9.1.3 Headers
Headers shall be examined to the requirements of Table 9.1-2.
Table 9.1-2 — NDT of header welds
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Types of welds |
Surface imperfection detection a |
Volumetric imperfection detection |
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|
Radiographic testing |
Ultrasonic testing |
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|
Longitudinal and circumferential welds |
100 % b |
100 % c |
OR |
100 %c |
|
|
Pressure connection welds |
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|
e d > 25 mm (full penetration) |
100%e |
100 %c f |
OR |
100 %cf |
|
|
15 mm < e d < 25 mm (full penetration) |
10 % e |
10%cf |
OR |
10%cf |
|
|
All other welds, including seal welds |
10 % 9 |
— |
— |
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|
Attachments welds |
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|
Load carrying |
100% |
— |
— |
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Table 9.1-2 (continued)
|
Types of welds |
Surface imperfection detection a |
Volumetric imperfection detection |
|
|
Radiographic testing |
Ultrasonic testing |
||
|
Non-load carrying |
10 % |
— |
— |
|
End plate welds |
100 % |
— |
100 % h |
a Magnetic particle testing, but penetrant testing is acceptable for steel groups 1 and 8.
b For steel groups 1 and 8 with a thickness d0< 25 mm: 10 % of circumferential welds.
c For steel groups 4 and 6 only ultrasonic testing is permitted.
de is the thickness of the pressure connection.
e Only 10 % for steel groups 1 and 8.
f No volumetric imperfection detection is required if d0< 142 mm.
9 Penetrant testing is also acceptable for tube stubs in steel groups 2 and 5 with a nominal diameter d0 < 80 mm.
h Only for full penetration welds with outside diameter d0 > 70 mm and for end plate thickness e > 8 mm.
Tubes
Tubes shall be examined to the requirements of Table 9.1-3. For circumferential welds at boiler tubes with d0< 76,1 mm tested by using elliptical radiographic technique it is sufficient to have 1 partial image per weld; percentage in Table 9.1-3 relates to the number of welds.
Table 9.1-3 — NDT of tube welds
|
Types of welds |
Surface imperfection detection a |
Volumetric imperfection detection |
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|
Radiographic testing |
Ultrasonic testing |
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|
Circumferential welds |
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|
e d > 25 mm or da > 142 mm |
100 % |
100 % bc |
OR |
100 % b |
|
|
Dissimilar welds between austenitic and martensitic steels with d0< 76,1 mm |
100 % ' |
100 % bi |
|
в » M |
|
|
Flash welded or pressure welded butt welds |
see 6.1 |
see 6.1 |
see 6.1 |
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|
Other welds J |
- |
10 % c |
OR |
10 % c or 10 % h |
|
|
Pressure connection welds |
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|
e d > 25 mm (full penetration) |
100 % b |
100 % cef |
OR |
100 % ef |
|
|
15 mm < e d < 25 mm (full penetration) |
100 % b |
10%cef |
OR |
10%ef |
|
|
All other welds |
10 % |
— |
— |
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Table 9.1-3 (continued)
|
Types of welds |
Surface imperfection detection a |
Volumetric imperfection detection |
|
|
Radiographic testing |
Ultrasonic testing |
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|
Attachments welds |
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|
Load carrying |
100 % |
— |
— |
|
Non-load carrying |
10 % |
— |
— |
|
Welds between fins and tubes for panel construction |
g |
— |
— |
|
a Magnetic particle testing; with lacking accessibility if necessary PT testing, penetrant testing is acceptable for steel group 1. b Only 10 % for steel groups 1 and 8. c For outside diameters above 80 mm in steel groups 4 and 6 only ultrasonic testing is permitted. de is the thickness of the pressure connection. e Radiographic testing is acceptable instead of ultrasonic testing when ultrasonic testing is not possible. f No volumetric imperfection detection is required if d0< 142 mm. 9 Limited to 100 % visual examination. h When applying the elliptical technique a partial image of the weld is sufficient. і For joints being welded with machines an inspection scope of 10 % is sufficient. j In case of the application ot the elliptical technique, a partial image is sufficient for the radiographic testing of welds with d0< 76,1 mm. |
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Extension procedure of random testing in case of repairs
When performing a 10 % rate of non-destructive testing, as permitted in 9.1.2, 9.1.3 and 9.1.4, and when the result of the testing is not acceptable in accordance with the requirements of 9.3 or 9.4, the principle for the extension of the rate of that NDT shall be as follows:
the basis for an extension of the rate of testing shall always be related to each individual component, to each welder involved in the manufacture of this component, and to the same type of welds (referring to an identical welding procedure specification);
when performing the random testing, if one weld, or more than one weld, is (are) revealed as not being acceptable according to the requirements of 9 3 or 9.4, the testing shall be extended to two additional welds of the same type, for each rejected weld;
if all the examined welds of that extension are acceptable, then the initial rate of 10 % may be resumed;
when one or more of the welds examined during that extension is (are) not acceptable, then the testing shall be extended to ten additional welds for each weld rejected during the first extension;
the extension procedure shall be continued on this principle until all the extension welds are acceptable;
if the extension procedure continues to reveal unacceptable welds, the extension procedure shall be increased until a rate of 100 % testing is being carried out.
Qualification of non-destructive testing (NDT) personnel
Personnel responsible for non-destructive testing, including interpretation, evaluation and reporting shall be certified in accordance with the general requirements of EN 473:2008.
An exception to this requirement shall be made for visual examination of welds and final inspection of boilers, for which EN 473:2008 is not applicable.
Magnetic particle testing shall be performed under the direct supervision of personnel qualified to level 2 of EN 473:2008 as a minimum.
Penetrant testing shall be performed under the direct supervision of personnel qualified to level 2 of EN 473:2008 as a minimum.
Ultrasonic testing shall be performed by an operator qualified to level 2 of EN 473:2008 as a minimum for UT.
Radiographs shall be viewed by personnel qualified to level 2 of EN 473:2008 as a minimum.
Visual examination shall be carried out by experienced personnel having sufficient knowledge in welding techniques, and a full comprehension of this European Standard, to identify and interpret imperfections that might occur at the surface of the weld and the heat affected zone.
The detection of surface imperfections
General
For application to water-tube boiler inspection during manufacture or erection, the welds shall be accepted in the undressed condition, unless dressing is necessary to carry out satisfactory non-destructive testing.
Indications which cannot be identified as being acceptable in accordance with Table 9.3-1, or which cannot be positively identified as not being cracks, lack of fusion, lack of penetration, overlap or poor stop or re-start, shall be identified by other means. If the indication cannot be identified, it shall be assumed to be an imperfection and shall be removed.
Visual examination
Visual examination shall be carried out in accordance with EN ISO 17637.
The acceptance criteria for the surface imperfections of welds shall be in accordance with Table 9.3-1.
Acceptance limits for imperfections occurring at the surface of welded components have been derived by reference to EN ISO 5817 and EN ISO 6520-1.
The requirements of the above standards have been supplemented to reflect current water-tube boiler manufacturing practice. Where this has been done, an identifying letter “S” has been utilized in the Table 9.3-1 in the column “EN ISO 5817 level”.
For the special case of longitudinal fin to tube welds, the acceptance criteria shall be in accordance with EN 12952-5:2011, AnnexC.
Penetrant testing
Penetrant testing shall be carried out in accordance with the provisions of EN 571-1 and EN ISO 23277.
Acceptance levels shall be in accordance with EN ISO 23277.
Magnetic particle testing
Magnetic particle testing shall be carried out in accordance with the provisions of EN ISO 17638:2009 and EN ISO 23278.
Acceptance levels shall be in accordance with EN ISO 23278.
Acceptance criteria for weld surface imperfections
Table 9.3-1 —Acceptance criteria for weld surface imperfections
|
Identification of imperfection |
Limit of imperfection |
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|
EN ISO 6520-1 Group No. |
EN ISO 6520-1 Reference No. |
Type of imperfection |
EN ISO 5817 level |
Maximum permitted |
|
1 |
100X |
Cracks (all) |
В |
Not permitted |
|
2 |
201X 202X |
Gas cavity (all) Shrinkage cavity (all) |
"S" (B) |
Where d is the diameter of pore in mm, e is the thickness of base material, in mm. |
|
3 |
301X 302X 303X 304X |
Slag inclusions (all) Flux inclusions (all) Oxide inclusions (all) Metallic inclusions (all) |
"S" |
Not permitted when occurring at the surface (shall be removed e.g. by grinding). |
|
4 |
401X |
Lack of fusion (all) |
в |
Not permitted. |
|
402 4021 |
Lack of penetration Lack of root penetration |
в |
Not permitted if a full penetration weld is required. |
|
|
5 |
5011 5012 |
Undercut, continuous Undercut, intermittent |
с |
h < 0,1 e, max. 0,5 mm (irrespective of length). A smooth transition is required where h is depth of the notch and e is thickness of base material, in mm. |
|
|
5013 |
Shrinkage groove |
с |
h < 0,1 e, max. 1,0 mm (irrespective of length). a smooth transition is required where h is depth of the notch and e is thickness of base material, in mm. |
|
|
502 |
Excess weld metal (butt joint) |
с |
Height < 1 mm + 0,15 b, maximum 7 mm where b is width of weld, in mm. A smooth transition is required. |
Table 9.3-1 (continued)
|
Identification of imperfection |
Limit of imperfection |
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|
EN ISO 6520-1 Group No. |
EN ISO 6520-1 Reference No. |
Type of imperfection |
EN ISO 5817 level |
Maximum permitted |
|
|
503 |
Excessive convexity (fillet weld) |
C |
Height < 1 mm + 0,15 b, maximum 4 mm where b is width of weld, in mm. A smooth transition is required. |
|
5 |
504 |
Excess penetration |
C |
Height < 1 mm + 0,6 b, maximum 4 mm where b is the width of the penetration, in mm. |
|
5041 |
Local excess penetration |
"S" |
Occasional local excess (see No. 504) is permitted with a maximum that shall be related to the operating conditions. |
|
|
505 |
Abrupt weld transition |
в |
butt welds: a > 150° fillet welds: a > 110° |
|
|
506 |
Overlap |
в |
Not permitted. |
|
|
507 |
Linear misalignment |
|
See EN 12952-5:2011, 7.4 and 8.11. |
|
|
508 |
Angular misalignment |
|
See EN 12952-5:2011, 7.4 and 8.11. |
|
|
509 |
Sagging |
с |
Long imperfections (> 25 mm) not permitted. Short imperfections (< 25 mm) not permitted if h > 0,10 e, Maximum 1,0 mm where h is the depth of sagging, in mm, e is the thickness of parent material, in mm. |
|
|
510 |
Burn through |
в |
Not permitted. |
|
|
511 |
Incompletely filled groove |
с |
Same as for sagging No. 509. |
|
|
512 |
Excessive asymmetry of fillet weld |
D |
h < 2 mm + 0,2 a where h is the excess of one leg, in mm; a is the throat of weld, in mm. |
|
|
515 |
Root concavity |
С |
Long imperfections (> 25 mm) are not permitted. Short imperfections (< 25 mm) are permitted if h < 0,1 x e , max. 1 mm where h is the root concavity, in mm; e is the thickness of base material, in mm. A smooth transition is required. |
|
|
516 |
Root porosity |
В |
Not permitted. |
|
|
517 |
Poor restart |
В |
Not permitted. |
|
Table 9.3-1 (continued)
|
Identification of imperfection |
Limit of imperfection |
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|
EN ISO 6520-1 Group No. 6 |
EN ISO 6520-1 Reference No. 601 602 |
Type of imperfection Stray arc Spatter |
EN ISO 5817 level "S" "S" |
Maximum permitted Not permitted. Grinding is required plus penetrant testing or magnetic particle inspection to ensure that no crack is left. Shall normally be removed from all pressure parts and from both load and non-load carrying attachment welds. Isolated, non- systematic spatter may however be permitted on components made from steel group 1. NOTE In the special case of circumferential welded fins which are attached to tubes by a mechanized welding process, spatter should be minimized, but any produced may remain, regardless of the material or heat treatment involved. |
|
|
603 |
Torn surface |
"S" |
Not permitted. Shall be ground. A smooth transition is required. |
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|
604 |
Grinding mark |
"S" |
Not permitted. Shall be flushed by grinding. A smooth transition is required. |
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|
605 |
Chipping mark |
"S" |
Not permitted, shall be flushed by grinding. A smooth transition is required. |
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|
606 |
Underflushing |
"S" |
Not permitted. Any local underflushing shall be related to the design characteristics (calculated thickness + corrosion allowance = minimum thickness for parent material). Thickness shall be measured by ultrasonic method in case of doubt. |
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