IEC 60332-3-21-2018 pdf free.Tests on electric and optical fibre cables under fire conditions – Part 3-21:Test for vertical flame spread of vertically-mounted bunched wires or cables – Category A F/R.
5.3 Mounting of the test sample
Each test piece shall be attached individually to each rung of the ladder by means of metalwire (steel or copper).For cables up to and including 50 mm diameter use wire between 0,5mm and 1,0 mm in diameter.For cables above 50 mm diameter use wire between 1,0 mmand 2,5 mm in diameter.
Mount all test pieces on the ladder with the bending (due to bending of the cable on the reel),if any, in the same direction, towards the back side of the test chamber as much as possible.
To achieve straight test pieces between the steel rungs below and above the burner position,it is permitted to fix the test pieces to an additional horizontal support 200 mm to 300 mmlower than the steel rung below the burner position.
NOTE The objective is to improve the repeatability and reproducibility of the test.
The standard ladder shall be used, and the test sample shall be such that at least four testpieces are used. A minimum of two test pieces shall be mounted on the rear of the ladder.
Where more that four test pieces are required for the test sample, each successive additionalpiece shall be mounted alternately on the front and then the rear of the ladder.
The completed test sample shall be mounted such that
– the space between each test piece of one layer (front or rear) shall be 0,5 times the cable diameter, but not exceeding 20 mm;
– the maximum width of a single layer shall be 3o0 mm;
– the minimum distance between the sample edge and the inside of the ladder upright shall be 50 mm;
5.4 Flame application time
The test flame shall be applied for 40 min, after which it shall be extinguished.The air flowrate through the test chamber shall be maintained until cable burning or glowing has ceased,or until a maximum duration of 1 h, after which any remaining cable burning or glowing shallbe extinguished.
6 Evaluation of test results
After all cable burning or glowing has ceased or been extinguished, the test sample shall bewiped clean.
All soot is to be ignored if,when wiped off, the original surface is undamaged.Softening orany deformation of the non-metallic material is also to be ignored.The flame spread shall bemeasured as the extent of the damage. lt shall be measured in metres to two decimal placesfrom the bottom edge of the burner to the onset of char.The onset of char is determined asfollows:
press against the cable surface with a sharp object, for example a knife blade. Where thesurface changes from a resilient to a brittle (crumbling) surface, this indicates the onset ofchar.
7Performance requirements
The performance requirements for a particular type or class of wire or cable should preferablybe given in the individual cable standard. In the absence of any given requirements，therecommended performance requirements given in Annex B should be used.
8Retest procedure
In case of dispute，two further tests shall be undertaken as detailed in Clause 5. The testshall be deemed as satisfactory if both tests meet the stated requirement.IEC 60332-3-21 pdf download.