Overview
ISO 17202:2002 - Textiles: Determination of twist in single spun yarns - Untwist/retwist method specifies an indirect laboratory method to determine the direction of twist (S or Z) and the amount of twist (reported as turns per unit length, preferably turns/m) in single spun yarns. The standard is designed primarily for ring-spun yarns in packages and lays out the untwist/retwist testing principle, two procedural variants (Method A and Method B), apparatus requirements, sampling, specimen preparation and reporting rules.
Key Topics and Requirements
- Scope and exclusions
- Applicable to single spun (ring) yarns; not applicable to open‑end (OE) yarns, false‑twist/self‑twist yarns, air‑jet yarns, yarns that stretch >0.5% between specified low tensions, or yarns too large to clamp without distortion.
- Principle
- The untwist/retwist indirect method: untwist a yarn specimen, then retwist in the opposite direction until the original length is recovered. The recorded turns (half the counter reading) give the yarn twist.
- Two variants:
- Method A (single): standard single untwist/retwist.
- Method B (double): includes a corrective second specimen to reduce sensitivity to pretension; more accurate but more time-consuming.
- Apparatus
- Twist tester or twist counter with clamps, rotatable clamp linked to a revolution counter; motorized testers typically ~1 000 turns/min ±200.
- Variable tensioning device to apply specified pretension and to remove tension during untwisting/retwisting.
- Specimen and conditioning
- Initial specimen length: 500 mm ± 1 mm.
- Tests must be done after conditioning in the standard atmosphere per ISO 139 (conditioning for at least 24 h).
- Sampling
- Sampling according to material specification, EN 12751, or the annex A procedure; guidance on number and random selection of specimens is provided.
- Reporting
- Includes direction (S/Z), twist value (turns per metre or per unit length), method used, pretension, and test conditions.
Applications and Users
- Used for quality control, acceptance testing and production monitoring in spinning mills, textile testing laboratories, yarn manufacturers, fabric inspection labs, and R&D departments.
- Useful when rapid, reproducible twist measurements are required across many samples of similar yarn type; particularly suited to routine testing of ring‑spun yarn packages.
Related Standards
- ISO 2:1973 - Direction of twist designation
- ISO 139:1973 - Standard atmospheres for conditioning and testing
- ISO 2060:1994 - Yarn linear density (skein method)
- EN 12751 - Sampling of fibres, yarns and fabrics
Keywords: ISO 17202:2002, untwist/retwist method, twist determination, single spun yarns, twist tester, ring‑spun yarns, yarn testing, textile standard.
