API 660 Shell & Tube Type Heat Exchanger ASME Petrochemical & Refinery Equipment

API 660 Shell & Tube Heat Exchanger | ASME Petrochemical & Refinery Equipment

What is API 660?

API 660 is the American Petroleum Institute's standard for shell-and-tube heat exchangers in the oil, gas, and petrochemical industries, specifying design, materials, testing, and inspection requirements to ensure safety and reliability in high-pressure, high-temperature, and corrosive environments. It aligns with ASME BPVC and ISO 16812, mandating robust construction, corrosion-resistant materials (like stainless steel), and strict quality control (including hydrostatic testing and NDE) for critical applications in refineries, gas plants, and offshore platforms. Compliance with API 660 signals industry-proven durability, reducing downtime and operational risks.

Core Function:

To transfer heat between two fluids (typically liquids or gas/liquid) without mixing them, using a bundle of tubes enclosed within a cylindrical shell. One fluid flows through the tubes (tube side), the other flows around the tubes within the shell (shell side).

Why S&THE Dominates Oil & Gas:

1. High Pressure & Temperature Capability: Robust construction handles extreme O&G process conditions (HP/HT wells, refining, compression).

2. Proven Reliability & Durability: Mature design with a long track record in critical service.

3. Design Flexibility: Adaptable to various fluids (crude, gas, water, chemicals), flow rates, temperatures, pressures, and fouling tendencies via configuration choices.

4. Ease of Maintenance: Tube bundles can often be removed for cleaning, repair, or replacement (especially floating head designs).

5. Efficiency: Can achieve high heat transfer coefficients, especially with turbulent flow and enhanced surfaces.

Key Components (API 660 Focused):

1. Shell: Cylindrical pressure vessel (ASME Sec VIII Div 1/2). Material selection critical for corrosion (CS, SS, Duplex, Nickel alloys, Clad).

2. Tube Bundle: Core heat transfer element.

   • Tubes: Seamless/welded; sized for pressure drop/fouling; material critical.

   • Tubesheets: Thick plates drilling for tubes; often clad; critical for differential expansion.

   • Baffles: Support tubes, induce shell-side turbulence (segmental, helical, rod). Spacing/design impacts vibration & performance.

   • Tie Rods & Spacers: Secure baffles.

3. Channel/Headers (Tube Side): Distributes tube-side fluid; allows access (removable cover - bolted, bonnet).

4. Nozzles: Inlet/Outlet for shell & tube side fluids. Sized per fluid velocity limits (API 660/API RP 14E).

5. TEMA Type: Defines mechanical configuration based on front header, shell type, rear header. Common O&G types: AES, BEM, AEP, AKT (Floating Heads common for thermal expansion).

Critical Oil & Gas Applications:

1. Production: Crude oil cooling, produced water cooling, gas cooling (after compression), glycol dehydration (reboilers/coolers).

2. Refining: Feed preheaters, product coolers, reboilers, condensers throughout distillation, hydrotreating, catalytic units.

3. Gas Processing: Gas/gas exchangers (regeneration/cooling), gas/liquid coolers, amine solution coolers/reboilers, refrigerant condensers/evaporators.

4. Transmission: Lube oil coolers, gas cooling after compression.

5. Utilities: Cooling water systems, heat recovery.

API 660 Compliance: The O&G Standard

API 660 is the mandatory standard for S&THE in the petroleum & natural gas industries. Compliance ensures:

1. Robust Design & Construction: Mandates minimum design margins, material requirements, fabrication standards (welding, NDE), pressure testing.
2. Safety & Reliability: Addresses specific O&G hazards (sour service, fire exposure, vibration).
3. Interchangeability & Consistency: Standardizes dimensions, nozzle loads, naming, documentation.
4. Specific O&G Requirements:

• Design Conditions: Clearly defined operating & design pressures/temperatures.
• Materials: Stricter requirements for sour service (NACE MR0175/ISO 15156), impact testing, corrosion allowances.
• Fabrication & Inspection: Rigorous welding procedures (WPQR), extensive NDE (RT, UT, PT, MT per defined criteria), strict dimensional tolerances.
• Tube-to-Tubesheet Joints: Strength welding + expansion often required; leak testing criteria specified.
• Nozzle Loads: Standardized acceptable external load limits (forces/moments) for interfacing piping.
• Vibration Analysis: Mandatory assessment (Annex N) to prevent tube failure from flow-induced vibration (FIV).
• Testing: Hydrostatic test pressures defined; optional pneumatic/sensitive leak tests.
• Documentation: Comprehensive Data Reports (Manufacturer's Data Report - MDR) including material certs, NDE reports, test results, drawings.
• Annexes: Address critical aspects like:

  • Annex F: Low-temperature service.

  • Annex G: Lethal service.

  • Annex H: Direct-fired heaters.

  • Annex K: Plate-and-frame exchangers (if included).

  • Annex M: Air-cooled exchangers (if included).

  • Annex N: Flow-induced vibration.

Advantages of API 660 Compliant S&THE:

• Enhanced Safety: Reduces risk of leaks/failures in hazardous environments.
• Predictable Performance: Meets stringent thermal and hydraulic requirements.
• Longer Service Life: Focus on corrosion control, vibration prevention, and quality fabrication.
• Easier Procurement & Maintenance: Standardized design simplifies spares and repairs.
• Regulatory Acceptance: Required for most major projects in the O&G sector.

Disadvantages:

• Higher Initial Cost: Due to stringent materials, fabrication, and inspection requirements.
• Size/Weight: Can be bulky and heavy, impacting offshore/platform installations.
• Fouling: Susceptible if fluid characteristics or velocities aren't managed properly (mitigated by design choices).
• Limited Approach Temperatures: Less efficient than plate exchangers for close temperature approaches.