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 Heat Exchanger Tubes
Shell-and-tube heat exchangers operating above 540 deg C (1000 deg F) on the process side fall outside the design envelope of carbon steel, low-alloy ferritic (P11 / P22 / P91) and the 300-series austenitic stainless grades. Hydrocracker effluent coolers, coal-gasification syngas exchangers, ammonia synthesis-loop interchangers and high-temperature process gas exchangers in petrochemical service routinely run 540 to 760 deg C process-fluid temperature with hydrogen, sulphur, ammonia, syngas or hydrocarbon vapours on one or both sides. Incoloy 800H (UNS N08810) is specified for the tube bundle and the tubesheet in these duties because it delivers the creep-rupture strength at the design temperature, the hydrogen attack resistance and the carburisation / sulphidation resistance the duty demands, while remaining welded and fabricable using established TEMA + API 660 procedures. This page documents the unit-by-unit service envelope, the tubesheet vs tube alloy selection logic and the supply specification.
Why Process-Side Exchanger Service Specifies Incoloy 800H
Process-side exchangers above 540 deg C face a multi-mode loading: creep-rupture under tube-side or shell-side pressure (often 5 to 25 MPa for hydroprocessing service), tube-to-tubesheet joint fatigue from differential thermal expansion between the tube bundle and the shell, and corrosion attack from the process fluid composition. Hydrogen at high partial pressure attacks ferritic and low-alloy materials at elevated temperature (Nelson-curve attack) and even 18Cr-8Ni austenitics suffer hydrogen-induced cracking on long exposure. The 30 to 35 percent nickel content of 800H sits well above the hydrogen-attack threshold for all practical refinery and gasification partial pressures and the 19 to 23 percent chromium chemistry resists the sulphidation attack from H2S-bearing streams. Where the service combines hydrogen + sulphur + heat (typical hydrocracker effluent), 800H is the cost-effective alternative to wrought Inconel 600 or Inconel 625, with comparable creep-rupture allowables to 815 deg C.
Service Envelope by Unit Type
| Unit | Stream A (typically tube side) | Stream B (typically shell side) | Design temperature | Design pressure |
|---|---|---|---|---|
| Hydrocracker effluent / feed exchanger | Hydrocracked liquid + H2 + H2S | Fresh feed liquid + recycle H2 | 425-460 deg C process / 540-595 deg C metal | 15-20 MPa |
| Coal-gasification syngas cooler | Syngas (CO + H2 + CO2 + H2O + H2S + traces) | Boiler feed water -> saturated steam | 650-870 deg C process / 700-815 deg C metal | 4-12 MPa |
| Ammonia synthesis loop interchanger | Reactor effluent (NH3 + H2 + N2) | Fresh syngas (H2 + N2) | 425-540 deg C process | 15-30 MPa |
| Methanol synthesis loop interchanger | Reactor effluent (MeOH + H2 + CO + CO2) | Fresh syngas | 250-400 deg C process | 5-10 MPa |
| HF alkylation isostripper feed-effluent | Reactor effluent (HF + iso-paraffin) | Fresh feed (iso-butane + olefin) | n/a (low temp; 800H rare) | n/a |
| SMR convection-section process gas cooler | Reformed gas (H2 + CO + CO2 + steam) | Boiler feed water -> saturated steam | 540-815 deg C process | 3-5 MPa |
Tubesheet vs Tube Alloy Selection
The tubesheet in a high-temperature process exchanger is loaded by tube-side and shell-side pressure plus differential thermal expansion. The classical practice is to specify the tubesheet at the same alloy as the tubes for differential-expansion compatibility, but for thick tubesheets (greater than approximately 200 mm) the cost-and-weight argument favours a clad tubesheet: low-alloy ferritic substrate (SA-336 F22V or SA-336 F91) with explosion-bonded or weld-overlay 800H clad on the process face. The clad thickness is typically 6 to 12 mm and the tube-to-tubesheet joint is made entirely in the 800H clad layer using GTAW with ERNiCrFe-7 filler. Solid 800H tubesheets are still specified where the thermal-cycling regime makes the bimetallic clad-to-substrate weld a fatigue-cracking risk, or where ammonia service requires no carbon-steel substrate at the process face.
Documented Failure Modes
- Tube-to-tubesheet joint cracking: differential thermal expansion between the bundle and the shell concentrates fatigue at the tube-to-tubesheet weld; cracking initiates after a few thousand thermal-cycle events in cyclic-service exchangers.
- Carburisation in the syngas cooler inlet rows: upstream of the saturated-steam transition, the high-temperature dry-gas zone exposes the tube OD to high carbon activity; the entry rows show carbon ingress over 60,000 to 100,000 hours.
- Stress relaxation cracking in the heat-affected zone: 800H welds with insufficient PWHT have shown SRC at the weld toe in services that combine sustained tension with elevated temperature (especially around 600 to 700 deg C).
- Tube-bundle vibration damage: high-velocity shell-side flow in syngas service induces flow-induced vibration; baffle-tube wear is the typical fail-mode signature.
- Tubesheet ligament cracking: ligament between adjacent tube holes in a thick tubesheet can crack from cyclic-pressure fatigue on the high-pressure side of a hydrocracker exchanger.
Documented Field References
- 2024, North America hydrocracker revamp: 3 effluent exchangers, each with 1,420 tubes of Incoloy 800H 19.05 mm OD x 2.11 mm wall x 12 m to ASTM B407, EN 10204 type 3.2 with LR witness, plus 800H weld-overlay tubesheet clad on SA-336 F22V substrate.
- 2023, Asia coal-to-chemicals gasification complex: 1 syngas cooler with 2,640 tubes of Incoloy 800H 25.4 mm OD x 3.05 mm wall x 14 m to ASTM B407, solid 800H tubesheet of 220 mm thickness.
- 2025, Middle East ammonia loop revamp: 4 loop interchangers, each with 720 tubes of 800H 19.05 mm OD x 2.41 mm wall x 9 m to ASME SB-407, with type 3.2 SGS witness.
- 2024, Europe hydrogen-plant convection-section gas cooler: 1 process gas cooler with 1,180 tubes of 800H 25.4 mm OD x 2.77 mm wall x 11 m to ASTM B407, replacing original 321H tubes after fireside-corrosion-driven retubing.
Sizing + Design Notes
- Tube OD selection: 19.05, 25.4 and 31.75 mm are the TEMA-standard ODs for refinery and gasification process exchangers; OD greater than this is custom.
- Tube wall thickness: set by the higher of (a) ASME Section VIII allowable stress at design temperature, (b) ASTM B407 minimum wall, (c) fouling-and-corrosion allowance per service.
- Tube-to-tubesheet joint: strength-welded plus mechanically expanded per TEMA RCB-7.2 and API 660 paragraph 7.2; GTAW with ERNiCrFe-7 filler.
- Baffle spacing: set by the OEM thermal-hydraulic design; segmental baffles at 0.4 to 0.6 x shell ID is typical.
- Anti-vibration sleeves or rod baffles: specified where the shell-side velocity exceeds the TEMA flow-induced vibration limit.
- Tube U-bend radius: minimum 1.5 x OD for cold-bent tubes; less is permitted with hot bending and PWHT consideration.
Standards That Govern
- ASTM B407: wrought 800H seamless tube specification.
- ASTM B564: forged 800H tubesheets and channel-head components.
- API 660: shell-and-tube heat exchanger for general refinery service.
- ASME Section VIII Division 1: pressure-vessel design basis for the shell + channel heads.
- TEMA: tube-to-tubesheet joint design + bundle tolerances.
- ASME Section IX: WPS / PQR for the tube-to-tubesheet welds and the longitudinal seam welds on welded-tube product where applicable.
Inspection + Documentation Expected
- EN 10204 type 3.2 mill certificate with classification-society witness on chemistry + mechanical + dimensional + NDT.
- Hydrostatic test on every tube length per ASTM B407 paragraph 11; some specifications additionally require shell-and-tube assembled hydro at 1.5 x design pressure.
- Eddy-current NDT to ASTM E309 on the full tube body.
- Visual + dye-penetrant inspection on every tube-to-tubesheet weld.
- Pneumatic test of the tubesheet-side joints with helium leak detection in critical hydrogen service.
- Tube-bundle straightness + concentricity inspection at the OEM fabrication shop.
Companion Components
- Incoloy 800H tubesheet and channel-head forgings for the bundle terminals.
- Incoloy 800H flanges for the shell-to-channel-head bolted joints.
- Incoloy 800H fasteners for the shell-flange bolted connections.
- Incoloy 800H seamless pipe for inlet + outlet nozzles in the same material as the bundle.
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
When is 800H specified over TP321H for high-temperature exchanger tubes?
When the design metal temperature exceeds approximately 620 deg C, when the service combines high hydrogen partial pressure with temperature above 540 deg C, or when the creep-rupture allowable controls the wall-thickness calculation. 800H delivers the creep-rupture stress envelope from 540 to 815 deg C that the 300-series stainless grades do not.
Is 800H acceptable in wet H2S service?
800H is qualified to NACE MR0175 / ISO 15156-3 with restrictions on cold-work and hardness. For wet H2S service at high temperature, 800H is preferred over 18-8 austenitic stainless grades that are vulnerable to polythionic acid stress corrosion cracking during shutdown.
Should the tubesheet be solid 800H or clad?
Below approximately 200 mm thickness, solid 800H is typically more cost-effective. Above this, clad construction with SA-336 F22V or F91 substrate plus 6 to 12 mm 800H weld-overlay or explosion-bonded clad on the process face is preferred. Project-specific design dictates the choice.
What is the largest cause of premature failure?
Tube-to-tubesheet joint fatigue cracking driven by differential thermal expansion in cyclic-service exchangers. Detailed FEA of the joint geometry combined with conservative cycle counting at the design stage and careful operating procedure for start-stop transients is the standard mitigation.
Are welded 800H tubes acceptable, or must they be seamless?
ASTM B515 / B516 welded 800H tube is acceptable in many process-exchanger services where the design code permits the welded-tube joint efficiency. Refinery hydroprocessing and gasification high-pressure exchangers typically require seamless tube to ASTM B407 because of the inherently lower NDT-burden and the absence of weld-line defects on hydrogen service.
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