Overview
ISO 21049:2004 - Pumps - Shaft sealing systems for centrifugal and rotary pumps - specifies requirements and recommendations for shaft sealing systems used in the petroleum, natural gas and chemical industries. The standard targets hazardous, flammable and/or toxic services where high reliability is required to improve equipment availability, reduce atmospheric emissions and lower life‑cycle sealing costs. It applies to seals for pump shaft diameters from 20 mm (0.75 in) to 110 mm (4.3 in) and covers seal spare parts and upgrade guidance for existing equipment.
Key topics and requirements
- Seal classification: Defines a systematic classification into Categories (1–3), Types (A, B, C) and Arrangements (1, 2, 3); each level carries specific selection and testing expectations.
- Operating limits: Specified temperature and absolute pressure ranges by category (e.g., Category 1 up to ~500 °F, Categories 2 and 3 up to ~750 °F; differing absolute pressure limits are given in the standard).
- Seal materials and face options: Recommends premium, blister‑resistant carbon and silicon carbide face combinations and material choices for bellows (e.g., Alloy C‑276, Alloy 718 for high‑temperature Type C).
- Seal hardware & design features: Cartridge designs, throttle bushing options (fixed or floating carbon, non‑sparking metal), gland plate metal‑to‑metal contact, and minimum chamber and reservoir sizing.
- Flush and barrier plans: Guidance on buffer/barrier fluids and commonly referenced flush plans (e.g., Plan 11, 13, 21, 23, 31, 32, 41, 53 variants) with notes on cooling, venting and contamination control.
- Testing and vendor qualification: Testing scope scales with category - minimal for Category 1, more rigorous for Category 2, and full assembly qualification for Category 3. Proposal and contract data requirements increase with seal criticality.
- Special features: Guidance for corrosive, abrasive, flashing and non‑flashing services; recommendations for elastomer types (including perfluoroelastomers) and hardface options for contaminated fluids.
Applications and who uses it
- Target users: pump OEMs, rotating equipment engineers, mechanical designers, procurement specialists, maintenance and reliability teams in petroleum, natural gas and chemical plants.
- Practical uses: selecting appropriate shaft sealing systems for hazardous services, specifying seal materials and arrangements, defining vendor testing/qualification, reducing fugitive emissions, and upgrading existing pump seals to meet safety and reliability objectives.
Related standards
- ISO 3069 (referenced chamber sizes)
- ISO 13709 and ASME B73.1 / B73.2 (pump/installation interfaces) - all cited within ISO 21049 for compatibility and mounting guidance.
Keywords: ISO 21049, shaft sealing systems, pumps, centrifugal pumps, rotary pumps, seal selection, seal arrangements, barrier fluid, flush plans, pump seal materials, hazardous services.