NB/T 47007-2018Air-cooled heat exchangers (English PDF)

Foreword

This document was issued on 25 December 2018 by the National Energy Administration of the PRC and takes effect on 1 May 2019.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 71.120.30, Chinese classification J 75.

It replaces NB/T 47007-2010, which is superseded.

This standard was drafted in accordance with the rules given in GB/T 1.1-2009 Directives for standardization - Part 1: Structure and drafting of standards.

During the revision of this standard, reference was made to ISO 13706:2011 Petroleum, petrochemical and natural gas industries - Air-cooled heat exchangers and to API 661-2013 Petroleum, petrochemical and natural gas industries - Air-cooled heat exchangers.

This standard replaces NB/T 47007-2010 Air-cooled heat exchangers. Compared with NB/T 47007-2010, the main technical changes are as follows.

Part of the terms have been modified and new terms have been added.

Requirements for the heat transfer performance test of a single finned tube have been specified.

Technical requirements for the embedded (inlaid) finned tube have been added.

A method for evaluating the energy efficiency of air-cooled heat exchangers has been added.

This standard was proposed by and is under the jurisdiction of the National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China (SAC/TC 262).

The chief drafting organizations of this standard are: Shanghai Lanbin Petrochemical Equipment Co., Ltd.; SINOPEC Engineering Incorporation; SINOPEC Guangzhou Engineering Co., Ltd.; Xi'an Jiaotong University; Harbin Air Conditioning Co., Ltd.; Hubei Changjiang Petrochemical Equipment Co., Ltd.; Baoding Hangji Fan Manufacturing Co., Ltd.; Kelvion Thermal Technology (Jiangsu) Co., Ltd.; Shanghai Institute of Special Equipment Inspection and Technical Research; China Special Equipment Inspection and Research Institute; Weihai Klaite Feier Fan Co., Ltd.; Shanghai Hetu Petrochemical Engineering Co., Ltd.

The chief drafters of this standard are: Ma Jun, Han Zhuo, Zhang Yanfeng, Zhang Yingkai, Li Qunsheng, Bai Bofeng, Zhao Liang, Yin Jiying, Zhao Tianbo, Zhou Feng, Han Ruichao, Beng Zhenhai, Wang Chunhui, Chen Zhanyang, Chen Zhiwei, Zhou Wenxue, Zhong Xiaoping, Lu Hongliang and Wang Xin.

The previous editions of the standard replaced by this standard are as follows: NB/T 47007-2010.

1 Scope

NB/T 47007-2018 covers air-cooled heat exchangers, replacing the 2010 edition. An air cooler rejects process heat to the atmosphere across finned tubes instead of to cooling water, which is why refineries, gas plants and petrochemical units in dry regions are built around them. The standard fixes the types and the general arrangement - forced and induced draught, horizontal, inclined and vertical bundles - and names every component of the machine, from the tube bundle and its headers to the plenum, fan ring, drive, structure and louvres. It sets the general provisions on design conditions, design pressure and temperature, and the codes the pressure-retaining parts must satisfy. Design rules follow for the tube bundle: tube and finned tube types and their materials, tube-to-tubesheet joints, plug and cover plate headers and their bolting, tube supports and the allowance for differential expansion, together with the nozzles and their loads. The air side is treated in its own right - fans and their blades, hubs and drives, motors, belt and gear transmissions, vibration switches, the plenum and the louvres and their control, and the recirculation arrangements used in cold climates. Fabrication, welding and heat treatment, inspection and testing including pressure and leak testing of the bundle, surface preparation and painting, marking, and the requirements for transport and site assembly complete the standard. It applies to air-cooled heat exchangers built in China.

This standard specifies the design, material, fabrication, inspection and acceptance requirements for forced-draught and induced-draught air-cooled heat exchangers (hereinafter referred to as air coolers), as well as the method for evaluating their energy efficiency.

1.1 This standard is applicable to air coolers with a design pressure not higher than 35 MPa.

1.2 The range of design temperature to which this standard applies is determined by the service temperature permitted for the material.

1.3 The following categories of air cooler do not fall within the scope of this standard:

1.3 a) air coolers whose headers are made of aluminium or of other non-ferrous metals;

1.3 b) air coolers for which a dedicated industry standard already exists (such as in the refrigeration and air conditioning industries).

1.4 Boundary of the air cooler.

1.4.1 Tube bundle.

1.4.1 a) the face of the first flange gasket in the connection between the header and the external piping;

1.4.1 b) the first threaded joint in the connection between the header and the external piping.

1.4.2 Structure (supporting frame): the steel structure above the base plate of the structure columns.

1.4.3 Fan: the terminal box of the electric motor and the first connection of the pneumatic control air supply of the fan.

1.4.4 Louver: the first connection of the pneumatic control air supply of the louver.

1.5 For pressure-containing parts of an air cooler whose structural dimensions cannot be determined by this standard, design by one of the following methods is permitted, but it shall be assessed and approved by the National Technical Committee on Boilers and Pressure Vessels:

1.5 a) design by analysis (except for organizations that have already obtained the qualification for design by analysis);

1.5 b) proof hydrostatic test;

1.5 c) comparative empirical design based on a comparable structure that has already been put into service.

2 Normative references

The following 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.

GB/T 150.1-2011 Pressure vessels - Part 1: General requirements

GB/T 150.2-2011 Pressure vessels - Part 2: Materials

GB/T 150.3-2011 Pressure vessels - Part 3: Design

GB/T 150.4-2011 Pressure vessels - Part 4: Fabrication, inspection and testing, and acceptance

GB/T 151-2014 Heat exchangers

GB/T 28712.6-2012 Types and basic parameters of heat exchangers - Part 6: Air-cooled heat exchangers

GB/T 27698.6-2011 Test methods of performance for heat exchangers and heat transfer elements - Part 6: Finned tubes for air coolers

GB/T 16507.4-2013 Water-tube boilers - Part 4: Strength calculation of pressure parts

GB/T 196 General purpose metric screw threads - Basic dimensions (GB/T 196-2003, ISO 724:1993, MOD)

GB/T 197 General purpose metric screw threads - Tolerances (GB/T 197-2018, ISO 965-1:2013, MOD)

GB/T 230.1 Metallic materials - Rockwell hardness test - Part 1: Test method

GB/T 231.1 Metallic materials - Brinell hardness test - Part 1: Test method (GB/T 231.1-2018, ISO 6506-1:2014, MOD)

GB/T 699 Quality carbon structural steels

GB/T 700 Carbon structural steels (GB/T 700-2006, ISO 630:1995, NEQ)

GB/T 985.1 Recommended joint preparation for gas welding, manual metal arc welding, gas-shielded arc welding and high energy beam welding

GB/T 985.2 Recommended joint preparation for submerged arc welding

GB/T 1171 General purpose V belts for power transmission

GB/T 1231 Specifications of high strength bolts with large hexagon head, large hexagon nuts and plain washers for steel structures

GB/T 1566 Thin type parallel keys - Sectional dimensions of keyways (GB/T 1566-2003, ASME B18.25.1M:1996, NEQ)

GB/T 1567 Thin type parallel keys (GB/T 1567-2003, ASME B18.25.1M:1996, NEQ)

GB/T 3077 Alloy structural steels

GB/T 3190 Chemical composition of wrought aluminium and aluminium alloys

GB/T 6892 Wrought aluminium and aluminium alloy extruded profiles for general industrial use

GB/T 3767 Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering method for an essentially free field over a reflecting plane (GB/T 3767-2016, ISO 3744:2010, IDT)

GB/T 3880.1 Wrought aluminium and aluminium alloy plates, sheets and strips for general engineering - Part 1: General requirements

GB/T 4437.1 Aluminium and aluminium alloy hot extruded tubes - Part 1: Seamless round tubes

GB/T 4437.2 Aluminium and aluminium alloy hot extruded tubes - Part 2: Seamed tubes

GB/T 4662 Rolling bearings - Static load ratings (GB/T 4662-2012, ISO 76:2006, IDT)

GB/T 5777 Seamless steel pipe and tubing - Methods for ultrasonic testing (GB/T 5777-2008, ISO 9303:1989, MOD)

GB/T 6391 Rolling bearings - Dynamic load ratings and rating life (GB/T 6391-2010, ISO 281:2007, IDT)

GB/T 6479 Seamless steel tubes for high pressure chemical fertilizer equipment

GB/T 5310 Seamless steel tubes for high pressure boilers

GB/T 6893 Aluminium and aluminium alloy drawn (rolled) seamless tubes

GB/T 9948 Seamless steel tubes for petroleum cracking

GB/T 10412 Classical and narrow V-pulleys (datum width system) (GB/T 10412-2002, ISO 4183:1995, MOD)

GB/T 10413 Narrow V-pulleys (effective width system) (GB/T 10413-2002, ISO 5290:2001, MOD)

GB/T 12730 Narrow V belts for general power transmission

GB/T 10715 Belt drives - Electrical conductivity of antistatic endless synchronous belts, banded belts and single V-belts including wide V-belts and hexagonal belts: Characteristics and test method (GB/T 10715-2002, ISO 1813:1998, MOD)

GB/T 13575.1 Classical and narrow V belt drives - Part 1: Datum width system

GB/T 13575.2 Classical and narrow V belt drives - Part 2: Effective width system

GB 19761-2009 Minimum allowable values of energy efficiency and energy efficiency grades for ventilation fans

GB/T 13296 Seamless stainless steel tubes for boilers and heat exchangers

GB/T 2882 Nickel and nickel alloy tubes

GB/T 3625 Titanium and titanium alloy tubes for heat exchangers and condensers

GB/T 8890 Seamless copper alloy tubes for heat exchangers

GB/T 13306 Nameplates

GB/T 13487 Synchronous belts for general power transmission

GB/T 8923.1 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

GB/T 13912 Metallic coatings - Hot dip galvanized coatings on fabricated iron and steel articles - Specifications and test methods (GB/T 13912-2002, ISO 1461:1999, MOD)

GB 18613 Minimum allowable values of energy efficiency and energy efficiency grades for small and medium three-phase asynchronous motors

GB 50009 Load code for the design of building structures

GB 50011 Code for seismic design of buildings (with provisions explanation)

GB 50017 Standard for design of steel structures (with provisions explanation)

GB 50018 Technical code of cold-formed thin-wall steel structures

GB 50205 Code for acceptance of construction quality of steel structures

JB/T 4711 Coating and transport package of pressure vessels

JB/T 10562 General specification of axial flow fans for general use

NB/T 47013.1-2015 Nondestructive testing of pressure equipment - Part 1: General requirements

NB/T 47013.2-2015 Nondestructive testing of pressure equipment - Part 2: Radiographic testing

NB/T 47013.3-2015 Nondestructive testing of pressure equipment - Part 3: Ultrasonic testing

NB/T 47013.4-2015 Nondestructive testing of pressure equipment - Part 4: Magnetic particle testing

NB/T 47013.5-2015 Nondestructive testing of pressure equipment - Part 5: Penetrant testing

NB/T 47013.6-2015 Nondestructive testing of pressure equipment - Part 6: Eddy current testing

NB/T 47014 Welding procedure qualification for pressure equipment

NB/T 47015 Welding specification for pressure vessels

YB/T 050 YNK gear speed reducers for metallurgical equipment

TSG Z6002 Examination rules for welding operators of special equipment

TSG Z8001 Examination rules for nondestructive testing personnel of special equipment

TSG 21 Supervision regulation on safety technology for stationary pressure vessels

3 Terms and definitions

The following terms and definitions apply to this standard.

3.1 pressure: unless otherwise stated, pressure always means gauge pressure.

3.2 working pressure: the highest pressure that may be reached inside the tube bundle of the air cooler under normal operating conditions.

3.3 design pressure: the highest pressure set for the inside of the tube bundle of the air cooler which, together with the corresponding design temperature, is taken as the design loading condition; its value shall not be lower than the working pressure.

3.4 calculated pressure: the pressure used, at the corresponding design temperature, to determine the calculated thickness of the pressure-containing parts of the tube bundle of the air cooler, including the liquid static head.

3.5 test pressure: the pressure at the top of the header when a pressure test or a leak test is carried out.

3.6 design temperature: the metal temperature set for the pressure-containing parts of the tube bundle under normal operating conditions.

3.7 minimum design air temperature: the inlet air temperature specified for winter freeze protection.

3.8 metal temperature: the average temperature through the section thickness of the pressure-containing parts of the tube bundle of the air cooler.

3.9 minimum design metal temperature: the lowest value of the metal temperature of a pressure-containing part able to withstand the design pressure, expected under all possible conditions during operation.

3.10 critical process temperature: the temperature related to an important physical property of the process fluid (such as freezing point, bubble point, dew point, cloud point, and the like).

3.11 specified minimum tube-wall temperature: the critical process temperature plus a safety margin.

3.12 test temperature: the metal temperature of the header of the air cooler when a pressure test or a leak test is carried out.

3.13 exposure temperature: the temperature imposed on mechanical components and instrument components by an external heat source.

3.14 bare tube surface: the outside surface area of the bare tube, based on the tube length between the two tubesheets.

3.15 finned surface: the outside surface area of the finned tube in contact with the air, based on the tube length between the two tubesheets.

3.16 calculated thickness: the thickness obtained from the formulae of the several clauses of this standard, not including the thickness addition. Where necessary, the thickness required for other loads (see 4.3) shall also be taken into account.

3.17 design thickness: the sum of the calculated thickness and the corrosion allowance.

3.18 nominal thickness: the design thickness plus the negative deviation of the steel thickness, rounded up to the thickness of a standard steel size, that is, the thickness marked on the drawing.

3.19 available thickness: the nominal thickness minus the corrosion allowance and minus the negative deviation of the material thickness.

3.20 seal-welded: welding which only ensures that the connection between the heat exchange tube and the tubesheet does not leak.

3.21 strength-welded: welding in which the strength of the welded connection between the heat exchange tube and the tubesheet meets the design requirements for the axial (tensile or compressive) mechanical load and the differential thermal load of the heat exchange tube, and which ensures the sealing performance.

3.22 strength-expansion: expansion in which the strength of the expanded connection between the heat exchange tube and the tubesheet meets the design requirements for the axial (tensile or compressive) mechanical load and the differential thermal load of the heat exchange tube, and which ensures the sealing performance.

3.23 light-expansion: a light expansion intended to eliminate the gap between the heat exchange tube and the tube hole of the tubesheet.

3.24 unit: one or more cells arranged on one continuous structure.

3.25 bay: one or more tube bundles served by one or more fans, including at the same time the structure, the plenum chamber and other ancillary equipment. NOTE: Figure 1 shows a typical arrangement of a bay.

3.26 forced-draught air-cooled exchanger: an air cooler in which the tube bundle is placed on the discharge side of the fan (see Figure 1).

3.27 induced-draught air-cooled exchanger: an air cooler in which the tube bundle is placed on the suction side of the fan (see Figure 2).

3.28 item: one or more tube bundles used for one single service.

3.29 item number: the identification number used by the purchaser for one item.

3.30 hydrogen service: a service condition in which the partial pressure of hydrogen in the process fluid exceeds 700 kPa (absolute).

4 General provisions

4.1 In addition to complying with the provisions of this standard, the design, fabrication, inspection and acceptance of air coolers shall also comply with the requirements of the relevant laws, regulations and rules promulgated by the State.

4.2 Qualification.

4.2.1 The organizations that design and fabricate air coolers shall have a sound quality management system.

4.2.2 The organization fabricating the air cooler product, the organization fabricating the finned tubes for the air cooler and the organization fabricating the fans for the air cooler should obtain the corresponding Safety Registration Certificate for Air-cooled Heat Exchanger Products.

4.3 Loads.

4.3.1 The following loads shall be considered when designing the pressure-containing parts of the air cooler:

4.3.1 a) design pressure;

4.3.1 b) liquid static head; when the liquid static head is less than 5 percent of the design pressure it may be neglected.

4.3.2 The following loads shall be considered when designing the steel structure of the air cooler:

4.3.2 a) gravity load of the material;

4.3.2 b) gravity load of the equipment;

4.3.2 c) live load of platforms and ladders;

4.3.2 d) dynamic load;

4.3.2 e) thermal thrust;

4.3.2 f) seismic load;

4.3.2 g) wind load;

4.3.2 h) snow load;

4.3.2 i) test load.

4.4 Allowable stress of pressure-containing parts: the allowable stresses of steel and of stud bolt materials at the various temperatures shall be selected in accordance with GB/T 150.

4.5 Weld joint coefficient. In the header of the air cooler, the welds joining the tubesheet and the plug sheet respectively to the top plate and to the bottom plate (longitudinal welds), as well as the welds joining the end plates to the tubesheet, to the plug sheet, to the top plate and to the bottom plate (end face welds), shall all be treated as Category A welds in accordance with GB 150.1-2011.

4.5 When the welds of the header of the air cooler are made by double-sided welding or single-sided welding, the weld joint coefficient of the corner joint against butt weld shall be selected according to the following provisions: a) single-sided welding: 100 percent nondestructive testing, phi equals 0.9; partial nondestructive testing, phi equals 0.8; nondestructive testing impossible, phi equals 0.6; b) double-sided welding: 100 percent nondestructive testing, phi equals 1.0; partial nondestructive testing, phi equals 0.85; nondestructive testing impossible, phi equals 0.6.

4.6 a) Determination of the design temperature: the maximum and minimum design temperatures of the pressure-containing parts shall be specified by the purchaser. The design temperature shall not be lower than the maximum temperature that the metal of the component may reach in the working condition. In any case the surface temperature of the metal of the component shall not exceed the service temperature permitted for the material.

4.6 b) The purchaser shall separately specify the maximum operating temperature (finned tube design temperature) in order to allow the selection of the finned tube type. The design temperature of the pressure-containing parts is not the temperature used to decide the finned tube type or to determine the exposure temperature of the mechanical components and of the instrument components.

4.7 Thickness addition. The thickness addition shall be determined by formula (1): C equals C1 plus C2, where C is the thickness addition, in mm; C1 is the negative deviation of the thickness of the steel plate or of the steel tube, determined in accordance with 4.7.1, in mm; C2 is the corrosion allowance, determined in accordance with 4.7.2, in mm.

4.7.1 Negative deviation of the material thickness: the negative deviation of the thickness of plate or tube shall follow the provisions of the material standard.

4.7.2 Corrosion allowance. In order to prevent the thickness of the header (including nozzles and flanges) from being weakened or thinned by corrosion or mechanical wear, a corrosion allowance shall be considered. The corrosion allowance of the pressure-containing parts in contact with the working medium shall be specified by the purchaser; if it is not given, for carbon steel and low alloy steel C2 is generally taken as not less than 3 mm. The determination of the corrosion allowance shall in addition meet the following requirements:

4.7.2 a) no corrosion allowance is taken for the heat exchange tubes, the gaskets and the sealing faces in contact with the gaskets;

4.7.2 b) a corrosion allowance shall be taken on both sides of the tube-pass partition plates and of the reinforcing plates;

4.7.2 c) when a partition plate groove is machined in the tubesheet and in the cover plate, the metal above the bottom of the partition plate groove may be taken as corrosion allowance; when the corrosion allowance is greater than the groove depth, the difference between the two shall be added.

4.7.3 Machining allowance: the fabricating organization shall add by itself a machining allowance according to the fabrication process and the actual thickness of the steel.

4.8 Pressure test: after the tube bundle has been assembled a pressure test shall be carried out; the items and requirements of the pressure test shall comply with the drawings and with the provisions of GB/T 150.

4.9 Leak test.

4.9.1 The leak test shall meet the requirements of 4.7 of GB/T 150.1-2011.

4.9.2 The type of leak test and the requirements shall be indicated on the drawings.

4.10 Data: the data requirements for the design, bidding and fabrication processes of the air cooler shall refer to Annex A.

5 Types, construction and model designation

5.1 Types of air cooler. The types of air cooler are divided into forced-draught air coolers (see Figure 1) and induced-draught air coolers (see Figure 2). The selection of the air cooler type may refer to Annex B. The types of air cooler, the nominal sizes and the basic parameters of the various components shall comply with the provisions of GB/T 28712.6-2012.

Figure 1 shows the forced-draught air cooler, in the two arrangements a) horizontal type and b) inclined roof type. Figure 2 shows the induced-draught air cooler.

5.2 Composition of the components of the air cooler and names of the parts and components.

5.2.1 An air cooler mainly comprises the following components:

5.2.1 a) tube bundle: an assembly consisting of headers, heat exchange tubes, tube bundle side beams, support beams and the like (see Figure 3);

5.2.1 b) fan: an assembly consisting of hub, blades, fan ring, support frame, driving mechanism and the like (see Figure 4);

5.2.1 c) louver: an assembly consisting of louver blades, adjusting mechanism, louver side beams and the like (see Figure 5);

5.2.1 d) structure: the steel structure used to support the tube bundle, the fan, the louver and their accessories (see Figure 1 and Figure 2);

5.2.1 e) plenum chamber: the assembly used to guide the air [for Figure 1 a), the plenum chamber is a part of the structure].

5.2.2 The names of the parts and components of the air cooler are given in Table 1 and in Figure 1 to Figure 5.

Table 1 Names of the parts and components of the air cooler, items 1 to 10: 1 structure (component); 2 fan (component); 3 fan ring (component); 4 platform (component); 5 plenum chamber (component); 6 louver (component); 7 tube bundle (component); 8 ladder (component); 9 tube bundle seat (component); 10 threaded plug.

Table 1, items 11 to 21: 11 plug gasket; 12 end plate; 13 plug sheet; 14 flange; 15 nozzle; 16 instrument connection (component); 17 top plate; 18 tubesheet; 19 lifting lug; 20 wind baffle plate; 21 diagonal brace (component).

Table 1, items 22 to 32: 22 upper cross beam (component); 23 finned tube (component); 24 support beam (component); 25 tube bundle side beam; 26 tube support; 27 wind baffle beam; 28 header wind baffle plate; 29 vent (component); 30 reinforcing plate; 31 bottom plate; 32 drain (component).

Table 1, items 33 to 43: 33 cover plate gasket; 34 cover plate; 35 stud bolt; 36 nut; 37 bonnet (component); 38 tube-pass partition plate; 39 U-shaped bend; 40 support plate; 41 connecting plate; 42 reinforcing joint; 43 header bracket (component).

Table 1, items 44 to 53: 44 L-shaped bend; 45 manifold header (component); 46 semicircular header; 47 blade; 48 hub (component); 49 bearing (component); 50 fan shaft; 51 fan support (component); 52 driving belt; 53 belt pulley (component).

Table 1, items 54 to 63: 54 electric motor (component); 55 speed reducer (component); 56 coupling (component); 57 bearing sleeve; 58 pin shaft; 59 louver side beam; 60 louver blade; 61 operating rod; 62 positioner (component); 63 handle.

Figure 3 shows the typical construction of the tube bundle and of the headers, in five arrangements: a) tube bundle with plug type header; b) tube bundle with removable cover plate type header; c) tube bundle with removable bonnet type header; d) tube bundle with manifold type header; e) tube bundle with semicircular tube type header.

In the plug type header of Figure 3 a) the identified parts are the flange, the nozzle, the instrument connection, the top plate, the tubesheet, the lifting lug, the wind baffle plate, the diagonal brace, the upper cross beam, the finned tube, the support beam, the tube bundle side beam, the tube support, the wind baffle beam, the header wind baffle plate, the vent, the reinforcing plate, the bottom plate and the drain, together with the threaded plug, the plug gasket, the end plate, the plug sheet and the tube bundle seat.

In the removable cover plate type header of Figure 3 b) the identified parts are the cover plate gasket, the cover plate, the stud bolt and the nut; in the removable bonnet type header of Figure 3 c) the identified parts are the bonnet and the tube-pass partition plate.

In the manifold type header of Figure 3 d) the identified parts are the U-shaped bend, the support plate, the connecting plate, the reinforcing joint, the header bracket, the L-shaped bend and the manifold header; the semicircular tube type header of Figure 3 e) identifies the semicircular header.