API 660

Key requirements (8)

• Shell-and-tube heat exchangers for petroleum, petrochemical, natural gas.
• Companion to TEMA — provides additional engineering / procurement requirements.
• Min tube wall: 2.1 mm (0.083") CS, 1.65 mm (0.065") SS — 25 mm OD typical.
• Tube-to-tubesheet joint: strength-welded + light-rolled OR full-strength expanded; expansion ≥ 2× tube wall.
• Shellside velocity: 0.6–1.5 m/s liquid; tubeside 1–3 m/s typical.
• Hydrotest per ASME VIII Div 1 (1.3 × MAWP).
• Vibration analysis (TEMA / HEDH): natural frequency, fluid-elastic instability, vortex shedding.
• Differential thermal expansion handled by floating head, U-tube, or expansion bellows.