Welding Acceptance inspection of electron beam welding machines

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1 BRITISH STANDARD BS EN ISO :2008 Welding Acceptance inspection of electron beam welding machines Part 1: Principles and acceptance conditions ICS

2 National foreword This British Standard is the UK implementation of EN ISO :2008. It supersedes BS EN ISO :2001 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee WEE/-/1, Briefing committee for welding. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2008 Amendments/corrigenda issued since publication Date Comments BSI 2008 ISBN

3 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN ISO May 2008 ICS Supersedes EN ISO :2000 English Version Welding - Acceptance inspection of electron beam welding machines - Part 1: Principles and acceptance conditions (ISO :2008) Soudage - Essais de réception des machines de soudage par faisceau d'électrons - Partie 1: Principes et conditions de réception (ISO :2008) Schweißen - Abnahmeprüfung von Elektronenstrahl- Schweißmaschinen - Teil 1: Grundlagen und Abnahmebedingungen (ISO :2008) This European Standard was approved by CEN on 26 April CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO :2008: E

4 Foreword This document (EN ISO :2008) has been prepared by Technical Committee ISO/TC 44 "Welding and allied processes" in collaboration with Technical Committee CEN/TC 121 Welding the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2008, and conflicting national standards shall be withdrawn at the latest by November Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO :2000. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO :2008 has been approved by CEN as a EN ISO :2008 without any modification. Copyright British ii Standards Institution

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6 Introduction Components, failure of which will endanger life, are subject to comprehensive test and acceptance specifications, which, among other things, require production equipment to be of proven type and in accordance with the state of the art. Similarly, in welding practice, standards apply that specify, for example, the required manual skills which a welder must have for controlling the weld. In welding processes that are not under direct manual control, such as in electron beam welding, requirements for various machine parameters are established. This standard series on acceptance inspection of electron beam welding machines is based on the concept that the production of continuously high-quality welds is ensured if, among other things, the settings, within defined limits, are reproducible during the operating period. Taking this into account, this standard specifies details of the main machine parameters (accelerating voltage, beam current, lens current and welding speed characteristics) together with deviations permitted in short-term or long-term operation. It also includes requirements regarding the run-out accuracy of the devices positioning the workpiece and regarding the stability of the spot position of the electron beam. Users, manufacturers, research experts and inspection bodies are all agreed that electron beam welding machines complying with the requirements are suitable for welding components subject to acceptance inspection, such as aircraft equipment, pressure vessels, valves, etc., within specified setting ranges, assuming that other conditions (e.g. qualified staff, quality control) are fulfilled. ISO [any part(s)] can be referred to in contracts for supply of electron beam welding machines. Further tests are not normally required if proof of satisfactory welding results is provided in the form of routine inspection documentation. However, the requirements of the standard can also be used for inspection as part of maintenance, if required by contract. iv

7 Welding Acceptance inspection of electron beam welding machines Part 1: Principles and acceptance conditions 1 Scope This part of ISO specifies requirements for acceptance inspection of electron beam welding machines preferably when first installed on the user's premises. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 17662, Welding Calibration, verification and validation of equipment used for welding, including ancillary activities 3 Symbols and abbreviated terms For the purposes of this part of ISO 14744, the following symbols apply: A F A W a x ; a y ; a z D I B I B max I B min I L focal distance, in millimetres work distance, in millimetres deviation, in millimetres, of electron beam axis from weld groove centre or of beam focus from groove centre on weld surface in the x-, y- or z-direction of feed, as a measure of the run-out accuracy diameter, in millimetres or in centimetres, of a circumference weld seam beam current, in milliamperes maximum beam current, in milliamperes, corresponding to U A max and U A min, respectively minimum beam current, in milliamperes, corresponding to U A max and U A min, respectively lens current, in milliamperes I L max lens current, in milliamperes, at U A max and for A F min I L min lens current, in milliamperes, at U A min and for A F max 1

8 m n t w t w max Q U A U A max U A min U a U b U v v load, in kilograms force, on the work table or on rotating fixture resulting from workpiece mass including that of any clamping device rotational frequency, in reciprocal minutes, of rotating fixture time, in seconds, for welding a seam maximum time, in seconds, for welding a seam pressure rise rate, in pascal cubic decimetres per second, or millibar litres per second indicated accelerating voltage, in kilovolts maximum indicated accelerating voltage, in kilovolts, within the setting range minimum indicated accelerating voltage, in kilovolts, within the setting range monitored voltage for measuring the accelerating voltage, in millivolts monitored voltage, in millivolts, for measuring the beam current, in millivolts monitored voltage, in millivolts, for measuring the welding speed welding speed, in millimetres per second, in centimetres per minute or in metres per minute 4 Conditions for acceptance inspection 4.1 General Acceptance inspection shall be performed after the first installation or before the first operation of the welding machine. The following tests shall be done: accelerating voltage characteristics; beam current characteristics; lens current characteristics; speed characteristics of movement devices; run-out accuracy of movement devices; stability of spot position. And the following test may be agreed: pressure rise rate. After changing of equipment location the following test shall be done: speed characteristics of movement devices; run-out accuracy of movement devices; stability of spot position. 2

9 And the following test may be agreed: pressure rise rate. After rebuilding, maintenance or changing the conditions of operation the following tests shall be done: tests of all affected machine components. The acceptance inspection may be extended on parameters, characteristics and additional devices, when there are no requirements described in ISO (all parts). In these cases, requirements and limit deviations shall be agreed. However, measurement of accelerating voltage may be performed prior to delivery of the welding machine in accordance with ISO Installation of electron beam welding machine Electron beam welding machines shall be installed so that acceptance inspection and machine performance are not interfered with by vibration or by electrical or magnetic fields. 4.3 Power source The power source for electron beam welding machines shall be an electrical mains system with voltage fluctuations not exceeding ± 10 %. 4.4 Safety precautions This part of ISO does not cover inspection of safety devices and other safety aspects. IMPORTANT Machines for electron beam welding have several features which assure safe operation. The electron beam generates x-rays during welding and the work chamber walls, the work chamber windows and other parts have to reduce the radiation outside the machine to low safe levels so as to permit operators and other personnel to work safely close to the machine. The parts of the machine subject to high-voltages should, of course, be protected and inaccessible when under high tension. Some of the features which assure safe operation may have to be tested after installation of the machine, prior to any use of the machine in production. Any such test is, however, outside the scope of this part of ISO The tests have to be specified by the supplier of the machine. In addition, it is important to consider that the design of machines for electron beam welding, protection against x-rays etc., are subject to several legal requirements at the European level (e.g. directives for: machines; electromagnetic compatibility; low-voltage equipment) and supplementary national requirements in at least some countries. See also IEC Operating instructions The operating instructions for the electron beam welding machine shall be complied with. 4.6 Instruments The accuracy of all instruments for measurement shall be compatible with the limit deviations specified in this part of ISO 14744, see Table 1. In accordance with ISO 17662, no calibration, no verification, and no validation of measurement equipment is necessary. 3

10 5 Principles of acceptance inspection 5.1 Setting range The setting range shall be specified for the machine to undergo the acceptance inspection, giving setting ranges for the following parameters: accelerating voltage; beam current; lens current; welding speed in all primary welding directions. Other parameters necessary for proper control of the welding machine shall also be specified, e.g.: focal distance; load resulting from workpiece and fixture mass; pressure rise rate (if necessary). 5.2 Limit deviations for machine parameters and characteristics The limit deviations given in Table 1 relate to the mean of the measured values concerned, unless otherwise specified. The limit deviations relate to the use of electron beam welding machines without special requirement. Alternative deviations may be agreed by contract for special machines or special applications. 4 --`,,```,,,,````-`-`,,`,,`,

11 Table 1 Limit deviations for machine parameters and characteristics Parameters and characteristics Limit deviations of the measured value Accelerating voltage: ripple stabilization reproducibility Beam current: ripple stabilization reproducibility Lens current: ripple stabilization reproducibility Welding speed: short-term stability long-term stability reproducibility Run-out accuracy, longitudinal and circumferential welds Stability of spot position in the plane perpendicular to the beam axis 2 % (peak-to-peak value) ±1 % ±1 % 5 % (peak-to-peak value) ±1 % ±1 % 0,5 % (peak-to-peak value) ±0,5 % ±0,5 % ±2 % ±1 % ±1 % ±0,1 mm Unless otherwise agreed, requirements may be relaxed for welding of large pieces ±0,1 mm up to a focal distance of 300 mm Pressure rise rate To be agreed (see Annex A) Stability of spot position for longer focal distance to be agreed 5.3 Test report All inspection results shall be recorded in a test report which includes: reference to this part of ISO 14744; all measured results; assessment of all measurement results; the name of the responsible welding supervisor; and description the setting range, which complies with the requirements of this part of ISO The test report has to be signed by the examiner. 5

12 6 Acceptance inspection 6.1 General The acceptance inspection specified below is applicable for general applications for electron beam welding machines. Alternative conditions may be agreed for special applications. However, the applicability of limit deviations specified in Table 1 has to be assessed for such special applications. 6.2 Accelerating voltage, beam current, and lens current Measurement procedure ISO specifies details of the method of measurement, the test arrangement and the procedure to be followed in measuring the accelerating voltage characteristics and ISO specifies the beam current characteristics. Lens current shall be measured by inserting a current meter into the lens current circuit or using special measuring connections at the lens current amplifier Ripple The ripple of the accelerating voltage and of the beam current shall be measured for the following settings: a) U A max and I B max ; U A max and 0,5 I B max ; U A max and 0,1 I B max ; and b) U A min and I B max ; U A min and 0,5 I B max ; U A min and 0,1 I B max. The lens current ripple shall be measured at I L max and I L min. Instead of 0,1 I B max the value of I B min may be related to the application Stability The measurement shall be made over an operating time of 2t w max, minimum 30 min, by continuous recording of the accelerating voltage, the beam current, and the lens current set at U A max, 0,1 I B max and 0,5 (I L max + I L min ) Reproducibility With the high voltage power supply of the welding machine set at average accelerating voltage 0,5 (U A max + U A min ), average beam current set at 0,5 I B max and average lens current set at 0,5 (I L max + I L min ) the machine shall be switched off and on five times with identical settings. The resulting accelerating voltage, beam current, and lens current shall be measured. 6.3 Welding speed characteristics Measurement procedure ISO specifies details of the method of measurement, test arrangement and measurement procedure. The welding speed characteristics shall be measured directly at the work table, at the rotating fixture or at the movable electron gun Short-term stability The welding speed, v, shall be measured in all the primary directions for welding, for m max and for m = 0. 6

13 6.3.3 Long-term stability In the case of devices positioning the workpiece and designed for an uninterrupted welding time of more than one minute, the long-term stability shall be measured, measurements being made by continuous recording at an average welding speed and a medium load over an operating time equal to at least twice the maximum welding time Reproducibility With the devices positioning the workpiece first set to v max and then to v min, at a medium load 0,5 m max, the moving devices shall be switched off and on five times without alteration to the settings, and the resulting welding speed measured. 6.4 Run-out accuracy ISO specifies details of the test arrangement and the measurement procedure. The run-out accuracy of the work table and rotational movements shall be measured both in the unloaded state and at maximum load. Where applicable, the run-out accuracy of the movable electron gun is also to be measured. 6.5 Stability of spot position ISO specifies details of the test arrangement and the measurement procedure. For testing the continuous operation mode of the welding machine (as specified in ISO :2000, Clause 5) the electron beam shall be set to U A max and 0,1 I B max, switched on and maintained at this setting for 15 min. Then the work chamber shall be ventilated, evacuated and continuous operation with the same parameters resumed for at least 15 min. 7 Supplementary acceptance inspections Annex A contains information on pressure rise rate. 7

14 Annex A (informative) Procedures for inspection of pressure rise rate A.1 General Measurement of evacuation time, residual pressure after evacuation, pressure rise rate and leak rate may be included as a part of the acceptance inspection of machines for electron beam welding. This annex specifies, for information, a procedure for inspection of pressure rise rate. A.2 Measurement of the pressure rise rate The pressure rise rate, Q, may be measured as follows: evacuating the chamber until the working pressure, p 0, for normal operation is reached; waiting until the pressure level is stable; separating the work chamber from the various pumping systems this point corresponds to the beginning of measurement, t 0 ; letting the pressure level evolve for a sufficient time so that the pressure increase is at least one power of 10 a common practice is to wait several hours, e.g. over a night or a weekend; then measuring pressure p 1 at time t 1 : where ( p1 p0) V Q = t t 1 0 Q is the pressure rise rate, in pascal cubic decimetres per second, or millibar litres per second; p 0 is the pressure, in pascals or millibars, in the chamber at time t 0 ; p 1 is the pressure, in pascals or millibars, in the chamber at time t 1 ; V is the volume, in cubic decimetres or litres, of the chamber; t 0 ; t 1 are respectively the start of the measurement time and the actual measurement time, in seconds. 8

15 Bibliography [1] ISO , Welding Acceptance inspection of electron beam welding machines Part 2: Measurement of accelerating voltage characteristics [2] ISO , Welding Acceptance inspection of electron beam welding machines Part 3: Measurement of beam current characteristics [3] ISO , Welding Acceptance inspection of electron beam welding machines Part 4: Measurement of welding speed [4] ISO , Welding Acceptance inspection of electron beam welding machines Part 5: Measurement of run-out accuracy [5] ISO :2000, Welding Acceptance inspection of electron beam welding machines Part 6: Measurement of stability of spot position [6] IEC , Safety of machinery Electrical equipment of machines Part 1: General requirements 9

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