BS EN 60811-401:2012 pdf download – Electric and optical fibre cables — Test methods for non-metallic materials Part 401 : Miscellaneous tests — Thermal ageing methods — Ageing in an air oven

BS EN 60811-401:2012 pdf download – Electric and optical fibre cables — Test methods for non-metallic materials Part 401 : Miscellaneous tests — Thermal ageing methods — Ageing in an air oven
The ageing test a) or b) and the loss of mass test d) may be combined and carried out on the
same test pieces when the aging time and aging temperature are the same.
Iln general，,mechanical characteristics are measured after treatment, but in some cases, theconductor and the separator, if any, cannot be removed without damaging the insulation and abending test is realized on the circular conductor up to and including 16 mm2.Ageing followedby the bending test is considered the acceptance procedure in case of dispute.
4.2Influence of the ageing treatment on the mechanical characteristics4.2.1 Apparatus
The ageing treatment is realized in an oven with natural air flow or air flow by pressure.Theair shall enter the oven in such a way that it flows over the surface of the test pieces andleaves near the top of the oven.The oven shall have not less than 8 and not more than 20complete air changes per hour at the specified ageing temperature.Two test methods formeasuring air flow through an oven are given in Annex A.
Unless otherwise specified in the relevant cable specification, a rotating fan inside the oven isallowed when testing rubber compounds.For all other compounds a fan shall not be usedinside the oven, and in cases of dispute,rubber compounds shall also be tested in an ovenwhich is designed to operate without a fan rotating inside it.
4.2.2Sample and test pieces preparation
The sample of the cable，or sheath removed from the cable，or samples of core,cut intopieces which are sufficiently long, shall be taken, preferably from positions close to that fromwhich the samples for the tensile tests without ageing are taken in accordance withIEC 60811-501.
Test pieces, dumb-bell or tubular, are prepared according to lEC 60811-501.
Test pieces can consist of samples of core, cut into pieces which are sufficiently long. lf, afterageing，the conductor and the separator，if any,can be removed without damaging theinsulation, preparation of test pieces shall be carried out according to Annex B(Clause B.2).For circular conductors up to and including 16 mm3and having plain or metal coated wiresand also when a separator around the conductor is included, a bending test is carried out onthe aged test pieces.
4.2.3Ageing procedure4.2.3.1General
This test shall be carried out not less than 16 h after the extrusion or cross-linking, if any, ofthe insulating or sheathing compounds. lt can be done on tubular or dumb-bell test piecesprepared according to lEC 60811-501 or insulated cores as described in the present standard.
4.2.3.2Ageing procedure for test pieces prepared according to IEC 60811-501 and Clause B.1 and B.2.2 and Annex C of this standard
This procedure shall be used for
– test pieces of insulating material without conductor and of sheathing material, according to
IEC 60811-501,
test pieces of cores with the original conductor (see Clause B.1),
Compounds of obviously different compositions shall not be tested at the same time in thesame oven.
Five test pieces, as specified in IEC 60811-501 shall be suspended vertically andsubstantially in the middle of the oven so that each test piece is at least 20 mm from anyother test pieces.
The test pieces shall not occupy more than 2 % of the volume of the oven.
The test pieces shall be kept in the oven at the temperature and for the time specified for thematerial in the relevant standard for the type of cable.
As soon as the ageing period is completed, the test pieces shall be removed from the ovenand left at ambient temperature,avoiding direct sunlight, for at least 16 h.
4.2.3.3 Ageing procedure for test pieces prepared from conductors above 16 mm2The following procedure shall be used when the conductor and the separator, if any,cannotbe removed without damaging the insulation after ageing.
The test pieces prepared as described in B.2.3.1 shall be placed substantially in the middle ofthe oven so that each test piece is at least 20 mm from any other test pieces. They shall besupported at both ends and the insulation shall not contact any object other than the bindingwire. The test pieces shall not occupy more than 2 % of the volume of the oven, and theyshall be kept in the oven at the temperature and for the time specified in the relevant standardfor the type of cable.
As soon as the ageing period is completed, the test pieces shall be removed from the oven,left at ambient temperature avoiding direct sunlight, for at least 16 h, dumb-bell are preparedas described in B.2.3.2.
4.2.3.4Ageing procedure for pieces of complete cable
The three test pieces of cable as described in Clause C.1 shall be suspended vertically andsubstantially in the middle of the oven at least 20 mm away from any other piece and shall notoccupy more than 2 %of the volume of the oven.
The test pieces of cable shall be kept in the oven at the temperature and for the timespecified in the relevant standard for the type of cable.
As soon as the specified heating period is completed，the test pieces of cable shall beremoved from the oven and left at ambient temperature，avoiding direct sunlight,for at least16 h.