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c. UT checks for laminations shall be made on all plate.

d. Forgings shall be subject to a 100% UT scan.

e. Plate edges after bevelling, but prior to welding root passes in shell, heads, and nozzles, weld build-ups on shell and heads, background surfaces, skirt to head or shell attachment welds, fillet welds, attachment welds and temporary welds after removal of attachments, shall be subject to MT.

f. Welds, including external and internal non-pressure containing welds, shall be subject to 100%

surface inspection (by MT or PT) after hydrotesting.

g. Pressure containing welds and skirt attachment or support welds shall be subject to RT or UT after hydrotesting. Radiographs shall be taken within 48 hours after weld completion.

h. Full penetration welds shall be subject to MT on the back-chipped surface and on finished weld surfaces prior to overlay.

B.4 1,25Cr-0,5Mo vessels (including Vanadium enhanced)

a. The measured tensile strength, as recorded on the material test certificate or report, shall be limited to 585 MPa (84,8 ksi) for plate and 655 MPa (95 ksi) for forgings.

b. The requirements included and guidance given in API 934-C and API 934-E shall apply.

c. Head or shell plate welds shall not be subjected to an austenitizing heat treatment without specific approval.

d. Minimum preheat temperature throughout thickness shall be 150°C (300°F). The actual interpass temperature for WPS qualification tests shall be determined and defined on PQR documents. Welding preheats shall be maintained until IPWHT has been performed.

e. Minimum PWHT temperatures shall be based on API RP 934-C or API RP 934-E as applicable. Note that for vessels with operating temperatures above 476°C (825°F), API RP 934-E applies.

B.5 2.25Cr-1Mo vessels (including Vanadium enhanced)

a. The vessel shall be made by the electric furnace or basic oxygen process.

b. The requirements included and guidance given in API 934-A shall apply.

c. A minimum and maximum PWHT shall be established. Two sets of weld procedure specimens shall be heat treated, one for each time. The strength of the vessel shall be such that at least two PWHT cycles remain available for BP in service, except that if the closing seam of the vessel requires an additional PWHT, only at least one remaining PWHT cycle shall be available for BP.

d. Materials for reactor vessels shall be vacuum degassed.

For ASME Code, see SA-20 supplementary requirement S1.

e. For plate and forgings:

1. The measured tensile strength for conventional shall not exceed 690 MPa (100 ksi).

2. Hot tensile tests at design temperature per API 934-A Paragraph 5.5.2.2 shall be required.

3. Test specimens shall be taken from the transverse ¼ t locations.

f. Plates shall be fine grain with a grain size of five (5) per ASTM E112 or finer (i.e. having a higher number than 5).

g. Step cooling tests of all materials (plates, forgings, and weld metals) shall be performed in accordance with paragraph 6.2.3 of API RP 934-A. Acceptance criteria shall be in accordance with API RP 934-A paragraph 6.2.3.3.

h. Welding wire heats and electrode and flux lots shall be selected and tested to confirm that tensile, impact, and step cooling requirements specified in B.6.3 are met in both the PWHTmin and PWHTmax conditions.

i. Preheat temperatures for welding, manual weld overlay and thermal cutting operations shall be in accordance with API RP 934-A. The following minimum preheat temperatures shall be maintained during machining/welding.

1. 200°C (392°F) for all welding.

2. 120°C (250°F) for machining.

3. 150°C (300°F) for manual weld overlay.

4. 150°C (300°F) for thermal cutting operations.

j. The actual maximum interpass temperature for WPS qualification tests shall be determined and defined on PQR documents, but shall not exceed 300°C (570°F).

k. During fabrication, intermediate PWHT shall be at temperatures lower than the final PWHT temperature. The latter shall not exceed the tempering temperature performed at the mill for any of the materials used.

Annex C (

)

Supplementary requirements for stainless steel vessels

C.1 Fabrication

a. When forming any austenitic stainless or nonferrous materials, the forming rolls shall covered to prevent carbon pickup or contamination of the formed material.

b. Formed heads shall be solution annealed after forming unless otherwise approved.

c. When cutting stainless steel by any thermal process (e.g., plasma arc or air arc), an allowance shall be made for the removal of not less than 3 mm (1/8 inch) of metal by machining or grinding to the finished dimension.

d. Grinding and cleaning of stainless steels shall be done with tools that do not leave detrimental deposits.

Examples of acceptable tools are aluminium oxide and silicon carbide grinding wheels and austenitic stainless steel wire brushes not previously used on other types of materials.

e. Only stainless steel brushes and clean, iron-free sand, ceramic, or stainless steel grit shall be used for cleaning stainless steel and non-ferrous surfaces.

f. Cleaning tools or materials shall not have been previously used on carbon steel.

C.2 Welding

g. The ferrite content of ASS weld metal, with the exception of type 904L (which is fully austenitic), shall be in the range 3 - 10% in the as-welded and post-weld heated condition.

h. Ferrite checks shall be made on at least 5% of the welds, unless a higher percentage is specified on the EDS.

i. Comparable low carbon austenitic filler materials shall be used when welding low carbon grade austenitic base materials.

C.3 Examination requirements

a. Welds shall be free from cracks and fissures. The extent of PT on welds shall be as specified on the EDS.

b. The pressure test fluid for ASS vessels shall not contain more than 50 ppm chlorides.

c. ASS vessels shall be dried within 48 hours of draining, using swabs or a flow of air at ambient temperature. Heat shall not be applied.

d. Unless directed otherwise, ASS vessels that operate in the range of 50°C to 150°C (120°F to 300°F) shall be painted externally to the specification listed on the EDS.

e. Insulated ASS vessels operating below 50°C (120°F) shall be painted externally to the specification listed on the EDS.

f. Equipment shall be protected such that chloride contamination cannot occur during shipment.

g. For vessel constructed to BSI PD 5500:

1. Inspection of forgings by PT shall be to BS EN 10228-2 and the required quality class shall be class 3 unless otherwise specified on the EDS.

2. Inspection of forgings by UT shall be to BS EN 10228-4 and the required quality class shall be class 3 unless otherwise specified on the EDS.

Annex D

(Normative)

Supplementary requirements for clad plate or weld-overlay construction