Carpet GradingTechnical Guidelines

Two similar constructions of different pile height but having identical surface pile mass will perform differently. The one having the lower pile height will have a higher density and a correspondingly better performance. This relationship is assessed against a pile height standard of 10mm for Residential gradings and 5.5mm for Contract gradings.

The Guideline Surface Pile Mass figure used in the ACCS calculations is based on a wealth of performance information on carpets of various constructions and of differing fibre composition. For each fibre the Guideline Surface Pile Mass is related to gauge and differs for cut or loop pile. For any blend, the figures are taken in the same proportion as the components of the blend.

It is a measure of the g/cm³ in the surface pile and is compared with a standard of 0.150g/cm³ for loop pile carpets and 0.175g/cm³ for cut pile carpets. Any carpet achieving these figures or better achieves the maximum points allocation.
To put this in perspective, a ‘balanced’ 1/8th gauge loop pile constructed of R800 Tex yarn just achieves the maximum.
Such a carpet would be expected to perform well.

During the period of development of the ACCS it became apparent that high tuft density, low pile height carpets in synthetic fibre were being under-rated. To redress this imbalance the tuft density parameter was introduced.

This is an experience based rating of resistance to soiling of the various carpet fibres. The relative values have been accepted by the various fibre interests. The allocation of points to particular fibres is monitored closely and reviewed with changes in fibre technology and developments in fibre treatments.

The variety of abrasion tests produce different relativities between the various fibres. There have also been large discrepancies between laboratories using the same test apparatus and method. It is very doubtful that any abrasion test can consistently and effectively rate all fibres across the range of constructions. For these reasons an experience based table of relative abrasion resistance has been established.

The Hexapod Tumbler Test is used by the ACCS to assess anticipated short term and long term appearance change in the texture and colour of carpets. Currently, assessments of texture and colour change are made at 1500 cycles (simulated 9-12 months in service) and 8000 cycles (3-4 years in service equivalent). In addition, the ACCS conducts an ongoing program of carpet floor trials to assess the predictability of the Hexapod across a wide range of carpet constructions. The trials are being used to monitor in situ appearance retention with corresponding Hexapod tests.

The Density Factor is the relationship between Surface Pile Weight above the backing and Pile Thickness. It measures surface weight of yarn per cubic centimetre as this provides a much better method of comparing one carpet to another, taking into account different pile thickness. The ACCS Panel has set a density ‘benchmark’ for each grading classification level, fibre and construction type.

The OAF is a point score derived from the Hexapod Tumbler Test – the internationally used short-term and long-term carpet appearance retention test. The OAF is a weighted system and uses the hexapod scores to better predict early appearance loss within the first twelve months of carpet life.

Carpet classifications are assigned by the ACCS Panel. While calculated factors and the results of performance testing remain the most important determinant of the classification awarded, all carpets are subject to review by the ACCS Panel. The Panel awards points for yarn and fibre characteristics (yarn twist, set, appearance and construction) and pile construction and character.

No carpet will be classified unless it meets all the mandatory criteria relating to the ACCS.