Overview
ISO 28721-3:2008 - "Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 3: Thermal shock resistance" defines requirements and procedures for assessing thermal shock resistance of glass-lined apparatus, components, accessories and pipes used mainly in chemical process plants. The standard covers heating and cooling limits, uses thermal shock and heating/cooling diagrams to specify permissible temperature changes, and applies to enamelled unalloyed and low-alloy carbon steels for operating temperatures from −25 °C to +230 °C.
Key topics and requirements
- Scope: Thermal shock limits for glass-lined steel in process equipment; distinction between shocks on the glass-lined side (e.g., product charging) and on the steel side (e.g., jacket heating/cooling).
- Diagrams: Two core diagrams define limits:
- Thermal shock diagram (glass-lined surface) - relates wall temperature (TW) and product temperature (TP).
- Heating/cooling diagram (steel side) - relates temperature of heating/cooling medium (THC) and product temperature (TP).
- Assumptions: Diagrams are calculated assuming essentially high heat-transfer coefficients (typical for aqueous media, steam or water). Where heat-transfer coefficients are low (gases, solids, viscous fluids, or oil in the jacket), wider or narrower limits may apply by agreement with the manufacturer.
- Operational conditions: Typical pressure range at time of shock is −0.1 MPa to +0.6 MPa; base steel often assumed to have a minimum yield strength of 210 N/mm² (see Annex A).
- Step heating/cooling: If intended temperature changes exceed diagram limits, operations must be performed in controlled steps (standard gives a practical example using staged steam pressures).
Practical applications
- Use ISO 28721-3:2008 to:
- Specify thermal-shock performance in procurement documents for glass-lined reactors, tanks, heat exchangers and piping.
- Guide safe start-up, charging and thermal-cycling procedures in chemical plants.
- Inform design and QA checks for equipment manufacturers (glass-lined steel fabricators) and QA/QC inspectors.
- Support maintenance, operations and process engineers in preventing enamel failure from rapid temperature changes.
- Typical users: process engineers, plant designers, equipment manufacturers, standards and quality managers, inspection bodies and owners of glass-lined process equipment.
Related standards
- ISO 28721-1 - Quality requirements for glass-lined apparatus (design and construction context referenced by Part 3).
- ISO 28721-2 - Designation and specification of resistance to chemical attack and thermal shock.
- DIN 2873 - Flanged pipes and fittings glass-lined (referenced for design details in Annex A).
ISO 28721-3:2008 is essential when specifying or assessing the thermal shock resistance of glass-lined steel equipment in chemical process plants, helping reduce enamel failure risk and ensuring reliable, safe operation.
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