Welding specifications

Welding inspections

 

The certification of the welding will be released after inspections in compliance with the class of execution.

The welds will be subjected to non destructive tests (NDT) to verify the consistency with the quality standards established by the designer on the basis of the applicable rules for the design.

 

Inspection before and during welding shall be included in the inspection plan according to the requirements given in the relevant part of EN ISO 3834.

 

Non destructive testing (NDT) methods shall be selected in accordance with EN 12062 by personnel qualified according to Level 3 as defined in EN 473.

Generally ultrasonic testing or radiographic testing applies to butt welds and penetrant testing or magnetic particle inspection applies to fillet welds.

 

NDT, with the exception of visual inspection, shall be performed by personnel qualified according to Level 2 as defined in EN 473.

 

The supplementary NDT of a weld shall generally not be completed until after the minimum hold time after welding shown in Table 23.

 

                                                             Table 23 - Minimum hold times

Weld size

(mm) a

Heat input Q (kJ/mm) b

Hold time (hours) c

S235 to S420

S460 and above

a or s ≤ 6

All

Cooling period only

24

6 < a or s ≤ 12

≤ 3

8

24

> 3

16

40

a or s > 12

≤ 3

16

40

> 3

40

48

a Size applies to the nominal throat thickness a of a fillet weld or the nominal material thickness s of a full penetration weld. For individual partial penetration butt welds the governing criterion is the nominal weld depth a, but for pairs of partial penetration butt welds welded simultaneously it is the sum of the weld throats a.

b Heat input Q to be calculated in accordance with Clause 19 of EN 1011-1:1998.

c The time between weld completion and commencement of NDT shall be stated in the NDT report. In the case of “cooling period only” this will last until the weld is cool enough for NDT to commence.

 

All welds will be inspected with Visual method throughout their entire length

 

If surface imperfections are detected, surface testing by penetrant testing or magnetic particle inspection shall be carried out on the inspected weld.

 

Unless otherwise specified no supplementary NDT is required for EXC1 welds. Only visual inspection is needed for this class.

 

For EXC2, EXC3 and EXC4 welds the extent of supplementary NDT is needed as specified below.

 

For the first 5 joints made to the same new WPS the following requirements shall be fulfilled:

the quality level B is required for demonstration of the WPS in production conditions;

the % to be tested shall be double of the values in Table 24 (max. 100 %);

the minimum length to be inspected is 900 mm.

 

If inspection gives non conforming results, investigation shall be carried out in order to find the reason and a new set of five joints shall be tested.

 

Once it has been established that production welding according to a WPS meets the quality requirements, the required extent of supplementary NDT shall be in accordance with Table 24 with further joints welded according to the same WPS treated as a single continuing inspection lot. The percentages apply to the extent of supplementary NDT treated as the cumulative amount within each inspection lot.

                                         Table 24 - Extent of supplementary NDT
 

Type of weld

Shop and site welds

EXC2

EXC3

EXC4

Transverse butt welds and partial penetration welds in butt joints subjected to tensile stress:

 

U ≥ 0,5

 

U < 0,5

 

 

 

10 %

 

0 %

 

 

 

 

20 %

 

10 %

 

 

 

100 %

 

50 %

Transverse butt welds and partial penetration welds:

 

·         in cruciform joints

 

·         in T joints

 

 

10 %

 

5 %

 

 

 

20 %

 

10 %

 

 

100 %

 

50 %

Transverse fillet welds in tension or shear:

 

With a > 12 mm or t > 20 mm

 

With a ≤ 12 mm and t ≤ 20 mm

 

5 %

 

0 %

 

 

10 %

 

5 %

 

20 %

 

10 %

Longitudinal welds and welds to stiffeners

0 %

5 %

10 %

NOTE 1 Longitudinal welds are those made parallel to the component axis. All the others are considered as transverse welds.

NOTE 2 U = Utilization grade for welds for quasi-static actions. U = Ed/Rd, where Ed is the largest action effect of the weld and Rd is the resistance of the weld in the ultimate limit state.

NOTE 3 Terms a and t refer respectively to the throat thickness and the thickest material being joined.

In general the following table can be taken as reference for the % of the inspections.

UNI EN 1090-2 /

UNI EN 1090-3

EN ISO 5817

Visual inspection

Additional NDT

EXC1

Quality level D

100 %

Not requested

EXC2

Quality level C

100 %

10 %

EXC3

Quality level B

100 %

20 %

EXC4

Quality level B+

100 %

100 %

 the minimum length to be inspected is 900 mm.
See previous Table 24 for more details