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Withdrawn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
Current Stage
9599 - Withdrawal of International Standard
Start Date
21-Nov-2011
Completion Date
21-Nov-2011
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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 13706:2005(E)
ISO 2005
---------------------- Page: 1 ----------------------
ISO 13706:2005(E)
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© ISO 2005

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ii © ISO 2005 – All rights reserved
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ISO 13706:2005(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 ................................................................................................................................ 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

© ISO 2005 – All rights reserved iii
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ISO 13706:2005(E)

Annex C (informative) Winterization of air-cooled heat exchangers........................................................... 66

Bibliography ................................................................................................................................................... 115

iv © ISO 2005 – All rights reserved
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ISO 13706:2005(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 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.
© ISO 2005 – All rights reserved v
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ISO 13706:2005(E)
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
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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 2005 – All rights reserved 1
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ISO 13706:2005(E)

ISO 9563, Belt drives — Electrical conductivity of antistatic endless synchronous belts — Characteristics and

test method
AGMA 6001 , Design and selection of components for enclosed gear drives
AGMA 6010, Standard for spur, helical, herringbone and bevel enclosed drives
ASME PTC 30 , Air cooled heat exchangers
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
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ISO 13706:2005(E)
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
© ISO 2005 – All rights reserved 3
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ISO 13706:2005(E)
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
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ISO 13706:2005(E)
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;
© ISO 2005 – All rights reserved 5
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ISO 13706:2005(E)
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
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ISO 13706:2005(E)
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.
© ISO 2005 – All rights reserved 7
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ISO 13706:2005(E)
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
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ISO 13706:2005(E)
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 (
...

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