EN ISO 13706:2000

SLOVENSKI STANDARD
01-december-2000
Petroleum and natural gas industries - Air-cooled heat exchangers (ISO
13706:1998)
Petroleum and natural gas industries - Air-cooled heat exchangers (ISO 13706:1998)
Erdöl- und Erdgasindustrien - Luftgekühlte Wärmetauscher (ISO 13706:2000)
Industries du pétrole et du gaz naturel - Echangeurs de chaleur refroidis a l'air (ISO
13706:2000)
Ta slovenski standard je istoveten z: EN ISO 13706:2000
ICS:
71.120.30 Prenosniki toplote Heat exchangers
75.180.20 Predelovalna oprema Processing equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 13706
First edition
2000-04-15
Petroleum and natural gas industries —
Air-cooled heat exchangers
Industries du pétrole et du gaz naturel — Échangeurs de chaleur refroidis
àl'air
Reference number
ISO 13706:2000(E)
©
ISO 2000
ISO 13706:2000(E)
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ii © ISO 2000 – All rights reserved

ISO 13706:2000(E)
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 .31
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 Postweld 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 General.41
10.2 Quality control.41
10.3 Pressure test .42
10.4 Shop run-in.42
10.5 Nameplates.42
11 Preparation for shipment .43
11.1 General.43
11.2 Surfaces and finishes.43
11.3 Identification, conditioning and notification.43
12 Supplemental requirements .43
12.1 General.43
12.2 Design .44
12.3 Examination.44
12.4 Testing .45
ISO 13706:2000(E)
Annex A (informative) Recommended practices.46
Annex B (informative) Checklist, data sheets and electronic data exchange.50
Annex C (informative) Winterization of air-cooled heat exchangers .67
Bibliography .116
iv © ISO 2000 – All rights reserved

ISO 13706:2000(E)
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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13706 was prepared by Technical Committee ISO/TC 67, Materials, equipment and
offshore structures for petroleum and natural gas industries, Subcommittee SC 6, Processing equipment and
systems.
Annexes A, B and C of this International Standard are for information only.
ISO 13706:2000(E)
Introduction
This International Standard is based on API standard 661, fourth edition, November 1997.
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 2000 – All rights reserved

INTERNATIONAL STANDARD ISO 13706:2000(E)
Petroleum 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 may also be applied to other configurations.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
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 drive — 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, Narrow V-belt drives for the automotive industry — Fatigue test.
ISO 5290, Belt drives — Grooved pulleys for joined narrow V-belts — Groove sections 9J, 15J, 20J and 25J
(effective system).
ISO 13706:2000(E)
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.
ISO 10436, Petroleum and natural gas industries — General-purpose steam turbines for refinery service.
1)
AGMA 6001 , Design and selection of components for enclosed gear drives.
AGMA 6010-E, Practice for enclosed speed reducers or increasers using spur, helical, herringbone and spiral bevel
gears.
2)
ICBO , Uniform Building Code.
3 Terms and definitions
For the purposes of this International Standard, 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
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
1) American Gear Manufacturers' Association, 1500 King Street, Suite 201, Alexandria, VA 22314, USA.
2) International Conference of Building Officials, 5360 South Workman Mill Road, Whittier, CA 90601, USA.
2 © ISO 2000 – All rights reserved

ISO 13706:2000(E)
3.8
item number
purchaser's identification number for an item
3.9
pressure design code
recognized pressure vessel standard specified or agreed by the purchaser
EXAMPLE ASME 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
ISO 13706:2000(E)
4 General
� 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 round bullet (�) at the beginning of a subclause indicates a requirement for the purchaser to make a decision or
provide information (see checklist in annex B). A triangular bullet (▲) at the beginning of a subclause indicates that this detail is
included on the air-cooled heat exchanger data sheet (see 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.
� 4.4 The vendor shall comply with the applicable local regulations specified by the purchaser.
4.5 In this International Standard, where practical, U.S. Customary units are included in brackets for information.
a) Forced draught b) Induced draught
Key
1 Tube bundle 6Fan
2 Header 7 Fan ring
3 Nozzle 8 Fan deck
4 Supporting column 9 Drive assembly
5 Plenum
Figure 2 — Typical components of an air-cooled heat exchanger
4 © ISO 2000 – All rights reserved

ISO 13706:2000(E)
5 Proposals
5.1 The vendor's proposal shall include a completed data sheet for each item (see 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 fabrication procedure and welding procedure shall be furnished for welded tube-to-tubesheet joints.
5.5 The proposal shall fully define the extent of shop assembly and include a general description of the
components to be assembled in the field.
5.6 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.
5.7 The proposal shall include a detailed description of any exceptions to the specified requirements.
� 5.8 The proposal shall include noise data. The proposal shall include a noise data sheet (see annex B) if
specified by the purchaser.
� 5.9 The proposal shall include fan performance characteristic curves if specified by the purchaser.
5.10 The proposal shall include details of the method used to secure the fin ends (7.1.11.7).
5.11 The vendor shall inform the purchaser if the vendor considers that the requirements specified by the
purchaser are in conflict with, or are not suitable for, the intended purposes or operation of the unit.
6 Documentation
6.1 Approval information
� 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) The 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;
ISO 13706:2000(E)
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.
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.
� 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.
� 6.1.4 If specified by the purchaser, weld maps, all proposed welding procedures and qualifications (including
impact test results, if applicable) shall be submitted for approval prior to fabrication.
� 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 5 years.
� 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;
j) louvre characteristic performance curve;
k) temperature recorder charts made during postweld heat treatment of the headers.
6 © ISO 2000 – All rights reserved

ISO 13706:2000(E)
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 1
( / inch) in both directions or at least 12 mm ( / inch) in only one direction, unless the purchaser and the vendor
4 2
agree on a greater movement.
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 1,8 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 per metre ( / inch per
foot) towards the outlet header.
7.1.1.7 Tubes of multipass 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 ( / inch) in width shall be sealed.
7.1.1.9 The minimum thickness of metal used for air seal construction shall be 2,5 mm (12 gauge USS,
0,105 inch) within the bundle side frame and 2,0 mm (14 gauge USS, 0,075 inch) outside the bundle side frame.
7.1.1.10 Bolts for removable air seals shall be at least 10 mm ( / inch) nominal diameter.
� 7.1.1.11 Winterization shall be as specified or agreed by the purchaser. Annex C should be used.
� 7.1.1.12 The exchanger shall be designed for an internal steam-out operation at the temperature, pressure, and
operating conditions 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 per metre ( / inch per foot) 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
� 7.1.3.1 The maximum and minimum design temperatures for pressure parts shall be as specified by the
purchaser or, if not specified by the purchaser, the maximum design temperature shall be at least the specified
process fluid inlet temperature plus 25 °C (50 °F).
ISO 13706:2000(E)
� 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
� The design pressure shall be as specified by the purchaser or, if not specified, shall be the greater of the following:
a) the inlet pressure plus 10 %;
b) the inlet pressure plus 170 kPa (25 psi).
7.1.5 Corrosion allowance
▲ 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 ( / inch) 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
� 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. 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.
Some of the above stresses are additive, and tube joint efficiency shall be considered.
b) For header and nozzle stress:
1) stress caused by temperature and pressure;
8 © ISO 2000 – All rights reserved

ISO 13706:2000(E)
2) stress caused by nozzle forces and moments;
3) stress caused by lateral header movement;
4) stress caused by differential tube expansion between rows/passes in the coil sections.
NOTE Set-in versus set-on nozzle attachments could greatly affect the above.
c) For header attachments and supports (including coil side frames and cooler structure):
1) stress caused by header mass and water;
2) stress caused by nozzle forces and moments;
3) stress caused by lateral header movement;
4) stress caused by tube expansion.
NOTE There may be additional loads and stresses imposed on the tube bundle which may not have 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 High-alloy steel or
low-alloy steel other material
3 5
Tubesheet 20 mm ( / inch) 15 mm ( / inch)
4 8
3 5
Plug sheet 20 mm ( / inch) 15 mm ( / inch)
4 8
1 3
Top, bottom and end plates 12 mm ( / inch) 10 mm ( / inch)
2 8
Removable cover plates 25 mm (1 inch) 22 mm ( / inch)
1 1
Pass partition plates and stay plates 12 mm ( / inch) 6 mm ( / inch)
2 4
NOTE The thickness indicated for any carbon or low-alloy steel component includes a
corrosion allowance of up to 3 mm ( / inch). 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).
ISO 13706:2000(E)
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 3 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 shows typical construction of tube bundles with removable bonnet headers.
� 7.1.6.2.3 The use of either through-bolts or stud bolts for cover plates shall be agreed between the purchaser
and the vendor. Bolted joints shall be designed with confined gaskets or unconfined full-faced gaskets.
Typical constructions are shown in Figure 4. The purchaser's enquiry shall specify the required design.
7.1.6.2.4 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 (annex A may be consulted for guidance
on this).
7.1.6.2.5 Either jackscrews or a minimum clearance of 5 mm ( / inch) shall be provided at the cover periphery
to facilitate dismantling.
7.1.6.2.6 Stay-bolts shall not be used.
7.1.6.2.7 Provisions (e.g. sliding pins) should be made to prevent damage to the studs during handling of the
cover plate.
7.1.6.2.8 The minimum nominal diameter of stud bolts shall be 20 mm ( / inch). The minimum nominal diameter
of through-bolts shall be 16 mm ( / inch).
7.1.6.2.9 The maximum spacing between bolt centres shall be in accordance with the pressure design code.
7.1.6.2.10 The minimum spacing between bolt centres shall be as shown in Table 2.
10 © ISO 2000 – All rights reserved

ISO 13706:2000(E)
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 9Sideframe 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
ISO 13706:2000(E)
a) Stud construction, b) Flanged construction, c) Flanged construction,
confined gasket confined gasket full-faced gasket
Figure 4 — Typical confined and full-faced gasket joint details
Table 2 — Minimum flange bolt spacing
Nominal bolt diameter Minimum bolt spacing
5 1
16 mm ( / inch) 38 mm (1 / inch)
8 2
3 3
19 mm ( / inch) 44 mm (1 / inch)
4 4
7 1
22 mm ( / inch) 52 mm (2 / inch)
8 16
25 mm (1 inch) 57 mm (2 / inch)
1 1
29 mm (1 / inch) 64 mm (2 / inch)
8 2
1 13
32 mm (1 / inch) 71 mm (2 / inch)
4 16
3 1
35 mm (1 / inch) 76 mm (3 / inch)
8 16
1 1
38 mm (1 / inch) 83 mm (3 / inch)
2 4
5 1
41 mm (1 / inch) 89 mm (3 / inch)
8 2
3 3
44 mm (1 / inch) 95 mm (3 / inch)
4 4
48 mm (1 / inch) 102 mm (4 inch)
51 mm (2 inch) 108 mm (4 / inch)
7.1.6.2.11 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 or 50 mm (2 inch), whichever is less. Figure 5 shows typical
construction of a tube bundle with plug headers.
7.1.6.3.2 The diameter of the plug holes shall be equal to the nominal outside diameter of the tube plus at least
0,8 mm ( / inch).
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 2000 – All rights reserved

ISO 13706:2000(E)
Key
1 Tubesheet 7 Stiffener 13 Tube keeper
2 Plug sheet 8Plug 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.
ISO 13706:2000(E)
7.1.7.6 Plugs shall be long enough to fill the plug sheet threads, with a tolerance of � 1,5 mm ( / inch),
except for galling materials or if the nominal plug sheet thickness is greater than 50 mm (2 inch), 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 / inch) 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 inch).
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 9 mm ( / inch).
7.1.8.8 Gaskets shall be of one piece.
7.1.8.9 Annex A.8 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.
1 1 1
7.1.9.2 Connections of nominal pipe size DN 10 (NPS / ), DN 32 (NPS 1 / ), DN 65 (NPS 2 /), DN90
2 4 2
(NPS 3 / ) or DN 125 (NPS 5) shall not be used.
7.1.9.3 Connections DN 40 (NPS 1 / ) 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 minimum nozzle neck thickness, including corrosion allowance, of carbon steel and low-alloy steel
flanged connections shall be as specified in Table 3.
14 © ISO 2000 – All rights reserved

ISO 13706:2000(E)
Table 3 — Minimum nozzle neck thickness
Pipe size Minimum nozzle neck thickness
DN (NPS) mm (inch)
15 ( / ) 4,78 (0,188)
20 ( / ) 5,56 (0,219)
25 (1) 6,35 (0,250)
40 (1 / ) 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 is 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 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 ( / inch).
7.1.9.11 Threaded connections shall be DN 25 (NPS 1), except that pressure gauge connections shall be
DN 20 (NPS / ).
ISO 13706:2000(E)
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.
�▲ 7.1.9.16 The size, type and location of chemical cleaning connections 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 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 fitted.
7.1.9.22 Bolts between connecting nozzles of stacked t
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