IEC 60332-3-21-2018 pdf 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.
4 Test apparatus
4.1 General
The apparatus specified in IEC 60332-3-1 0 shall be used.
4.2 Ignition source
The ignition source shall be one ribbon-type propane gas burner as specified in
IEC 60332-3-1 0.
5 Test procedure
5.1 Test sample
The test sample shall comprise a number of test pieces of cable from the same production length, each having a minimum length of 3,5 m.
The total number of test pieces in the test sample shall be that number required to provide a nominal total volume of non-metallic material of 7 l/m of test sample.
The test sample for type approval shall be in accordance with Annex A.
The test pieces forming the test sample shall be conditioned at a temperature of (20 ± 1 0) °C for at least 1 6 h before commencing the test. The test pieces shall be dry.
5.2 Determination of the number of test pieces
In order to calculate the appropriate number of test pieces, it is necessary to determine the volume per metre of non-metallic material of one test piece.
A length of cable which shall be not less than 0,3 m long is carefully cut to ensure that the surfaces are at right angles to the cable axis, thus enabling precise measurements of its length.
The density of each nonmetallic component (including cellular material) shall be measured in an appropriate way, for example according to IEC 6081 1 -606, in order to obtain values expressed to the second decimal place.
Each non-metallic material C i shall be removed from the test piece and weighed. Any non- metallic material making up less than 5 % of the total non-metallic mass of the test piece
shall be assumed to have a density of 1 ,0 kg/dm 3 .
Where semi-conducting screens cannot be removed from the insulating material, the components may be considered as one for the purpose of measuring their mass and density.
The volume V i (litres per metre of cable) of each non-metallic material C i is calculated as follows:
where
M i is the mass of the component C i (kg);
ρ i is the density of the component C i (kg/dm 3 );
l is the length of the test piece of cable (m).
The total volume, V, of the non-metallic materials contained in 1 m of cable is equal to the sum of the individual volumes V 1 , V 2 , etc.
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 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.IEC 60332-3-21 pdf download.