Overview
ISO 21787:2006 defines requirements for globe valves made from thermoplastic materials used in industrial pipe systems for isolating and control service. The standard covers design, functional characteristics, materials, pressure/temperature ratings, manufacturing, testing, marking and documentation. It applies to hand- or power-operated valves for a lifetime of 25 years, rated for service temperatures between −40 °C and +120 °C, and covers nominal sizes DN 10–DN 150 and pressure classes PN 6, PN 10, PN 16 and Class 150.
Key topics and requirements
- Scope & applicability: Valves for industrial pipe systems (including general water supply, drainage and sewerage); applicable irrespective of field or fluid conveyed.
- Design characteristics:
- Body bore may be full bore (≥ 90% of DN) or reduced bore (manufacturer must declare pressure loss factor).
- Valve obturation may be for one or both flow directions; one‑way tightness must be marked on the body.
- Spindle must be fixed and blow-out proof with stem sealing by a stuffing box or self-sealing elements. Soft-seat designs are permitted.
- Materials:
- Body/bonnet materials permitted include ABS, PE, PP, PVC-C, PVC-U, PVDF (or equivalent materials meeting referenced ISO specs).
- Trim and internal components are the manufacturer’s responsibility and must pass required tests.
- Pressure/temperature rating:
- Valves are designed using material MRS values (ISO 12162) and a rating factor (f) that determines allowable PMA (maximum operating pressure) at temperature. Minimum f values depend on body material and temperature and must be declared.
- End connections: Butt fusion, spigot (cementing/welding), socket types (electrofusion/heated tool/cementing), flanged, wafer, threaded, union, etc.
- Testing & compliance:
- Specifies initial type tests, pressure and functional tests, documentation of results, declaration of compliance, marking and storage/transport preparation.
Practical applications
- Specification and procurement of thermoplastic globe valves for chemical processing, water treatment, HVAC, drainage, and other industrial piping systems.
- Selection guidance for engineers evaluating pressure/temperature performance, service lifetime and compatibility of thermoplastic valves with process fluids.
- Quality and compliance checks by manufacturers, testing labs and procurement teams to verify designs meet ISO 21787 requirements.
Who uses this standard
- Valve manufacturers and designers
- Piping system engineers and specifiers
- Procurement and QA/QC professionals
- Testing laboratories and certification bodies
- Asset owners in water, chemical, and industrial sectors
Related standards
ISO 21787 references and aligns with other standards such as ISO 12162, ISO 15493 / 15494 / 10931 (thermoplastics materials and systems), and valve testing standards like EN 12266-1. These are relevant when specifying materials, pressure/temperature ratings and test methods.
Keywords: ISO 21787, globe valves, thermoplastics, pressure/temperature rating, DN sizes, PN, Class 150, PVDF, PVC-U, valve testing.