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Table 4.5-1 (continued)

5. Non-destructive testing (NDT) of parent materials

The NDT of parent materials shall be in accordance with EN 12952-2.

6. Qualification of welding procedure specification

   1. General

The welding procedure specifications shall be qualified for all welds in components forming the pressure circuit or attached to that circuit.

For application to water-tube boilers, these qualifications shall be in accordance with EN ISO 15614-1:2004 or EN ISO 15613:2004 as appropriate. Qualification records and fusion welding procedure specifications shall be approved as part of the design qualification process. The general rules of EN ISO 15614-1:2004 shall be supplemented for the purpose of this European Standard by application of the specific rules detailed in 6.2.

The manufacturer shall include as part of the technical documentation, a list of all the welding procedure specifications required for the manufacturing of the water-tube boiler.

Where a manufacturer has previously carried out successful procedure qualification tests in accordance with the requirements of this European Standard, he shall be deemed exempt from the necessity for re­qualification is not required, as long as the current welding procedure specification standard is met within the essential variables covered by the previous test.

NOTE A document on 'Flash butt welding procedures' is in preparation. See Bibliography

In addition to the requirements of EN ISO 15613:2004, procedure qualification test for welded water-tube wall construction shall comply with the requirements of EN 12952-5:2011, Annex A.

The welding procedure tests shall be in accordance with the requirements of EN ISO 15614-1:2004.

In addition, the following requirements shall be met for drums and headers made from steel groups 1, 2.1, 4 or 5:

1. Boiler drums: For longitudinal and circumferential welded joints in drums of thicknesses greater than 20 mm, the welding procedure qualification test shall include a longitudinal tensile test on weld metal. This test shall be performed at not less than the following minimum temperatures:

1. 250 °С for steel group 1.1 and 1.2;

2. 350 °С for steel group 2.1, 4 or 5.

2. Headers: For headers containing longitudinal welds having a thickness greater than 20 mm, the welding procedure qualification test for the longitudinal welds shall include a longitudinal tensile test on weld metal. This test shall be performed at not less than the following minimum temperatures:

1. 250 °С for steel group 1.1 and 1.2;

2. 350 °С for steel group 2.1, 4 or 5.

All mechanical tests performed during the welding procedure qualification shall be carried out in accordance with EN ISO 15614-1:2004.

The Charpy V-notch impact tests shall be carried out at room temperature in accordance with EN ISO 148-1.

The test values to be achieved shall be as defined in EN ISO 15614-1:2004 and 6.2 2.2 to 6.2.2.5.

Є.2.2.2 Longitudinal tensile test on weld metal

The test result shall meet the specified minimum R_p02 value for parent material at testing temperature (see 6.2.1).

The test results shall meet the following requirements, depending on the position where the fracture occurs during the test:

• if the fracture occurs in parent material, the minimum ultimate tensile strength specified for the relevant parent material used for the qualification;

• if the fracture occurs in the weld, the minimum ultimate tensile strength specified for the relevant parent material used for the qualification, or, for designs based on the R_p0,2 proof strength, 90 % of the minimum ultimate tensile strength specified for the relevant parent material used for the qualification.

The test results shall meet the following requirements, depending on the parent material and the position where the tests are performed:

1. For ferritic steels:

1. Charpy V-notch impact test in the weld deposit:

• minimum average value: the average value specified for the parent material used in the welding procedure qualification at the test temperature (room temperature);

• minimum single value: one single value may be lower than the value required for the minimum average value, but shall not be less than 70 % of the minimum average value;

2. Charpy V-notch impact tests in the heat affected zone:

• minimum average value of 27 J, except for steel group 6 where 24 J is permitted;

• minimum single value: one single value may be lower than the value required for the minimum average value, but shall not be less than 21 J, or 19 J for steel group 6;

2. For austenitic steels:

Impact testing shall not be required for austenitic steels.

Depending on the parent material and whether post-weld heat treatment is required in accordance with EN 12952-5:2011, 10.4, hardness values shall be as specified in EN ISO 15614-1:2004.

For non-heat treated steel group 5, the maximum value shall not exceed 380 HV10.

Provided that the ductility of the weld has been adequately demonstrated in accordance with the bend tests as specified in EN ISO 15614-1:2004 and the impact tests as specified in 6.2.2.4, local deviations in the heat affected zone hardness values shall be acceptable.

In the case of dissimilar joints, the weld metal values shall meet the lower of the specified minimum values for the parent material as required in 6.2.2.2, 6.2.2.3 and 6.2.2.4.

7. Welder and welding operator qualification

All welders and welding operators engaged on the welding of pressure parts of water-tube boilers fabricated in accordance with this European Standard shall pass the welder qualification tests which are designed to demonstrate their ability to make sound welds of the types on which they are to be employed.

Qualification testing of welders and welding operators shall be carried out, recorded and reported in accordance with EN 287-1:2004 or EN 1418:1997, 4.2.1 and 4.2.2, as appropriate. Verification of qualification of welders testing shall be part of final inspection.

When a welder or and welding operator is qualified according to EN 287-1:2004 or EN 1418:1997, 4.2.1 and 4.2.2, as appropriate, for the welding of butt welds, no additional qualification shall be required for the welding of branches, nozzles or attachments, provided that the welding operations are carried out in the range of qualification of the welder or and welding operator qualification given in EN 287-1:2004 or EN 1418:1997, 4.2.1 and 4.2.2 as appropriate.

A list of welders and welding operators, together with records of their qualification tests, shall be retained by the manufacturer who may be required to provide evidence of qualification of any welder engaged in the manufacturing of water-tube boilers.

7. Production test plates for drums

   1. General

The material used for production test plates shall comply with the same standard and grade, or the same specification, as that used for the construction of the drums of the water-tube boiler. As a minimum, plates shall be from the same steel making process and of the same nominal thickness as the drum plates. Where possible, the plates shall be selected from the same cast as that used for the manufacture of the drum.

The dimensions of the test plates shall be large enough to allow the preparation of all the test specimens required by 8.3.2, and in no case shall their length be shorter than 350 mm.

The test plates shall be attached, wherever practical, to the drum plate so that the weld carried out on the production test plate is a continuation of the longitudinal weld.

Production test plates shall receive an identical post-weld heat treatment or stress relief as that applied to the production weld.

The number of production test plates required shall be as follows:

1. longitudinal welds: One production test plate per welding procedure qualification per drum and per header;

2. circumferential welds: If the welding procedure qualification is the same as that for the longitudinal seam of the drum, no additional production test plate is required. If the welding procedure qualification differs from that of the longitudinal joint, then one production test plate shall be performed per welding procedure qualification per year.

The test plates shall be subjected to non-destructive testing identical with the production welds they are representing.

The test plates and methods of testing shall be in accordance with the requirements of EN ISO 15614-1 for welding procedure qualification.

The following destructive test shall be performed on each production test plate:

1. 1 transverse tensile test at room temperature;

2. 1 longitudinal tensile test on weld metal for production test plates with thickness greater or equal to 20 mm. The test shall be performed at the design temperature of the drum;

3. 1 transverse root bend test;

4. 1 transverse face bend test;

5. 1 transverse side bend test;

6. a series of Charpy V-notch impact tests at room temperature on the deposited material, the number of test specimens depending on the thickness of the parent material:

1. 3 specimens for thickness less than or equal to 50 mm - taken at the mid thickness;

2. 6 specimens for thickness greater than 50 mm - 3 at the surface of the material, and 3 at the mid

thickness;

7. a series of impact tests at room temperature in the heat affected zone, the number of test specimens depending on the thickness of the parent material:

1. 3 specimens for thickness less than or equal to 50 mm - taken at the mid thickness;

2. 6 specimens for thickness greater than 50 mm - 3 at the surface of the material, and 3 at the mid

thickness;

8. 1 macroscopic examination;

9. 1 hardness test in accordance with EN ISO 15614-1.

The results obtained from the non-destructive testing of production test plates shall meet the same acceptance criteria as those required for production welds.

The test results shall meet the following requirements, depending on the position where the fracture occurs during the test:

— if the fracture occurs in the parent material: the minimum ultimate tensile strength specified for the relevant parent material;

— if the fracture occurs in the weld: the minimum ultimate tensile strength specified for the relevant parent material or, for designs based on the 7?_pO,₂ proof strength, 90 % of the minimum ultimate tensile strength specified for the relevant parent material.

The test result shall meet the specified minimum R_{p0 2} value for parent material at the design temperature.

During testing, the test specimens shall not reveal any open imperfections greater than 3 mm in any direction. Imperfections appearing at the corners of a test specimen during testing, shall be ignored in the evaluation.

The test results shall meet the following requirements, depending on the parent material and the position where the tests for ferritic steels are performed:

1. Charpy V-notch impact tests in the weld deposit:

1. minimum average value: the average value specified for the parent material used in the welding pro­cedure qualification at the test temperature;

2. minimum single value: one single value may be lower than the value required for the minimum average value, but shall not be less than 70 % of the minimum average value;

2. Charpy V-notch impact tests in the heat affected zone:

1. minimum average value: 27 J, except for steel group 6 where 24 J is permitted;

2. minimum single value: one single value may be lower than the value required for the minimum average value, but not be less than 21 J, or 19 J for steel group 6.

Imperfections detected shall be accepted in accordance with the acceptance levels in 9.3 and 9.4.

In addition, the sequence of weld deposition in multi-layer welds, shall be examined, and shall show no significant deviations in layer sequence, or in weld bead shape, from those defined in the relevant welding procedure specification.

For non-post-weld heat treated situations, the maximum acceptable hardness value shall be 350 HV10. Where post-weld heat treatment is applied, the maximum acceptable hardness value shall be 320 HV10.

Provided that the ductility of the weld has been adequately demonstrated in accordance with the bend tests as specified in 8.4.4 and the impact tests as specified in 8.4.5, local deviations in the heat affected zone hardness values specified above shall be acceptable.

In the case of joints of dissimilar joints, the weld metal values shall meet the lower of the specified minimum values for the parent material as required by 8.4.2, 8.4.3, 8.4.5 and 8.4.7.

If the results from any test performed on a production test plate do not comply with the requirements of 8.4, the reasons for the failure shall be investigated by the manufacturer who shall ensure that any remedial action considered necessary will not impair the safety of the boiler.

When the failure of a destructive test is due to a weld defect in the section, two identical additional tests shall be performed:

• if both retests comply with the requirements of 8.4, the test results shall be deemed to comply with this European Standard;

• if either retest does not comply with the requirements of 8.4, the cause shall be investigated by the manufacturer who shall ensure that any remedial action considered necessary will not impair the safety of the boiler.

In the event of the results of the Charpy V-notch impact re-test failing to comply with the requirements of 8.4.5, the provisions of either a) or b) shall be permitted:

1. the manufacturer shall carry out further heat treatment of the production test plate provided that the same heat treatment cycle is applied to those parts of the boiler drum(s) represented, and provided that no significant adverse effects are caused. After such repeat heat treatment, all the tests required on a production test plate shall be carried out. The results shall comply with the initial requirements;

2. the welds represented by the test specimens having particular Charpy V-notch values less than required by 8.4.5 shall be accepted as fit for the intended purpose after due consideration of the specified cause and level of impact test results and of the weld quality.

NOTE There are no requirements in this European Standard for fracture mechanics testing. Where such tests are carried out, they should be carried out at the manufacturer's responsibility using the latest state of the art procedures which should ensure that, by their use, the safety of the boiler is not impaired.

7. Non-destructive testing of welds

   1. Type and extent of non-destructive testing

      1. General

Non-destructive testing (NDT) shall be carried out by experienced personnel following written procedures. Personnel responsible for non-destructive testing, including interpretation, evaluation and reporting, shall be certified in accordance with the requirements of 9.2.

All welds carried out during the manufacture and erection of a water-tube boiler shall be visually examined.

Non-destructive testing shall be performed on each component of a water-tube boiler as given in 9.1.2, 9.1.3 and 9.1.4, to the following extent:

1. Surface imperfection detection:

1. on drums: magnetic particle testing shall be used;

2. on headers and tubes: magnetic particle testing shall be used, except in the cases of steel group 1 and steel group 8 and for pressure connection welds for tube stubs on headers with a nominal diameter less than or equal to 80 mm for steel group 2 and steel group 5, where penetrant testing may be used;

2. Volumetric imperfection detection:

1. in general, ultrasonic testing shall be preferred to radiographic testing for ferritic steels. The volumetric imperfection detection requirements are specified in 9.1.2, 9.1.3 and 9.1.4.

For steel group 1.1 and 1.2, the required non-destructive testing of welds shall be performed before or after any required post-weld heat treatment. For all other materials, the required non-destructive testing of welds shall be performed after any required post-weld heat treatment, except in the case of circumferential welds in tubes of steel group 5.1 and 5.2 with an outside diameter less than 120 mm and a nominal thickness less than 13 mm, where testing may be carried out before final post-weld heat treatment.

When in 9.1.2, 9.1.3 and 9.1.4, the non-destructive testing is specified on a basis of 10 %, the selected welds for testing shall include a sample of each welder's work for each welding procedure specification on the component concerned. The number of welds to be fully examined shall then be, as a minimum, 10 % of the total number of welds performed by this welder following the same welding procedure specification on the same component.

Where this European Standard requires non-destructive testing on a percentage of 10 % of welds, and when that testing reveals imperfections that do not comply with the acceptance levels stated in 9.3 and 9.4, the percentage rate of testing for the concerned welder shall be increased in accordance with 9.1.5.

When examined welds reveal imperfections that do not comply with the acceptance levels stated in 9.3 or 9.4, these imperfections shall be repaired. After repairing, these welds shall be post-weld heat treated in accordance with the requirements specified for the original weld. The original non-destructive testing shall then be repeated.

9.1.2 Drums

Drums shall be examined to the requirements of Table 9.1-1.

Table 9.1-1 — NDT of drum welds