ISO 3790 Netting Yarn Elongation Test | UnitedTest Fishing Net Yarn Tensile Tester

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ISO 3790 Netting Yarn Elongation Tester | UnitedTest

UnitedTest manufactures ISO 3790 fishing net yarn elongation testing machine for dry and wet elongation measurement of netting yarns sourced from packages or finished fishing nets. Ideal for fishery textile quality control, lab testing and compliance verification.

ISO 3790 sets out a reliable laboratory tensile test procedure to measure the elongation performance of netting yarns, sampled directly from cones, bobbins, spools or assembled fishing nets. Testing is carried out on yarn in its original physical condition without structural modification. Both dry and wet elongation testing modes are supported, and wet testing is highly recommended to replicate real underwater service conditions and accurately predict how fishing net yarn stretches during marine operation. Our UnitedTest ISO 3790 compliant tester delivers stable tensile control, precise elongation recording and repeatable test results for fishing net manufacturers, third-party testing laboratories and fishery material suppliers.

Test principle:

A prescribed length of netting yarn in the dry or wet state, without knot, is extended under increasing tensile load until that load reaches half the value of the corresponding dry or wet knot breaking load. The test is performed using a suitable apparatus that records the amount of elongation.

In other words: first establish the yarn's knot breaking load (per ISO 1805), then load a fresh, unknotted specimen only up to 50 % of that value and read the elongation from the recorded curve. The dry elongation result must be paired with the dry knot breaking load; the wet result with the wet knot breaking load.

Why half the knot breaking load? In knotted netting the knot is the weakest point, so the service load a net can safely carry is a fraction of the knot strength. Using 50 % of knot breaking load gives a non-destructive, service-relevant "working elongation" that is automatically normalised across different yarn linear densities (tex), fibre types and constructions — far more meaningful for gear design than elongation at break.

Test equipment required for ISO 3790 Netting Yarn Elongation Test

Tensile testing machine

Recommend UnitedTest tensile testing machine

Tensile testing machine, either (a) constant rate of elongation (CRE) machine or (b) constant rate of traverse (CRT) machine.

Preference is given to CRE, which shall always be used for arbitration purposes.

Capable of operating with a starting distance between grips of 500 mm.

Facilities for producing different speeds of traverse so specimens can be tested in the specified testing time.

An autographic recorder for the load/elongation curve, with dynamic response fast enough to accurately record the steepest part of the curve.

ISO 3790 Netting Yarn Elongation Test

Wetting equipment

Water bath at (20±2) °C for soaking wet-state specimens

Test Specimen Information:

Source	From netting yarn packages or directly from knotted netting
Length (from netting)	At least 600 mm of yarn must be obtained by carefully untying knots
Precaution	Avoid damaging, stretching, or altering the structure of specimens during sampling
Gauge length (nominal)	500 mm between grip faces after pre-tension
Conditioning (dry)	Equilibrate under ISO 139 standard atmosphere; synthetic fiber yarns typically require 24 h
Conditioning (wet)	Soak in tap water (no wetting agent) at (20±2) °C for ≥ 12 h; shake off excess water before testing. A wetting agent may be used and soaking time shortened by mutual agreement.

Key Test Parameters

Starting / nominal gauge length	500 mm, accurately measured between grip faces after pre-tension
Minimum yarn length from netting	≥ 600 mm after untying knots
Pre-tension	Equal to the weight of (250 ± 25) m of the yarn under test; if insufficient to straighten the specimen, a higher value may be used but must be specially recorded in the report because it affects the result
Target load	50 % of the corresponding mean dry or wet knot breaking load, determined per ISO 1805 (or yarn extracted from netting per ISO 1806-2002, 10.7)
Duration of testing	Mean (30 ± 3) s to reach the target load, established by preliminary tests; if machine/grip limits prevent this, keep as close to 30 s as possible and record the actual mean and range
Loading mode	Continuously increasing tensile force (not a fixed crosshead speed)
Force/record	Full load/elongation curve for each test
Replicates	≥ 10 valid tests per batch
Result	Mean elongation (%) = elongation increment after pre-tension ÷ nominal gauge length × 100; optionally CV and confidence interval

ISO 3790 Netting Yarn Elongation Test Procedures:

Pre-determine knot breaking load — Per ISO 1805, determine the average dry and/or wet knot breaking load of the yarn. If sampling from netting, take yarn per ISO 1806-2002 clause 10.7.
Condition the specimen — Dry: condition to equilibrium per ISO 139. Wet: soak ≥12 h at (20±2) °C; test immediately after removal from water.
Mount the specimen — Install in the tensile machine so the specimen axis is aligned with the loading direction to prevent slipping or grip damage.
Apply pre-tension — Apply the pre-tension equal to the weight of (250±25) mm of yarn to straighten the specimen and knot.
Verify gauge length — Confirm the distance between grip faces under pre-tension is exactly 500 mm.
Load until 50% breaking load — Continuously increase load over (30±3) s until reaching 50% of the predetermined knot breaking load.
Record the load/elongation curve — The auto-graphic recorder captures the full curve.
Discard invalid tests — Remove and count specimens that slipped or broke prematurely.
Calculate average elongation — Compute mean elongation at 50% knot breaking load across all valid specimens.

Application / industry fields

This standard applies specifically to the fishing net / fishery gear industry:

Netting yarn manufacturers — quality control and product specification of synthetic fiber netting twines (nylon, polyester, polyethylene, polypropylene, etc.)
Fishing net makers — ensuring netting materials meet performance specs for seine nets, trawl nets, gill nets, etc.
Fisheries research & regulatory bodies — standardized performance evaluation of fishing gear materials
Third-party testing laboratories — providing uniform, reproducible test data

Related standard:

ISO 1806	Fishing nets - Determination of mesh breaking force of netting
GB/T 21292	Fishing nets Determination of mesh breaking force of netting
ISO 3790	elongation of netting yarns, tensile method: 500 mm gauge, ~30 ± 3 s, and uses the knot breaking load determined by ISO 1805 / ISO 1806 as the reference load
IS 5815-5	Textiles - Fishing nets - Determination of mesh breaking force of netting
ISO 2062	Single-end breaking force, elongation at break and tenacity of yarns from packages, CRE, 500 mm gauge, 100 % gauge length/min, pretension 0.5 cN/tex
ASTM D2256	Single-strand yarn tensile properties
ISO 1805	Fishing nets — Determination of breaking force and knot breaking force of netting yarns
BS 5414-1976 (UK), NF G36-152-1972 / NF ISO 3790:2019 (France), DIN 53846-1982 (Germany, literally "testing the elongation behaviour of netting yarns under load up to half the maximum knot breaking force") national standards adopting or derived from the same method .

Importance of the Test:

Real-world performance prediction — Fishing nets operate under dynamic loading during hauling, trawling, and wave action. Knowing how much a yarn stretches at 50% of its knot breaking load directly predicts net mesh distortion, catch retention, and deformation in service.
Knot integrity indicator — Because the yarn is tested with a weaver's knot, the elongation measurement reflects the combined behavior of both the yarn material and the knot, which is the critical failure point in fishing nets.
Dry vs. wet comparison — Nylon (polyamide) yarns absorb water and change mechanical properties significantly; wet-state testing reveals actual in-water behavior that dry testing alone cannot capture.
Quality control & specification — Provides a uniform, internationally reproducible basis for buyers and sellers to specify netting yarn elongation, ensuring consistent net performance across manufacturers and countries.
Design input for fishing gear — Net designers rely on elongation data to calculate mesh geometry, drag forces, and catch selectivity — critical for both commercial fishing efficiency and fisheries management (e.g., escape gaps for juvenile fish).
Material comparison — Allows objective comparison between fiber types (PA, PET, PE, PP), twist levels, and construction methods on a standardized basis.

Keywords: ISO 3790 tester,netting yarn elongation tester,fishing net yarn tensile tester,wet elongation test machine,dry elongation testing,fishery textile tester,fishing net quality test,netting yarn tensile equipment,marine net yarn elongation,polyamide net yarn test,polyethylene fishing net tester,textile tensile tester for fishing industry,netting material lab testing,ISO 3790 testing equipment,UnitedTest tensile machine

WDW Series Computer Control Electronic Universal Testing Machine made by UNITEDTEST range from 100N to 600KN load capacity with various models like single columns, table type, door frame type etc., is used to perform tension, compression, flexure/bending, shearing, peeling etc., test for metal and nonmetal specimens.

Snubbing and Capstan grips are all engineered to perform high strength tensile tests where the test samples are long compared to their cross-sectional area, such as wire, rope and strapping.

Plastic tube, wire bollard tensile test grips are used on a Universal Testing Machine to perform tensile tests on filament material such as string, thread, wire and yarn. The specimen is wrapped around a bollard or post and then secured with a vise grip mechanism.

Q1. What is the ISO 3790 test?

A. ISO 3790:1976 specifies a laboratory method for determining the elongation of netting yarns taken from packages or from netting, in their final physical state, in either the dry or wet state. An unknotted specimen is stretched under increasing load until the force reaches 50 % of the corresponding dry or wet knot breaking load, and the elongation is read from a recorded load–elongation curve.

Q2. Why is the ISO 3790 test important for fishing net materials?

A. It measures working elongation, not rupture elongation. Nets normally operate well below breaking load, so elongation at 50 % of knot breaking load predicts how much a yarn will stretch in service, how much mesh opening will change, and how shock loads are distributed into knots. Referencing the load to knot breaking load also normalises results across yarn counts and fibre types, and wet-state testing reflects real in-water behaviour.

Q3. What does “elongation at half the knot breaking load” mean?

A. It is the elongation produced on a specimen after pre-tension is applied, measured when the increasing tensile force reaches half of the mean dry or wet knot breaking load. It is expressed as a percentage of the nominal gauge length, which is the 500 mm distance between grip faces after pre-tension.

Q4. Why does ISO 3790 use 50 % of knot breaking load instead of pulling the yarn to break?

A. In knotted netting, the knot is usually the weakest point, so service loads are a fraction of knot strength. Stopping at 50 % gives a non-destructive, service-relevant elongation value that is automatically scaled to the finished net structure. Elongation at break would describe failure, not normal gear behaviour.

Q5. Is ISO 3790 a breaking-strength test?

A. No. ISO 3790 stops at half the knot breaking load and does not require the specimen to rupture. For breaking force or knot breaking force, use ISO 1805; for mesh breaking force, use ISO 1806:2002; for general single-end yarn elongation at break, use ISO 2062 or ASTM D2256.

Q6. Should I test netting yarn dry or wet?

A. ISO 3790 allows both, but explicitly says wet-state testing is particularly appropriate for indicating in-use behaviour. Dry specimens must reach equilibrium in the ISO 139 standard atmosphere; wet specimens are immersed in tap water at (20 ± 2) °C without wetting agent for at least 12 h and tested immediately after removal. Never pair a wet elongation result with a dry knot breaking load, or vice versa.

Q7. Why is a CRE machine preferred, and when is it mandatory?

A. A constant rate of elongation machine gives more consistent control of specimen extension, which matters because elongation is the measured output. ISO 3790 permits constant-rate-of-traverse machines for routine testing, but states that a CRE machine shall always be used for arbitration purposes.

Q8. What specimen length and gauge length are used in ISO 3790?

A. When yarn is taken from netting, untie the knots to obtain pieces at least 600 mm long, avoiding damage, stretching or structural change. The tested portion between grip faces must be exactly 500 mm after pre-tension; this is the nominal gauge length. The specimen itself is unknotted.

Q9. How is pre-tension set in ISO 3790?

A. Pre-tension shall equal the weight of (250 ± 25) m of the yarn under test. If that is not enough to straighten the specimen, a higher pre-tension may be used, but it must be specially recorded in the report because it affects the elongation result.

Q10. What is the ISO 3790 test duration, and how do I set the machine speed?

A. The mean duration shall be (30 ± 3) s, counted from the moment force is applied after pre-tension until the load reaches 50 % of knot breaking load. The speed is established by preliminary tests, not by a fixed mm/min value. If machine or grip limits prevent 30 ± 3 s, keep as close to 30 s as possible and record the actual mean duration and range.

Q11. Is SC/T 4023-2007 the same as ISO 3790?

A. Yes, technically. SC/T 4023-2007 is marked IDT (identical) to ISO 3790:1976. Its foreword lists only two editorial changes: “this standard” replaces “this International Standard”, and the ISO cover/foreword are removed. It is therefore a reliable full-text reference when only a partial ISO 3790 scan is available.

Q12. How does ISO 3790 differ from ISO 2062?

A. ISO 3790 measures sub-break elongation at 50 % of knot breaking load, allows dry/wet states, accepts CRE or CRT, and controls time to target load (30 ± 3 s). ISO 2062 measures breaking force and elongation at break of single yarns from packages, uses CRE only, applies a fixed extension rate based on gauge length, and does not use knot breaking load as the reference.

Q13. Can one UnitedTest tensile tester cover both ISO 3790 and ISO 1805?

A. In principle, yes — if the system can be configured with both flat grips for unknotted ISO 3790 specimens and the knot-test fixture required by ISO 1805, with a load cell range covering the full knot breaking force and software that records force–elongation curves and computes means. Confirm the exact fixture, force range and software options with UnitedTest before ordering.

Q14. What should I verify before buying an ISO 3790 testing machine from UnitedTest?

A. Check: 500 mm grip separation, flat non-slip grips, specimen alignment with the force axis, controllable pre-tension, variable traverse speed for the 30 ± 3 s duration, recorder response fast enough for steep curve sections, force range suitable for your yarn, wet-specimen handling at 20 ± 2 °C, and software that exports each load–elongation curve plus mean elongation, CV and confidence interval. Publish only specifications UnitedTest can substantiate.

Q15. Why does wet-state testing matter so much for netting yarns?

A. Netting yarns are viscoelastic polymer structures, and water uptake — especially in polyamide — can change stiffness, modulus and elongation. A dry elongation value can misrepresent how the yarn behaves during towing, currents or loading in water. That is why ISO 3790 explicitly favours wet testing for indicating in-use behaviour.

Q16. Why Choose UnitedTest for ISO 3790 Testing Machines?

A. ISO 3790:1976 is an international standard developed by ISO/TC 38 (Textiles) that specifies a method for determining the elongation of netting yarns used in fishing nets. The test measures how much a knotted netting yarn stretches under a tensile load equal to 50% of its knot breaking load, in both dry and wet conditions.

UnitedTest manufactures high-precision constant rate of elongation (CRE) tensile testing machines designed specifically to meet ISO 3790 requirements, including 500 mm gauge length, flat grip systems, auto-graphic load/elongation recording, and programmable test duration control.

ISO-compliant design — Factory-calibrated to 500 mm gauge length, CRE loading mode, and (30±3) s test duration.
Multi-standard capability — One machine covers ISO 3790, ISO 1805, and ISO 1806 testing needs.
Automatic curve recording — Built-in load/elongation recorder captures the full steepest-portion curve required by the standard.
Global support — Serving netting yarn manufacturers, fishing net factories, and third-party labs across Asia, Europe, and the Americas.
Custom grips — Flat grip systems tailored to prevent slipping on knotted netting yarns of various deniers.

We offer customization to meet your specific needs. Our expert team will collaborate with you to develop the perfect product for you