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
Incoloy 800H ASME VIII Pressure Vessels
An ASME Section VIII Division 1 pressure vessel built from Incoloy 800H is the standard solution for hydrocarbon and chemical service that combines moderate pressure (1 to 10 MPa typical) with sustained temperature above 540 deg C (1000 deg F). Refinery delayed-coker drums on the upper-shell zones, steam-methane reformer waste-heat boiler shells, ethylene-plant transfer-line exchanger shells, ammonia reformer outlet manifolds, methanol synthesis reactor heads and high-temperature separator vessels in petrochemical service are typical applications. This page is the APPLICATION-oriented companion to the ASME Section VIII code-reference page and documents the vessel-design context, the heat-treat practice, the PWHT logic, the NDT scope and the supply specification for fabricated 800H pressure vessels. The vessel components covered are: cylindrical shells, ellipsoidal and hemispherical heads, nozzles, tubesheets, channel heads, internal trays and supports, and bolting.
Why Pressure-Vessel Service over 540 deg C Specifies Incoloy 800H
The ASME Section II Part D allowable design stress envelope for the low-alloy ferritic grades (SA-387 Grade 22 Class 2, SA-387 Grade 91) drops sharply above 540 deg C and runs out entirely at 600 to 650 deg C. The 18Cr-8Ni austenitic grades (SA-240 304H, SA-240 321H, SA-240 347H) extend the envelope to 800 deg C nominally but with reduced allowable stress and known polythionic acid stress-corrosion cracking risk during shutdown. Incoloy 800H sustains a useful design-stress envelope from 540 to 815 deg C per ASME Section VIII Division 1, with allowable stress at 650 deg C of approximately 95 MPa against approximately 50 MPa for SA-387 Grade 91 at the same temperature. The combination of allowable-stress headroom, sustained hydrogen attack resistance, sulphidation resistance and welded fabricability is what makes 800H the standard alloy for new-build pressure vessels in this temperature window.
Vessel Applications by Unit
| Refinery / petchem unit | Vessel | Design temperature | Design pressure | Typical material |
|---|---|---|---|---|
| SMR hydrogen plant | Outlet manifold + waste-heat boiler inlet shell | 815-870 deg C | 2.5-4.0 MPa | 800H plate + forging |
| Ethylene cracker | Transfer-line exchanger (TLE) shell | 540-650 deg C steam side | 4-12 MPa | 800H shell with clad option |
| Delayed coker | Upper-shell zone (above feed inlet) | 480-540 deg C | 0.3-0.6 MPa | 800H rarely; usually SA-387 |
| Methanol reactor | Reactor head + tubesheet zone | 250-400 deg C | 5-10 MPa | 800H clad on SA-387 substrate |
| Ammonia secondary reformer | Outlet manifold + waste-heat boiler shell | 815-980 deg C | 3-5 MPa | 800H + 800HT plate + forging |
| Coal-gasification syngas cooler | Shell (saturated steam side) | 320-380 deg C | 4-12 MPa | SA-516 typical; 800H for inlet section |
| Fluidised catalytic cracker (FCC) | Stripper + dilute-phase regenerator | 700-780 deg C | 0.2-0.4 MPa | 800H lining or 800H plate full shell |
Heat-Treat and PWHT Logic
Incoloy 800H plate (ASTM B409) and forgings (ASTM B564) are supplied in the solution-annealed condition: hold at 1149 deg C (2100 deg F) minimum followed by rapid cool (water quench or accelerated air). This delivers the ASTM grain size 5 or coarser that the 800H qualification requires. Post-weld heat treatment on fabricated 800H vessels is a separate topic from the mill solution anneal. ASME Section VIII Division 1 paragraph UF-31 does NOT mandate PWHT on 800H welds for the typical petrochemical vessel-wall thickness; this is a notable departure from the SA-387 ferritic grades that require mandatory PWHT above 19 mm wall. PWHT on 800H vessels is specified in two cases: (1) where stress relaxation cracking risk in the heat-affected zone is a concern (typically 600 to 700 deg C continuous service), and (2) where the customer specifies it for residual-stress reduction in thick-section components above approximately 50 mm wall thickness. When PWHT is applied to 800H, the standard cycle is 870 to 900 deg C for 1 hour per 25 mm of thickness, followed by furnace cool to below 540 deg C.
Weld Procedures + Filler Selection
- Root pass: GTAW with ERNiCrFe-7 filler (AWS A5.14). Argon back-purge with dew-point below minus 50 deg C.
- Fill passes: SAW or GMAW with ERNiCrFe-7 filler; alternatively SMAW with ENiCrFe-2 (AWS A5.11) coated electrode for site-fabrication and repair welds.
- Interpass temperature: 150 deg C maximum to limit hot-cracking risk in the highly austenitic weld pool.
- Heat input: 1.0 to 2.5 kJ/mm typical for high-thickness shell welding; minimised on root pass to limit dilution from the parent metal.
- Backing strip: not permitted for hydrogen or H2S service; root must be open and back-purged.
- Bimetallic welds (800H to SA-387 or 800H to 304L cladding): ENiCrFe-3 or ERNiCrFe-7 filler bridges the substrate-to-overlay metallurgy; project-specific weld procedure qualification required.
Documented Field References
- 2024, Middle East hydrogen plant: SMR outlet manifold of 800H plate (ASTM B409) 32 mm wall, 1.8 m ID x 7 m straight section, with 800H tubesheet forging (ASTM B564) 240 mm thickness, EN 10204 type 3.2 with LR third-party witness.
- 2025, Asia ammonia revamp: secondary reformer waste-heat boiler shell of 800H + 800HT plate, 50 mm wall in the inlet section + 30 mm wall in the outlet section, full vessel weld inspection per ASME Section V + ASME Section VIII Division 1.
- 2023, Europe ethylene cracker turnaround: TLE shell replacement with 800H plate (ASTM B409) 25 mm wall, 2.4 m ID x 6 m straight section, with 800H weld-overlay on SA-336 F22V tubesheet substrate.
- 2024, North America FCC unit revamp: regenerator dilute-phase 800H lining of 8 mm sheet (ASTM B409) attached to SA-516 Grade 70 substrate with seal welds, supplied with full chemistry + mechanical + grain-size certification on every sheet.
Sizing + Design Notes
- Shell wall thickness: set by the ASME Section VIII Division 1 allowable stress at design temperature; allowable stress at 650 deg C of approximately 95 MPa, at 750 deg C of approximately 50 MPa.
- Nozzle reinforcement: integral 800H reinforcement pads from ASTM B564 forgings are preferred over welded-on doubler plates for thermal-cycling service.
- Head geometry: ellipsoidal 2:1 (Code Type E) or hemispherical heads from 800H plate are the standard; torispherical heads are acceptable for low-pressure service.
- External support: skirt or saddle supports designed for the differential thermal expansion between the 800H vessel and the carbon-steel support steel; sliding feet permitted on saddle supports.
- Bolting (flanged joints): use ASTM B564 or B408 800H bolting on the vessel-side flanges; never mix 800H vessel with low-alloy bolting on flanged connections in cycling service.
- Internals (trays, baffles, distributors): 800H sheet to ASTM B409, attached to the vessel shell via seal-welded clips at points that allow differential thermal expansion.
Standards That Govern
- ASME Section VIII Division 1: pressure-vessel design code (UNF / UHA appendices for nickel-alloy specific rules).
- ASME Section II Part D Table 1A: 800H allowable design stress to 815 deg C.
- ASTM B409 (ASME SB-409): 800H plate, sheet and strip.
- ASTM B564 (ASME SB-564): 800H forgings (flanges, tubesheets, manhole covers).
- ASTM B407 (ASME SB-407): 800H seamless pipe + tube for nozzle connections.
- ASME Section V: NDT methods for the vessel weld inspection.
- ASME Section IX: WPS / PQR for the vessel construction welds.
- National Board Inspection Code: in-service inspection of erected 800H vessels.
Inspection + Documentation Expected
- EN 10204 type 3.2 mill certificate with classification-society witness on every plate, forging and pipe length used in the vessel construction.
- 100 percent radiography on category A (longitudinal shell) and category B (circumferential shell) welds per ASME Section VIII Division 1 UW-11.
- PT on every nozzle reinforcement weld and every internal-attachment weld.
- Hardness survey on every PWHT cycle to confirm acceptance.
- Hydrostatic test at 1.3 x design pressure per ASME Section VIII Division 1 UG-99.
- Form U-1 Manufacturer Data Report signed by the Authorised Inspector.
- Photographic record of every accessible weld with weld map referenced to the radiography records and serialised by NDT report number.
Companion Components
- Incoloy 800H plate for vessel shells, heads and internal trays.
- Incoloy 800H forgings for tubesheets, flanges and nozzle reinforcement pads.
- Incoloy 800H seamless pipe for vessel nozzles and inlet / outlet piping stubs.
- Incoloy 800H fittings for nozzle-to-piping butt-weld transitions.
- Incoloy 800H fasteners for the bolted flange and manway connections.
Related Incoloy 800H Fasteners for This Application
TorqBolt supplies the matched fastener range for this service from Incoloy 800H bar (ASTM B408) and forged blanks (ASTM B564), heat-treated to retain ASTM grain size 5 or coarser for ASME Section VIII design stress qualification.
Stud Bolts
Primary flange bolting form, M12-M64, both-end-threaded with matched heavy hex nuts.
Heavy Hex Bolts
ASME B18.2.1 heavy-pattern bolts, 1/2" to 2", petrochem flange service.
Heavy Hex Nuts
ASME B18.2.2 matched-grade nuts paired with heavy hex bolts and stud bolts.
Washers
Flat DIN 125 + spring DIN 127 + locking DIN 6798 in matched Incoloy 800H chemistry.
U-Bolts
Pipe-support clamps for high-temperature piping in petrochem and refinery service.
Threaded Rod
Continuous threaded rod M12-M48, cut to length for hanger and tie-rod assemblies.
Frequently Asked Questions
Is PWHT mandatory on Incoloy 800H pressure vessels?
No, ASME Section VIII Division 1 does not mandate PWHT on 800H welds at the typical petrochemical-vessel thickness. PWHT is applied when stress-relaxation cracking risk is a concern (typically 600 to 700 deg C continuous service) or where the customer specifies residual-stress reduction on thick-section components.
When should I choose solid 800H plate vs clad construction?
Solid 800H is cost-effective for shell wall thickness up to about 40 mm. Above this, clad construction with SA-387 Grade 22 Class 2 or SA-387 Grade 91 substrate plus 6 to 12 mm 800H weld overlay on the process face is typically more economical, provided the thermal cycling regime does not raise clad-bond fatigue concern.
What is the maximum design temperature in ASME Section VIII Division 1 for 800H?
815 deg C (1500 deg F) for 800H per the current code edition. 800HT extends this to 899 deg C (1650 deg F) where the gamma-prime precipitation lifts the allowable design stress envelope. Above 899 deg C, the design moves into ASME Section VIII Division 2 or proprietary high-temperature codes.
How is a bimetallic flange joint between 800H and SA-105 handled?
For service temperature above 425 deg C, a transition spool of 800H pipe between the SA-105 flange and the 800H vessel nozzle is preferred over a direct bimetallic flange face contact. The transition spool absorbs differential thermal expansion via length compliance and isolates the gasket seating from the bimetallic thermal-stress concentration.
Are 800H vessels subject to creep monitoring during service?
Yes, vessels operating continuously above 540 deg C are typically subject to a creep-monitoring programme covering periodic wall thickness measurement, in-situ metallographic replica testing for creep cavity development at the weld toes, and dimensional checks of bulging or distortion at the shell. The monitoring frequency is set by the owner's risk-based-inspection programme.
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