Overview
ISO 6993-2:2006 specifies requirements for buried, high‑impact poly(vinyl chloride) (PVC‑HI) fittings used to supply gaseous fuels in underground distribution systems. It covers non‑end load‑bearing fittings with elastomeric sealing elements for pipelines operating between 0 °C and +30 °C and a maximum operating pressure of 200 mbar (20 kPa). The standard applies to fittings manufactured from PVC‑HI compositions (PVC‑A, PVC‑CPE, PVC‑EPR) and defines material, dimensional, mechanical and performance requirements plus relevant test methods.
Key topics and technical requirements
- Scope and application: Buried PVC‑HI fittings for gaseous fuels - non‑end load‑bearing, pressure ≤ 200 mbar (20 kPa).
- Materials: Fittings must be made of high‑impact PVC with an impact modifier ≥ 7% by mass; acceptable compositions include mixtures, blends, copolymers or combinations.
- Long‑term strength: Injection‑moulding material MRS (minimum required strength) ≥ 14 MPa, verified by long‑term testing in accordance with ISO 9080 (tests at 20 °C, 40 °C and 60 °C).
- Thermal resistance: Vicat softening temperature ≥ 74 °C (ISO 2507).
- Elastomeric seals: Sealing elements must conform to EN 682:2002 (type G) and must not adversely affect fittings.
- Dimensional and geometric requirements: Measurements per ISO 3126; detailed socket/spigot diameters, wall thicknesses and engagement depths (nominal sizes shown in the standard, typically DN 50–400).
- Manufacturing and appearance: No contaminants > 50 µm; surfaces free from defects that impair function.
- Performance and testing: Includes oven/thermal tests (injection‑moulded fittings tested at 150 °C), leaktightness (Annex B/C), resistance to gas constituents (Annex A), mechanical and physical testing (ISO 3127, ISO 580 and others). Limits on crack/delamination depths and blister size are specified.
Applications and who uses it
- Utility companies and gas network operators specifying buried plastic fittings for low‑pressure gas distribution.
- Manufacturers and designers of PVC‑HI fittings and injection‑moulded components for underground gas pipelines.
- Installers, engineers and procurement teams who need to ensure compliance with material, dimensional and performance criteria for safe low‑pressure gas supply.
- Test laboratories and conformity assessors performing required material and joint tests.
Related standards
- ISO 6993 series: Part 1 (pipes, 1 bar), Part 3 (fittings/saddles, 1 bar), Part 4 (code of practice).
- ISO 9080 (long‑term hydrostatic strength), ISO 3126 (dimensions), ISO 2507 (Vicat), ISO 3127 (impact resistance), ISO 580 (visual heating effects), EN 682 (elastomeric seals), EN 922 (K‑value).
ISO 6993-2 is essential for safe, compliant design and manufacture of PVC‑HI fittings used in buried, low‑pressure gas distribution systems. Keywords: ISO 6993-2, PVC-HI fittings, buried PVC piping, gaseous fuels, 200 mbar, elastomeric seals, underground gas distribution.