Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
21CrMoV5-7 Power Plant Bolting (EN 10269 / 1.7709)
21CrMoV5-7 power plant bolting is specified across the subcritical, transition supercritical, and selected supercritical bolting positions on conventional fossil and biomass power plants. The grade covers drum-head flange bolting, steam-line flange bolting, valve-body bolting, and casing-half-joint bolting at metal temperatures to 550 deg C. Above 550 deg C the design steps up to Durehete 1055.
Service Envelope
| Steam cycle | Typical main-steam temperature | 21CrMoV5-7 use |
|---|---|---|
| Subcritical (industrial) | 480 to 540 deg C | Primary choice for all bolting positions |
| Subcritical (utility) | 540 deg C | Primary choice |
| Transition supercritical | 540 to 568 deg C | Primary choice up to 550; Durehete 1055 above |
| Supercritical | 568 to 600 deg C | Selected positions; main bolting Durehete 1055 |
| Ultra-supercritical | 600 to 620 deg C | Outside envelope; Durehete 1055 or nickel-base |
Bolting Form Factors Used
- Stud Bolts: drum-head and steam-line flange bolting
- Heavy Hex Bolts: valve-body bolting to ASME B18.2.1
- Tap Studs: turbine casing half-joint and valve-body bolting
- Body-Bound Studs: cyclic-load casing joints
- Anchor Bolts: foundation anchorage for skirted equipment
Mechanical Floors for Power Plant Bolting Service
| Property | Value | Condition |
|---|---|---|
| Tensile (Rm) | 700 to 850 MPa | RT, Q+T |
| 0.2 percent proof stress (Rp0.2) | ≥550 MPa | RT, Q+T |
| Elongation A5 | ≥16 percent | RT, longitudinal |
| Charpy V impact (KV) | ≥63 J | 20 deg C |
| 0.2 percent proof at 500 deg C | ≥450 MPa | elevated-temp |
| Hardness | 210 to 250 HBW | Q+T |
Standards Anchor
21CrMoV5-7 power-plant bolting to EN 10269. Cross-procurement on US-design power plants (GE / Westinghouse) uses ASTM A193 Grade B16 with dual-certification. Pressure-vessel parallel approval to VdTUV Wb 350 for unfired pressure-vessel bolting in the steam cycle.
When to Step Up the Grade
For service above 550 deg C metal temperature, the design steps up to Durehete 1055 (Alloy T41 / Werkstoff 1.7729 / 20CrMoVTiB4-10) with Ti+B microalloying for extended creep envelope. For heavier sections of the same temperature window, sister grade 21CrMoV5-11 (1.8070) provides extended hardenability.
Frequently Asked Questions
Q. Which subsystems of a power plant use 21CrMoV5-7 bolting?
Main steam-line flanges, drum-head flanges, valve-body bolting (main steam stop and control valves), turbine casing half-joints (LP, IP, lower HP), boiler-feed-water heater bolting, deaerator bolting, and selected pressure-vessel bolting on the steam side.
Q. Where does Durehete 1055 take over from 21CrMoV5-7 in a power plant?
On the high-pressure main bolting above 550 deg C metal temperature: HP turbine upper-stage casing, supercritical main-steam line, ultra-supercritical valve bodies. 21CrMoV5-7 stays the workhorse for everything below 550 deg C.
Q. Are 21CrMoV5-7 bolts used in nuclear power plants?
Yes, for selected secondary-side bolting positions where the temperature envelope and the chemistry allowability match. Primary-side and safety-class bolting typically uses ASTM A540 or ASME-coded SA-540 grades with separate nuclear-quality requirements.
Q. What is the typical lifetime for a 21CrMoV5-7 power-plant bolt?
Design life is typically set at 100,000 hours service to EN 10269 Annex A stress-rupture envelope. Actual replacement is on inspection-driven cadence: bolt hardness, dimensional check, and visual at each major outage with replacement when below acceptance.
Related Applications
More 21CrMoV5-7 service applications: Steam Turbine Bolts · Gas Turbine Bolts · Pressure Vessel Bolts · Boiler Bolts · Heat Exchanger Bolts · Fired Heater Bolts · Petrochem Reactor Bolts. Back to the 21CrMoV5-7 Alloy Hub.
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