Category
Heat Transfer Equipment
Subcategory
Heat Exchanger
Applicable standards
3
Issuing bodies
2
Description
Forced or induced draft air-cooled heat exchanger with finned tubes.
Applicable Standards (3)
API — 2 standards
API 661
Petroleum, Petrochemical, and Natural Gas Industries — Air-Cooled Heat Exchangers
Air-cooled heat exchangers for refining/petchem/gas. Identical to ISO 13706.
Key requirements (9)
- Air-cooled heat exchangers (ACHE) for petroleum, petrochemical, natural gas.
- Forced draft (fan below tubes) or induced draft (fan above tubes).
- Standard tube: 1" OD, 11 fpi (fins per inch), 1/2" fin height typical.
- Tube types: embedded G-fin (high temp), extruded bimetal (medium), L-foot/wrapped (low cost).
- Air-side face velocity: typically 3–4 m/s.
- Fan blade tip speed: ≤ 60 m/s.
- Plenum geometry minimums per Section 5.6.
- Vibration: fan natural frequency well separated from rotational frequency.
- Louvers / variable-pitch fans for cold-climate temperature control.
API 673
Centrifugal Fans for Petroleum, Chemical and Gas Industry Services
Centrifugal fans for refinery / petrochemical service (FCC, FD/ID, etc.).
Key requirements (8)
- Centrifugal fans for petroleum, chemical, gas industries.
- Hydrotest: not applicable (atmospheric); structural test instead.
- Mechanical run test: 4 hours minimum.
- Maximum allowable speed: 105% rated for warning, 110% for trip.
- Vibration: bearing housing typically ≤ 7.6 mm/s rms.
- Performance test per ASME PTC 11.
- Materials: CS housing, CS or SS impeller depending on service.
- Bearing L10 life: 25,000 hrs continuous typical.
ASME — 1 standard
ASME BPVC Sec VIII Div 1
Rules for Construction of Pressure Vessels
Mandatory rules for design, fabrication, inspection, testing and certification of pressure vessels operating above 15 psig (~1 barg).
Key requirements (12)
- Applies to vessels with internal pressure > 15 psig (1.03 barg) up to ~3000 psi (Div 1 sweet spot).
- Joint efficiency E: 1.0 (full radiography), 0.85 (spot RT), 0.70 (no RT) for Type 1 butt joints.
- Shell thickness: t = P·R/(S·E – 0.6·P) for circumferential stress (UG-27).
- Head thickness: t = P·D/(2·S·E – 0.2·P) for 2:1 ellipsoidal heads (UG-32).
- Hydrostatic test pressure: 1.3 × MAWP × (S_test/S_design) — UG-99.
- Pneumatic test (when hydro impractical): 1.1 × MAWP — UG-100.
- Corrosion allowance is added to calculated thickness (not included in S formula).
- MDMT and impact testing per UCS-66 / Figure UCS-66; below the curve, Charpy V-notch impacts are required.
- PWHT thresholds per UCS-56 — generally required above 19 mm thickness for P-No. 1 carbon steels.
- Nozzle reinforcement: area replacement method (UG-37) within reinforcement zone.
- Maximum allowable stress S: from ASME II Part D, Table 1A/1B/3 — temperature dependent.
- Flanges per ASME VIII-1 Appendix 2 (or B16.5 for standard sizes).
Note: Most widely used pressure vessel code worldwide.