ISO 13706:2005

Petroleum, petrochemical and natural gas industries - Air-cooled heat exchangers

ISO 13706:2005 gives requirements and recommendations for the design, materials, fabrication, inspection, testing and preparation for shipment of air-cooled heat exchangers for use in the petroleum and natural gas industries. ISO 13706:2005 is applicable to air-cooled heat exchangers with horizontal bundles, but the basic concepts can also be applied to other configurations.

Industries du pétrole, de la pétrochimie et du gaz naturel — Échangeurs de chaleur refroidis à l'air

General Information

• Status: Withdrawn
• Publication Date: 13-Oct-2005
• Withdrawal Date: 13-Oct-2005
• ICS: 27.060.30 - Boilers and heat exchangers
• ICS: 75.180.20 - Processing equipment
• Technical Committee: ISO/TC 67/SC 6 - Processing equipment and systems
• Drafting Committee: ISO/TC 67/SC 6/WG 8 - Process heat transfer equipment
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 21-Nov-2011
• Completion Date: 13-Dec-2025

Relations

• Consolidates: ISO/IEC 8482:1993 - Information technology - Telecommunications and information exchange between systems - Twisted pair multipoint interconnections
• Effective Date: 06-Jun-2022
• Revised: ISO 13706:2011 - Petroleum, petrochemical and natural gas industries - Air-cooled heat exchangers
• Effective Date: 15-Apr-2008
• Revises: ISO 13706:2000 - Petroleum and natural gas industries - Air-cooled heat exchangers
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 13706
Second edition
2005-10-15
Petroleum, petrochemical and natural gas
industries — Air-cooled heat exchangers
Industries du pétrole, de la pétrochimie et du gaz naturel — Échangeurs
de chaleur refroidis à l'air
Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved

Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 General. 4
5 Proposals. 5
6 Documentation. 5
6.1 Approval information. 5
6.2 Final records . 6
7 Design . 7
7.1 Tube bundle design. 7
7.2 Air-side design . 19
7.3 Structural design . 30
8 Materials . 35
8.1 General. 35
8.2 Headers. 36
8.3 Louvres . 36
8.4 Other components. 36
9 Fabrication of tube bundle. 37
9.1 Welding . 37
9.2 Post-weld heat treatment . 37
9.3 Tube-to-tubesheet joints. 37
9.4 Gasket contact surfaces . 39
9.5 Thread lubrication. 39
9.6 Alignment and tolerances. 39
9.7 Assembly . 39
10 Inspection, examination and testing. 41
10.1 Quality control. 41
10.2 Pressure test . 42
10.3 Shop run-in. 42
10.4 Equipment performance testing. 42
10.5 Nameplates. 42
11 Preparation for shipment . 42
11.1 General. 42
11.2 Surfaces and finishes. 43
11.3 Identification and notification. 43
12 Supplemental requirements . 43
12.1 General. 43
12.2 Design . 43
12.3 Examination. 44
12.4 Testing . 44
Annex A (informative) Recommended practices . 45
Annex B (informative) Checklist, data sheets and electronic data exchange. 49
Annex C (informative) Winterization of air-cooled heat exchangers. 66
Bibliography . 115

iv © ISO 2005 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 13706 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 6, Processing equipment and
systems.
This second edition cancels and replaces the first edition (ISO 13706:2000), which has been technically
revised.
Introduction
Users of this International Standard should be aware that further or differing requirements may be needed for
individual applications. This International Standard is not intended to inhibit a vendor from offering, or the
purchaser from accepting, alternative equipment or engineering solutions for the individual application. This
may be particularly applicable where there is innovative or developing technology. Where an alternative is
offered, the vendor should identify any variations from this International Standard and provide details.

vi © ISO 2005 – All rights reserved

INTERNATIONAL STANDARD ISO 13706:2005(E)

Petroleum, petrochemical and natural gas industries — Air-
cooled heat exchangers
1 Scope
This International Standard gives requirements and recommendations for the design, materials, fabrication,
inspection, testing and preparation for shipment of air-cooled heat exchangers for use in the petroleum and
natural gas industries.
This International Standard is applicable to air-cooled heat exchangers with horizontal bundles, but the basic
concepts can also be applied to other configurations.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 76, Rolling bearings — Static load ratings
ISO 281, Rolling bearings — Dynamic load ratings and rating life
ISO 286 (all parts), ISO system of limits and fits
ISO 1081, Belt drives — V-belts and V-ribbed belts, and corresponding grooved pulleys — Vocabulary
ISO 1459, Metallic coatings — Protection against corrosion by hot dip galvanizing — Guiding principles
ISO 1461, Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods
ISO 2491, Thin parallel keys and their corresponding keyways (Dimensions in millimetres)
ISO 3744, Acoustics — Determination of sound power levels of noise sources using sound pressure —
Engineering method in an essentially free field over a reflecting plane
ISO 4183, Belt drives — Classical and narrow V-belts — Grooved pulleys (system based on datum width)
ISO 4184, Belt drives — Classical and narrow V-belts — Lengths in datum system
ISO 5287, Belt drives — Narrow V-belts for the automotive industry — Fatigue test
ISO 5290, Belt drives — Grooved pulleys for joined narrow V-belts — Groove sections 9N/J, 15N/J and 25N/J
(effective system)
ISO 8501-1, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel
substrates and of steel substrates after overall removal of previous coatings
ISO 9563, Belt drives — Electrical conductivity of antistatic endless synchronous belts — Characteristics and
test method
1)
AGMA 6001 , Design and selection of components for enclosed gear drives
AGMA 6010, Standard for spur, helical, herringbone and bevel enclosed drives
2)
ASME PTC 30 , Air cooled heat exchangers
3)
ICC , International Building Code
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
bank
one or more items arranged in a continuous structure
3.2
bare tube surface
total area of the outside surfaces of the tubes, based on the length measured between the outside faces of the
header tubesheets
3.3
bay
one or more tube bundles, serviced by two or more fans, including the structure, plenum and other attendant
equipment
NOTE Figure 1 shows typical bay arrangements.
3.4
finned surface
〈of a tube〉 total area of the outside surface exposed to air
3.5
forced-draught exchanger
exchanger designed with the tube bundles located on the discharge side of the fan
3.6
induced-draught exchanger
exchanger designed with the tube bundles located on the suction side of the fan
3.7
item
one or more tube bundles for an individual service
3.8
item number
purchaser's identification number for an item

1) American Gear Manufacturers' Association, 1500 King Street, Suite 201, Alexandria, VA 22314, USA.
2) American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990, USA.

3) International Code Council Foundation, 10624 Indian Woods Drive, Cincinnati, OH 45242, USA.
2 © ISO 2005 – All rights reserved

3.9
pressure design code
recognized pressure vessel standard specified or agreed by the purchaser
EXAMPLE ASME Section VIII.
3.10
structural code
recognized structural standard specified or agreed by the purchaser
EXAMPLES AISC M011 and AISC S302.
3.11
tube bundle
assembly of headers, tubes and frames

a)  One-bay b)  Two-bay
Key
1 tube bundle
Figure 1 — Typical bay arrangements
4 General
z 4.1 The pressure design code shall be specified or agreed by the purchaser.
Pressure components shall comply with the pressure design code and the supplemental requirements given in
this International Standard.
NOTE A bullet (z) at the beginning of a subclause indicates a requirement for the purchaser to make a decision or
provide information (see checklist in Annex B).
4.2 The air-cooled heat exchanger shall be either a forced-draught exchanger or an induced-draught
exchanger and shall include the components shown in Figure 2 and any auxiliaries such as ladders, walkways
and platforms.
4.3 Annex A, which may be consulted if required, includes for information some recommended mechanical
and design details. Annex A also includes precautions for consideration when specifying certain design
aspects, including temperature limitations, type of extended surface, tube support methods, type of air-cooled
heat exchanger, materials of gasket construction and operational considerations such as walkway access.
z 4.4 The vendor shall comply with the applicable local regulations specified by the purchaser.
4.5 In this International Standard, where practical, US Customary units are included in brackets for
information.
a)  Forced draught b)  Induced draught
Key
1 tube bundle 6 fan
2 header 7 fan ring
3 nozzle 8 fan deck
4 supporting column 9 drive assembly
5 plenum 10 fan guard
Figure 2 — Typical components of an air-cooled heat exchanger
4 © ISO 2005 – All rights reserved

5 Proposals
5.1 The vendor's proposal shall include a completed data sheet for each item (see example in Annex B).
5.2 A proposal drawing shall be furnished which shows the major dimensions in plan and elevation, and the
nozzle sizes and their orientation.
5.3 The proposal shall state whether vertically mounted electric motors shall be shaft up or shaft down.
5.4 The proposal shall fully define the extent of shop assembly and include a general description of the
components to be assembled in the field.
5.5 Any proposal for a design that is not fully described in this International Standard shall include
additional drawings sufficient to describe the details of construction.
5.6 The proposal shall include a detailed description of any exceptions to the specified requirements.
z 5.7 The proposal shall include noise data. The proposal shall include a noise data sheet (see example in
Annex B) if specified by the purchaser.
5.8 The proposal shall include fan performance characteristic curves with the design point marked on the
curves.
5.9 The proposal shall include details of the method used to secure the fin ends, see 7.1.11.7.
6 Documentation
6.1 Approval information
z 6.1.1 For each item number, the vendor shall produce documents which include the following information.
The purchaser shall specify which documents shall be submitted and which of them shall be subject to
approval:
a) purchaser's item number, the service, the project name and location, the purchaser's order number and
the vendor's shop order number;
b) design pressure, maximum allowable working pressure, test pressure, maximum and minimum design
temperature, and corrosion allowance;
c) any applicable codes and purchase specifications of the purchaser;
d) material specifications and grades for all pressure parts;
e) overall dimensions;
f) dimensions and locations of supports and sizes of holding-down bolts;
g) nozzle size, rating, facing, location, projection beyond header surface, allowable loadings (forces and
moments) and direction of flow;
h) drive mount details;
i) masses of the tube bundle, the exchanger empty and full of water, and the mass of the heaviest
component or combination of components intended by the vendor to be handled in a single lift;
j) column reactions for each load type listed in 7.3.3;
k) post-weld heat treatment requirements;
l) radiographic and other non-destructive examination requirements;
m) surface preparation and painting requirements;
n) design exposure temperatures for mechanical and instrumentation components;
o) nameplate and its position;
p) tube-to-tubesheet joint and details of joint preparation.
q) plug torque values with recommended thread lubrication.
6.1.2 The vendor shall also furnish gasket detail drawings, field assembly drawings, and drawings for all
auxiliary equipment and controls furnished. Drawings shall show electrical and control connections, including
those of motive and signal air for any pneumatically actuated louvres or fans. The gasket details shall include
type and material, and shall be shown on a separate drawing.
z 6.1.3 Calculations required by the pressure design code shall be made for the design of pressure
components, including header boxes, tubes and tube joints. Additionally, sufficient detail shall be supplied for
any non-standard pressure boundary components, such as swage-type transition nozzles. If specified by the
purchaser, the calculations shall be submitted for approval.
z 6.1.4 If specified by the purchaser, weld maps, all proposed welding procedures, including tube to
tubesheet welding procedures and qualifications (including impact test results, if applicable) shall be submitted
for approval prior to fabrication.
z 6.1.5 Further engineering information required from the vendor for installation, operation, maintenance, or
inspection shall be a matter of agreement between the purchaser and the vendor.
6.2 Final records
6.2.1 The vendor shall maintain records of the materials used and fabrication details for at least 10 years.
z 6.2.2 The purchaser shall specify which of the following shall be furnished, and shall specify if any of them
shall be in an electronic medium:
a) an “as-built” data sheet, including material specifications and grades for all pressure parts;
b) a manufacturer's data report in accordance with the pressure design code;
c) certified material test reports for all pressure parts;
d) fan and hub data, including shaft bore and keyway dimensions and coupling and sheave data;
e) a schematic diagram for automatically controlled fan pitch or louvre blade adjustment, if the controller is
furnished by the vendor;
f) installation, operation and maintenance instructions, including the type of lubrication furnished for gears
and bearings;
g) parts list;
h) a certified noise data sheet for the air-cooled heat exchanger with the fans operating at rated speed and
at design conditions;
i) fan performance characteristic curves showing the operating point and shaft power consumption;
6 © ISO 2005 – All rights reserved

j) louvre characteristic performance curve;
k) temperature recorder charts made during post-weld heat treatment of the headers;
l) non-destructive testing records.
7 Design
7.1 Tube bundle design
7.1.1 General
7.1.1.1 Tube bundles shall be rigid, self-contained, and designed for handling as a complete assembly.
7.1.1.2 The vendor shall make provision for lateral movement of exchanger tube bundles of at least 6 mm
(1/4 in) in both directions or 12,7 mm (1/2 in) in only one direction, unless the purchaser and the vendor agree
on a different value.
7.1.1.3 Provision shall be made to accommodate thermal expansion of tubes.
7.1.1.4 All tubes shall be supported to prevent sagging and meshing or deformation of fins. Tube
supports shall be spaced not more than 1,83 m (6 ft) from centre to centre.
7.1.1.5 A hold-down member (tube keeper) shall be provided at each tube support. Hold-down members
shall be attached to side frames by bolting.
7.1.1.6 Tubes of single-pass condensers shall be sloped downward at least 10 mm/m (1/8 in/ft) towards
the outlet header.
7.1.1.7 Tubes of multi-pass condensers need not be sloped.
7.1.1.8 Air seals shall be provided throughout the tube bundle and the bay to minimize air leakage and
bypassing. Any air gap that exceeds 10 mm (3/8 in) in width shall be sealed.
7.1.1.9 The minimum thickness of metal used for air seal construction shall be 2,7 mm (12 gauge USS)
(0,105 in) within the bundle side frame and 1,9 mm (14 gauge USS) (0,08 in) outside the bundle side frame.
NOTE USS is US Standard for sheet and plate iron and steel.
7.1.1.10 Bolts for removable air seals shall be at least 10 mm (3/8 in) nominal diameter.
z 7.1.1.11 Winterization shall be as specified or agreed by the purchaser. Annex C should be used.
z 7.1.1.12 The exchanger shall be designed for an internal steam-out operation at the temperature,
pressure, and operating conditions if specified by the purchaser.
7.1.2 Heating coils
7.1.2.1 Heating coils provided to protect the tube bundle against freeze-up shall be in a separate bundle,
and not part of the tube bundle.
7.1.2.2 Heating coils shall cover the full width of the tube bundle.
7.1.2.3 The tube pitch of the heating coil shall not exceed twice the tube pitch of the tube bundle.
7.1.2.4 If steam is used as heating fluid, heating coils shall be single pass, and the tubes shall be sloped
downward at least 10 mm/m (1/8 in/ft) towards the outlet.
7.1.2.5 Pipe-type headers with welded-in tubes may be used for steam service.
7.1.3 Tube bundle design temperature
z 7.1.3.1 The maximum and minimum design temperatures for pressure parts shall be as specified by the
purchaser.
z 7.1.3.2 The purchaser shall separately specify the maximum operating temperature to be applied for fin
type selection (the fin design temperature). The design temperatures for pressure parts are not intended to
govern fin type selection or to apply in determining exposure temperatures of mechanical and instrumentation
components.
7.1.4 Tube bundle design pressure
z The design pressure shall be as specified by the purchaser.
7.1.5 Corrosion allowance
z 7.1.5.1 The corrosion allowance shall be as specified by the purchaser for all surfaces exposed to the
process fluid, except that no corrosion allowance shall be provided for tubes, gaskets or gasket contact
surfaces. If not specified, a minimum corrosion allowance of 3 mm (1/8 in) shall be provided for carbon and
low-alloy steel components.
7.1.5.2 The corrosion allowance shall be provided on each side of pass partition plates or stiffeners.
7.1.5.3 A thickness equal to the depth of the pass partition groove may be considered as available
corrosion allowance on grooved cover plate and tubesheet surfaces.
7.1.6 Headers
7.1.6.1 General
z 7.1.6.1.1 Headers shall be designed to prevent excessive warpage of tubesheets and/or leakage at tube
joints. The analysis shall consider maximum operating temperature and maximum cooling conditions at
minimum ambient air temperature. If specified by the purchaser, the analysis shall consider alternative
operations such as low process flow at low ambient air temperature, freezing of fluids in tubes, steam-out, loss
of fans due to power failure, and cycling conditions.
7.1.6.1.2 If the fluid temperature difference between the inlet and the outlet of a multi-pass bundle exceeds
110 °C (200 °F), U-tube construction, split headers or other methods of restraint relief shall be employed.
7.1.6.1.3 The need for restraint relief in single- or multi-pass bundles shall be investigated regardless of the
fluid temperature difference between the inlet and outlet of the bundle. The designer shall provide calculations
to prove the adequacy of the design. Some of the stresses are additive, and tube joint efficiency shall be
considered. Calculations shall consider the following stress combinations:
a) For tube stress and/or tube joint stress:
1) stress caused by pressure and temperature;
2) stress caused by nozzle forces and moments;
3) stress caused by differential tube expansion (including that caused by waxing or fouling) between
rows/passes in the coil sections;
4) stress caused by lateral header movement.
8 © ISO 2005 – All rights reserved

b) For header and nozzle stress:
1) stress caused by temperature and pressure;
2) stress caused by nozzle forces and moments;
NOTE Forces and moment can induce movement of the header, see Note in 7.1.10.2.
3) stress caused by differential tube expansion between rows/passes in the coil sections.
c) For header attachments and supports (including coil side frames and cooler structure):
1) stress caused by mass of header full of water;
2) stress caused by nozzle forces and moments;
NOTE Forces and moment can induce movement of the header, see Note in 7.1.10.2.
3) stress caused by tube expansion.
NOTE There can be additional loads and stresses imposed on the tube bundle that have not been stated above
(e.g. seismic).
7.1.6.1.4 Headers shall be designed so that the cross-sectional flow area of each pass is at least 100 % of
the flow area in the corresponding tube pass.
7.1.6.1.5 The lateral velocity in the header shall not exceed the velocity in the nozzle. Multiple nozzles or
an increased header cross-sectional area may be required.
7.1.6.1.6 The minimum nominal thickness of header components shall be as shown in Table 1.
Table 1 — Minimum nominal thickness of header components
Component Minimum thickness
Carbon or low-alloy High-alloy steel or
steel other material
Tubesheet 19 mm (3/4 in) 16 mm (5/8 in)
Plug sheet 19 mm (3/4 in) 16 mm (5/8 in)
Top, bottom and end plates 12 mm (1/2 in) 10 mm (3/8 in)
Removable cover plates 25 mm (1 in) 22 mm (7/8 in)
Pass partition plates and stay plates 12 mm (1/2 in) 6 mm (1/4 in)
NOTE The thickness indicated for any carbon or low-alloy steel component includes a corrosion
allowance of up to 3 mm (1/8 in). The thickness indicated for any component of high-alloy steel or other
material does not include a corrosion allowance. The thickness is based on an expanded tube-to-
tubesheet joint with one groove.
7.1.6.1.7 Pass partitions used as stay plates for the tubesheet and plug sheet shall be made of one integral
plate.
7.1.6.1.8 Header types other than those described in 7.1.6.2 or 7.1.6.3 may be proposed as an alternative
design (see Clause 12).
7.1.6.2 Removable cover plate and removable bonnet headers
7.1.6.2.1 The cover plate header design shall permit removal of the cover without disturbing header piping
connections. Figure 3a) shows typical construction of tube bundles with removable cover plate headers.
7.1.6.2.2 The bonnet header design shall permit removal of the bonnet with the minimum dismantling of
header piping connections. Figure 3 b) shows typical construction of tube bundles with removable bonnet
headers.
7.1.6.2.3 Bolted joints shall be designed using through bolts with either confined gaskets or unconfined full-
face gaskets. Stud bolt construction may be used if approved by the purchaser. Gasket contact surfaces on
cover plates, matching header box flanges and tubesheets shall be machined. The surface finish shall be
appropriate for the type of gasket (A.7 may be consulted for guidance on this).Typical constructions are shown
in Figure 4.
7.1.6.2.4 Either jackscrews or a minimum clearance of 5 mm (3/16 in) shall be provided at the cover
periphery to facilitate dismantling.
7.1.6.2.5 Stay-bolts shall not be used.
7.1.6.2.6 For stud type construction, provision (e.g. sliding pins) shall be made to prevent damage to the
studs during handling of the cover plate.
7.1.6.2.7 The minimum nominal diameter of through-bolts shall be 16 mm (5/8 in). The minimum nominal
diameter of stud bolts shall be 20 mm (3/4 in).
7.1.6.2.8 The maximum spacing between bolt centres shall be in accordance with the pressure design
code.
7.1.6.2.9 The minimum spacing between bolt centres shall be as shown in Table 2.
10 © ISO 2005 – All rights reserved

a)  Removable cover-plate header

b)  Removable bonnet header
Key
1 tubesheet 6 pass partition 11 tube support cross-member
2 removable cover plate 7 gasket 12 tube keeper
3 removable bonnet 8 nozzle 13 vent
4 top and bottom plates 9 side frame 14 drain
5 tube 10 tube spacer 15 instrument connection
Figure 3 — Typical construction of tube bundles with removable cover plate and removable
bonnet headers
a)  Flanged construction, b)  Flanged construction, c)  Flanged construction,
confined gasket semi-confined gasket non-confined gasket
Figure 4 — Typical confined and full-faced gasket joint details
Table 2 — Minimum flange bolt spacing
Nominal bolt diameter Minimum bolt spacing
16 mm (5/8 in) 38 mm (1 1/2 in)
19 mm (3/4 in) 44 mm (1 3/4 in)
22 mm (7/8 in) 52 mm (2 1/16 in)
25 mm (1 in) 57 mm (2 1/4 in)
29 mm (1 1/8 in) 64 mm (2 1/2 in)
32 mm (1 1/4 in) 71 mm (2 13/16 in)
35 mm (1 3/8 in) 76 mm (3 1/16 in)
38 mm (1 1/2 in) 83 mm (3 1/4 in)
41 mm (1 5/8 in) 89 mm (3 1/2 in)
44 mm (1 3/4 in) 95 mm (3 3/4 in)
48 mm (1 7/8 in) 102 mm (4 in)
51 mm (2 in) 108 mm (4 1/4 in)
7.1.6.2.10 Spacing between bolts straddling corners shall be such that the diagonal distance between bolts
adjacent to the corner does not exceed the lesser of the spacing on the sides or the ends.
7.1.6.3 Plug headers
7.1.6.3.1 Threaded plug holes shall be provided opposite the ends of each tube for access. Holes shall be
threaded to the full depth of the plug sheet. Figure 5 shows typical construction of a tube bundle with plug
headers.
7.1.6.3.2 The nominal thread diameter of the plug holes shall be equal to the outside diameter of the tube
plus at least 3 mm (1/8 in).
7.1.6.3.3 Gasket contact surfaces of plug holes shall be spot-faced. The edges of the facing shall be free of
burrs.
12 © ISO 2005 – All rights reserved

Key
1 tubesheet 7 stiffener 13 tube keeper
2 plug sheet 8 plug 14 vent
3 top and bottom plates 9 nozzle 15 drain
4 end plate 10 side frame 16 instrument connection
5 tube 11 tube spacer
6 pass partition 12 tube support cross-member
Figure 5 — Typical construction of a tube bundle with plug headers
7.1.7 Plugs for tube access
7.1.7.1 Plugs shall be the shoulder type with straight-threaded shanks.
7.1.7.2 Hollowed plugs shall not be used.
7.1.7.3 Plugs shall have hexagonal heads. The minimum dimension across the flats shall be at least
equal to the plug shoulder diameter.
7.1.7.4 The pressure seal shall be maintained by means of a gasket between the flange of the plug and
the plug sheet.
7.1.7.5 Positive means (such as a self-centring taper) shall be provided to ensure seating of the gasket in
the spot-faced recess.
7.1.7.6 Plugs shall be long enough to fill the plug sheet threads, with a tolerance of ± 1,5 mm (1/16 in),
except for galling materials or if the nominal plug sheet thickness is greater than 50 mm (2 in), for which
alternative designs may be used with the approval of the purchaser. Additional factors to consider in selecting
the plug design are thread interference, erosion, crevice corrosion and retention of fluid in cavities.
7.1.7.7 The thickness of the plug head from its gasket surface to the top face shall be at least 50 % of the
nominal tube outside diameter. Greater thickness may be required due to pressure rating and material
considerations.
7.1.7.8 Threads of plugs having nominal diameters 30 mm (1 1/4 in) and smaller shall be fine series
threads.
7.1.8 Gaskets
7.1.8.1 Plug gaskets shall be of the solid-metal or double-metal-jacketed, filled type, of the same general
material classification as the plug.
7.1.8.2 Plug gaskets shall be flat and free of burrs.
7.1.8.3 The minimum thickness of solid metal plug gaskets shall be 1,5 mm (0,060 in).
7.1.8.4 For joint type a) in Figure 4, cover plate and bonnet gaskets shall be of the double-metal-jacketed,
filled type. Filler material shall be non-asbestos and shall be suitable for sealing, exposure resistance and fire
safety performance.
7.1.8.5 For joint type b) in Figure 4, double-metal-jacketed, filled type gaskets or [at design pressures of
2 100 kPa gauge (300 psig) or less] compressed sheet composition gaskets suitable for the service shall be
used. Gaskets shall be non-asbestos and shall be suitable for sealing, exposure resistance and fire safety
performance.
7.1.8.6 For joint type c) in Figure 4, compressed sheet composition gaskets suitable for the service may
be used at design pressures of 2 100 kPa gauge (300 psig) or less. Gaskets shall be non-asbestos and shall
be suitable for sealing, exposure resistance and fire safety performance.
7.1.8.7 The width of removable cover plate and removable bonnet gaskets shall be at least 10 mm
(3/8 in).
7.1.8.8 Gaskets shall be of one piece.
7.1.8.9 A.7 may be consulted for further guidance on gaskets.
7.1.9 Nozzles and other connections
7.1.9.1 Flanges shall be in accordance with the pressure design code unless otherwise specified by
purchaser.
7.1.9.2 Connections of nominal size DN 32 (NPS 1 1/4), DN 65 (NPS 2 1/2), DN 90 (NPS 3 1/2), DN 125
(NPS 5) or less than DN 20 (NPS 3/4) shall not be used.
7.1.9.3 Connections DN 40 (NPS 1 1/2) and larger shall be flanged.
7.1.9.4 In hydrogen service [i.e. if the partial pressure of hydrogen is greater than 700 kPa (100 psia)] all
connections shall be flanged and slip-on flanges shall not be used.
7.1.9.5 If design conditions require the equivalent of PN 150 (ANSI 900) or higher flange ratings, all
connections shall be flanged.
7.1.9.6 The nominal thickness of the nozzle neck, of carbon steel and low-alloy steel flanged connections
shall not be less than specified in Table 3.
14 © ISO 2005 – All rights reserved

Table 3 — Minimum nozzle neck nominal thickness
Pipe size Nozzle neck thickness
DN (NPS) mm (in)
20 (3/4) 5,56 (0,219)
25 (1) 6,35 (0,250)
40 (1 1/2) 7,14 (0,281)
50 (2) 8,74 (0,344)
80 (3) 11,13 (0,438)
100 (4) 13,49 (0,531)
150 (6) 10,97 (0,432)
200 (8) 12,70 (0,500)
250 (10) 15,09 (0,594)
300 (12) 17,48 (0,688)
NOTE The data in this table are taken from ASME B36.10M,
using Schedule 160 for sizes up to DN 100 (NPS 4) and Schedule 80
for the larger sizes.
7.1.9.7 The facing of process flanges shall be in a horizontal plane unless another arrangement is
specified by the purchaser.
7.1.9.8 Flanged carbon steel connections shall be one of the following types:
a) a forged or centrifugally cast, integrally flanged welding neck;
b) a pipe welded to a forged or centrifugally cast welding neck flange;
c) a seamless transition piece attached to a forged or centrifugally cast welding neck flange;
d) a cast or fabricated transition, if allowed by the purchaser;
e) a pipe or a seamless transition welded to a forged slip-on flange.
7.1.9.9 If a transition is used, stay bars, greater header thickness or greater nozzle thickness may be
required to provide adequate mechanical strength.
7.1.9.10 Except in hydrogen service (see 7.1.9.4), forged carbon steel slip-on flanges may be used on
connections to headers that are limited to:
a) a maximum design pressure of 2 100 kPa gauge (300 psig);
b) a maximum design temperature of 450 °C (850 °F);
c) a maximum service corrosion allowance of 3 mm (1/8 in).
7.1.9.11 Threaded connections shall be DN 25 (NPS 1), except that pressure gauge connections shall be
DN 20 (NPS 3/4).
7.1.9.12 Threaded connections shall be one of the following types and shall comply with the pressure
design code:
a) forged steel full-coupling threaded one end only, with a suitable rating (e.g. ASME B16.11, class 6 000);
b) forged steel fitting with integral reinforcement;
c) tapped holes for vent and drain connections, where header plate thickness permits;
d) equivalent boss connection.
7.1.9.13 If a thermowell connection is specified, it shall be located in the nozzle unless the nozzle is
smaller than DN 100 (NPS 4), in which case the connection shall be located on the header adjacent to the
nozzle.
7.1.9.14 If a pressure gauge connection is specified it shall be located on the nozzle unless the nozzle is
smaller than DN 80 (NPS 3), in which case the connection shall be located on the header adjacent to the
nozzle.
7.1.9.15 Pipe threads shall be taper pipe threads (e.g. ASME B1.20.1) and shall comply with the pressure
design code.
z 7.1.9.16 The size, type and location of chemical cleaning connections, if any, shall be specified by the
purchaser.
7.1.9.17 If specified, instrument connections shall be located in at least one inlet and outlet nozzle per
bundle, except that none are required in intermediate nozzles of stacked bundles.
7.1.9.18 All threaded piping connections shall be closed with a round-headed solid plug.
7.1.9.19 Flanged auxiliary connections, if any, shall be closed with blind flanges. The gasket and bolting
materials shall be suitable for the specified operating conditions.
7.1.9.20 Vent and drain connections shall be provided at high and low points respectively on each header.
Header nozzles installed at high and low points may serve as vents and drains. Connections serving as vents
and drains shall not extend into the header beyond the inside surface.
7.1.9.21 If the header thickness will not permit minimum thread engagement of vent and drain plugs,
couplings or built-up bosses shall be installed.
7.1.9.22 Bolts between connecting nozzles of stacked tube bundles shall be removable without moving the
bundles.
7.1.10 Maximum allowable moments and forces for nozzles and headers
7.1.10.1 Each nozzle, in its design corroded condition, shall be capable of withstanding the simultaneous
application of the moments and forces defined in Figure 6 and Table 4.
7.1.10.2 The design of each fixed or floating header, the design of the connections of fixed headers to side
frames, and the design of other support members shall ensure that the simultaneous application (sum) of all
nozzle loadings on a single header will cause no damage. The components of the nozzle loadings on a single
header shall not exceed the following values:
M 6 100 N ⋅ m (4 500 ft ⋅ lbf)
x
M 8 130 N ⋅ m (6 000 ft ⋅ lbf)
y
M 4 070 N ⋅ m (3 000 ft ⋅ lbf)
z
F 10 010 N [2 250 lbf]
x
F 20 020 N [4 500 lbf]
y
F 16 680 N [3 750 lbf]
z
NOTE The application of the moments and forces shown in Table 4 will cause movement that will tend to reduce the
loads to the values given here.
16 © ISO 2005 – All rights reserved

Key
1 fin tubes
Figure 6 — Nozzle loads
Table 4 — Maximum allowable nozzle loads
Nozzle size Moments Forces
DN (NPS) N⋅m (ft⋅lbf) N (lbf)
M M M F F F
x y z x y z
40 (1 1/2) 110 (80) 150 (110) 110 (80) 670 (150) 1 020 (230) 670 (150)
50 (2) 150 (110) 240 (180) 150 (110) 1 020 (230) 1 330 (300) 1 020 (230)
80 (3) 410 (300) 610 (450) 410 (300) 2 000 (450) 1 690 (380) 2 000 (450)
100 (4) 810 (600) 1 220 (900) 810 (600) 3 340 (750) 2 670 (600) 3 340 (750)
150 (6) 2 140 (1 580) 3 050 (2 250) 1 630 (1 200) 4 000 (900) 5 030 (1 130) 5 030 (1 130)
200 (8) 3 050 (2 250) 6 100 (4 500) 2 240 (1 650) 5 690 (1 280) 13 340 (3 000) 8 010 (1 800)
250 (10) 4 070 (3 000) 6 100 (4 500) 2 550 (1 880) 6 670 (1 500) 13 340 (3 000) 10 010 (2 250)
300 (12) 5 080 (3 750) 6 100 (4 500) 3 050 (2 250) 8 360 (1 880) 13 340 (3 000) 13 340 (3 000)
350 (14) 6 100 (4 500) 7 120 (5 250) 3 570 (2 630) 10 010 (2 250) 16 680 (3 750) 16 680 (3 750)

7.1.10.3 The total of all nozzle loads on one multi-bundle bay shall not exceed 3 times that allowed for a
single header.
7.1.10.4 See 7.1.6.1.3 for further details.
7.1.11 Tubes
7.1.11.1 The outside diameter of cylindrical tubes should be at least 25,4 mm (1 i
...