ISO 2016:1981

Overview

ISO 2016:1981 - Capillary solder fittings for copper tubes - Assembly dimensions and tests - defines the dimensional, material and test requirements for capillary (soldered/brazed) fittings used with copper tubes. This International Standard cancels ISO Recommendation R 2016‑1971 and covers assembly diameters from 6 mm up to and including 108 mm. It specifies permitted materials, assembly diameters and tolerances, lengths of engagement, minimum wall thickness, gauging (GO / NOT GO), and required inspection and proof tests.

Key topics and technical requirements

• Scope and denominations: Designation rules for equal, reducing and adapter fittings; abbreviated forms for common reducing tees and crosses.
• Assembly diameters and tolerances: Nominal assembly diameters 6–108 mm with tolerances and dimensional checks defined (see Tables 2 and 3 in the standard).
• Lengths of engagement: Minimum engagement lengths (L1, L2, etc.) and tolerances for reliable capillary action are tabulated.
• Materials: Acceptable materials include copper alloys similar to Cu‑DHP (ISO 1337), certain copper‑tellurium alloys (ISO 1336), gunmetal castings (ISO 1338) and brass (ISO 426/ISO 1338). Other materials may be used if they give equivalent performance.
• Minimum wall thickness and tube stop: Minimum wall thickness values and requirement for an effective abutment (tube stop) to control joint depth.
• Threads and chamfers: Requirements for threaded outlets (ISO 7 for pressure-tight threads; ISO 228 for non-pressure threads), chamfer geometry and flats for spanners.
• Gauging: GO and NOT GO plug and ring gauges are specified (Tables 5 and 6) and are used for dimensional verification; adaptation of ISO/R 1938 limit‑gauging practices is referenced.
• Tests:
  • Leak‑tightness test for castings (hydraulic or air immersion) - manufacturer to prove porosity-free bodies.
  • Type proof strength test: after brazing (example conditions given in the standard), fittings must withstand defined hydraulic pressures (e.g., 80 bar for diameters up to 54 mm; 40 bar for larger diameters - as specified in the document).
  • Manufacturer certification of material compliance when requested.

Practical applications

ISO 2016:1981 is directly applicable to the design, manufacture and quality control of capillary solder fittings used in:

• Plumbing and potable-water systems
• HVAC and refrigeration piping
• Heating systems and hydronic distribution
• Copper‑tube assemblies in industrial process installations

Using the standard helps ensure reliable capillary solder joints, repeatable assembly, and interchangeability of fittings from different manufacturers.

Who should use this standard

• Fitting manufacturers and foundries
• Plumbing and HVAC component designers
• Quality and inspection personnel (gauging & pressure testing)
• Test laboratories and compliance officers
• Procurement/specification engineers writing product requirements

Related standards

Relevant cross-references include ISO 7, ISO 228, ISO 272, ISO 274, ISO 426, ISO 1336 / 1337 / 1338, ISO/R 1938 and ISO 1085 (all referenced in the standard for threads, materials and gauging).