IEC 60332-3-21 pdf free download
IEC 60332-3-21 pdf free download.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.
The number of test pieces to be mounted is obtained by taking the closest integer (0,5 and above corresponding to 1) of the ratio of the volume per metre specified in 5.1 and the total volume, V, of non-metallic material per metre of cable, subject to a minimum number of four test pieces (two test pieces in each layer).
5.3 Mounting of the test sample
Each test piece shall be attached individually to each rung of the ladder by means of metal wire (steel or copper). For cables up to and including 50 mm diameter use wire between 0,5
mm and 1,0 mm in diameter. For cables above 50 mm diameter use wire between 1,0 mm D and 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 mm lower 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 test pieces 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 additional piece 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 300 mm;
— the minimum distance between the sample edge and the inside of the ladder upright shall be 50 mm;
— test pieces mounted on the rear of the ladder shall be centred relative to the space between pieces on the front of the ladder;
— the completed array of test pieces is approximately centred on the ladder.
Figure 1 illustrates the arrangement.
5.4 Flame application time
The test flame shall be applied for 40 mm, after which it shall be extinguished. The air flow rate 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 shall be extinguished.
6 Evaluation of test results
After all cable burning or glowing has ceased or been extinguished, the test sample shall be wiped clean.
All soot is to be ignored if, when wiped off, the original surface is undamaged. Softening or any deformation of the non-metallic material is also to be ignored. The flame spread shall be measured as the extent of the damage. It shall be measured in metres to two decimal places from the bottom edge of the burner to the onset of char. The onset of char is determined as follows:
press against the cable surface with a sharp object, for example a knife blade. Where the surface changes from a resilient to a brittle (crumbling) surface, this indicates the onset of char.
7 Performance requirements
The performance requirements for a particular type or class of wire or cable should preferably be given in the individual cable standard. In the absence of any given requirements, the recommended performance requirements given in Annex B should be used.
8 Retest procedure
In case of dispute, two further tests shall be undertaken as detailed in Clause 5. The test shall be deemed as satisfactory if both tests meet the stated requirement.IEC 60332-3-21 pdf download.
