IEC 60331-25:1999 pdf download.Tests for electric cables under fire conditions – Circuit integrity – Part 25: Procedures and requirements – Optical fibre cables
1 Scope
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 specified 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 text,
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 60793-1 -4:1 995, Optical fibres – Part 1 : Generic specification – Section 4: Measuring
methods for transmission and optical characteristics
IEC 60331 -1 1 :1 999, Tests for electric cables under fire conditions – Circuit integrity – Part 1 1 :
Apparatus – Fire alone at flame temperature of at least 750 °C
IEC Guide 1 04:1 997, The preparation of safety publications and the use of basic safety
publications and group safety publications
3 Definition
For the purpose of this part of IEC 60331 , 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, if 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 IEC 60331 -1 1 .
6.2 Mount the sample in the clamp and supports. 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) to an
optical apparatus to monitor and/or measure the change in optical transmittance in accordance
with IEC 60793-1 -4, method C1 0. 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 -1 1 ). 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 , after
which the flame shall be extinguished but the cable sample shall remain connected to the
optical monitoring apparatus for a further 1 5 min. The total test duration shall be the flame
application time together with the 1 5 min cooling period.
7 Performance requirement
7.1 Flame application time
The flame application time shall be as specified in the relevant cable standard. In the absence
of such a cable specification, a 90 min flame application is recommended.
7.2 Acceptance criteria
With reference to the test procedure given in clause 6, the cable possesses the characteristics
for 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.
IEC 60331-25:1999 pdf download
