Standard Tests for Carpet Tiles
Specifying floor covering for a commercial application requires at least a passing understanding of how it will perform in the workplace.Unfortunately, markings like “contract quality” or “heavy domestic” are open to interpretation, making it difficult for the specifier to make an informed decision.
Simon Lawrence of UK carpet tile specialist, Bürofloor, offers some insight into the standard tests that can be applied to carpet that has to perform – and last – in the punishing commercial environment.
Commercial premises place heavy performance requirements on any sort of floor covering. When coffee gets spilt at home there’s an immediate flurry of mopping and spraying with stain remover. In the workplace it’s more likely to be ignored and then walked on by unwiped outdoor shoes. Your sofa at home gets moved when you need to remove dust or dinky toys from underneath it. The castor chairs in your office travel miles, boring holes in the carpet tiles as they do so.
This means that we need a benchmark by which we can judge the suitability of carpet or carpet tiles for commercial contract use. Fortunately there are standardised tests to provide Euronorm (EN) and International Standards Organisation (ISO) certification. Genuine heavy contract products should carry the standards described here.
ISO 8543 – Effective Pile Weight
Carpet tiles need dense, closely-grouped pile to provide the required wear resistance. To provide a standard for this, ISO 8543 specifies a method of shaving the carpet down to its backing. It simply measures the mass of the pile removed in grams per square metre. In general, the greater the pile mass, the harder-wearing will be the carpet tile.
ISO 1765 – Total thickness
This is another relatively simple test. In this case the carpet tile is compressed by a standard weight, and then its thickness is measured to the nearest 0.1mm.
EN 1963 – Lisson Treadwheel Test
This test measures the carpet’s resistance to scuffing, in particular highlighting how strongly the pile tufts are secured. The treadwheel is positioned above the carpet to be tested and rolled to and fro across the sample 400 times. The wheel turns slightly faster than it moves across the carpet creating a severe scuffing effect. The tested carpet sample is compared to the master samples and is rated accordingly. This is a particularly aggressive test, literally ripping some types of carpet tile to shreds. A pass under EN1963 is a strong indicator of good wear resistance.
ISO 10361 – Accelerated Wear Testing
This standard is particularly relevant for carpet tiles that will be used in an office. It’s composed of two tests, the Vetterman drum test and the castor chair test.
Vetterman Drum Test
The Vetterman Drum Test is intended to simulate heavy, focused footfall. Foot traffic tends to be concentrated around doorways or narrow passages between desks, and these areas can quickly become threadbare.
The carpet for testing is fixed inside a revolving metal drum. A heavy (7.5Kg) ball, covered in hard rubber protrusions, is placed inside the drum and is allowed to bounce around freely. The carpet is subjected to two test programmes, one of 5,000 rotations of the drum and one of 22,000 rotations.
The carpet is then visually judged against master wear samples and is given a rating for how well it has withstood the effects of the test.
The visual inspections of the carpet give results from 1 to 5 for both 5,000 and 22,000 rotations and the final result is a combination of the two results according to the formula below;
Total Result = 0.75 x Result after 5,000 rotations + 0.25 x result after 22,000 rotations
A result of 2 or more is a pass
A result of 2.4 or more is a pass for intensive use
Castor Chair Test
Castor chairs are particularly damaging, and the ragged holes they wear in floor coverings can represent a tripping hazard. The results of this test should be an essential part of the office carpet specification.
The test rig rolls a three-castored chair, carrying a weight of 90kg, across the carpet. Two samples are used, one run for 5,000 and one for 25,000 cycles.
The tested samples are visually assessed against standard samples and are rated on a scale of 1-5. The final result for the test is given according to the formula below;
Total Result = 0.75 x Result after 5,000 rotations + 0.25 x result after 25,000 rotations
ISO/DIS 10965 – Electrical Resistance
This test is particularly important for contract carpet that could well find itself in computer rooms where a build up of static electricity could damage valuable equipment.
The carpet sample to be tested must be acclimatized for at least 7 days before the test at a temperature of 23+/-1°C and 25+/-2% relative humidity. This is because humidity impacts so greatly on conductivity of textiles and must be controlled rigorously to get a meaningful test.
In this test regime the horizontal resistance and vertical resistance of the carpet is measured (in Ohms).
Horizontal resistance: An isolating underlay is placed under the carpet tile sample which should be pile upward. 2 electrodes are connected to the tile 200 mm apart and the resistance in Ohms is measured between them.
Vertical resistance: Here the electrodes are above and below the carpet tile and the resistance in Ohms is measured between them.
Measurements of less than 1010 Ohms are necessary for computer rooms.
ISO 3415 – Static Loading (Compression test)
This test is designed to see how much the carpet is compressed by a weight placed on it. It replicates the effect of furniture on the carpet.
The thickness is measured before compression
A pressure of 220 kPa is applied for 15, 30 and 60 minutes.
The result is simply given in the loss of thickness in mm after
a recovery period of 1 hour.
ISO 140-8 Acoustic Properties
The test equipment for this standard consists of two spaces, one above the other and 5 hammers, each of 500 gr. The first test is to measure impact absorption – i.e. how much impact noise is absorbed by the carpet sample.
First of all the hammers are allowed to free fall onto the floor of the upper space from a height of 4 cm, each striking the floor 10 times / second. The noise in decibels is recorded in the space below.
The test is then repeated with the addition of the sample carpet to the floor of the higher space.
The difference in decibels is the amount of impact noise that has been absorbed by the carpet sample. This test is interesting in that it shows how well carpet performs to stop noise transmission compared to other floorcoverings like wood or vinyl.
For ISO 354 the absorption of ambient noise is measured. Noise of different frequencies; (125 – 250 – 500 – 1000 – 2000) are broadcast down into a room of 200m³ and the amount of noise bounced back from the floor is measured. This is then compared with the noise reflected by the floor when covered with sample material. A result of 0.5 in this test shows that 50% of the noise that would have been reflected was absorbed by the test sample and that the remaining 50% was reflected by it.
ISO 2551 – Dimensional Stability and EN 986 for tiles
Carpet tiles must maintain their dimensions ±0.02% after the following treatments:
Heating to a temperature of 60°C for 2 hours
Bathing in water at a temperature of 20°C for 2 hours
Further heating to a temperature of 60°C for 24 hours
Conditioning in normal atmospheric conditions for 48 hours
These treatments demonstrate that the tiles will retain their integrity in the toughest conditions like hot water cleaning and extreme temperatures.
Cost of Ownership
All floor coverings carry a hidden expense in the form of replacement costs. In commercial premises this cost is raised further by the business disruption of installing new carpet tiles. Buying unwisely will inevitably lead to higher expense. A reputable supplier should respond positively to a request for test data. Hopefully the information in this article will help make sense of the test specifications and support a properly informed choice.
Source by Simon Lawrence