IEC 60794-1-211 pdf – Optical fibre cables – Part 1-211: Generic specification – Basic optical cable test procedures – Environmental test methods – Sheath shrinkage, method F11
4.6Details to be specified
The detail specification shall include the following information:a) nominal test length of cable samples;
b) low and high exposure temperature;c) soak time;
dnumber of cycles;
e) maximum sheath shrinkage.4.7Details to be reported
The test report shall include,beside the specified parameters in the detail specification(see 4.6), the following information, if applicable;
a) method of marking and length measurement;
b) sample configuration and arrangement on the surface;c) type and preparation of the surface;
d)individual shrink values of all samples;e) any deviations from this test method.
5Method F11B- Sheath shrinkage (general purpose)
The purpose of this test method is to determine the linear dimensional changes in extrudedplastic cable sheath due to exposure at elevated temperatures.
See Annex A for a comparison between method F11A and method F11B.
A 2 m length of cable shall be cut from the end of the cable and discarded in order to avoid endeffects.The cable sample(s) shall be whole-cable section(s), with all components, including thecore, in place, unless otherwise specified.The number of samples specified shall be cut fromthe adjoining cable and shall be 150 mm long.
A convection oven capable of maintaining a temperature within ±3 “C at the specified exposuretemperature.
A horizontal surface where the test sample(s) are placed that permit free movement of thesheath. For example, talc, paper or paper dusted with talc on the surface permits free movement
of the sheath.
Alinear scale or a precision calliper of sufficient length graduated in 0,15 mm or less divisions.
The cable length shall be conditioned for a minimum of 24 h at ambient temperature prior to thesample preparation.
Each sample shall be marked with reference marks along the longitudinal axis of the cablesample.The marks shall be made at convenient positions as close as practical to the ends of
the sample. The marks shall not damage the cable sheath. Measure and record the initialdistance L., between the opposite edges of the sample(s) at the reference marks.Alternatively,
the sample may be cut to length and the length between the cut sheath ends measured.
Place the sample(s) on a horizontal surface in the oven that permit free movement of the sheath.
Expose the sample(s) for the time period and at the temperature specified in the detailspecification.
At the end of the oven exposure period, recondition the sample(s) at ambient temperature forminimum 1 h.
Measure and record the final distance L2 between the opposite edges of the sample(s) at thereference marks.
The (absolute) sheath shrinkage of each test sample is calculated as showed in Formula (2):
L1,iis the initial distance measured between the marks;L2,iis the final distance measured between the marks;
i is the sample number ( i = 1 to the number of test samples).5.5Requirements
Each sheath sample shrinkage (Li) shall not exceed the value specified in the relevant detailspecification.
5.6Details to be specified
The detail specification shall include the following information:a)number of cable samples;
b)exposure temperature;c) time period;
d)maximum allowable sheath shrinkage.5.7 Details to be reported
The test report shall include,beside the specified parameters in the detail specification(see 5.6), the following information, if applicable:
a)method of marking and length measurement;b) type and preparation of the surface;
c) individual shrink values of all samples;d) any deviations from this test method.