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 Fired Heater Bolts (EN 10269 / 1.7709)
21CrMoV5-7 fired heater bolts are specified into refinery and petrochem fired-heater bolting on convection-section header flanges, lower-radiant-section flanges, and tube-support anchor bolts. The Cr-Mo-V Q+T chemistry handles the lower-radiant temperature window (450 to 550 deg C); the upper-radiant section above 550 deg C steps up to Durehete 1055 or to nickel-base alloys.
Service Envelope
| Fired heater zone | Typical metal temp | 21CrMoV5-7 use |
|---|---|---|
| Stack damper bolting | 200 to 350 deg C | Acceptable; 42CrMo4 also acceptable |
| Convection-section header flange | 350 to 480 deg C | Primary choice |
| Lower-radiant section flange | 450 to 540 deg C | Primary choice |
| Upper-radiant section flange | 540 to 590 deg C | Above envelope; Durehete 1055 / T22 / T91 |
| Tube-support anchor bolts | 400 to 540 deg C | Primary choice |
Bolting Form Factors Used
- Stud Bolts: header flange and tube-support flange bolting
- Anchor Bolts: tube-support anchor bolting cast into refractory
- Heavy Hex Bolts: stack damper and air-preheater bolting
- Matched-grade heavy hex nuts and hardened washers
Mechanical Floors for Fired Heater Bolts 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 fired-heater bolting to EN 10269. API 560 fired-heater bolting cross-references to ASTM A193 Grade B16 with dual-certification for US-spec heaters. Upper-radiant section bolts above 540 deg C step up to Durehete 1055 (Alloy T41).
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. What is the temperature split between 21CrMoV5-7 and Durehete 1055 in fired heaters?
Below 540 deg C metal temperature: 21CrMoV5-7. From 540 to 568 deg C: Durehete 1055 (Alloy T41 / 1.7729). Above 568 deg C: T22 / T91 / nickel-base alloys depending on the design temperature and service environment.
Q. Which API standard governs fired-heater bolting?
API 560 (Fired Heaters for General Refinery Service) and API 530 (Calculation of Heater Tube Thickness in Petroleum Refineries) reference the bolting material requirements through ASTM A193 / ASME SA-193 grades. 21CrMoV5-7 cross-references via A193 Grade B16.
Q. Are fired-heater bolts replaced on a fixed cadence?
No. Replacement is inspection-driven at each major turnaround (typically 4 to 6 year cadence). Bolts in the radiant section that have seen extended high-temperature service are replaced as a matter of policy on most refineries due to creep-relaxation risk.
Q. Do you supply special-geometry tube-support anchor bolts?
Yes. Custom-bent tube-support anchor bolts per the customer drawing in 21CrMoV5-7 ship from forged blank. Standard L-bolt and J-bolt configurations also available.
Related Applications
More 21CrMoV5-7 service applications: Steam Turbine Bolts · Gas Turbine Bolts · Power Plant Bolting · Pressure Vessel Bolts · Boiler Bolts · Heat Exchanger Bolts · Petrochem Reactor Bolts. Back to the 21CrMoV5-7 Alloy Hub.
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