in accordance with PIP VEFV1101. The nameplate shall include: •

MAWP and associated Maximum Allowable Working Temperature (MAWT)

•

Design external pressure and associated temperature

•

MDMT at the MAWP

•

Purchaser’s vessel identification

•

Manufacturer’s name

•

Manufacturer’s serial number

•

Year built


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11.


Required Information 11.1

Reports The Manufacturer shall furnish Purchaser with:

11.2

•

Material test reports or certificates of compliance in accordance with Code requirements

•

Heat treatment charts (time/temperature record)

•

Hydrostatic test report or record

Drawings and Calculations Copies of certified drawings, calculations, and other pertinent data required by this Practice and the referenced documents shall be submitted to Purchaser (see Section 6).

12.

Cleaning, Painting, and Shipping Protection 12.1

Drying and Cleaning Immediately after completion of the hydrostatic test, the vessel interior shall be completely drained, thoroughly dried, and cleaned of foreign matter.

12.2

Painting 12.2.1 All required coatings shall be as specified in the Low-Pressure Vessel Specifications. Only surfaces that are required by the Low-Pressure Vessel Specification to be painted and that will be inaccessible after assembly (e.g., mating surfaces between lap-joint flanges and associated nozzle necks, shells, lap rings or stub ends; bolt holes; and welded joints) shall be painted prior to assembly and hydrostatic testing (see Section 8.14). Otherwise, all painting shall be performed after hydrostatic tests (see Section 9.1). 12.2.2 All PWHT vessels shall have the following notice painted on two sides of the shell and insulation covering, if present, in 3-inch (75 mm) high letters visible in the shipping position from grade: POSTWELD HEAT TREATED - DO NOT BURN OR WELD 12.2.3 All vessels with nonmetallic linings shall have the following notice painted on two sides of the shell and insulation covering, if present, in 3-inch (75 mm) high letters visible in the shipping position from grade: LINED VESSEL - DO NOT BURN OR WELD

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TECHNICAL REVISION


September 2007

12.3

Protection of Machined Surfaces 12.3.1 All gasket seating, threaded, or other machined surfaces shall be protected for shipment as follows: 12.3.1.1 Assembled Joints

Body joints, manways, blind-flanged nozzles, plugged couplings, and other connections specified to be furnished with service covers shall be shipped assembled if practicable (see Section 7.3.2.2). 12.3.1.2 Exposed Surfaces

For carbon and low-alloy steels, all exposed machined or threaded surfaces shall be cleaned with solvent and coated with temporary rust preventive grease. The following products are acceptable: Ashland Oil-Tectyl 858C, Sanchem No-Ox-Id-A, Exxon-Beacon 325, Houghton-Rust Veto Heavy. Other equivalent products are acceptable. Shipping covers shall be furnished in accordance with Section 12.3.2. 12.3.2 All flange faces other than those furnished with permanent blinds shall be covered with 1/2 inch (13 mm) thick wood or 1/8 inch (3 mm) thick steel plate no smaller than the flange OD. These covers shall be secured with a minimum 25% complement of evenly spaced carbon steel bolts, but no fewer than four. All flange faces furnished with permanent blinds or metal covers shall have full face non-asbestos gasket installed between the flange face and the metal cover. 12.3.3 Welding stub ends shall be provided with bevel protectors. 12.4

Welded Attachments Welding of attachments to vessels for shipping purposes shall not be permitted (see Section 8.13).

12.5

Loading for Shipment The Manufacturer shall take all necessary precautions in loading, blocking, and bracing the vessel to prevent damage during shipment.


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veslp001-0907

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