ES&H Manual



6151 Appendix T2

Pressure Systems Design Program



This document is currently under review.  All requirements outlined within this document apply to current laboratory operations until new content is approved, released, and published.


1.0            Purpose


The purpose of this technical appendix is to provide guidance to the Design Authority in the design of pressure systems.  This document provides insight to help apply and interpret the American Society of Mechanical Engineers (ASME) codes to the design process.  The Design Authority will have many choices to make throughout the design process.  This appendix provides direction for those choices but is not intended as a stand-alone document.  The Design Authority must refer to the ASME Codes applicable to the system being designed.  The Pressure Systems Committee shall be available for assistance throughout the design process.


2.0            Scope


The Pressure Systems Design Program provides guidance in two distinct areas: pressure vessel design and pressure piping design.  Together, or by themselves, these will represent a pressure system. 


In the determination of which ASME code to apply, the Design Authority shall apply the exclusions identified in ASME B31 Pressure Piping and ASME BPV Code Section VIII, Rules for Construction of Pressure Vessels.  Exclusion under one of these codes does not provide exclusion under the other.


Piping systems that can be excluded from the application of ASME B31 include:  [ASME B31.3, ¶300.1.3]


·         piping systems designed for internal gage pressures at or above zero but less than 15 psi, provided the fluid handled is nonflammable, nontoxic, and not damaging to human tissue as defined in ASME B31.3 Para. 300.2 and its design temperature is between -20°F through 366°F

·         tubes, tube headers, crossovers, and manifolds of fired heaters, which are internal to the heater enclosure


Pressure vessels that can be excluded from the application of ASME BPV Code Section VIII include: [ASME BPV Sec. VIII, ¶U-1(c)(2)]

·         pressure containers which are integral parts or components of rotating or reciprocating mechanical devices

·         a vessel for containing water under pressure including those containing air the compression of which serves only as a cushion, when none of the following limitations are exceeded:

o   a design pressure of 300 psi

o   a design temperature of 210°F

·         a hot water supply storage tank heated by steam or any other indirect means when none of the following limitations is exceeded:

o   a heat input of 200,000 Btu/hr

o   a water temperature of 210°F

o   a nominal water containing capacity of 120 gallons

·         vessels having an internal or external operating pressure not exceeding 15 psi with no limitation on size

·         vessels having an inside diameter, width, height, or cross section diagonal not exceeding 6 inches, with no limitation on length of vessel or pressure


3.0            Responsibilities


3.1              Design Authority

The Design Authority is responsible for interpretation and application of the engineering requirements set forth in the ASME Codes deemed necessary for the safe design and construction of pressure systems.


The Design Authority is responsible for identifying the design parameters for a pressure system and verifying that design output is documented and accurately reflects the design basis.  The Design Authority is responsible for design control and ultimate technical adequacy of the design process.  The Design Authority may delegate design work but not its responsibilities.  These responsibilities are applicable whether the process is conducted fully in-house, partially contracted to outside organizations or fully contracted to outside organizations.


4.0            Process Steps or Expectations


In applying ASME Codes to pressure systems, it is important to note that the codes (ASME B31.3, Process Piping and ASME Boiler and Pressure Vessel (BPV) Section VIII, Rules for Construction of Pressure Vessels) are not design handbooks.  The ASME Codes are to be used as a guide to the analyses that should be performed and do not eliminate the need for competent engineering judgment.  The ASME Codes set forth engineering requirements deemed necessary for safe design and construction of pressure systems.


To the greatest possible extent, code requirements for design are stated in terms of basic design principles and formulas.  These are supplemented, as necessary, with specific requirements to assure uniform application of principles and to guide selection and application of pressure system elements.


4.1              Design of Pressure Piping

ASME B31.3 Process Piping, a subset of the B31 Pressure Piping Code, should be considered first by the Design Authority.  This code will provide guidance for all piping typically installed to support Jefferson Lab’s mission.  The Design Authority may, however, choose any of the other ASME B31 piping codes that may be more appropriate for a particular design.


The Design Authority should understand that B31.3 originated from the need to guide piping designs in the petroleum refining and chemical industry at design temperatures above those found at Jefferson Lab.  Designs meeting this code will result in a 3:1 safety factor with an in-service life of 20-30 years and includes 7000 thermal cycles.


Cryogenic piping was added to the B31.3 code around 1983 but, as yet B31.3 has not fully addressed the superconductivity temperature ranges typical at Jefferson Lab.


This code allows the Design Authority considerable latitude, with the owner’s consent, to use materials and fittings that the code has not previously considered.  B31.3 does not prohibit the use of materials that are not included in the tables (Appendix A Table A-1) nor does it prohibit the use of listed materials outside of the temperature ranges listed.  The Design Authority may also use fittings that are not designed and fabricated in accordance with standards for piping components listed in Table 326.1.


Piping designs that can be accomplished using piping components listed and rated through Table 326.1 standards relieves the Design Authority from the task of determining the component pressure design adequacy.  The Design Authority is required by B31.3 to qualify any materials or fittings selected for a piping design that have not been previously considered by the code using the rules presented in ¶304.  If, because of special geometry or operating conditions etc., a design element cannot be qualified by these rules, the Design Authority is required to provide a level of safety greater than or equal to the level of protection provided by the code.  These Non-Code Qualified Design Elements must be Peer Reviewed.


The following are suggested tasks and sequence for performing design and analyses of pressure piping or components.  Parenthetical references refer to ASME B31.3.


4.1.1        Identify operating conditions such as design pressure (¶301.2) and design temperature.  (¶301.3)  Identify fluid service, pressure and temperature extremes.  (Chapter II, Part 1)

4.1.2        Use the design temperature and design pressure for the following purposes:

·         Determine the wall thickness of the selected pipe OD and pipe material (¶304.1.2)

·         Determine the pressure rating of the piping components (¶303)

·         Determine the leak test pressure (¶345)

·         Determine the set pressure for pressure relieving devices (¶322.6.3)

4.1.3        Identify potential material candidates.  (Chapter II, Part 3 and Chapter III)

4.1.4        Review ASME 16.5 Pipe Flanges and Flanged Fittings pressure and temperature extremes to determine American National Standards Institute (ANSI) Class valves and flanges.

4.1.5        Determine if special design or fabrication requirements are necessary, i.e. B31.3 Appendix M Special Fluid Service.

4.1.6        Perform basic calculations for pressure design and joint configurations and preliminary weld detail of piping components.  (Chapter II, Parts 2 and 4)

4.1.7        Review pipe size and valves for intended flow, pressure drop, heat transfer, cost and availability.  If design is unacceptable, go back to Task 4.1.4.

4.1.8        Identify other forces on piping such as ambient, dynamic, weight, thermal expansion and contraction, support movement, reduced ductility, cyclic and air condensation effects.  (Chapter II, Part 1)

4.1.9        Reanalyze piping and supports with all loads.  (Chapter II, Parts 1, 2 and 5, consider Code Cases.)  If design is unacceptable, go back to Task 4.1.4.

4.1.10    Finalize design details and materials including:

·         Pipe schedule specifications, fittings and valve specifications, flange configuration, gasketing and bolting

·         Support details such as weight, hangars, anchors, slides, etc.

·         Welding details such as joint classification, configuration, filler material, preheat requirements, post-weld examinations, and acceptance criteria.

·         Pressure testing requirements and examinations.


4.2              ASME B31.3 Guidance

ASME B31.3, Process Piping is the primary standard for Jefferson Lab piping system construction.  Other sections of B31 can be applied as appropriate based on the sound judgment of the Design Authority and proven practices in the field. 


ASME B31.3 was derived from ASME B31.1, Power Piping.  ASME B31.1 is written for a longer plant life and higher factor of safety; however, the corresponding paragraphs between the two codes cover the same subject matter.  Where a B31.3 paragraph may not be clear to the reader, the corresponding paragraph in B31.1 may offer additional insight.


While each section of the ASME B31 piping codes follows the same general setup of chapters described below, ASME B31.3 is used as the reference here.


4.2.1        Chapter I Scope and Definitions (¶300) includes general information on responsibilities, intent of the Code, Code requirements, and scope.  The chapter also includes specific nomenclature and definitions.

4.2.2        Chapter II Design (¶301 through 322) defines the minimum sections that are required in the engineering design process.  They are divided into six sub-sections:

Part 1 Conditions and Criteria

Part 2 Pressure Design of Piping Components

Part 3 Fluid Service Requirements for Piping Components

Part 4 Fluid Service Requirements for Piping Joints

Part 5 Flexibility and Support

Part 6 Systems


Part 1, Conditions and Criteria, (¶301 through 302) describes the design pressure, design temperatures and forces to consider in design.  Forces include ambient, dynamic, weight, thermal expansion and contraction, support movement, reduced ductility, cyclic and air condensation effects.  Part 1 provides pressure-temperature ratings, stress criteria, design allowances, and the minimum design values along with permissible variations.  Discussion is provided on how the allowables were generated and the application of allowables for different design conditions.


Part 2, Pressure Design of Piping Components, (¶303 through 304) describes the design of straight pipe, bends, branches, closures, flanges, and reducers along with other pressure components under pressure only.  Components manufactured in accordance with standards listed in Table 326.1 of B31.3 shall be considered suitable for use at the listed pressure-temperature ratings.  The rules provided in ¶304 are intended for pressure design of components not covered in Table 326.1.


Piping components that form part of the pressure boundary of a piping system, that are fabricated at Jefferson Lab require qualification to the requirements of the B31.3 Code.  The pressure design of these components is specified in ¶304.7.2.  B31.3 requires that calculations be performed to support the design of these components.  These calculations must be consistent with the design criteria of the B31.3 and must consider all applicable ambient and dynamic loads (¶301.4 through 301.11).  B31.3 also requires that the calculations be substantiated by one of the following methods:

·         Extensive successful service of the component under comparable conditions including loading, environment and fabrication of like materials,

·         Experimental stress analysis to code requirements,

·         Proof testing to code requirements, or

·         Detailed stress analysis to ASME BPV Code Section VIII, Div. 2.


The rules in B31.3 address the pressure design of components in ¶304.  The rules and equations in ¶304 can be applied to simple shapes, such as cylinders and other common piping geometry.  Equations and rules for additional shapes can be found in the ASME BPV Code Section VIII.  The design methodology in ASME BPV Code Section VIII is acceptable for unlisted component analysis in B31.3.  Additional methods used to evaluate unlisted components include the use of equations in “Roark’s Formulas for Stress and Strain.”  The use of all these equations requires that the components be idealized into bounding shapes for which the equation is valid.  Manufacturers generally use simple shapes in the design of components to minimize fabrication costs.  Design qualification of unlisted components can also be accomplished by comparison to listed components with established pressure/temperature ratings.  The comparison involves a review of the wall thicknesses and geometry to demonstrate that the unlisted component is bounded by a component with an established pressure rating.


Part 3, Fluid Service Requirements for Piping Components (¶305 through 309), discusses the types of components which can be used in the intended Fluid Service.


Part 4, Fluid Service Requirements for Piping Joints (¶310 through 318), discusses the acceptable types of and limitations of weld, braze, solder, threaded, or other joint configurations.


Part 5, Flexibility and Support (¶319 through 321.4), provides basic and specific requirements for flexibility analyses as well as providing the design requirements and analyses for piping supports.  Formal flexibility analysis is not necessary if the design temperature is at or below 150°F and the piping is laid out with inherent flexibility or the design temperature is at or below 250°F and the piping is analyzed for flexibility using simplified methods of calculation.  Design of pipe supports are addressed in Standards such as Manufacturers Standardization Society of the Valve and Fittings Industry MSS-SP-58.  Allowable stress levels for supports are provided in the American Institute of Steel Construction (AISC) Manual of Steel Construction and the AISC Standard N690.


Part 6, Systems (¶322), defines requirements for instrument piping and pressure relieving devices.


4.2.3        Chapter III Materials (¶323 through 325) describes where to find materials, how they are specified, and their limitations.  Chapter III also describes how the materials are to be marked.


Typically, unlisted components are fabricated from B31.3 listed materials.  When the materials are not listed by the ASME code, the material must be qualified in accordance with the requirements of the ASME Code.  Reviewing the material of an unlisted component is done to ensure a specified minimum allowable stress at the design temperature.  The sources for allowable stress values include the ASME B31 Codes of Pressure Piping and the ASME BPV Code Section II.  BPV Code Cases should also be reviewed for allowable stresses for specific materials.  The material should also be reviewed for susceptibility to degradation mechanisms associated with the service conditions, including a review of brittle fracture.


4.2.4        Chapter IV Standards for Piping Components (¶326) describes where to find piping dimensional requirements.


4.2.5        Chapter V Fabrication, Assembly, and Erection (¶327 through 335) describes how to create joints, form, or bend materials for system fabrication.  Chapter V describes how to qualify the joint being manufactured and how to qualify personnel to perform joint fabrication (refers to ASME Section IX).  Chapter V describes joint preparation, pre-heat requirements, filler material to use, performance of the weld detail, post heat treatment, and joint repair.


The Jefferson Lab Welding and Brazing Program contained in ES&H Manual Welding and Brazing Program Supplement

 provides guidance for all welding and brazing operations.


4.2.6        Chapter VI Inspection, Examination, and Testing (¶340 through 346) explains responsibilities for inspection to B31.3 requirements.  Chapter VI addresses the non-destructive examination (NDE) required for a particular service, qualification of the person performing the NDE, and the acceptance criteria for the NDE.  Chapter VI describes the minimum pressure testing required and how to determine the testing requirements.


4.3              Design of Pressure Vessels

The Boiler and Pressure Vessel (BPV) Code of the American Society of Mechanical Engineers (ASME) serves as the standard for pressure vessel construction at Jefferson Lab.


BPV Code Section VIII titled Rules for Construction of Pressure Vessels consists of three Divisions:

·         Division 1 contains mandatory requirements, specific prohibitions, and nonmandatory guidance for pressure vessel materials, design, fabrication, examination, inspection, testing, certification, and pressure relief.  This Division requires that manufacturers of any vessel or part to be marked with the Code Symbol must comply with all of the applicable requirements of the Division (¶U-2(b)(1)).

·         Division 2 titled Alternative Rules covers vessels to be installed at a fixed location for a specific service where operation and maintenance control is retained during the useful life of the vessel by the user who prepares or causes to be prepared the Design Specifications, (¶AG-100(b)(1)).  Division 2 also provides alternative rules for cases where application of Division 1 rules for pressure systems are difficult to apply (i.e., combined mechanical loads use Division 2, Part 4 and Part 5).

·         Division 3 titled Alternative Rules for Construction of High Pressure Vessels.  (not expected to be used at Jefferson Lab)


In cases where the BPV Code cannot be met, such as for special materials not previously considered by the BPV Code or unusual vessel structures, the Design Authority must exercise substantial professional judgment to produce a design that implements measures to provide equivalent protection and ensure a level of safety greater than or equal to the level of protection afforded by the BPV.  These Non-Code Qualified Design Elements must be Peer Reviewed.


The BPV Code is usable for vacuum vessel design and it is Jefferson Lab’s policy to apply it where practical to vacuum vessel design.  If a vacuum vessel can be pressurized beyond 15 psi under regular or failure conditions, the Code must be applied to its design.


In order to ensure that design and use of pressure vessels at Jefferson Lab meet the intent of the ASME Code, procedural and documentation requirements must be met.  See ES&H Manual Chapter 6151 Appendix T1 Pressure System Project Implementation and Documentation Requirements  for details.


4.4              Pressure Vessel Considerations


4.4.1        Thin windows in pressure vessels call for additional controls to prevent exposure to hazards associated with failure of the component.  Controls that must be considered include:

4.4.2        Pressure Vessel Marking (¶UG-115 through UG-120)

Each pressure vessel shall be marked with the following:

·         maximum allowable working pressure (MAWP) at specified temperature (there may be more than one),

·         minimum design metal temperature at specified MAWP,

·         type of construction,

·         year built, and

·         Jefferson Lab Pressure System Identification Number.


Pressure vessels that are stamped shall also be marked with the official Code U symbol, name of the manufacturer preceded by the words “certified by” and the Manufacturer’s serial number.



·         For vessels having more than one independent pressure chamber the markings may be made in one location on the vessel, or each chamber may be separately marked.

·         Specifications must be in US customary units.  Metric units may be shown in parenthesis.

·         For internal vessels, markings are not required.

·         For vessels whose failure poses zero risk to personnel or property, markings are not required.


4.5              Pressure Relief (¶UG-125 through UG-137 for BPV Code and ¶322 for B31.3 Code)

Relief devices and their discharge piping must be positioned so that they do not discharge at people, delicate apparatus, or in such a manner as to hinder escape.  The codes contain requirements for pressure relief and requirements for pressure relief device marking.  Commercially purchased pressure relief devices must be code certified.  When non-Code reliefs must be installed, the vessel is to be considered non-code and a Peer Review is required.


Refer to the ASME codes for specifics on:

·         Rupture disk devices, including instructions for deriving the burst pressure, test burst requirements, and instructions for determining the capacity rating

·         Pressure reliefs designed for liquid service

·         Installation and the location of the pressure relief valve, prohibition of stop valves between the vessel and the relief device

·         Requirements for vessels with single pressure relief device, multiple devices, and required tolerances

·         Venting requirements for lethal contents


4.6              Gages

·         Pressure gages must be calibrated before being put into service.

·         Gages must be visible at a safe distance from the system.

·         Use specific-use gages where required: e.g. oxygen, ammonia, acetylene and hydrogen.

·         Full scale reading of the gage must equal twice the operating pressure.

·         Gages should be of the full blow out type with integral sides and front.  Gages that do not have this type of construction must have a tested, approved gage safety shield installed, minimum thickness 3/8 inch polycarbonate.

·         Valves that can isolate gages must be clearly visible.

·         Protect gages that are subject to excessive pressure surges or cyclic pulses by installing a throttling device such as a pulsation dampener.


5.0            References


ASME Boiler and Pressure Vessel Code Section VIII – Rules for Construction of Pressure Vessels


ASME Boiler and Pressure Vessel Code Section II – Materials


ASME Boiler and Pressure Vessel Code Section IX –Welding and Brazing Qualifications


CASTI Guidebook to ASME B31.3 Process Piping (Fourth Edition): Glynn E. Woods; Roy B. Baguley, CASTI Publishing Inc. Edmonton, Alberta, Canada


Roark’s Formulas for Stress and Strain (Seventh Edition): Young, W.C.; Budynas, R.G. © 2002 McGraw-Hill



6.0            Revision Summary


Revision 3.2 – 05/17/13 – Added notice to reflect current laboratory operations.

Revision 3.1 – 04/14/11 – Updated links to ES&H Manual Welding and Brazing Supplement.









ESH&Q Division

Dave Kausch




This document is controlled as an on line file.  It may be printed but the print copy is not a controlled document.  It is the user’s responsibility to ensure that the document is the same revision as the current on line file.  This copy was printed on 5/17/2013.