Testing grades

The following carpet tile test procedures illustrate the relevance of these ratings in choosing the correct carpet tile for a specific installation.

International Testing Methods

Vetterman Drum Test

(SABS STM 1184 EQUIVALENT TO DIN 54323)

In this test, a 7,5 kg metal ball, into which fourteen rubber covered studs are affixed, is placed in a drum the circumference of which is covered with carpet tile. The drum is rotated at 16 revs/min, reversing every five minutes. The carpet tile is then assessed at 5 000 and finally 22 000 revs and accorded an appearance retention rating.

Lisson (Pedal Wheel) Test

(SABS STM 1186 EQUIVALENT TO DIN 54322)

Four equally spaced rubber shoes are connected to a central shaft. When rotated from the central shaft, each shoe in turn comes in contact with the carpet tile. The device is rotated backwards and forwards in a manner that causes the shoes to create slippage and wear. After 2 000 reciprocating revolutions the carpet tile is assessed for wear and a rating given for durability.

Castor Chair Test

(SABS STM 1185 EQUIVALENT TO DIN 54324)

A carpet tile sample >60 cm in diameter is placed onto a metal base plate. Three castor wheels attached to a chair-like frame are then lowered onto the carpet tile under a weight of 90 kg. The base plate is rotated at 19 revs/min while the castors revolve at 50 revs/min. The centre of the base mounting and the castor wheels are offset by approximately 20 cm to simulate wear conditions. Wear is assessed after 5 000 and 25 000 revolutions. If there is no damage to the carpet tile and the rating of 2,4 or greater is achieved, the material is declared suitable for castor chairs.

Dimensional Stability

(ISO 2551 EQUIVALENT TO DIN 54318)

This test subjects the tiles to complete immersion in water and to heating in an oven. The tiles thereafter are measured for extension or shrinkage. Initially the tile is heated to 60¡C for two hours and then measured. It is then immersed in water at 20¡C and measured. The tile is then dried in an oven at 60¡C for 24 hours and re-measured. It is then allowed to “condition” in a standard atmosphere for 48 hours and measured again. If any of these measurements indicate an extension of more than 0,2%, or a shrinkage of more than 0,4%, for stick down or 0,2% for looselay, the carpet tile will not comply with the requirements.

Fire Resistance SABS 0177-IV

In most countries, a specific fire index class is required in terms of the relevant Building Regulations. In the SABS test method, the spread of flame, heat contributed, and smoke emission is measured to attain a fire index and class rating. The rating is from 1 to 5 Ð 1 being the most fire resistant and 5 the least resistant. It is essential to use carpet tiles of the correct fire rating which conform to the regulations. A table listing the requirements of sundry locations is obtainable from the SABS.

Acoustics And Sound Absorption

DIN 52210 AND DIN 52212

Certain acoustic requirements, although not always essential, are very desirable if the following are to be achieved:
voice audibility
protection of the natural quality of sound and
prevention of intrusion of unwanted sound. Carpet tiles greatly assist in creating a suitable acoustic environment.
Correctly specified carpet tiles supplemented with acoustic wall and ceiling treatment, can satisfy the most critical acoustic requirements. In fact, for floorings, there are very few acoustically competitive alternatives to carpet tiles. Sound can be transmitted through gases, liquids and solids. In addition, sound is reflected from floors, walls, ceilings etc. Airborne sounds will be transmitted into a room via open windows and doors, and sounds will be created by impact inside a room via walking, dropping of articles, moving of furniture etc. Consequently, any surface that absorbs this sound will improve the overall acoustics. In DIN 52212, the carpet tile is tested for sound absorption by comparing the mean reverberation time, over a frequency range of 100 to 5 000 Hz of an empty room with the same room that has been fitted with carpet tiles. In DIN 52210, an impact sound transmission reduction test is carried out, observing how many decibels of sound are absorbed over a frequency range of 100 Ð 4 000Hz.

Antistatic Properties

DIN 54345

The control of the generation of static electricity in carpet tiles is very important. The build-up of static electricity is caused by the repeated frictional contact and release of an object such as a shoe walking over a carpet tile. The build-up of this static charge is influenced by many variables. The lower the relative humidity, the quicker a charge will be generated. The type of base floor upon which the carpet tile is laid will affect the overall conductivity and its ability to dissipate any charge generated. The fibre and construction of the carpet tile will affect the amount of static produced. If this charge is not dissipated, it will reach a magnitude whereby it will discharge itself to earth and can give a person an unpleasant electric shock.

Such discharges can cause electronic equipment to malfunction and, in areas containing flammable liquids, initiate fires. Consequently, carpet tiles are usually constructed and treated to give varying degrees of antistatic properties. Some fibres, such as Antron¨ Excel contain built-in static controlling filaments made from carbon sheathed in nylon enabling the carpet tile to be permanently anti-static. This contains the generation of static to a level below the threshold of human sensitivity being 2kV at 20% Relative Humidity (RH). To meet the demands of a computer room, additional antistatic elements are incorporated in the primary and secondary backing components of the carpet tile. However, one must ensure that the base floor upon which the carpet tile is laid is sufficiently conductive and connected to earth with copper strips/bands, otherwise the antistatic properties of the carpet tile will be to no avail.

Similarly, if a person’s footwear has a high insulation value, the static body charges cannot be dissipated, even though the floor covering may have a low leakage resistance. The STROLL test DIN 54345 (Part 2) measures the build-up of an electrostatic charge on a person, whereas DIN 54345 (Part 1) measures the capability of a carpet tile to dissipate electrostatic charges. In DIN 54345 (Part 1), the surface and internal conductivities of the carpet tile are measured through two electrodes to assess electrical resistance. The results are expressed as volume resistance related to area and referred to in ohms/cmý.