Overview
IEC TR 62470:2011 - "Guidance on techniques for the measurement of the coefficient of friction (COF) between cables and ducts" - provides practical test techniques to evaluate frictional interaction between cables (including fibre units) and ducts or microducts. The report describes three measurement methods and explains how results relate to installation performance for pulling, pushing or blowing operations. Results are intended for comparative assessment rather than as a single reference test.
Key Topics
- Three test methods:
- Method A – Wheel test: a duct is wrapped around a wheel (suggested radius ~50 ± 2 cm); a cable with a tail weight is pulled through while measuring pulling force. Typical wrap is 360° and test speeds often used are 1.0 or 1.8 m/min.
- Method B – Sloped duct test: a duct specimen containing a cable specimen is clamped and tilted; the angle at which the cable begins to slide or sustains sliding is measured (yields static and kinetic COF).
- Method C – Sloped cable test: a cable specimen is clamped and straightened, the duct is placed around it and the assembly is tilted to measure sliding behaviour (also yields static and kinetic COF).
- Static vs. kinetic COF: static COF (when there is no relative motion) is generally higher than kinetic (sliding) COF; Methods B and C provide both values, Method A yields kinetic COF.
- Specimen and preparation requirements: clean, grease-free samples; cable length and duct length sufficient for wraps and gauge lengths; dummy cables sometimes used to control stiffness effects.
- Influencing factors: test speed, lubrication, duct/cable construction, and tail mass (for blowing simulations the tail mass ≈ mass of 2 m of cable) can significantly affect measured COF.
- Comparability: methods are qualitatively comparable but not equivalent; none is designated as the Reference Test Method.
Applications
- Manufacturers and R&D: evaluate new cable and microduct designs for ease of installation and material choices.
- Test laboratories: perform standardized COF measurements to support product data sheets and comparative testing.
- Installation engineers and planners: select appropriate cable/duct combinations and installation methods (pull/push/blow) based on relative COF values.
- Procurement and specification writers: incorporate comparative friction data into tender documents and performance specifications.
- Troubleshooting field problems: assess whether friction contributes to difficult pulls or blowing failures and evaluate lubrication strategies.
Related Standards
- IEC 60794-1-1 (optical fibre cables – generic specification)
- IEC 60794-3-10 (outdoor cables – duct, directly buried and lashed aerial)
- IEC 60794-5 (microduct cabling for installation by blowing)
IEC TR 62470:2011 is a practical guidance report for measuring COF between cables and ducts and is useful for anyone involved in fibre-optic cable design, testing, installation planning or specification.