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VdTUV Wb 350 (German Pressure-Vessel Approval) (21CrMoV5-7 / EN 10269 / 1.7709)
VdTUV Werkstoffblatt 350 (Wb 350) is the German pressure-vessel approval scope for bolting steels, issued by the Verband der Technischen Uberwachungs-Vereine (VdTUV, Association of German Technical Inspection Agencies). 21CrMoV5-7 (Werkstoff 1.7709) is approved under Wb 350 for unfired pressure-vessel bolting service.
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Scope
Wb 350 supplements the EN 10269 mechanical-property qualification with German pressure-vessel-specific testing: extended creep-rupture qualification, expanded temperature-range elevated-temperature testing, and additional inspection-document categories for German PED-compliant pressure-vessel construction. The Wb 350 approval is parallel to (not a replacement for) the EN 10269 base qualification.
Wb 350 Scope
VdTUV Wb 350 covers bolting steels for unfired pressure-vessel construction under the German AD 2000 Code and the European Pressure Equipment Directive (PED). The Wb 350 approval is required for German pressure-vessel fabricators (Siemens Energy, Babcock, Linde, BASF, Bayer) when the bolting grade is to be qualified for elevated-temperature service.
Wb 350 Qualification Testing
| Test | EN 10269 base | Wb 350 addition |
|---|---|---|
| Creep-rupture (100,000 h) | Annex A envelope | Extended Larson-Miller envelope with 200,000 h projection |
| Elevated-temperature 0.2 percent proof | RT + design temp | Full 20 to 600 deg C step-test |
| Stress-relaxation | not required | 1,000 h stress-relaxation at design temperature |
| Charpy V impact | RT minimum | RT + low-temperature qualification (-40 deg C) |
Wb 350 Approval Documentation
The Wb 350 approval is documented on the EN 10204 type 3.1 or 3.2 inspection certificate as a separate compliance statement. The certificate references the Wb 350 issue number, the qualified Werkstoff number (1.7709 for 21CrMoV5-7), and the applicable thickness and temperature envelope. German PED-notified bodies (TUV Rheinland, TUV SUD, TUV Nord, DEKRA) accept the Wb 350 approval directly without additional re-qualification.
When Wb 350 Is Required
Wb 350 approval is required when 21CrMoV5-7 bolting is to be installed in a German-built or German-PED-notified-body-certified pressure vessel above 500 deg C design temperature. For pressure vessels below this threshold, the EN 10269 base qualification is sufficient. For non-German PED pressure vessels (Italian, Spanish, Polish), the local notified body may accept Wb 350 directly or may require parallel national qualification.
Frequently Asked Questions
Q. Is VdTUV Wb 350 mandatory for all 21CrMoV5-7 pressure-vessel bolting?
No. Wb 350 is required only when the pressure vessel is German-built or certified by a German PED-notified body (TUV Rheinland, TUV SUD, TUV Nord, DEKRA). For other PED notified bodies or for ASME pressure vessels, the EN 10269 base qualification (with cross-reference to ASTM A193 B16) is the path.
Q. What does the Wb 350 testing add to the EN 10269 qualification?
Extended Larson-Miller creep envelope projection to 200,000 hours, full 20 to 600 deg C step-test elevated-temperature 0.2 percent proof, 1,000 hour stress-relaxation testing, and low-temperature (-40 deg C) Charpy V impact qualification.
Q. Do you supply 21CrMoV5-7 with Wb 350 approval as standard?
Wb 350-qualified material is supplied on call-out. The Wb 350 approval is documented on the EN 10204 type 3.1 or 3.2 certificate as a separate compliance statement with the Wb 350 issue number referenced.
Q. Is Wb 350 the same as TUV approval?
Wb 350 is the underlying material approval issued by the VdTUV federation. TUV (TUV Rheinland, TUV SUD, etc.) are the inspection agencies that perform the EN 10204 type 3.2 witness inspection and the Wb 350 qualification testing. The Wb 350 approval is referenced in TUV inspection certificates.
Related Standards and Properties
Related standards: EN 10269 · EN 10278 · ASTM A193 · EN 10269 Equivalents. Properties pages: Chemistry · Mechanicals · Heat Treatment · Hardness · Creep-Rupture. Back to the 21CrMoV5-7 Alloy Hub.
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