ISO 21787:2006

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.