APIStatic Equipment

API 662

Plate Heat Exchangers

US / International
Static Equipment

Reference profile

Designation
API 662
Title
Plate Heat Exchangers
Issuing body
American Petroleum Institute (API)
Current edition
API 662 Parts 1 & 2 (ISO 15547 Parts 1 & 2 Equivalent)
Status
Active; international standard for gasketed and welded plate heat exchangers in process industries.
Category
Plate Heat Exchanger Standard
1

Overview

API Standard 662 (ISO 15547 Parts 1 & 2) gives requirements for the mechanical design, materials, fabrication, inspection, testing, and preparation for shipment of plate heat exchangers (PHE) used in petroleum, petrochemical, and natural gas processing.

Plate heat exchangers provide exceptionally high overall heat transfer coefficients, extremely compact footprints, and close temperature approach capabilities (under 1-2°C), replacing traditional shell-and-tube units in space-constrained or high-efficiency process duties.

2

Scope & Applicability

Covers

  • Part 1 Gasketed Plate Heat Exchangers: Corrugated plates (Chevron/Herringbone pattern), elastomeric gaskets (NBR, EPDM, FKM), frame covers, tie bolts, and carrying/guide bars.
  • Part 2 Welded & Semi-Welded Plate Heat Exchangers: Welded plate packs and block heat exchangers for high-temperature, high-pressure, or hazardous chemical services exceeding gasket limits.
  • Mechanical & material requirements: Minimum plate thickness (0.5 to 0.8 mm depending on alloy), zero-corrosion-allowance design rule, and corrosion-resistant nozzle linings.
  • Inspection and pressure testing: Hydrostatic testing of individual sides and differential pressure testing to detect cross-contamination leaks.

Does NOT cover (exclusions)

  • Shell-and-tube heat exchangers—covered by API 660 or TEMA Standards.
  • Air-cooled heat exchangers—covered by API 661.
  • Thermal & hydraulic performance sizing—refer to manufacturer proprietary sizing software (e.g. Alfa Laval, SWEP, Kelvion).
  • In-service inspection and maintenance procedures—refer to API 510 and manufacturer integrity guidelines.
3

Key Requirements

Part 1 (Gasketed PHE) Materials & Construction Rules

  • Plate Materials: Must be cold-formed from corrosion-resistant alloys (e.g., 316L Stainless, Titanium Grade 1/2, Hastelloy C-276, 254 SMO, Nickel 200).
  • Gasket Attachment: Gaskets must be clip-on or snap-on type (glue-free) for easy field replacement during maintenance overhauls.
  • Frame Deflection Limits: Fixed and movable frame covers must be designed with sufficient rigidity to prevent excessive deflection when tie bolts are fully torqued.

Part 2 (Welded Plate Exchanger) Special Provisions

  • Application Limits: Specified for temperatures exceeding 180°C (356°F) or pressures above 25 bar, or for aggressive hydrocarbons where elastomer gaskets are unsafe.
  • Welded Pack Inspection: Plate pack seam welds must undergo 100% liquid penetrant testing (PT) and helium mass spectrometer leak testing.

Nozzle Linings & Piping Connection Integrity

  • Corrosion Protection: Nozzles must be lined with corrosion-resistant sleeves (rubber liners or metallic sleeves matching the plate material) to prevent fluid contact with carbon steel frame.
  • External Nozzle Loads: Frames must be capable of supporting external piping nozzle forces and moments without causing gasket unseating.

Testing & Cross-Contamination Prevention

  • Differential Hydrotest: Hydrostatic pressure tests must be performed on each side independently at 1.3x MAWP to verify individual channel integrity.
  • Cross-Leakage Test: Dual-gasket barrier design with telltale weep holes must be used to vent any internal gasket failure directly to the atmosphere rather than cross-contaminating fluids.
4

Technical Details

Zero Corrosion Allowance Principle: Because PHE plates are very thin (0.5 - 0.8 mm), zero corrosion allowance is assumed. Material selection MUST provide absolute corrosion immunity in the process fluid.

API 662 Hydrotest Pressure: Minimum hydrostatic test pressure is 1.3 times the Maximum Allowable Working Pressure (MAWP), held for a minimum of 30 minutes per chamber.

Tie Bolt Anti-Seize & Thread Protection: All tie bolts must be equipped with stainless steel lock nuts, heavy washers, and plastic or metallic thread protection sleeves.

Where to find it in the codeRefer to API 662 Part 1 Section 6 for Mechanical Design of Gasketed PHEs (Plates, Gaskets, Frames, Tie bolts), Section 7 for Materials, Section 8 for Inspection & Testing. Refer to Part 2 for Welded Plate Units.
5

Engineering Notes

  • Never add corrosion allowance to plate thickness calculations; if mild corrosion is expected, upgrade the plate alloy immediately (e.g. from 316L to Titanium or 254 SMO).
  • Always install a suction strainer (mesh size <= 1.5 - 2.0 mm) upstream of the PHE to prevent debris and scale from clogging the narrow inter-plate channels (2-5 mm gap).
  • Elastomer gaskets (NBR, EPDM, Viton) suffer thermal hardening over time; schedule gasket replacement during major plant turnarounds every 3 to 5 years.
6

Related Standards

  • API 660

    Standard for shell-and-tube heat exchangers in refinery service.

  • ASME BPVC VIII-1

    Mandatory construction code for pressure-retaining frame components and welded plate packs.

7

Source, Edition & Status

Publisher
API
Edition Year
N/A
Industries
Petrochemical, Chemical, Power
Content Status
reviewed
Last Reviewed
2026-07-01
Last Updated
2026-07-01
Verified By
Engineering Reviewer
Official Link
www.api.org

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