Overview
ISO 3790:1976 - "Fishing nets - Determination of elongation of netting yarns" specifies a laboratory method to measure how much netting yarn stretches under tensile load. The standard covers testing in both dry and wet states, with wet testing considered particularly representative of in‑use behaviour. The procedure defines specimen preparation, test apparatus, test speeds, and reporting requirements to ensure comparable, reproducible elongation data for fishing-net yarns.
Key topics and requirements
- Scope: Measures elongation of netting yarns taken from packages or from netting in their final physical state.
- Test states: Dry and wet testing allowed; wet specimens should be immersed in tap water at 20 ± 2 °C for at least 12 hours (alternative shorter wetting with wetting agent permitted by agreement).
- Apparatus:
- Tensile testing machine - either a constant rate of elongation machine or a constant rate of traverse machine; preference is given to constant rate of elongation machines, which are required for arbitration.
- Machine must have flat grips to prevent slippage/damage, a starting gauge of 500 mm, variable traverse speeds, and an autographic recorder for load/elongation curves.
- Specimen preparation: Yarn removed without altering construction; knots undone when taken from netting to produce specimens of sufficient length.
- Test procedure:
- Apply a pre‑tension to straighten the specimen (value specified in the standard).
- Confirm nominal gauge length of 500 mm between grip faces under pre‑tension.
- Increase tensile force continuously until it reaches half the knot breaking load (knot breaking load is determined per ISO 1805/ISO 1806).
- Mean test duration should be approximately 30 ± 3 seconds (determine by preliminary tests).
- Validity and repeats:
- Discard observations where slippage or premature breakage occurs; report number discarded.
- At least 10 valid single tests per sample are required (more if specific confidence intervals are needed).
- Reporting: Test report must include material description, test date, machine type, mean elongation at half knot breaking load, mean duration and range, number of tests, any deviations, and related details.
Applications and users
ISO 3790:1976 is essential for:
- Fishing‑net manufacturers and yarn suppliers for quality control and specification of netting yarn elongation.
- Textile and materials testing laboratories performing comparative tensile tests.
- R&D and product development teams assessing performance of materials in wet environments.
- Regulatory bodies and procurement agents specifying performance criteria for commercial and industrial fishing gear.
Keywords: ISO 3790:1976, fishing nets, netting yarns, elongation, tensile testing, wet testing, constant rate of elongation machine.
Related standards
- ISO 1805 - Determination of breaking load and knot breaking load of netting yarns
- ISO 1806 - Determination of mesh breaking load of netting
- ISO 139 - Standard atmospheres for conditioning and testing (textiles)
- ISO 858 - Designation of netting yarns (textile system)