IEC 60331-25:1999 pdf download – Tests for electric cables under fire conditions -circuit integrity – Part 25: Procedures and requirements -Optical fibre cables

IEC 60331-25:1999 pdf download – Tests for electric cables under fire conditions -circuit integrity – Part 25: Procedures and requirements -Optical fibre cables.
This part of IEC 60331 specIfies the test procedure, and gives the performance requirement. including a recommended flame application time, fOr optical fibre cables required to maintain Circuit integrity when subjected to fire under specihed conditions
It describes the means of sample preparation, continuity checking arrangements, optical testing procedures, the method of burning the cables and gives requirements for evaluating test results.
2 NormatIve references
The following normative documents contain provisions which, through reference in this te*t, constitute provisions of this part of IEC 60331. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this part of IEC 60331 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of IEC and ISO maintain registers of currently valid International Standards
IEC 80793.1 •4:1 995, Optical fibres — Part 1: Generic specification — Section 4: Measuring methods for transmission and optical characteristics
lEG 60331•11 :1999. Tests for electric cables under fire conditions — Circuit integrity — Part II:
Apparatus — Fire alone at flame temperature of at least 750 C
IEC Guide 104:1997. The preparation of safety publications and the use of basic safety publications and group safety publica lions
3 DefInItion
For the purpose of this part of IEC 80331, the following definition applies.
3.1
cIrcuIt Integrity
ability to continue to operate in the designated manner whilst subjected to a specified flame source for a specified period of time
4 Sample preparation
A sample shall comprise a length of the completed cable (at least 5 m) sufficiently long so that the two ends emerge from the test chamber. At each end of the sample, lengths of identical optical fibre shall be connected. II necessary, to give a total length appropriate to the optical test method used.
5 Continuity checking arrangement
At the conclusion of the test, check each fibre (or those fibres indicated in the relevant cable specification) for continuity.
6 Test procedure
6.1 The test procedure defined in this clause shall be carried out using the apparatus detailed in 1EC6O331-11.
6.2 Mount the sample in the clamp and support5. Adjust the burner to the correct position relative to the sample, as defined by the values of x and y arising from the verification procedure (see IEC 60331-1 1)
6.3 Connect the fibre(s) (or those fibres Indicated In the relevant cable specification) io an optical apparatus to monitor and/or measure the change in optical transmittance in accordance with IEC 60793-1-4. method ClO. Unless otherwise stated in the appropriate standard, the test shall be carried out at the declared nominal wavelength of operation.
6.4 Ignite the burner and adjust the propane and air flow rates to those obtained during the verification procedure (see IEC 60331.11). Switch on the optical apparatus and monitor the attenuation.
6.5 The test shall continue for the duration of the flame application, as given in 7.1, alter which the flame shalt be extinguished but the cable sample shall remain connected to the optical monitoring apparatus for a further 15 mm. The total test duration shall be the flame application time together with the 15 mm cooling period.
7 Perlormance requirement
7.1 Flame application time
The flame application lime shall be as specified in the relevant cable standard. In the absence of such a cable specification, a 90 mm flame application Is recommended.
7.2 Acceptance criteria
With reference to the test procedure given in clause 6. the cable possesses the characteristics fr providing circuit integrity so long as, during the course of the test, the maximum increase in attenuation, which shall be measured, does not exceed the value stated in the relevant specification.