DEP SPECIFICATION
Copyright Shell Group of Companies. No reproduction or networking permitted without license from Shell. Not for resale
EQUIPMENT CRITICALITY IN PRESSURE VESSEL DESIGN
DEP 31.22.00.30-Gen.
February 2017
ECCN EAR99
DESIGN AND ENGINEERING PRACTICE
DEM1
© 2017 Shell Group of companies
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PREFACE
DEP (Design and Engineering Practice) publications reflect the views, at the time of publication, of Shell Global Solutions
International B.V. (Shell GSI) and, in some cases, of other Shell Companies.
These views are based on the experience acquired during involvement with the design, construction, operation and
maintenance of processing units and facilities. Where deemed appropriate DEPs are based on, or reference international,
regional, national and industry standards.
The objective is to set the standard for good design and engineering practice to be applied by Shell companies in oil and
gas production, oil refining, gas handling, gasification, chemical processing, or any other such facility, and thereby to help
achieve maximum technical and economic benefit from standardization.
The information set forth in these publications is provided to Shell companies for their consideration and decision to
implement. This is of particular importance where DEPs may not cover every requirement or diversity of condition at each
locality. The system of DEPs is expected to be sufficiently flexible to allow individual Operating Units to adapt the
information set forth in DEPs to their own environment and requirements.
When Contractors or Manufacturers/Suppliers use DEPs, they shall be solely responsible for such use, including the
quality of their work and the attainment of the required design and engineering standards. In particular, for those
requirements not specifically covered, the Principal will typically expect them to follow those design and engineering
practices that will achieve at least the same level of integrity as reflected in the DEPs. If in doubt, the Contractor or
Manufacturer/Supplier shall, without detracting from his own responsibility, consult the Principal.
The right to obtain and to use DEPs is restricted, and is typically granted by Shell GSI (and in some cases by other Shell
Companies) under a Service Agreement or a License Agreement. This right is granted primarily to Shell companies and
other companies receiving technical advice and services from Shell GSI or another Shell Company. Consequently, three
categories of users of DEPs can be distinguished:
1)
Operating Units having a Service Agreement with Shell GSI or another Shell Company. The use of DEPs by these
Operating Units is subject in all respects to the terms and conditions of the relevant Service Agreement.
2)
Other parties who are authorised to use DEPs subject to appropriate contractual arrangements (whether as part of
a Service Agreement or otherwise).
3)
Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) or 2)
which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said
users comply with the relevant standards.
Subject to any particular terms and conditions as may be set forth in specific agreements with users, Shell GSI disclaims
any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person
whomsoever as a result of or in connection with the use, application or implementation of any DEP, combination of DEPs
or any part thereof, even if it is wholly or partly caused by negligence on the part of Shell GSI or other Shell Company. The
benefit of this disclaimer shall inure in all respects to Shell GSI and/or any Shell Company, or companies affiliated to these
companies, that may issue DEPs or advise or require the use of DEPs.
Without prejudice to any specific terms in respect of confidentiality under relevant contractual arrangements, DEPs shall
not, without the prior written consent of Shell GSI, be disclosed by users to any company or person whomsoever and the
DEPs shall be used exclusively for the purpose for which they have been provided to the user. They shall be returned
after use, including any copies which shall only be made by users with the express prior written consent of Shell GSI. The
copyright of DEPs vests in Shell Group of companies. Users shall arrange for DEPs to be held in safe custody and Shell
GSI may at any time require information satisfactory to them in order to ascertain how users implement this requirement.
All administrative queries should be directed to the DEP Administrator in Shell GSI.
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Page 3
TABLE OF CONTENTS
1.
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
INTRODUCTION ........................................................................................................ 4
SCOPE ....................................................................................................................... 4
DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS ......... 4
DEFINITIONS ............................................................................................................. 5
CROSS-REFERENCES ............................................................................................. 6
SUMMARY OF MAIN CHANGES............................................................................... 6
COMMENTS ON THIS DEP ....................................................................................... 6
DUAL UNITS............................................................................................................... 6
NON NORMATIVE TEXT (COMMENTARY) .............................................................. 6
2.
2.1
2.2
2.3
GENERAL .................................................................................................................. 7
BACKGROUND AND OBJECTIVES .......................................................................... 7
DESIGN CLASS VERSUS SHELL VESSEL CATEGORY ........................................ 7
WORK PROCESS ...................................................................................................... 8
3.
3.1
3.2
3.3
3.4
CRITICALITY TABLES .............................................................................................. 9
INSTRUCTIONS FOR USE OF TABLES ................................................................... 9
MODIFICATION OF VESSEL CATEGORY ............................................................. 10
CRITICALITY TABLES ............................................................................................. 10
TABLE CRITERIA ..................................................................................................... 11
4.
REFERENCES ......................................................................................................... 17
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1.
INTRODUCTION
1.1
SCOPE
This DEP specifies requirements and give recommendations for defining equipment
criticality categories that are to be applied during equipment design and fabrication.
The categorization is based on the criticality of the equipment as assessed against the
following:
•
Operational risk-loss of containment and loss of production risks.
•
Design complexity-high operating temperatures and pressures, potentially high
corrosion rates, hydrogen service.
•
Fabrication complexity-complex materials of fabrication, heavy wall, complex
internals, postweld heat treatment (PWHT) requirements, clad vessels.
DEP 31.22.00.31-Gen. specifies design, fabrication, inspection, and testing requirements
for pressure vessels based on the vessel criticality category resulting from this DEP.
This DEP is applicable to heat exchangers, unless the heat exchanger is supplied as part of
an original equipment manufacturer (OEM) equipment package (e.g., lube oil heat
exchangers on rotating equipment skid packages).
This DEP is not applicable to atmospheric pressure storage tanks.
This DEP contains mandatory requirements to mitigate process safety risks in accordance
with Design Engineering Manual (DEM) 1-Application of Technical Standards.
This is a revision of the DEP of the same number dated February 2014; see (1.5) regarding
the changes.
1.2
DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS
Unless otherwise authorised by Shell GSI, the distribution of this DEP is confined to Shell
companies and, where necessary, to Contractors and Manufacturers/Suppliers nominated
by them. Any authorised access to DEPs does not for that reason constitute an
authorization to any documents, data or information to which the DEPs may refer.
This DEP is intended for use in facilities related to oil and gas production, gas handling, oil
refining, chemical processing, gasification, distribution and supply/marketing. This DEP
may also be applied in other similar facilities.
When DEPs are applied, a Management of Change (MOC) process shall be implemented;
this is of particular importance when existing facilities are to be modified.
If national and/or local regulations exist in which some of the requirements could be more
stringent than in this DEP, the Contractor shall determine by careful scrutiny which of the
requirements are the more stringent and which combination of requirements will be
acceptable with regards to the safety, environmental, economic and legal aspects. In all
cases, the Contractor shall inform the Principal of any deviation from the requirements of
this DEP which is considered to be necessary in order to comply with national and/or local
regulations. The Principal may then negotiate with the Authorities concerned, the objective
being to obtain agreement to follow this DEP as closely as possible.
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1.3
DEFINITIONS
1.3.1
General definitions
The Contractor is the party that carries out all or part of the design, engineering,
procurement, construction, commissioning or management of a project or operation of a
facility. The Principal may undertake all or part of the duties of the Contractor.
The Manufacturer/Supplier is the party that manufactures or supplies equipment and
services to perform the duties specified by the Contractor.
The Principal is the party that initiates the project and ultimately pays for it. The Principal
may also include an agent or consultant authorised to act for, and on behalf of, the
Principal.
The word shall indicates a requirement.
The capitalised term SHALL [PS] indicates a process safety requirement.
The word should indicates a recommendation.
The word may indicates a permitted option.
1.3.2
Specific definitions
Term
Definition
Cyclic Service
Pressure equipment subject to frequent fluctuations in pressure and/or
temperature, mechanical vibration or external loading that may lead to
damage from fatigue. Severe cyclic service refers to equipment that
requires a fatigue analysis as part of the detailed design assessment.
Hydrogen
Service (H2
Service)
Service in which the hydrogen partial pressure is greater than 700 kPa
absolute (100 psia) at any temperature. See also API RP 941, Figure 1.
Pressure
Vessel
Vessel used for containing, storing, distributing, processing or otherwise
handling an expansible fluid under pressure. This excludes rotating or
reciprocating equipment, fired heaters, and piping.
PWHT
Post weld heat treatment; aimed at reducing hardness and residual
stresses in welds.
Very Toxic
(Substances)
A substance that is very hazardous for the environment or human
health. For this DEP, the term “very toxic” includes Very toxic-acute,
chronic, and environment categories unless otherwise specified.
Refer to DEP 01.00.01.30-Gen. Part III for further information regarding
toxic fluid classification
1.3.3
Abbreviations
Term
Definition
CBL
Consequential Business Loss
OEM
Original Equipment Manufacturer
PWHT
Post Weld Heat Treatment
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1.4
DEP 31.22.00.30-Gen.
February 2017
Page 6
CROSS-REFERENCES
Where cross-references to other parts of this DEP are made, the referenced section or
clause number is shown in brackets ( ). Other documents referenced by this DEP are listed
in (4).
1.5
SUMMARY OF MAIN CHANGES
This DEP is a minor revision of the DEP of the same number dated February 2014. The
following are the main, non-editorial changes.
1.6
Section/Clause
Change
Entire DEP
Restructured and clarified requirements, enforced use of
shall/should/may for normative statements.
3.3, Item 1
Clarified the content in the table associated with the DEM1
requirement further.
COMMENTS ON THIS DEP
Comments on this DEP may be submitted to the Administrator using one of the following
options:
Shell DEPs Online
(Users with access to
Shell DEPs Online)
Enter the Shell DEPs Online system at
https://www.shelldeps.com
Select a DEP and then go to the details screen for
that DEP.
Click on the “Give feedback” link, fill in the online
form and submit.
DEP Feedback System
(Users with access to
Shell Wide Web)
DEP Standard Form
(other users)
Enter comments directly in the DEP Feedback
System which is accessible from the Technical
Standards Portal http://sww.shell.com/standards.
Select “Submit DEP Feedback”, fill in the online form
and submit.
Use DEP Standard Form 00.00.05.80-Gen. to record
feedback and email the form to the Administrator at
standards@shell.com.
Feedback that has been registered in the DEP Feedback System by using one of the above
options will be reviewed by the DEP Custodian for potential improvements to the DEP.
1.7
DUAL UNITS
This DEP contains both the International System (SI) units, as well as the corresponding
US Customary (USC) units, which are given following the SI units in brackets. When
agreed by the Principal, the indicated USC values/units may be used.
1.8
NON NORMATIVE TEXT (COMMENTARY)
Text shown in italic style in this DEP indicates text that is non-normative and is provided as
explanation or background information only.
Non-normative text is normally indented slightly to the right of the relevant DEP clause.
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2.
GENERAL
2.1
BACKGROUND AND OBJECTIVES
It is recognized that all pressure vessels do not carry the same level of risk when placed
into operation and, as a result, do not need to be designed and fabricated in the same
manner. With limited available resources, risk reduction efforts can be focused on the
higher risk (higher criticality) vessels during design and fabrication by applying the vessel
criticality concept. When applied properly, this will result in a reduction of the overall risk
to personnel and equipment integrity.
It is the intent of this DEP to identify the higher risk vessels and, together with
DEP 31.22.00.31-Gen., to specify requirements for vessel design and fabrication such
that the more stringent requirements are placed on the higher risk vessels.
The Shell vessel categories as applied in this DEP are shown in Table 2.1.
Table 2.1
Shell vessel categories
Category
Description
Category 1
Highest category, associated with potentially high operational risk.
Warrants the most stringent design and fabrication requirements.
Category 2
Medium category, associated with potentially moderate
operational risk. Warrants some special design and fabrication
requirements.
Category 3
Lowest category, associated with reduced operational risk.
Standard design and fabrication requirements are sufficient.
It is intended that Category 3 vessels have the lowest cost of construction, and that the
vessels that are considered Category 2 and Category 1 warrant extra design, fabrication,
and surveillance requirements.
The vessel categories as applied in this DEP are specific to this DEP and are not the
same as the Category definition that may be used in other construction codes such as
PD-5500.
2.2
DESIGN CLASS VERSUS SHELL VESSEL CATEGORY
The vessel categories as defined in this DEP are different than the design class as
specified in DEP 00.00.07.89-Gen. Design class determines an overall project
philosophy for items such as plant layout, equipment capacities, equipment sizing or
equipment sparing, and is evaluated early in the project development process. The Shell
vessel categories in this DEP are used to provide a qualitative comparison of the relative
hazards affecting the safety of particular pieces of equipment, as they relate to potential
loss of containment only. These two classification systems are developed and used at
different stages of a project for different purposes and are not linked.
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2.3
WORK PROCESS
2.3.1
General
1.
An equipment criticality category shall be determined for each pressure vessel
(see 1.3.2) in accordance with this DEP.
The activity of determining the equipment criticality categories will normally take
place during the define phase of a project to ensure that the required design
elements are included in the vessel specification and the bidders list includes
qualified manufacturers.
The equipment criticality category is used in the application of
DEP 31.22.00.31-Gen. during design development, prior to procurement.
2.
The pressure vessel criticality category shall be determined by the project design
team.
The project design team includes discipline representatives, where appropriate, to
evaluate each of the criteria in the critically tables.
2.3.2
Risk register and mitigation measures
1.
For Category 1 and Category 2 vessels, the project team shall develop a risk register
for all Category 1 and Category 2 threats.
2.
Each identified threat shall have a clear mitigation that provides effective barriers to
mitigate the risk.
Table 2.2 is an example of a risk register.
Table 2.2
Risk
Description
1
“Very toxic” (1.3.2) material
2
Cyclic pressure
3
High stored energy
4
Internal overlay
5
Duplex SS tubes
6
Low temperature service
3.
Example of a risk register
Mitigation
For Category 1 and Category 2 vessels, the risk register shall accompany the
pressure vessel data sheet.
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3.
CRITICALITY TABLES
3.1
INSTRUCTIONS FOR USE OF TABLES
Three tables are provided in (3.3) to evaluate the criticality of vessels, and to determine
the vessel category. These three tables are:
Table 3.1
Criticality tables
Table
Description
Table 3.2
Operational risk
Loss of containment risk. This table does not currently
address proximity to personnel or public.
Table 3.3
Design complexity
High operating temperatures and pressures, potentially high
corrosion rates, cyclic service, design methodology, complex
internals, vessels in hydrogen service
Table 3.4
Fabrication complexity
Complex materials of fabrication, heavy wall, PWHT
requirements, clad vessels
For each of these tables, the threats to be assessed are listed in separate columns to
the right of the first column.
1.
For every vessel, the design team shall evaluate each column in (Table 3.2),
(Table 3.3), and (Table 3.4).
2.
Unless modified in (3.2), the highest category from each of the columns shall become
the category for that table.
3.
Unless modified in (3.2), the highest category from each of the three tables shall
become the overall vessel criticality category.
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3.2
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MODIFICATION OF VESSEL CATEGORY
1.
Where information is available at the time of the criticality assessment, asset cost and
consequential business loss (CBL) may be considered in determining the final vessel
category.
Asset cost is the cost of the specific pressure vessel.
Consequential business loss (CBL) is the indirect loss due to asset damage,
environmental impact or impact to company reputation. It includes the financial
impact of items such as lost production (expressed as profit margin), process unit
downtime, product quality costs, cost of environmental clean-up, cost of
recovery/disposal of waste and cost of reprocessing off-spec material. CBL is
influenced by the operational flexibility around the piece of equipment considered. If
the equipment can be bypassed or the unit operated without it, perhaps at reduced
rate, the CBL will be reduced. If the piece of equipment is required to maintain
operation of the unit, then the CBL will likely be higher.
The additional design, fabrication and surveillance requirements associated with a
higher vessel category may be small compared to the effect of increased reliability.
3.3
2.
A high combined asset cost and CBL (>$10 million) may warrant an increase in the
vessel category by one level.
3.
If only one column in one table is setting the highest vessel category, and the
combined asset cost and the consequential business loss (CBL) is low (<$1 million),
then the vessel category may be reduced by one level.
4.
In some cases, increasing the vessel category may be warranted based on specific
requirements and constraints on the vessel that cannot be foreseen in this DEP.
5.
Any modification of the vessel category subsequent to (3.1) shall be subject to
approval by the Principal with the risks documented as acceptable.
CRITICALITY TABLES
1.
The criticality of each pressure vessel SHALL [PS] be determined in accordance with
Tables 3.2, 3.3, and 3.4, following the instructions in (3.1) and (3.2).
Table 3.2
Operational
Risk Category
Explosive/fire potential
1
Release >10 tonnes (11
tons) of flammable fluid
2
Release >2 tonnes (2.2
tons) of flammable fluid
3
Release < 2 tonnes (2.2
tons) of flammable fluid or
release of non-flammable
fluid
Hydrogen
Service
Operational risk
Toxicity
Stored
energy
Potential for rapid
corrosion or cracking
>1000 MJ
(737 MM ft-lb)
Yes
“Very toxic”
(1.3.2)
<1000 MJ
(737 MM ft-lb)
Potential
“Not very toxic”,
per Part III of DEP
01.00.01.30-Gen.
<300 MJ
(221 MM ft-lb)
None
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Page 11
Table 3.3
Design complexity
Lower Design
Temperature
Cyclic
service
Design
Complexity
Category
Design
Pressure
based on
flange class
Design
Temperature
Design
methodology
1
Class 1500
and higher
>510 °C (950
°F)
2
Class 600
and 900
>440 °C (824
°F) or when a
creep analysis
is required
<-50 °C
(-58 °F)
Yes
Stress
analysis
Proprietar Supplemental or
alternate design
y design
compone analysis
nt
3
Class 150
and 300
<440 °C (824
°F)
>-50 °C
(-58 °F)
No
Vessel design
software/desig
n by rule
No
specialty
design
elements
Specialty Heat
design
Exchanger
Specifics
Prototype
design
Severe
cyclic
service
Table 3.4
Fabrication complexity
Exchangers of
standard TEMA
types
Fabrication
Complexity
Category
Wall
Thickness
Vessel
Outside
Diameter
(m)
Base
Material
Overlay/
Cladding/
internal
coating
PWHT
1
>100 mm
(4 in)
>7 m
(23 feet)
Difficult
materials
requiring
specialized
fabrication
procedures
Other overlay
materials
Stainless
steel or
Nickel
alloys with
PWHT
2
>50 mm
(2 in)
>5 m
(16.4 feet)
The balance
of fabrication
materials
austenitic
stainless
steel, internal
coatings
Local
PWHT
Complex
internals
3
<50 mm
(2 in)
<5 m
(16.4 feet)
CS <510 MPa
(74 ksi)
No overlay.
No coating or
non-critical
coating
No PWHT
or
complete
PWHT
Simple
Standard
trays,
fabrication
packing,
processes
distributors
304/304L or
316/316L SS
Internals
Proprietary
closures and
TEMA Type ‘D’
front channel
Heat exchanger
Specifics
Refractory, external
jacketed or internal
bundle shrouds
Non-standard
fabrication
processes
For Tables 3.2, 3.3, and 3.4, a blank cell in a column means there is no driver
for that column criterion to specify the increased vessel category. For each
column choose a non-blank cell.
The items in Table 3.3 and Table 3.4 that are specific to heat exchangers are
intended to be in addition to, not in-lieu of, the other columns in the table.
3.4
TABLE CRITERIA
3.4.1
Explosive/fire potential
1.
Flammability should be determined based on the fluid service and the normal
operating temperature of the vessel.
2.
If release of the fluid at the operating temperature of the vessel is likely to create a
flammable mixture, or if the flash point of the fluid is less than ambient temperature,
then the fluid should be considered flammable.
The explosion or fire potential is the risk of explosion or fire based on the fluid mass
contained in the vessel and the flammability of the fluid. In Table 3.2, the “release”
mass is based on volume of the total vessel contents.
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3.4.2
Toxicity
1.
3.4.3
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Toxicity of the process fluid shall be determined from DEP 01.00.01.30-Gen. Part III.
Stored energy
1.
Equation 3.4 shall be used to estimate the stored energy:
E = [1/(k − 1)]* Pd* V *[1 − (Pa/Pd)
[(k − 1)/k]
]
Equation 3.4
where,
E
=
stored energy, MJ (ft-lb)
K
=
ratio of specific heat for the contained fluid
Pd
=
Design pressure of the vessel, MPa (psfa)
Pa
=
atmospheric pressure, MPa (psfa)
V
=
volume of the vessel, m (ft )
3
3
The stored energy assessment is for vessels containing gas or vapour.
2.
The stored energy of flashing liquid shall be determined if both of the following are
true:
a.
the stored energy for the vapour portion is above 300 MJ (221 MM ft-lb);
b.
the liquid will expand to vapour at the operating temperature and atmospheric
pressure.
Because of the complexity of a flashing liquid scenario, a single equation cannot be
provided for this energy calculation. The methodology used to determine the stored
energy of flashing liquid will be case specific.
3.4.4
Potential for rapid corrosion or cracking
1.
3.4.5
Based on the sensitivity regarding material performance in the specified process
service conditions, as compared to predicted upset conditions, the potential for rapid
corrosion or cracking shall be determined as follows:
a.
if there is potential for rapid unmitigated corrosion to occur in the specified vessel
material or welds; or
b.
if there is potential for stress corrosion cracking (SCC) of the specified vessel
material or welds.
Design pressure
1.
The design pressure for the vessel, as listed on the vessel data sheet, shall be used in
determining the vessel category.
Increased design pressure increases the complexity of the design and fabrication
requirements of the vessel and increases the consequence of failure.
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3.4.6
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Design temperature
1.
The design temperature for the vessel, as listed on the vessel data sheet, shall be
used in determining the vessel category.
Elevated design temperature increases (1) complexity of the design, including
decreased allowable stresses, (2) thermal expansion stresses, and (3) insulation
requirements.
Elevated design temperature may require use of controlled heat-up or cool-down
procedures to manage the thermal stresses in the equipment.
3.4.7
Lower design temperature
1.
3.4.8
Cyclic service
1.
3.4.9
3.4.10
3.4.11
Part II, Section 2.1.6 of DEP 01.00.01.30-Gen shall be used to determine the Lower
Design Temperature (LDT).
Transient or cyclic fluctuations in pressure, temperature or other loads shall be clearly
identified on the vessel data sheet.
Design methodology
1.
If the vessel is designed using manual calculations or commercially available pressure
vessel design software using design by rule methods, the vessel shall be a minimum
of Category 3.
2.
If the vessel has complex geometrical details and/or loading conditions (for example,
thermal transient loads, or dynamic loads) necessitating use of finite element stress
analysis, the vessel shall be a minimum of Category 2.
3.
Vessels designed per the ASME Section VIII, Division 2 code shall be a minimum of
Category 2.
Specialty design
1.
If the vessel uses proprietary components or specialty closures in the pressure
retaining envelope, the vessel shall be a minimum of Category 2.
2.
If the vessel pressure retaining envelope is of a unique and prototype design, the
vessel shall be a Category 1.
Heat exchanger design specifics
1.
Design complexity Category 3 heat exchangers shall include:
a.
Standard TEMA type exchangers with the exception of the ‘D’ type front channel
for which the primary tube bundle and pressure retaining envelope design can be
produced through the use of commercially available standard pressure
vessel/heat exchanger software packages. These include fixed tubesheet heat
exchangers with thick walled (flanged and flued) expansion joints.
b.
Hairpin and other types of vendor-proprietary heat exchangers utilizing Supplier
standard designs and/or closures that are fully described in their published
catalogues.
c.
Standard air cooled heat exchangers.
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2.
DEP 31.22.00.30-Gen.
February 2017
Page 14
Design complexity Category 2 heat exchangers shall include:
a.
3.
3.4.12
Heat exchangers that require supplemental calculation or analysis for the design
of the tube bundle or pressure retaining envelope. Examples include:
i.
Single-pass floating head heat exchangers with internal tailpipe expansion
joints.
ii.
Exchangers incorporating double tubesheet designs.
iii.
Fixed tubesheet heat exchangers with thin walled (bellows type) expansion
joints.
iv.
Exchangers incorporating inlet and/or outlet distribution belts.
b.
Exchangers incorporating girth flange and/or tubesheets that require additional
analysis due to radial or through-wall operating temperature differences that
exceed 140 °C (250 °F), including those flange designs utilizing spring washers,
lip seals and/or diaphragms.
c.
Exchangers incorporating girth flange and/or tubesheets and that will be
subjected to rapid transient heating or cooling events.
d.
Air cooled heat exchangers that require split header box designs, internal or
external warm air winterization schemes, ‘A-frame’ bundles with or without noncondensable vent cooling sections, or ambient air misting systems.
e.
Supplier proprietary heat exchangers for which the pressure retaining envelope
design is determined through the use of proof-testing or non standard pressure
vessel code calculations including finite element analysis or similar methods (e.g.,
printed circuit heat exchangers or brazed aluminium heat exchangers).
Design complexity Category 1 heat exchangers shall include:
a.
TEMA ‘D’ type front channel and non-standard TEMA exchangers.
b.
Exchangers using proprietary or non-standard enclosures (e.g., Breechlock,
Hemilock, or Taperlock).
c.
Flexible tubesheet exchangers.
Wall thickness
1.
The maximum nominal wall thickness of the primary pressure envelope, excluding
overlay thickness, shall be used as the basis for the wall thickness assessment.
The thickness of integrally reinforced nozzles need not be considered when
determining the maximum wall thickness.
3.4.13
Outside diameter
1.
3.4.14
The largest outside diameter of the vessel shall be used to determine the category.
Base material
1.
The primary material of construction shall be used to determine the category:
a.
Carbon steel and 304/316 series stainless steels are considered Category 3.
b.
Unique or difficult to fabricate materials such as vanadium modified Cr-Mo
materials, 9% Ni, P91 material, quenched and tempered material, titanium or
other non-ferrous materials are considered Category 1.
c.
The balance of material types or grades not listed in a or b above are considered
Category 2.
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ECCN EAR99
3.4.15
3.4.16
3.4.17
DEP 31.22.00.30-Gen.
February 2017
Page 15
Overlay/cladding
1.
Vessels that utilize austenitic stainless steel clad material or weld overlay shall be a
minimum of Category 2.
2.
Weld overlays with materials other than austenitic stainless steel shall be Category 1.
3.
Consideration should be given to increasing the vessel Category to 2 if an internal
coating is critical to the safe operation of the vessel.
PWHT
1.
Vessels that do not require PWHT, or that can be heat treated as a complete vessel in
a furnace, shall be Category 3.
2.
Vessels requiring localized PWHT shall be a minimum of Category 2.
3.
Stainless steel or nickel alloy vessels requiring PWHT shall be Category 1.
Internals
1.
If the vessel internals are complicated or of a specialty nature beyond the normal
distillation trays, packing, distributors and baffles, then the vessel is considered to be a
of minimum of Category 2.
Examples of increased complexity internals are internal bellows, cyclones, internal
pressure head (vessels with multiple pressure chambers), and high loads from
internals transfered to the pressure retaining envelope.
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3.4.18
DEP 31.22.00.30-Gen.
February 2017
Page 16
Heat exchanger fabrication specifics
•
•
•
Fabrication complexity Category 3 heat exchangers are those that require only
standard heat exchanger fabrication processes. Standard processes include the
following:
o
Roller expanded and/or seal or strength welded tube-to-tubesheet joints.
o
Bare or extended surface tubing.
o
Impingement plates or rods.
o
Hairpin and other types of Supplier-proprietary heat exchangers, unless there
are fabrication or testing processes as noted for fabrication complexity
Category 2 heat exchangers.
Fabrication complexity Category 2 heat exchangers are those that require one or
more non-standard heat exchanger fabrication processes and/or test. Non-standard
processes include the following:
o
Specialty tube end joining procedures (e.g., hydraulic or explosive expanding,
internal bore welding, etc.) or designs that require local post weld heat treatment
of the tube joint.
o
Tube bundles not designed for independent tube and shell side pressurization.
o
Welded-in or removable shell side longitudinal baffles.
o
Channels incorporating internally bolted pass partition boxes.
o
Internal bellows type expansion joints.
o
Specialty internals such as perforated distribution plates, U-bend intermediate
anti-vibration supports, and vapour/liquid distribution or disengagement devices
(e.g., spider pipes, demisting pads, chevron separators, etc.).
o
U-bends in materials that are subject to work hardening and may require special
bending and/or heat treatment procedures.
o
Special tube internals (e.g., twisted tape inserts, fixed or moving wire and coil
type tube inserts, tube end distribution ferrules, etc.).
o
Specialty baffle or bundle designs (i.e., twisted tube bundles, rod baffles, helical
baffles, and EMbaffles, etc.).
o
Coatings such as epoxy coated channels/tubesheets, high-flux coated tubes for
boiling enhancement and tubes with anti-corrosion and/or anti-fouling specialty
coatings.
o
Supplier proprietary heat exchangers for which non-standard metal joining
fabrication techniques are used on the pressure retaining envelope, including
brazing, laser or plasma arc welding, fusion bonding, etc.
Fabrication complexity Category 1 heat exchangers are those that require complex
fabrication processes or tests. Complex processes include the following:
o
Internal refractory linings.
o
Exchangers with internal bundle shrouds.
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4.
DEP 31.22.00.30-Gen.
February 2017
Page 17
REFERENCES
In this DEP, reference is made to the following publications:
NOTES:
1. Unless specifically designated by date, the latest edition of each publication shall be used,
together with any amendments/supplements/revisions thereto.
2. The DEPs and most referenced external standards are available to Shell staff on the SWW (Shell
Wide Web) at http://sww.shell.com/standards/.
SHELL STANDARDS
DEP feedback form
DEP 00.00.05.80-Gen.
Design Classes – Pressure Vessels
DEP 00.00.07.89 (Std
Form)
Definition of temperature, pressure and toxicity levels
DEP 01.00.01.30-Gen.
Unfired pressure vessels
DEP 31.22.00.31-Gen.
Shell HSSE & SP Control Framework, Design Engineering Manual
(DEM) 1 – Application of Technical Standards
https://eu001-sp.shell.com/sites/AAAAA8432/CF/default.aspx
DEM1
AMERICAN STANDARDS
Steels for hydrogen service at elevated temperatures and pressures in
petroleum refineries and petrochemical plants
Standards of the Tubular Exchanger Manufacturers Association 9
edition
th
API RP 941
TEMA Standards
ASME boiler and pressure vessel code – Division 1 rules for
construction of pressure vessels
ASME Section VIII Division
1
Specification for unfired fusion welded pressure vessels (2009 edition)
PD 5500
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