API RP 2Z:2005 pdf download
API RP 2Z:2005 pdf download.Recommended Practice for Preproduction Qualification for Steel Plates for Offshore Structures.
3.1.3 The three butt welds shall be welded with pre-heat, heat input, and interpass temperature that span the pre-qualification range. The heat input (arc energy) range for pre-qualification shall encompass at least 0.8 to 4.5 kJ/mrn (21 to 114 kJ/in.), unless the manufacturer elects a more restrictive heat input range for their particular steel supply (see 1.3.6). One weld shall be made at the lowest heat input to be pre-qualified with the lowest preheat/interpass temperature to be qualified in Section 4 [100°C (212°F) or lower] at the start of each weld pass adjacent to the tested HAZ. Preheat!interpass may increase 60°C (140°F) for weld passes further from I-IAZ. Another weld shall be made at the highest heat input to be pre-qualified with preheatlinterpass temperature at 250°C (482°F) or higher at the start of each weld pass. The third weld shall be made with heat input at 3.0 kJ/inm (76 id/in.); the preheat temperature shall be 100°C (212°F), and the interpass temperature shall be allowed to build naturally, but not to exceed 250°C (482°F). Suitable equipment shall be employed for measuring these parameters quantitatively (temperature-indicating crayons are not acceptable). The heat input may be varied temporarily for initial or final passes if of practical necessity to complete a weld of the desired shape.
3.2 The HAZ of each test weld shall be evaluated by CTOD testing and by Charpy impact testing. Prior to evaluation, the test weld shall receive post-weld heat treatment if applicable. As-welded and post-weld heat-treated weldment conditions must be pre-qualified separately. Where PWHT is to be applied, the PWHT thermal cycle shall be recorded and reported.
3.3 CTOD TESTING
For the lowest heat input weld, a minimum of eight valid CTOD tests are required, and for the 3.0 kJ/mm (76 kJ/in.) weld and the highest heat input weld, five valid CTOD tests are required. All CTOD tests will be performed at —10°C (14°F), or at the lowest anticipated service temperature (LAST). All CTOD tests shall be in accordance with either British Standard BS 7448 Part 1 & 2 or ASTM E 1290 (at Manufacturer’s option), employing the preferred (Tx2T) test specimen (See Note 1) with a through-thickness notch and fatigue precrack extending halfway through the specimen width, nominally. The CTOD specimen length dimension shall be perpendicular to the weld and plate rolling direction (T-L orientation). The straight side of the weld should be straight enough so that a through-thickness notch can be placed normal to the plate surface and intersect the etched HAZ for at least 75% of the notch length over the central 2/3 of the specimen thickness. More specimens than the number of required valid specimens may be necessary to allow for invalid results (per the CTOD test method) or failure to meet the notch placement criteria. The weld reinforcement may be removed, and the original plate surfaces cleaned to remove scale and superficial roughness, prior to the preparation of the specimens.
Note 1: The notch comprising machined notch and fatigue crack shall have a depth of 45% — 55% of the specimen thickness. TxT test specimens may be used for plate thickness T over 63 mm (2.5 in.).
Note 2: Test specimens in the as-welded condition may be mechanically stress relieved by lateral compression prior to fatigue precracking to
promote crack front straightness. This procedure is described in lracture mechanics Tests on Welded Joints” by M.G. Dawes, et. al., in ASTM
STP 995 Non-Linear Fracture Mechanics: Jblwne II- Elastic Plastic Fracture and BS 7448 Part 2: Method jbr determination of critical
CTOD, and critical J values of welds in metallic materials.
Note 3: These CTOD testing requirements are summarized in Table 1.
3.3.1 If more that one test fails to meet the required acceptance value, the steel fails the pre-qualification requirement. If only one of the initial valid CTOD tests fails to meet the required acceptance value, additional tests may be made duplicating the welding and precrack location conditions of the single specimen with the low CTOD value. All retests must meet the required number of retests as defined in section 3.3.8.
