EN ISO 13706:2011

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Erdöl- und Erdgasindustrien - Luftgekühlte Wärmeaustauscher (ISO 13706:2011)Industries du pétrole, de la pétrochimie et du gaz naturel - Échangeurs de chaleur refroidis à l'air (ISO 13706:2011)Petroleum, petrochemical and natural gas industries - Air-cooled heat exchangers (ISO 13706:2011)75.180.20Predelovalna opremaProcessing equipment71.120.30Prenosniki toploteHeat exchangersICS:Ta slovenski standard je istoveten z:EN ISO 13706:2011SIST EN ISO 13706:2012en,fr01-marec-2012SIST EN ISO 13706:2012SLOVENSKI
STANDARDSIST EN ISO 13706:20061DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN ISO 13706
December 2011 ICS 27.060.30; 75.180.20 Supersedes EN ISO 13706:2005English Version
Petroleum, petrochemical and natural gas industries - Air-cooled heat exchangers (ISO 13706:2011)
Industries du pétrole, de la pétrochimie et du gaz naturel - Échangeurs de chaleur refroidis à l'air (ISO 13706:2011)
Erdöl- petrochemische und Erdgasindustrie - Luftgekühlte Wärmeaustauscher (ISO 13706:2011) This European Standard was approved by CEN on 26 November 2011.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 13706:2011: ESIST EN ISO 13706:2012

Reference numberISO 13706:2011(E)© ISO 2011
INTERNATIONAL STANDARD ISO13706Third edition2011-12-01Petroleum, petrochemical and natural gas industries — Air-cooled heat exchangersIndustries du pétrole, de la pétrochemie et du gaz naturel — Échangeurs de chaleur refroidis à l'air
ISO 13706:2011(E)
©
ISO 2011 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.
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ii © ISO 2011 – All rights reserved
ISO 13706:2011(E) © ISO 2011 – All rights reserved iii Contents Page Foreword . v Introduction . vi 1 Scope . 1 2 Normative references . 1 3 Terms and definitions . 2 4 General . 5 5 Proposals . 6 6 Documentation . 7 6.1 Approval information . 7 6.2 Final records . 8 7 Design . 9 7.1 Tube bundle design . 9 7.2 Air-side design . 22 7.3 Structural design . 33 8 Materials . 38 8.1 General . 38 8.2 Requirements for carbon steel in sour or wet hydrogen sulfide service . 38 8.3 Headers . 38 8.4 Louvres . 38 8.5 Other components . 39 9 Fabrication of tube bundle . 39 9.1 Welding . 39 9.2 Postweld heat treatment . 40 9.3 Tube-to-tubesheet joints. 40 9.4 Gasket contact surfaces . 41 9.5 Thread lubrication . 41 9.6 Alignment and tolerances . 41 9.7 Assembly . 42 10 Inspection, examination and testing . 43 10.1 Quality control . 43 10.2 Pressure test . 45 10.3 Shop run-in . 45 10.4 Equipment performance testing . 45 10.5 Nameplates . 45 11 Preparation for shipment . 45 11.1 General . 45 11.2 Surfaces and finishes . 46 11.3 Identification and notification . 46 12 Supplemental requirements . 46 12.1 General . 46 12.2 Design . 46 12.3 Examination . 47 12.4 Testing . 48 Annex A (informative)
Recommended practices . 49 Annex B (informative)
Checklist and data sheets . 55 SIST EN ISO 13706:2012

ISO 13706:2011(E) iv © ISO 2011 – All rights reserved Annex C (informative)
Winterization of air-cooled heat exchangers . 66 Annex D (informative)
Recommended procedure for airflow measurement of air-cooled heat exchangers . 117 Annex E (informative)
Measurement of noise from air-cooled heat exchangers . 124 Bibliography . 141
ISO 13706:2011(E) © ISO 2011 – All rights reserved v 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 third edition cancels and replaces the second edition (ISO 13706:2005), which has been technically revised. SIST EN ISO 13706:2012

ISO 13706:2011(E) vi © ISO 2011 – All rights reserved Introduction It is necessary that users of this International Standard be aware that further or differing requirements can 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 can be particularly applicable where there is innovative or developing technology. Where an alternative is offered, it is the responsibility of the vendor to identify any variations from this International Standard and provide details.
INTERNATIONAL STANDARD ISO 13706:2011(E) © ISO 2011 – All rights reserved 1 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, petrochemical 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), Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes ISO 1081, Belt drive — V-belts and V-ribbed belts, and corresponding grooved pulleys — Vocabulary 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 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 ISO 15156 (all parts), Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production SIST EN ISO 13706:2012

ISO 13706:2011(E) 2 © ISO 2011 – All rights reserved
AGMA 60011), Design and Selection of Components for Enclosed Gear Drives ANSI/AGMA 6010, Spur, Helical, Herringbone and Bevel Enclosed Drives ASME PTC 302), Air-Cooled Heat Exchangers ICC3), International Building Code NACE MR01034), Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments NACE SP0472, Methods and Controls to Prevent In-Service Environmental Cracking of Carbon Steel Weldments in Corrosive Petroleum Refining Environments 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 critical process temperature temperature related to important physical properties of a process stream EXAMPLES Freezing point, pour point, cloud point, hydrate formation temperature and dew point. 3.5 cyclic service process operation with periodic variation in temperature, pressure, and/or flowrate 3.6 exhaust air air that is discharged from the air-cooled heat exchanger to the atmosphere 3.7 external recirculation process that uses an external duct to carry recirculated air to mix with and heat the inlet air 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. 4) NACE International, P.O. Box 218340, Houston, TX 77218-8340, USA. SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 3 3.8 finned surface total area of the outside surface exposed to air 3.9 forced-draught exchanger exchanger designed with the tube bundles located on the discharge side of the fan 3.10 geometric centre location at the centre of a bay on a plane midway between the air inlet and the air outlet for both forced-draft and induced-draft units NOTE The geometric centre is also considered the acoustic centre of a bay for calculations. 3.11 hydrogen service services that contain hydrogen at a partial pressure exceeding 700 kPa (100 psi) absolute 3.12 induced-draught exchanger exchanger designed with the tube bundles located on the suction side of the fan 3.13 inlet air atmospheric or ambient air that enters the air-cooled heat exchanger 3.14 internal recirculation process that uses fans (possibly with louvres) to recirculate air from one part of the process bundle to the other part 3.15 item one or more tube bundles for an individual service 3.16 item number purchaser's identification number for an item 3.17 measurement surface surface of the bay or the cylinder or sphere on which sound-pressure level is measured 3.18 minimum design air temperature specified inlet air temperature that is used for winterization 3.19 minimum design metal temperature lowest metal temperature at which pressure-containing elements can be subjected to design pressure 3.20 octave bands preferred frequency bands SIST EN ISO 13706:2012

ISO 13706:2011(E) 4 © ISO 2011 – All rights reserved 3.21 pressure design code recognized pressure vessel standard specified or agreed by the purchaser EXAMPLE ASME BPVC VIII. 3.22 recirculated air air that has passed through the process bundle and is redirected to mix with and heat the inlet air 3.23 specified minimum tube-wall temperature critical process temperature plus a safety margin 3.24 structural code recognized structural standard specified or agreed by the purchaser
EXAMPLES AISC M011 and AISC S302. 3.25 tube bundle assembly of headers, tubes and frames 3.26 seal-welded tube-to-tubesheet joint weld of unspecified strength applied between the tubes and tubesheets for the sole purpose of reducing the potential for leakage 3.27 sound level sound-pressure level when frequency is weighted according to the standardized A, B, or C weighting used in sound-level meters NOTE Only A-weighted readings [dB(A)] are referenced in this International Standard. 3.28 sound-power level ten times the logarithm to base 10 of the ratio of the total acoustic power radiated by a sound source to the reference power of 1012 W 3.29 sound-pressure level twenty times the logarithm to base 10 of the ratio of the root mean square sound pressure to the reference sound pressure of 2  105 N/m2 3.30 strength-welded tube-to-tubesheet joint welded so that the design strength is equal to, or greater than, the axial tube strength specified by the pressure design code 3.31 unit one or more tube bundles in one or more bays for an individual service 3.32 wind skirt vertical barrier either above or below an air-cooled heat exchanger that minimizes the effect of wind SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 5 3.33 winterization provision of design features, procedures, or systems for air-cooled heat exchangers to avoid problems with the process fluid as a result of low-temperature inlet air NOTE Problems related to low-temperature inlet air include fluid freezing, cooling to the pour point, wax formation, hydrate formation, laminar flow, and condensation at the dew point (which can initiate corrosion).
a)
One-bay b)
Two-bay Key 1 tube bundle Figure 1 — Typical bay arrangements 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 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). 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 (see A.2). 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. SIST EN ISO 13706:2012

ISO 13706:2011(E) 6 © ISO 2011 – All rights reserved  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 (USC) and other commonly used units are included in brackets for information.
a)
Forced draught b)
Induced draught Key 1 tube bundle 2 header 3 nozzle 4 supporting column 5 plenum
6 fan 7 fan ring 8 fan deck 9 drive assembly 10 fan guard Figure 2 — Typical components of an air-cooled heat exchanger  4.6 The purchaser shall specify if the service is designated as sour in accordance with ISO 15156 (all parts) for oil and gas production facilities and natural gas sweetening plants, or designated as wet hydrogen sulfide service in accordance with NACE MR0103 for other applications (e.g. petroleum refineries, LNG plants and chemical plants), in which case all materials in contact with the process fluid shall meet the requirements of the applicable NACE standard to mitigate the potential for sulfide stress cracking (SSC). Identification of the complete set of materials, qualification, fabrication, and testing specifications to prevent in-service environmental cracking is the responsibility of the user (purchaser). NOTE For the purpose of this provision NACE MR0175 is equivalent to ISO 15156 (all parts).  4.7 The requirement for winterization and its type shall be specified by the purchaser. Annex C contains guidance on various methods of winterization for air-cooled heat exchangers. 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 that shows the major dimensions in plan and elevation, and the nozzle sizes and their orientation shall be furnished. 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 for assembly in the field. SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 7 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.  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. 5.10 The proposal for an air-cooled exchanger with a recirculation system (as described in Annex C) shall include drawings showing the duct and plenum sizes, net free flow area, louvre type and arrangement, drive location, and proposed control schematic. 6 Documentation 6.1 Approval information  6.1.1 For each item number, the vendor shall produce documents that 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, service, project name and location, purchaser's order number and vendor's shop order number; b) design pressure, maximum allowable working pressure, test pressure, maximum and minimum design temperature, and corrosion allowance; c) fan performance characteristic curves with the design point marked on the curve, including fan critical speeds for use with variable-frequency drives; d) any applicable codes and purchase specifications of the purchaser; e) material specifications and grades for all pressure parts; f) overall dimensions; g) dimensions and locations of supports and sizes of holding-down bolts; h) nozzle size, rating, facing, location, projection beyond header surface, allowable loadings (forces and moments) and direction of flow; i) drive mount details; j) 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 for handling in a single lift; k) column reactions for each load type listed in 7.3.3; l) post-weld heat treatment requirements; m) U-bend heat treatment or annealing procedure; n) radiographic and other non-destructive examination requirements; o) surface preparation and painting requirements; SIST EN ISO 13706:2012

ISO 13706:2011(E) 8 © ISO 2011 – All rights reserved p) design exposure temperatures for mechanical and instrumentation components; q) nameplate and its position; r) tube-to-tubesheet joint and details of joint preparation; s) maximum and minimum plug torque values with recommended thread lubrication; t) when sour or wet sulfide service is specified by the purchaser, a certified material test report (CMTR) shall be supplied for all carbon steel materials in contact with the process fluid. 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 If specified by the purchaser, calculations required by the pressure design code shall be provided for the design of pressure components, including header boxes, tubes and tube joints. Sufficient detail shall be supplied for any non-standard pressure boundary components, such as swage type transition nozzles. Calculations shall also be provided for restraint relief in accordance with 7.1.6.1.3, and also for the defined external moments and forces on nozzles in accordance with 7.1.10.  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. 6.1.5 If a hot air recirculation system is utilized for winterization, documents showing duct and plenum sizes, net free flow areas, louvre types and arrangement, louvre drive location(s), heating coil and heating medium consumption, and control scheme schematic shall be provided.  6.1.6 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.  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) “as-built” data sheet, including material specifications and grades for all pressure parts; b) as-built shop drawings including details of headers and tube bundles; as-built shop drawings shall also be provided for any heating coils; c) calculations as required by the pressure design code, including nozzle load confirmation, restraint relief and any finite element analysis; d) certified motor drawing and completed motor data sheet for each size and type of motor; e) manufacturer's data report in accordance with the pressure design code; f) certified material test reports for all pressure parts; g) fan and hub data, including shaft bore and keyway dimensions and coupling and sheave data; h) schematic diagram for automatically controlled fan pitch or louvre blade adjustment, if the controller is furnished by the vendor; SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 9 i) installation, operation and maintenance instructions, including the type of lubrication furnished for gears and bearings; j) parts list; k) certified noise data sheet for the air-cooled heat exchanger with the fans operating at rated speed and at design conditions; l) fan performance characteristic curves showing the operating point and shaft power consumption; m) louvre characteristic performance curve; n) temperature recorder charts made during postweld heat treatment of the headers; o) non-destructive testing records; p) nameplate rubbing or facsimile. 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 The last pass of tubes in multi-pass condensers shall be sloped downward at least 10 mm/m (1/8 in/ft) towards the outlet header (see A.3.1). 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.  7.1.1.11 The exchanger shall be designed for an internal steam-out operation at the temperature, pressure, and operating conditions if specified by the purchaser.  7.1.1.12 The purchaser shall specify if cyclic service design is required. If cyclic service is specified, the purchaser shall specify the type and magnitude of variation in pressure, temperature and flowrate, the time for SIST EN ISO 13706:2012

ISO 13706:2011(E) 10 © ISO 2011 – All rights reserved the variation (hours, weeks, etc.) and the number of cycles or frequency for this variation expected during the life of the equipment. The extent and acceptance criteria of any required analysis shall be subject to the agreement of the purchaser (see A.2). 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 the smaller of twice the tube pitch of the tube bundle or 4,75 times the nominal heating coil tube diameter. 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 Design temperature  7.1.3.1 The maximum and minimum design temperatures for pressure parts shall be as specified by the purchaser.  7.1.3.2 The purchaser shall separately specify the maximum operating temperature to apply 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 Design pressure  The design pressure shall be as specified by the purchaser. 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 (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  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 cyclic 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. SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 11 7.1.6.1.3 The requirement for restraint relief in single- or multi-pass exchangers shall be investigated regardless of the fluid temperature difference between the inlet and outlet of the exchanger. The vendor shall provide calculations to prove the adequacy of the design. Some of the stresses are additive, and tube-to-tubesheet joint efficiency shall be considered. Calculations shall consider the following stress combinations: a) for tube stress and/or tube-to-tubesheet joint stress: 1) stress caused by differential tube expansion between rows/passes in the coil sections in both clean and fouled conditions, 2) stress caused by pressure, 3) stress caused by nozzle forces and moments, 4) stress caused by lateral header movement; b) for header and nozzle stress: 1) stress caused by temperature and pressure, 2) stress caused by nozzle forces and moments, NOTE Forces and moments 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 the header full of
water, 2) stress caused by nozzle forces and moments, NOTE Forces and moments 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 mentioned above (e.g. seismic). 7.1.6.1.4 Headers shall be designed so that the corresponding cross-sectional flow area of each pass is at least 100 % of the flow area in the following tube pass. 7.1.6.1.5 The lateral velocity in the header inlet compartment shall not exceed the velocity in the inlet nozzle. Multiple nozzles or an increased header cross-sectional area can be required. SIST EN ISO 13706:2012

ISO 13706:2011(E) 12 © ISO 2011 – All rights reserved 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 steel mm (in) High-alloy steel or other material mm (in) Tubesheet 19 (3/4) 16 (5/8) Plug sheet 19 (3/4) 16 (5/8) Top, bottom and end plates 12 (1/2) 10 (3/8) Removable cover plates 25 (1) 22 (7/8) Pass partition plates and stay plates 12 (1/2) 6 (1/4) 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 3 a) shows the 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 (See A.3.12). Typical constructions are shown in Figure 4. For hydrogen, sour, or wet hydrogen sulfide service, only confined gasket construction shall be used [see Figure 4 a) or 4 b)]. 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. SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 13
a)
Removable cover-plate header b)
Removable bonnet header Key
1 tubesheet 2 removable cover plate 3 removable bonnet 4 top and bottom plates 5 tube 6 pass partition 7 gasket 8 nozzle 9 side frame 10 tube spacer 11 tube support cross-member 12 tube keeper 13 vent 14 drain 15 instrument connection Figure 3 — Typical construction of tube bundles with removable cover plate and removable bonnet headers 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. SIST EN ISO 13706:2012

ISO 13706:2011(E) 14 © ISO 2011 – All rights reserved
a)
Flanged construction, confined gasket b)
Flanged construction,semi-confined gasket c)
Flanged construction, non-confined gasket Figure 4 — Typical confined and full-faced gasket joint details Table 2 — Minimum flange bolt spacing Nominal bolt diameter mm (in) Minimum bolt spacing mm (in) 16 (5/8) 38 (1 1/2) 19 (3/4) 44 (1 3/4) 22 (7/8) 52 (2 1/16) 25 (1) 57 (2 1/4) 29 (1 1/8) 64 (2 1/2) 32 (1 1/4) 71 (2 13/16) 35 (1 3/8) 76 (3 1/16) 38 (1 1/2) 83 (3 1/4) 41 (1 5/8) 89 (3 1/2) 44 (1 3/4) 95 (3 3/4) 48 (1 7/8) 102 (4) 51 (2) 108 (4 1/4)
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. 7.1.6.2.11 Allowable stresses that have been established on the basis of short-time tensile strength shall not be used for the design of flanges and gasketed flat covers. NOTE 1 These allowable stresses can cause permanent deformation. NOTE 2 In ASME BPVC II, the allowable stresses of some stainless steel alloys and high-nickel alloys have been established in this way. SIST EN ISO 13706:2012

ISO 13706:2011(E) © ISO 2011 – All rights reserved 15 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.
Key
1 tubesheet 2 plug sheet 3 top and bottom plates 4 end plate 5 tube 6 pass partition 7 stiffener 8 plug 9 nozzle 10 side frame 11 tube spacer 12 tube support cross-member 13 tube keeper 14 vent 15 drain 16 instrument connection 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. SIST EN ISO 13706:2012

ISO 13706:2011(
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