BS 6990

Licensed copy: University of Teknologi Mara, University of Teknologi Mara, Version correct as of 13/07/2010 04:34, (c) BSI BRITISH STANDARD Code of practice for Welding on steel pipes containing process fluids or their residuals ICS 25.160.10 BS 6990:1989 Including Amendment No. 1 not issued separately Licensed copy: University of Teknologi Mara, University of Teknologi Mara, Version correct as of 13/07/2010 04:34, (c) BSI BS 6990:1989 This British Standard, having been prepared under the direction of the Welding Standards Committee, was published under the authority of the Board of BSI and comes into effect on 28 February 1989 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Welding Standards Committee (WEE/-) to Technical Committee WEE/21, upon which the following bodies were represented: Associated Offices Technical Committee British Gas plc British Non-Ferrous Metals Federation British Steel Industry Electricity Supply Industry in England and Wales Engineering Equipment and Materials Users’ Association Health and Safety Executive Heating and Ventilating Contractors’ Association Institute of Refrigeration Institution of Gas Engineers Institution of Mechanical Engineers Joint Industry Board for Plumbing Mechanical Engineering Services in England and Wales National Association of Plumbing, Heating and Mechanical Services Contractors Power Generation Association (BEAMA Ltd.) Stainless Steel Fabricators’ Association of Great Britain Tubes Investments Limited United Kingdom Atomic Energy Authority Water Tube Boilermakers’ Association Welding Institute Welding Manufacturers’ Association (BEAMA Ltd.) The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Association of Consulting Engineers British Institute of Non-destructive Testing Department of Energy (Petroleum Engineering Division) Institution of Production Engineers Pipeline Industries Guild United Kingdom Offshore Operators Association Water Research Centre © BSI 04-1999 First published as DD 39, July 1974 First published as BS 6990, February 1989 The following BSI references relate to the work on this standard: Committee reference WEE/21 Draft for comment 86/78728 DC ISBN 0 580 16672 4 Amendments issued since publication Amd. No. Date of issue Comments 9772 February 1998 Indicated by a sideline in the margin University of Teknologi Mara. General 1 Scope 1 2 Definitions 1 3 Information. temperature and internal pressure 6 8 Pipe material 6 9 Fitting material 6 10 Welding equipment 6 11 Electrodes and filler metals 6 12 Shielding gases 7 13 Approval and testing of welding procedures 7 14 Approval and testing of welders 12 15 Preparation of pipe 12 16 Inspection of fittings 13 17 Fusion faces 13 18 Preparation for encirclement fitting 13 19 Preparation for set-on fitting 16 20 Alignment of flanged fittings 16 21 Working clearance 17 22 Stray arcs 17 23 Weather conditions 17 24 Preheating 17 25 Sequence of welding 17 26 Inter-run cleaning 18 27 Inspection 18 28 Non-destructive testing acceptance criteria 19 29 Rectification of welds 19 Figure 1 — Typical fittings 3 Figure 2 — Typical longitudinal weld preparation for fitting: dimensions and tolerances 14 Figure 3 — Attachment of run-on/run-off plates to backing material 15 Figure 4 — Typical yoke-type clamp for encirclement tee fittings 16 Table 1 — Welding procedure details 10 Table 2 — Changes affecting procedure approval (essential variables) 11 Publications referred to Inside back cover © BSI 04-1999 i . Version correct as of 13/07/2010 04:34. Safety considerations 4 Legal requirements 4 5 Preliminary considerations 4 6 Factors affecting safety 4 Section 3.Licensed copy: University of Teknologi Mara. Welding 7 Pipe thickness. (c) BSI BS 6990:1989 Contents Page Committees responsible Inside front cover Foreword ii Section 1. items to be approved and items to be agreed and to be documented 2 Section 2. It has been assumed in the drafting of this code that the execution of its provisions is entrusted to appropriately qualified and experienced people. © BSI 04-1999 . Unless otherwise qualified. welding technology and non-destructive testing. The up-dating has been extensive. particularly with regard to off-shore exploration. Version correct as of 13/07/2010 04:34. shapes and positions of these anomalies and on the suitability of the whole weld for its specific service. the methods and recommendations in this code are considered to reflect up to date knowledge and sufficient experience of practical use to merit their adoption. choice of materials and methods of construction are not covered by this code. general guidance has been given on some aspects. University of Teknologi Mara. BS 4677 and BS 8010-1. such as CP 2010-2. Pipe dimensions. The acceptance criteria have been based on the present technical analysis of the various types. for the purposes of this code nominal values of outside diameter and thickness of pipe apply. Specific details will be for agreement between the contracting parties after due consideration of the prevailing service conditions. To this knowledge has been added the expertise gained in the process plant field. BS 2633. To ensure that the workmanship and welding follow the details of this code. Since the design. The use of the words “imperfection” or “flaw” or other phrases containing the words “imperfection” or “flaw” in this code is not intended to imply a defective condition or any lack of integrity of the weld as it is known that all welds contain certain features described as artefacts. testing and acceptance criteria. This method of attachment is sometimes. imperfections or discontinuities. resulting in an unified code which covers both spheres. but incorrectly. Reference to current legislation is essential before any attempt to undertake work of this nature. and covers welding operations where attachments are required and where it is not necessary or practical to decommission and/or decontaminate the system. Since the preparation of DD 39 in 1974 considerable experience has been gained as the result of both on-shore and off-shore North Sea developments. Because of the wide range of pipelines and pipework and the products that can be conveyed and the range of attachments that may be required. (c) BSI BS 6990:1989 ii Foreword This British Standard Code of Practice has been prepared under the direction of the Welding Standards Committee. It is based on an up-dating of Draft for Development DD 39 which is withdrawn.Licensed copy: University of Teknologi Mara. it would be normal for the contractor as well as the organization undertaking this specialist work to have and employ a suitable quality control system such as is recommended in BS EN ISO 9000. Although new developments and refinements can be expected to emerge in the future. flaws. It reflects the latest knowledge in the welding on steel pipelines and pipework which contain or have contained process fluids or the residuals of such process fluids. sizes. termed “hot tapping”. BS 4515. covering practically every aspect of the technical changes in materials. The main purpose of this code is to give general details for welding. and to follow the details of this code. reference should be made to the appropriate standards. The techniques and equipment described herein require extensive facilities and specialist personnel and as such should not be attempted without such specialist equipment and personnel. © BSI 04-1999 iii . University of Teknologi Mara. This standard has been updated (see copyright date) and may have had amendments incorporated. (c) BSI BS 6990:1989 A British Standard does not purport to include all the necessary provisions of a contract.Licensed copy: University of Teknologi Mara. an inside back cover and a back cover. Version correct as of 13/07/2010 04:34. This will be indicated in the amendment table on the inside front cover. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover. an inside front cover. Users of British Standards are responsible for their correct application. (See clause 4). pages 1 to 20. pages i to iv. University of Teknologi Mara. Version correct as of 13/07/2010 04:34.Licensed copy: University of Teknologi Mara. (c) BSI iv blank . 3 inspector the body. Version correct as of 13/07/2010 04:34.6 welding procedure* a specific course of action followed in welding. semi-automatic and mechanized arc welding by the following processes or combination of processes: a) manual metal-arc welding.1 employer a welder who has demonstrated his ability to produce welds meeting the details of this code the owner of the pipeline or pipework 2. during and after all these operations. an inspector or other authorized representative. 2. where necessary. representative of that to be used on an actual job. regulates the requirements with which particular pipelines or pipework have to comply NOTE One way in which such requirements may be promulgated is by making reference to British Standards. a section of pipe to a fitting or two fittings 2. stress corrosion cracking or embrittlement.5 joint the completed weld joining two sections of pipe. It is essential that the items listed in clause 3 should be fully documented and followed. University of Teknologi Mara. NOTE 2 The titles of the publications referred to in this code are listed on the inside back cover.9 welder* the operator who performs the welding NOTE Terms marked with an asterisk (*) are taken from BS 499-1. association or employee that ensures that the materials and construction are in accordance with this code 2.7 welding procedure test the making and testing of a welded joint. BS 4677 and BS 4515. This code does not relate to a pipeline or pipework containing a process fluid or its residuals that will become explosively unstable upon the application of heat or will affect the pipe material by rendering it susceptible to ignition. through the power vested in it by Government Statute.Licensed copy: University of Teknologi Mara.10 approved welder 2. Welding operations needing post-weld heat treatment for adequate weld quality are not within the scope of this code. General 1 Scope This code covers operations relating to and involving arc welding on ferritic steel and austenitic stainless steel land or offshore pipelines and process plant pipework which contain or have contained a process fluid and which are at least 5 mm thick.8 approved welding procedure a documented welding procedure that has been approved by an inspecting authority either by means of a welding procedure test or as a result of authentic documented experience gained with the welding of joints similar to that to which the welding procedure applies 2. The code covers manual. e) non-shielded welding. 2 Definitions For the purposes of this code the definitions given in BS 499-1 apply together with the following. 2. This code is not applicable to a pipeline or pipework that has been fully isolated and decontaminated or has not been commissioned. b) MIG/MAG welding. It gives details of procedures prior to. d) flux cored arc welding. (c) BSI BS 6990:1989 Section 1. tools to be used 2.2 contractor the firm undertaking the contract and any subcontractors engaged in work covered by this code © BSI 04-1999 the first run deposited in the root of a multi-run weld NOTE Also known as a “stringer bead” in vertical-down welding. 1 .4 statutory authority the body or organization that. including a list of materials and. in order to prove the feasibility of a welding procedure NOTE This term is not usually applied to any tests that may have been made during the development of a welding procedure.11 root run* NOTE The employer may act through a consultant. c) TIG welding. 2. 2. 2. These are covered by other standards such as BS 2633. NOTE 1 Welding on pipes of thickness below 5 mm is not covered by this code although it can be undertaken. (c) BSI BS 6990:1989 2. NOTE Typical fittings are shown in Figure 1. Version correct as of 13/07/2010 04:34. items to be approved and items to be agreed and to be documented 3. g) The period for which records of approved welding procedures should be kept (see 13.5) and the Examination Level to be used when ultrasonic examination in accordance with BS 3923-1 is to be applied (see 27.1).1 b)].3. e) Use of a plate butt joint to simulate a longitudinal butt weld for welding procedure approval [see 13.14 mechanized welding* welding in which the welding parameters are controlled mechanically or electronically and may be manually varied during welding to maintain the required welding conditions 3 Information.3).1). b) The type of process fluid and its temperature. a) The location and identification of the pipeline or pipework.Licensed copy: University of Teknologi Mara. c) Documentation relating to welding procedure approval (see 13. i) The methods of non-destructive testing (see 27. a) The minimum pipe thickness on which welding is to be carried out when the conditions are other than those detailed in clause 7 (see clause 7).3).1).1).1.5). (See also 5. d) Use of diameter and thickness grouping for welding procedure approval [see 13. 3. j) Inspection personnel (see 27.2 4) ii)]. c) The definition of a batch when batch testing of electrodes and filler metals is required (see 11. University of Teknologi Mara. i) Non-destructive testing procedures (see 27. a) The minimum tensile strength of weld metal for fillet welds when this need not be as high as the minimum specified for the parent metal [see 11. b) The specification of the material for a fitting (see clause 9). 27. NOTE The agreement of the statutory authority may also be required. 2 © BSI 04-1999 .1).8.1 Information to be supplied by the employer The following information to be supplied by the employer should be fully documented and followed.) c) The composition of the pipe material if known.4 and 27. e) Whether batch testing of electrodes and filler metals is required (see 11.4 c)]. 27.13 semi-automatic welding* welding in which some of the welding variables are automatically controlled. f) The welding procedure used for repairing defects in an encirclement fitting (see 18. h) Repair or rejection of arc strikes (see clause 22). NOTE The agreement of the statutory authority may also be required.4 b)].1).1). f) The interval before testing the test welds if other than 24 h [see 13. NOTE This information may not be able to be supplied until the appropriate stage of the work is reached. 3. pressure and flow rate.12 positional welding welding wherein the pipe or assembly is held stationary 2.2 Items to be approved by the employer The following items to be approved by the employer should be fully documented and followed.3 Items to be agreed The following items to be agreed between the contracting parties should be fully documented and followed. but manual guidance is necessary 2. h) Whether prevailing weather conditions are such that welding is not to be carried out (see clause 23).3 and 5. d) The type of fitting to be used and its position on the pipe. b) Electrodes and filler metals to be used (see 11. g) The thermal cutting method for making large modifications to the radius of a set-on fitting (see 19. Licensed copy: University of Teknologi Mara. University of Teknologi Mara. Version correct as of 13/07/2010 04:34. (c) BSI BS 6990:1989 Figure 1 — Typical fittings © BSI 04-1999 3 . 7 Text deleted 5. b) Identify the pipe and process conditions (fluid content and its pressure. by sampling and analysis if necessary. 5. work involving the application of heat should not start until that doubt is resolved. For these reasons all such operations should always be carefully considered before any work is started so that the risks are known and fully understood. c) Any chemical that may cause corrosion or stress corrosion cracking. where potential hazards are identified. approval requirements. and expert advice should always be sought. may cause operational difficulties or may in itself create hazards greater than those presented by the welding operation.6 However. and if the risks associated with welding are known to be acceptably small. If there is any doubt as to the nature or the properties of the fluid inside the pipe. equipment required and fittings required. explosion. it is essential to identify the relevant chemical and physical characteristics of the process fluid.Licensed copy: University of Teknologi Mara. 5 Preliminary considerations 5. circumstances do arise when the removal of the process fluid may not be practicable. 5. taking into account the requirements of a permit to work and any exemption certificate. the first consideration should be to remove the hazardous substances and to ensure that any remaining inside the pipe will no longer present a risk to health and safety. d) Produce detailed plan of action. very hazardous. In particular welding operations should be avoided on pipes containing acetylene. 5.2 Initial requirements a) Establish the necessity for welding on pipe containing a process fluid or residuals. Version correct as of 13/07/2010 04:34. including the responsibilities of each individual. In many cases this advice will be available from the owner of the contents in the pipe. the factory occupier or the pipeline operator. (c) BSI BS 6990:1989 Section 2. Documents should include not only the details of the welding procedures but also safety instructions and an indication of who is responsible for each of the items.1 The application of heat to a pipe containing a process fluid or a residue during preheating or welding operations can be. University of Teknologi Mara. potentially. In these circumstances.1 General In drawing up a safe system of work there are a number of factors that need to be taken into account. 4 5. Flammable substances may explode. or any residue it may leave and of any contaminant that may arise and be present inside the pipe. including any reaction between the pipe metal and the substances and any long or short-term effect on the corrosion resistance and integrity of the finished weld and the heat-affected zone. This may include hydrogen present in the pipe material introduced as a product of corrosion or other reactions. 5. c) Ensure compliance with legal requirements. b) Substances which undergo any reaction or decomposition that leads to a dangerous increase in pressure. it is essential that expert advice is taken as to the effect of heat on those properties. oxygen. e) Confirm welding procedure. In other instances the advice may be available from HM Factory Inspectorate. toxic materials may escape and some chemicals when heated may react with the metal of the pipe itself.3 Once the chemical and physical properties of all substances inside the pipe have been established. other unsaturated hydrocarbons.8 If toxic or reactive substances are present in the pipe detailed guidance should be sought on the safe approach to the welding operation. In all cases procedures should be written down and fully understood by those involved in the operation. temperature and flow rate) and verify that adequate experimental work has been completed to prove the safety of the operation. 6 Factors affecting safety 6. 5. a) Mixtures of gases or vapours within their flammable range.4 Pre-heating or welding operations should not be carried out on pipes that contain the following. © BSI 04-1999 .5 In all cases. The list that follows is intended to be a check list. welding operations may be carried out. 6. hydrogen or ammonia. services required. not detailed guidance. Safety considerations 4 Legal requirements All persons involved in welding operations on steel pipes have a duty to make themselves aware of all current legislation relative to their industry.2 Before any work is started involving the application of heat to a pipeline or pipework that may contain or have contained a process fluid. or attack or embrittlement of the metal. 7 Action during welding Whenever possible the pressure. chemical and water) and to all affected landowners and occupiers. 6. c) Install marker posts if necessary. If possible access by ramp is preferable to step ladders. oil. d) Check provision of portable ammeter for accurate measuring of welding current. b) Ensure adequate excavation and shoring or scaffolding where necessary. welding should cease. f) Issue courtesy notices to common wayleave users (e.4 Site preparation a) Provide good access to and from site. f) Check adequate quantities of the correct welding consumables are available and that they are stored under correct conditions. communications. e) Check welding cables are routed away from areas containing flammable fluids. Version correct as of 13/07/2010 04:34. g) Clean and test all equipment used prior to return to storage. b) Restore work site to original condition. c) Ensure breathing apparatus is available. © BSI 04-1999 6. temperature and flow rate in the pipeline should be monitored during the welding operation. d) Ensure resuscitation equipment is available. e) Check distribution of procedures to necessary personnel and establishment of communications. h) Carry out de-briefing among key personnel. d) Check provision for removal of ground water and protection from the weather. cranage.3 Documentation a) Provide location plan showing access routes including emergency access. 6.g. b) Ensure firefighting equipment is available. f) Advise all necessary persons of completion and remove all equipment. University of Teknologi Mara. c) Provide adequate support for pipe — preferably of non-combustible materials. compressed air and gases. d) Prove area is hazard free.6 Action immediately prior to welding a) Check pipe is correct one and that the required non-destructive testing has been carried out. Where these exceed the previously agreed and authorized limits.Licensed copy: University of Teknologi Mara. obstructions and any other adjacent pipes including the proximity of drains and ducts where hazardous liquids and vapours may be present and valves which are carrying hazardous liquids. g) Check temperature of pipe wall and fitting. 6. e) Stand down emergency services. 6. electric.5 Emergency services a) Ensure first aid is available. g) Provide emergency procedures. 6. fire and police. f) Provide adequate lighting. b) Check process conditions (pressure. gas. 5 .8 Action on completion a) Prior to reinstatement. c) Check all approved welders and supervisors have a clear understanding of the approved welding procedure. (c) BSI BS 6990:1989 f) List the services required (e. check all work and testing is completed. b) Prepare drawing or sketch of work area showing excavations. particularly for escape routes.g. electrical power). It is particularly important that a communication system is established between the proposed work site and the pipeline control centre in order that pipeline or pipework conditions may be controlled prior to and during welding. temperature. flow rate and fluid) are within limits authorized. c) Check notice of entry to site. e) Ensure the welding area is adequately ventilated. h) Re-check to ensure hazard-free conditions still exist. d) Ensure compliance with employer’s requirements and procedures. If this is not possible. c) microstructure (replica technique). cables and accessories should comply with the requirements of the appropriate British Standard where it exists. Adequate means of measuring current should be available. by wet chemical. b) hardness (portable hardness tester). The selection of the material for a fitting should take account of the composition of the pipe. d) colour.g. Particularly when welding austenitic stainless steel or low alloy ferritic steel pipes. means should be provided for measuring the arc voltage. The return current cable connecting clamp should at all times be connected to the work at a point as close as possible to the actual weld. Experience and research show that for materials of yield strength not greater than 450 N/mm2. In the case of joints between dissimilar metals. in which case the definition of a batch should be agreed between the contracting parties. b) as an alternative. for fillet welds only. Guidance on the appropriate British Standards covering suitable types of weld metal for welding carbon. BS EN 168. or. chromatographic. When required by the employer batch testing of electrodes and filler metals should be carried out. The following are examples of features that can be checked for this purpose: a) chemical composition. temperature and internal pressure It is necessary to ensure that during the welding operation the material in the region of the weld pool has sufficient strength to contain safely the internal pressure and avoid a blow-out. BS EN 60974-11 and BS EN 60974-12. pipe material. University of Teknologi Mara. 11 Electrodes and filler metals 11.4. carbon-manganese and low-alloy ferritic steels is given in BS 2633. the operating conditions and the process fluid. Version correct as of 13/07/2010 04:34. BS EN 169. Welding plant. Only electrodes and filler metals which have received the prior approval of the employer should be used. BS 638. For other materials or conditions. either as part of the welding plant or by the provision of a portable ammeter. instruments. pipe thickness.1 General The electrodes. © BSI 04-1999 . filler wires or rods used should produce weld metal that has a minimum tensile strength either: a) at least equal to the minimum specified for the parent metal. a minimum pipe thickness of 5 mm or greater should be agreed between the contracting parties. operating at temperatures of not greater than 350 °C and with a hoop stress of not greater than 72 % of the specified minimum yield stress. e. due to chemical reaction. BS EN 167. radiation pattern or spectrographic analysis. All instruments should be calibrated regularly (see BS EN 30012-1). The risk of blow-out is a complex interaction of welding conditions. e) magnetism. Welding 7 Pipe thickness. NOTE For some products.g. blow-out can be prevented during welding provided the minimum pipe thickness is not less than 5 mm. the safe pipe temperature may be much lower than 350 °C. pipe temperature and hoop stress. 6 10 Welding equipment The contractor should maintain all welding plant and ancillary equipment in good working order. (c) BSI BS 6990:1989 Section 3. steelwork or structures should not be used. The welding equipment should be capable of controlling the parameters given in Table 2 to within the limits stated in that table.Licensed copy: University of Teknologi Mara. Return paths via pipe hangers. it is essential that sufficient information is determined about the pipe material to enable a welding procedure to be developed. a level approved by the employer lower than the minimum specified for the parent metal. f) reaction to chemical etchants (identification kits). the weld metal should be of a composition which is compatible with that of the parent metal. based on either specific previous experience and/or data from trials. see 5. e. 8 Pipe material Under no circumstances should any welding be undertaken on pipe of an unknown material. the weld metal should have a tensile strength at least equal to that of the lower strength parent metal. In the case of mechanized and semi-automatic welding. Normally the type and condition of the pipe material can be obtained from records. 9 Fitting material The specification of the material for a fitting should be agreed between the contracting parties. NOTE The agreement of the statutory authority may also be required. then additional precautions.g.3 Welding parameters. limiting the maximum heat input to avoid blow-out. there may be occasions where the desired balance is unobtainable and under these circumstances it may be necessary to reduce the pressure or flow rate of the product to maintain safe operation. There will be many instances where the allowable heat input will be adequate to provide good properties and the above balance will not be critical. The most common process is manual metal-arc welding. However.g.1. but these are in less common use. will have to be included. e. 11. with a low heat input it may not be possible to avoid high cooling rates in the weld area and this could give unsatisfactory hardness. 12 Shielding gases 12. thus reducing the possibility of blow-out: the low hydrogen deposit is also of advantage where the weld and heat-affected zone may be of high hardness. When the electrode manufacturer makes specific recommendations for re-drying and/or storage of electrodes. e. the use of argon/CO2 mixtures reduces penetration as compared to pure CO2. 13. should be used. Version correct as of 13/07/2010 04:34. MIG/MAG and flux cored arc welding. including the relevant British Standard designations. Detailed consideration of the metallurgy and welding are also required. preheating or weld bead placement. 7 . the variation of such addition should not exceed ± 10 % of that stated.2 Storage and handling Electrodes.1 as supplied by the manufacturers. Moisture content should correspond to a dewpoint of – 30 °C or lower. 5 % CO2. low hydrogen electrodes where the depth penetration of this type of electrode is less than with others. Safety is obviously of paramount importance and this will involve. among other considerations. c) gas mixtures that have been proved to be satisfactory as a result of procedure approval tests. There should be no mixing of gases in the field. only gases specified in 12. the contractor should follow such recommendations.2 Welding processes and consumables. University of Teknologi Mara. 2 % O2. Gases that are of questionable purity and those in containers which show signs of damage should not be used.1 Safety considerations in formulating a welding procedure 13. Thus a compromise has to be reached and if the maximum heat input allowable for safety is insufficient to provide adequate material properties. The final welding procedure chosen will be a balance between the safety of the technique on one hand and the prevention of unsatisfactory material properties on the other. When a gas mixture is used which has specified additions. Other processes have been investigated. In MIG/MAG welding. filler wires and rods should be stored and handled so as to avoid damage or deterioration to them and to the containers in which they are transported. An increased safety factor may be attained by the use of basic. 12.Licensed copy: University of Teknologi Mara. © BSI 04-1999 13 Approval and testing of welding procedures 13.g. it is also the best documented. e. In the field. However. unless this is an integral part of a mechanized process which utilizes a fail-safe cut-off when the proportions fall outside those specified in the approved welding procedure. The principal welding parameters of concern in formulating a safe procedure are welding current and travel speed. Detailed consideration of the metallurgy and welding are also required. b) carbon dioxide complying with BS EN 439.1 General. 13. (c) BSI BS 6990:1989 Guidance on suitable types of weld metal for welding similar and dissimilar austenitic stainless steels is given in BS 4677. filler wires and rods that show signs of damage or deterioration should not be used. gases or gas mixtures of the following quality should be used: a) argon complying with BS EN 439.1 General Where appropriate. The development of a welding procedure for welding on pipe containing a process fluid or residuals requires the careful consideration of a number of items and some of these should be verified experimentally.1. in specially marked containers. Electrodes.1.2 Storage and handling Shielding gases should be kept in the containers in which they are supplied and these should be stored away from extremes of temperature. The flow rate. High pressure will increase the possibility of blow-out but it is less significant than other factors. 8 Chemical analysis and thickness of both pipe and fittings will influence the hardness. The flow of product through the pipe may exert a considerable cooling effect upon the weld area which may result in the weld and/or its heat-affected zone having an unsatisfactory micro-structure. the approval and testing of welding procedures should consist of the following stages. The flow conditions during welding should be maintained within the range used for procedure development to avoid such increases in cooling rates or build-up of heat which could affect the heat-affected zone micro-structure or the safety of the pipeline or pipework. If the electrode is made negative then penetration may be reduced by up to 25 %.2 Stages in obtaining approval Before a contractor carries out welding in accordance with this code he should either: a) obtain exemption from making welding procedure tests by submitting previously approved welding procedures for inspection by the employer. © BSI 04-1999 . absolute values can only be found by experimentation. Product pressure and flow rate can have a considerable influence upon the safety of welding. Consideration should be given to the effect of heat input on the in-service performance of corrosion resistant pipe. The principal means of determining these parameters is by experimentation on similar materials under simulated pressure. 13. Comparisons of hardness may be made between materials welded under identical conditions by comparing carbon equivalent values but. The welding process can affect the micro-structure: MIG/MAG welding is a low heat input process and thus the hardness tends to be high but it has the advantage of being a low hydrogen process. but a minimum travel speed should be determined to avoid heat build-up. Normal methods of post-weld heat treatment are usually impossible to apply as the strength of the material decreases at higher temperatures and the pipe probably will not be able to withstand the internal pressure. A reduction in the corrosion resistance of the internal surface can result from microstructural changes and oxide scaling.4 Operating conditions. 13. The travel speed is less easy to control than the welding current. after any discussion with the contractor. (c) BSI BS 6990:1989 The welding current and travel speed should be adjusted to ensure that the penetration is insufficient to cause blow-out but sufficient to avoid lack of fusion. or b) satisfactorily carry out the relevant welding procedure test(s) as detailed below. One successful way of controlling travel speed is to utilize vertical-down welding where the speed of travel is controlled by the fluidity of the weld pool.1. NOTE Welding procedure approval tests carried out in accordance with this code and witnessed by an independent inspector may be offered for consideration by other employers provided that all the provisions have been fulfilled. Preheating can have a considerable influence upon the micro-structure but unfortunately there can be difficulties in applying preheat as it is affected by the temperature and flow rate of the product which may rapidly remove the heat. 1) The contractor should submit to the employer details of the proposed welding procedure. rather than the use of vertical-up welding where the speed is a function of the welder’s personal performance and where excessive weaving may be practised. Version correct as of 13/07/2010 04:34. However it is possible to influence the hardness of the weld and in particular the weld toe by the judicious placement of weld beads and/or the use of heating electrodes to “temper” the weld toe. A low flow rate may allow a greater build-up during welding which may have a lower safety factor. can greatly influence the heat extraction rates from the preheated area and from the weld pool. Electrode polarity can also be used effectively to reduce penetration. High flow rates and consequent rapid cooling may lead to excessive hardening and the possibility of associated hydrogen cracking in ferritic steels. When required as in b) above. 13. coupled with the nature of the product. 2) The employer should indicate his acceptance of the proposed welding procedure. 3) Before site welding begins. Manual metal-arc welding with basic electrodes will have comparatively moderate hardness and the low hydrogen characteristics are of advantage. It may be necessary to develop special preheating techniques with this phenomenon. a test weld using the procedure should be made by the contractor. University of Teknologi Mara. because of the influence of the product flow.5 Prevention of unsatisfactory micro-structures. It may be advisable to control or eliminate the weld weave to ensure limited local heating.Licensed copy: University of Teknologi Mara.1. © BSI 04-1999 NOTE Although it is not always possible to simulate content of pipe. and pressure and flow rate (see items t). All documentation relating to procedure approval welds including the test results (see 13. as far as possible. u) and v) in Table 1). In particular the effect on weld quality and service performance of such parameters as the product. 13. procedure approval test joints should be tested and assessed in accordance with BS 4515 or BS EN 288-3 as appropriate.g. The period for which records should be kept should be specified by the employer. that the procedure employed is consistent with that specified. 9 . r) and s) in Table 2). If the simulation test uses actual product it is essential that the safety of the simulation is carefully considered (see section 2). All weld runs should be cleaned until free from slag and visible flaws prior to the deposition of subsequent runs. or ii) a duration specified by the employer. or b) when approved by the employer. Where welding procedure tests are undertaken they should adequately reflect the conditions that would be encountered when the welding is done. Alternatively it should be shown that there is adequate documentary evidence from authenticated sources that the procedure is safe. these are parameters where changes can affect the relevance of a welding procedure to a particular situation (see items q). including such simulation as is necessary. should be considered.Licensed copy: University of Teknologi Mara. a pipe and fitting of diameters and thicknesses from the same respective groups in Table 1 c) and Table 1 d) as those to be used for the actual job. and should therefore always be carefully checked.6 Testing of joints for procedure approval Except for the hardness survey. use of a plate butt joint to simulate a longitudinal butt weld. The documentation should include authenticated results of mechanical tests and a chemical analysis carried out on the parent metal used for procedure approval. 7) The agreement of the statutory authority should be obtained when required. c) when approved by the employer. to show that the procedure is safe. Version correct as of 13/07/2010 04:34.6) should be submitted to the employer for acceptance prior to the commencement of the approval of welders. University of Teknologi Mara. 13. the results of the tests on the welds should show that sound welds having the required mechanical properties can be made using these procedures. 5) For the procedure to be approved. Consideration should be given to carrying out any special tests relevant to the service conditions. 6) Recorded details for each welding procedure approval test should be submitted by the contractor to the employer for his acceptance (see 13. sufficient development work should be done. Procedure approval tests should be carried out using a pipe and fitting of similar specification and composition as those for the pipe and fitting on the actual job. its flow. Welds should be inspected by the employer during the deposition of individual weld runs to ensure. temperature of pipe and its contents. (c) BSI BS 6990:1989 4) The quality of the test weld should be determined by non-destructive and destructive testing after the weld has been allowed to cool to ambient temperature in simulated site conditions and held for either: i) 24 h after completion of welding. corrosion. pressure and temperature.3 Records The details of each approved procedure should be recorded and should show the complete results of the procedure approval tests. it should be regarded as a new welding procedure and as such should be fully re-approved. 13. For the hardness survey for ferritic steels the testing method and requirements should be in accordance with BS 4515. Procedure approval tests should be carried out on one of the following: a) a pipe and fitting of the same respective outside diameters and thicknesses as those to be used for the actual job. Weld stop/start positions should be staggered. The welding procedure should include those items detailed in Table 1. e. 13.4 Welding procedure During the establishment of a welding procedure. If water spraying to cool the pipe will be used on site to facilitate rapid inspection the same conditions should be simulated in the welding procedure approval.5 Changes affecting procedure approval (essential variables) When any of the changes given in Table 2 are made to a welding procedure.3). Pipe diameter group and fitting diameter The groups for outside diameter of pipes and inside group (see 13.5 mm up to and including 25. semi-automatic or mechanized process or a combination of those processes. including run-out length.3 mm Over 114. Pipe containing test weld to be fixed vertically. Cleaning Whether by power driven or hand tools. fitting to be positioned as for actual job.0 mm Over 25. temperature control and method of temperature measurement [see item s)].c. Electrical characteristics Current (a. or d. Pipe and fitting position For pipe: 1) Within 20° of horizontal.c.0 mm The thickness groups for fittings are: Up to and including 12.3 mm Pipe thickness group and fitting thickness The thickness groups for pipes are: groups (see 13. For fitting: For any of above pipe positions. 3) Between 20° to vertical and 20° to horizontal. © BSI 04-1999 . polarity. The type and model of the welding power source and the type and length of the secondary cable should be recorded. Direction of welding Vertical-up or vertical-down. University of Teknologi Mara. Temper bead technique Technique details when applied. Pipe containing test weld to be fixed horizontally. minimum and maximum temperatures. width of root gap and use of backing material. weaving and speed of travel. 2) Number and sequence of runs. Version correct as of 13/07/2010 04:34. angle(s) of bevel.4) diameter of fittings are: Up to and including 114.4) 5 mm up to and including 12. Preheating Method. torch or gun leading or trailing. Welding heat input Full details of relevant parameters.5 mm Over 12. Material specification Pipe and fitting specifications. Number of welders See item r).5 mm up to and including 25.Licensed copy: University of Teknologi Mara. Pipe containing test weld to be fixed at 45° to vertical. Partially completed weld Minimum number of runs before joint is allowed to cool to ambient temperature. Filler metal and number of runs 1) Size. 2) Shape and dimension of fillet welds. voltage and current value for each size of electrode or filler metal.).5 mm Over 12.0 mm Over 25. Interpass temperature Minimum and maximum temperatures. 2) Within 20° of vertical. (c) BSI BS 6990:1989 a) b) c) d) e) f) g) h) i) j) k) l) m) n) o) p) q) 10 Table 1 — Welding procedure details Welding process The specific arc welding process using a manual. trade name and classification of filler metal for each run. Shielding gas and flow rate Composition of gas and flow rate. size of root face.0 mm Joint configuration 1) Longitudinal joint preparation including shape of groove. h) Electrical characteristics Any change in type of current (a. Version correct as of 13/07/2010 04:34. number of welders and electrical characteristics.. av) Pressure and flow rate of content of pipe Pressure range and flow rate range of content of pipe at the time of welding.c.4. (c) BSI BS 6990:1989 Table 1 — Welding procedure details r) Sketches and tabulations Sketches on separate detail sheets showing diameter and thickness of pipe and fitting. Table 2 — Changes affecting procedure approval (essential variables) a) Welding process Any change from one arc welding process to another. but should always be carefully checked. r) and s) of Table 2). n) Interpass temperature Any change to the temperatures. r) Temperatures of pipe and its content Any change beyond the range specified in the temperature of the pipe and its content at the time of welding. f) Filler metal size An increase or decrease in diameter of electrode or filler metal. d. m) Preheating Any change to the approved procedure. s) Ambient temperature Minimum ambient temperature below which preheating is to be applied [see item n)]. e) Filler metal type A change from one trade name or classification to another. © BSI 04-1999 11 .c. weld run sequence. s) Pressure and flow rate of content of pipe Any increase in pressure or any change in flow rate of content of pipe at the time of welding to outside of the specified range. d) Joint configuration Any change in joint configuration outside specified tolerances. l) Partially completed weld Any change in minimum number of runs. as any changes may affect welding procedure approval (see note to 13. p) Welding heat input Any change in the welding parameters that would result in a change of heat input greater than 10 %. University of Teknologi Mara.4 and items q). a These parameters cannot always be simulated in a welding procedure test. except as permitted in 13.Licensed copy: University of Teknologi Mara. at) Content of pipe Product conveyed by the pipe. j) Direction of welding Any change in direction. q) Content of pipe Any decrease in the flash point of the product conveyed by the pipe. c) Outside diameter of pipe or inside diameter of fitting or thickness Any change in diameter or thickness of pipe or fitting. joint configuration. g) Shielding gas and flow rate Any change in gas.) or change in polarity. gas mixture or flow rate. au) Temperature of pipe and its contents Temperature range of pipe and its content at the time of welding. i) Pipe and fitting position Any change in pipe position outside the group in which approval was obtained [see Table 1 i)] or any change in fitting position greater than 20°. k) Number of welders Any change in the number of welders. o) Temper bead technique Any change to the approved procedure. b) Material specification Any change in specification of steel for pipe or fitting. 4 Prior to welding the weld area should be properly identified and non-destructively inspected for: a) diameter and ovality where applicable. 15.5 and the magnetic particle flaw detection as in 27. particular attention is required for dead ends of pipes where deposits may restrict the flow. precautions should be taken to prevent the serviceability of the pipe being affected. Consideration should be given to the need for an approval test in the special techniques referred to in the approved procedure. 14.4 Branch connections A welder appropriately approved on a branch connection to BS 4515 or BS EN 287-1 should be considered approved for welding branch connections to this code within the extent of his approval. d) laminations or inclusions in the region where welding will be carried out (see 15. The ultrasonic technique should be as in 15. the welder who makes the approved manual welding procedure test is considered to be sufficiently experienced in the appropriate welding process and technique not to require testing in accordance with this clause. The area should be scanned on a 75 mm square grid. 15. c) presence of external or internal corrosion.2 The exposed pipe should be checked to ensure that the dimensions are within acceptable limits related to the fitting to be used at that particular location.3 The section of pipe to which the fitting is to be attached should be thoroughly cleaned with a wire brush for a distance extending 150 mm on each side of the location of the fitting.6). Version correct as of 13/07/2010 04:34. 15.Licensed copy: University of Teknologi Mara. (c) BSI BS 6990:1989 14 Approval and testing of welders 14.6 The areas where the attachment welds are to be made should be subject to 100 % ultrasonic examination and magnetic particle flaw detection over a band of 150 mm minimum width centred over the proposed weld locations to check freedom from laminations which might prejudice welding and to confirm adequate pipe thickness. in order to assess the soundness of the pipe material in the vicinity of the welding area.4) may be used as an alternative to magnetic particle inspection. b) actual pipe thickness.1 General It is essential that any welder appointed to work on pipe containing hazardous fluids is familiar with the precise techniques involved. Where seamless pipe is under examination penetrant testing (see 27. Lamination should not exceed 25 mm in any direction. When there is any doubt on this matter the welder should satisfactorily carry out a demonstration weld.2 Butt welds A welder appropriately approved on either a butt joint or a branch connection to BS 4515 or BS EN 287-1 should be considered approved for welding butt joints to this code within the extent of his approval. 14. 15. Ultrasonic and radiographic examination should be used for the inspection prior to welding. 15 Preparation of pipe 15. e) soundness of any existing weld in the vicinity of the welding area in cases where the distance to the nearest weld is less than 6 times the thickness of the thicker material.3 Fillet welds A welder appropriately approved on a fillet weld to BS 4515 or BS EN 287-1 should be considered approved for making fillet welds to this code within the extent of his approval. pitting and any signs of mechanical damage. For the purpose of this code. Paint or wrapping material should be carefully removed from the pipe in the proposed area of attachment on each side of the proposed location of the fitting to ensure that there is no interference with the welding operation. © BSI 04-1999 . Lamination of an area exceeding 500 mm2 should be considered unacceptable for welding.3. the pipe should be visually examined for surface imperfections. Previous inspection reports should also be evaluated. After cleaning. A welder approved on a butt joint to BS EN 287-1 should not be considered approved for making fillet welds to this code. University of Teknologi Mara. 15.5 The area of pipe beneath the fitting location should be examined ultrasonically to ensure freedom from lamination which might interfere with plugging operations. 12 The fitting should be located to avoid minor flaws in the pipe.1 The identity of the pipeline should be confirmed as being correct and a tag should be attached. Where circumstances do not permit a change of location. and ultrasonic testing practice should be in accordance with BS 5996. 14. f) build-up of process of deposits or fouling inside. b) Backing material fitting tightly into machined recesses with square or sharp corners. If the measured pipe thickness is less than the nominal pipe thickness. grease or other foreign matter.9 When a fitting that is to be subsequently drilled after attachment is being located on a pipeline. tears. b) A check that the correct certificate for the fitting is available.7 Positive confirmation of pipe thickness should be obtained over the complete length of the weld.3 to 15. This operation should be carried out under constant supervision. care should be taken to avoid where possible weld seams within the drilling area.1 Any alteration to a weld preparation profile supplied on a fitting should be carried out by grinding to a smooth finish with a disc grinder.3 The two halves of the tee fitting should be clamped together around the pipe. 15. It is preferable for fittings not to be located at or within a distance of 6 times the thickness of the thicker material to existing welds in the pipe.2 If backing material. 15. If the pipeline is constructed of longitudinally or spirally welded pipe. c) A check that all weld preparations are clean and are in accordance with the fitting specification. paint. 18 Preparation for encirclement fitting 18. Cleaning to base metal should extend for at least 25 mm from the edge of the fusion faces on both the internal and external surfaces of the parts to be welded. Any defects should be removed by grinding and repaired where necessary by welding to a procedure accepted by the employer. Permanent backing material should be of a sufficient length to provide at least 50 mm overlap at each end of the fitting. a) Backing material with integral projections or spacers intended to facilitate the establishment and maintenance of root gap.8 Where there is a delay of more than 48 h between the operations specified in 15. After clamping the tee fitting. moisture. is to be used. To each overlap steel plates should be attached to form run-on/run-off plates at the ends of the longitudinal seams. 18. the fusion faces and the adjacent material should be free from fins. (c) BSI BS 6990:1989 15. planar defects not complying with clause 28.11 The area should be thoroughly cleaned in preparation for the next operation. A typical weld preparation is shown in Figure 2. Where there is undue delay between this cleaning and the start of welding.7 inclusive and the start of welding. permanent or temporary. 16 Inspection of fittings The following checks should be carried out on the fitting to be attached. scale. Version correct as of 13/07/2010 04:34. The following types of backing material should not be used. 18. 13 . 15. it should be compatible with the fitting material and should be slid into the machined recess at the roots of the longitudinal seams before clamping the two halves of the fitting together. If the measured pipe thickness is less than 5 mm the conditions are outside the scope of this code. c) Backing material of a shape that restricts contraction. all visible surface grease in and around the recess of the branch flange should be removed.Licensed copy: University of Teknologi Mara. 15. consideration should be given to repeating some of these checks before the start of welding. a) Dimensional check of the fitting.10 The reinforcement of any welds to be covered by the fitting should be ground flush with the pipe surface over a length extending 50 mm beyond each side of the fitting. A typical yoke type clamp is shown in Figure 4. University of Teknologi Mara. © BSI 04-1999 17 Fusion faces Immediately prior to welding. the employer should undertake a design study to determine whether such a thickness is acceptable. then the choice of location should be made so that the area where the pilot drill will penetrate is clear of the weld seam. rust. as shown in Figure 3. The gap where the branch abuts the pipe should be packed with clean rag to prevent any grease contained within the recess melting during preheating and running down on to the pipe and into the longitudinal weld preparations. allowing for the negative tolerance. the appropriate areas should be suitably protected and re-cleaning should be carried out if necessary. Licensed copy: University of Teknologi Mara. Version correct as of 13/07/2010 04:34. University of Teknologi Mara. (c) BSI BS 6990:1989 14 Figure 2 — Typical longitudinal weld preparation for fitting: dimensions and tolerances © BSI 04-1999 . Version correct as of 13/07/2010 04:34.Licensed copy: University of Teknologi Mara. (c) BSI BS 6990:1989 Figure 3 — Attachment of run-on/run-off plates to backing material © BSI 04-1999 15 . University of Teknologi Mara. or. 20 Alignment of flanged fittings When welding a flanged fitting to a pipe. The final preparation should be a smooth finish using a disc grinder. 16 19.1 Any alteration to the radius of a fitting where it contacts the pipe should be carried out by grinding. for large modifications. by a thermal cutting method approved by the employer.Licensed copy: University of Teknologi Mara.2 The fitting should be set up on the pipe with a root gap where appropriate. care should be taken to ensure that the flange is kept parallel and square to the pipe. (c) BSI BS 6990:1989 Figure 4 — Typical yoke-type clamp for encirclement tee fittings 19 Preparation for set-on fitting 19. University of Teknologi Mara. © BSI 04-1999 . All tack welds should be made using the welding procedure to be employed for the root run and the ends should be dressed to a taper to ensure full fusion with the root run. Version correct as of 13/07/2010 04:34. The fitting should be fixed in position by clamping or tack welds. blending of the excavation. blowing sands or high winds. When the pipe is welded in a trench the bell hole should be of sufficient size to provide the welder or welders with ready access to the joint. c) Any soak periods to ensure adequate through-wall heating. Where permission to repair arc strikes has been given by the employer. f) The extent of the zones to be preheated including the limits of any localized heating applied as welding proceeds. b) Clamping is preferred to tack welding. The following are basic guidelines.e. Version correct as of 13/07/2010 04:34. The detailed procedure should take into consideration the following factors. (See also 6. An earth saddle making good electrical contact with the workpiece should be placed conveniently near to the weld for striking the electrode where this is necessary for removing slag from the tip or to facilitate the starting of the arc.1 As the type of fitting used may vary considerably. below which no welding may proceed. Where the minimum thickness is below tolerance. This work should be subject to thorough inspection. a) The maximum preheating temperature. 21 Working clearance The working clearance around the pipe at the weld should be not less than 400 mm. as approved by the employer. and where practicable. It is important therefore that careful consideration is given to those factors that may affect the quality and strength of the subsequent weld and to the safety of the preheating operation (see section 2). pressure testing. (c) BSI BS 6990:1989 NOTE During manufacture of the fitting strict tolerances should have been maintained regarding the alignment of the flange to the branch and the branch to the body of the fitting. b) Welds which are separated from the live or pressurized pipe by an air gap or backing material. checking by magnetic particle or penetrant inspection as appropriate and confirmation that the thickness of the pipe or fitting is within permitted tolerances. the mechanical removal of the affected material. b) The minimum interpass temperature. i. Certification to cover this work should be available. e) The method of control of heating. d) The type and size of the heating source. a maximum amount of pre-fabrication should be carried out off site by normal welding techniques. welding may be continued. University of Teknologi Mara. the procedure should include. but not necessarily be limited to. i) Details of any supplementary heating placed upstream of the preheating zone. © BSI 04-1999 24 Preheating To preheat pipelines or pipework effectively. repairs to an approved welding procedure may be carried out and subjected to further non-destructive testing. it is not possible to give definitive rules to suit each fitting. Places where any stray arcs have accidentally occurred should be either repaired or rejected. 17 . h) The frequency of temperature measurement. a) The amount of in-situ welding should be kept to a minimum.4.2 The in-situ welding may be divided into two types: a) Welds which involve a direct connection on to the live or pressurized pipe. Welding should not be done when the quality of the completed weld would be impaired by airborne moisture. Where necessary protection from the weather can be provided. When tack welding is necessary it should be made in positions that do not restrict expansion or contraction of the fitting along the longitudinal axis of the live or pressurized pipe. 25 Sequence of welding 25. 25.Licensed copy: University of Teknologi Mara. 23 Weather conditions The employer should state when welding should not be done because prevailing weather conditions would impair the quality of the completed weld.) 22 Stray arcs Arcs shall be struck only on fusion faces and contact of the electrode or of the non-insulated parts of the electrode holder with the outer surface of the pipe or fitting should be avoided. g) The type and distribution of temperature measuring devices. including emergency shut-down procedure. heat input may need to be high. particularly where product flow is maintained for safety reasons during welding and associated operations. Electrode holders should be of the fully insulated type. back-step welding and balanced welding techniques. All welds should be visually examined on completion and should have a good profile with positive reinforcement. penetrant testing as described in BS 6443 should be used. usually on procedure weld tests. Bridge welding of gaps between the fitting and pipe is not recommended unless the gap is less than 1. weld stop-start positions should be overlapped and should not coincide between adjoining weld layers. Version correct as of 13/07/2010 04:34. run-off plates should be used to prevent over-welding on to the live or pressurized pipe. University of Teknologi Mara. magnetic particle flaw detection. cavities and other deposition faults should be removed and particular attention paid to the cleanliness of the junctions between the weld metal and the fusion faces before deposition of further weld metal. Every effort should be made to offset distortion effects during the welding of b) type welds. as described in BS 6072. On completion of welding.g. For type a) welds.1 General All welds should be inspected by visual examination during and after welding. Operators of all types of non-destructive examination equipment should be required to demonstrate to the approval of the employer the capability of the examination procedure to detect rejectable imperfections and their ability to make correct interpretations of the indications given by the equipment. A record of approved personnel should be kept by the employer. Non-destructive testing procedure specifications should be submitted to the employer for approval and should be approved prior to the commencement of welding. Visible flaws such as cracks.5 Ultrasonic examination When required by the employer. 27. ultrasonic examination should be applied to welds as described in BS 3923-1 using an Examination Level stated by the employer. stops and starts and high points should be removed by grinding. current and travel speed. The method of non-destructive testing used should be capable of producing indications of imperfections which can be accurately interpreted and evaluated in order to assess whether the acceptance criteria specified in clause 28 have or have not been obtained.5 mm. NOTE The agreement of the statutory authority may also be required. This record should include inspection procedures in which each person is approved. size and nature of all flaws detected. It is important that after completion of the first fillet weld the fitting be allowed to cool to ambient temperature before welding commences on the fillet weld at the opposite end of the tee. grinding should be carried out to maintain a smooth profile. NOTE Run-off plates should be removed in a controlled manner so that there is minimal damage to the pipe. (c) BSI BS 6990:1989 In general b) type welds will be made before a) type welds. supplemented as appropriate with the relevant requirements of BS 4515. e. should be applied. Where necessary. All inspection personnel should have been approved by the employer. are normal requirements. inter-run cleaning is properly carried out and an acceptable weld profile is being achieved. using an appropriate technique. 27. before a further run is applied. 27. welding without weave and with strict control of electrode diameter. for welds on austenitic stainless steel pipe.3 Magnetic particle flaw detection When required by the employer. 26 Inter-run cleaning Each run of weld metal should be thoroughly cleaned. 27 Inspection 27. The acceptance criteria in clause 28 should be applied. When applicable. 27. With both a) and b) weld types. 18 © BSI 04-1999 . The results of the non-destructive examination should be recorded and should include a clear indication of the location.Licensed copy: University of Teknologi Mara. including checking that preheating requirements are met. either by hand or power tools. Clusters of surface porosity. visual examination should be followed by a method or combination of methods of non-destructive testing as specified by the employer.2 Visual examination Visual examination (see BS 5289) should be maintained throughout the welding cycle. Stop and start positions in adjacent runs should be staggered by at least 20 mm.4 Penetrant testing When required by the employer. Weld buttering techniques should be used to reduce any gap. the authority granting the approval and the date of approval. 29. 29.g. If there are any doubts as to the safety of such a repair option then the entire weld and fitting should be abandoned and an alternative course of action taken. b) if the size or nature of the flaw requires removal of a weld then the entire fitting should be removed. nature. the following information: a) maximum internal pressure during repair.2 Imperfections positioned within the original pipe surface. e) method of restoring wall thickness.1 Imperfections confined to the weld metal alone. c) depth of flaw that can be removed (advisable to be related to a) above). Imperfections found which extend below the original pipe surface should be treated with utmost caution. The requirements of BS 4515 should be followed except that extensive flaws may be repaired in sections to retain the preheating temperature within a manageable area. © BSI 04-1999 The form.2. and size of the imperfection should be assessed by an appropriately qualified and experienced person before repairs are carried out. but not be limited to. BS 4515.2 Fillet welds 29. 19 .Licensed copy: University of Teknologi Mara. b) method of flaw removal. University of Teknologi Mara.1 Butt welds The requirements of BS 4515 should be taken into account but with the following provisos: a) it is preferable to make a local repair to a joint. 29 Rectification of welds 29. Version correct as of 13/07/2010 04:34. e.2. An individual repair procedure for the specific flaw should be formulated by an appropriately qualified and experienced person. BS 2633. remachined and the reweld treated as a completely new weld. (c) BSI BS 6990:1989 28 Non-destructive testing acceptance criteria The acceptance criteria for non-destructive testing should be in accordance with the standard to which the pipeline or pipework was originally constructed. It is advisable that the pipe internal pressure is reduced to 85 % of that during the original welding (or to the pressure giving the equivalent of 30 % of the specified minimum yield stress of the pipe if the flaw is of a cracklike appearance) and maintained at this level until the repair is completed. The details of this should include. BS 4677. d) action to be taken if flaw depth exceeds c) above. University of Teknologi Mara.Licensed copy: University of Teknologi Mara. (c) BSI 20 blank . Version correct as of 13/07/2010 04:34. BS 4677. Code of practice for pipelines. University of Teknologi Mara. Personal eye protection — Optical test methods. BS EN 167. 1) Referred to in the foreword only. Arc welding equipment — Part 12: Coupling devices for welding cables. BS 5289. Specification for filters for use during welding and similar industrial operators. CP 2010-2. Specification for Class I arc welding of ferritic steel pipework for carrying fluids. brazing and thermal cutting. BS 6072. BS 6443. Visual inspection of fusion welded joints. BS 3923-1. industrial. (c) BSI BS 6990:1989 Publications referred to BS 499. Welding terms and symbols. Approval testing of welders for fusion welding — Part 1: Steels. Specification for acceptance levels for internal imperfections in steel plate. Specification and approval of welding procedures for metallic materials — Part 3: Welding procedure tests for the arc welding of steels. Personal eye protection — Non-optical test methods. BS 679. Methods for manual examination of fusion welds in ferritic steels. BS EN 168. Method for penetrant flaw detection.Licensed copy: University of Teknologi Mara. BS EN 287-1. BS 3923. Method for magnetic particle flaw detection. BS EN 30012-1. Specification for welding of steel pipelines on land and offshore. Quality management and quality assurance standards1). BS 4515. BS EN 60974-12. BS EN 169. BS EN 60974-11. Ultrasonic examination of welds. © BSI 04-1999 . Pipelines on land: general. CP 2010. Code of practice. equipment and accessories. Torches and guns for arc welding. Quality assurance requirements for measuring equipment — Part 1: Metrological confirmation system for measuring equipment. Design and construction of steel pipelines in land. BS 5996. Specification for liquid carbon dioxide. Specification for arc welding of austenitic stainless steel pipework for carrying fluids. BS EN 288-3. Version correct as of 13/07/2010 04:34. Code of practice for pipelines. BS 2633. Arc welding equipment — Part 11: Electrode holders. BS 499-1. Glossary for welding. BS 8010. Welding consumables — Shielding gases for arc welding and cutting. BS EN ISO 9000. BS 638. BS EN 50078. Specification for filters for personal eye-protection equipment used in welding and similar operations. BS EN 439. based on ultrasonic testing. Arc welding power sources. BS 4105. strip and wide flats. BS 8010-1. photocopying. in the course of implementing the standard. Various BSI electronic information services are also available which give details on all its products and services. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. (c) BSI BS 6990:1989 BSI 389 Chiswick High Road London W4 4AL BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards. Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards. Tel: 020 8996 7111. Users of British Standards should make sure that they possess the latest amendments or editions. Tel: 020 8996 9000. of the publications of the internationalstandardization bodies. of necessary details such as symbols. type or grade designations. Designs and Patents Act 1988 no extract may be reproduced. If permission is granted. Tel: 020 8996 7070. Copyright Copyright subsists in all BSI publications. Fax: 020 8996 7001. in the UK. For details of these and other benefits contact Membership Administration. recording or otherwise – without prior written permission from BSI. Details and advice can be obtained from the Copyright Manager. It presents the UK view on standards in Europe and at the international level. Fax: 020 8996 7001. Except as permitted under the Copyright. and size. unless otherwise requested. This does not preclude the free use. BSI also holds the copyright. University of Teknologi Mara. Tel: 020 8996 9001. the terms may include royalty payments or a licensing agreement. In response to orders for international standards. Fax: 020 8996 7400. Buying standards Orders for all BSI. We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible. . Fax: 020 8996 7048. It is the constant aim of BSI to improve the quality of our products and services. Version correct as of 13/07/2010 04:34. stored in a retrieval system or transmitted in any form or by any means – electronic. Contact the Information Centre.Licensed copy: University of Teknologi Mara. Information on standards BSI provides a wide range of information on national. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. the identity of which can be found on the inside front cover. international and foreign standards publications should be addressed to Customer Services. Tel: 020 8996 7002. 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