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21 Mechanical strength8 m' J3 Y. _4 w
21.1 Appliances shall have adequate mechanical strength and be constructed to withstand such rough handling that may be expected in normal use.
9 A% x2 W* l, DCompliance is checked by applying blows to the appliance in accordance with test Ehb of IEC 60068-2-75, the spring hammer test.: `+ T& C+ n. e9 w. X4 h( D+ Z% }" e
The appliance is rigidly supported and three blows, having an impact energy of 0,5 J, are applied to every point of the enclosure that is likely to be weak.+ k7 O, v3 f+ z4 y3 Z
NOTE 1 Void.( }0 S7 q4 V& h2 Z- u/ F
If necessary, the blows are also applied to handles, levers, knobs and similar parts and to signal lamps and their covers but only if the lamps or covers protrude from the enclosure by more than 10 mm or if their surface area exceeds 4 cm2. Lamps within the appliance and their covers are only tested if they are likely to be damaged in normal use.7 x6 P. v4 \/ |2 `( g
NOTE 2 When applying the release cone to the guard of a visibly glowing heating element, care is to be taken that the hammer head passing through the guard does not strike the heating element.2 o7 `( [& x" i3 a' Q V1 i
After the test, the appliance shall show no damage that could impair compliance with this standard and compliance with 8.1, 15.1 and clause 29 shall not be impaired. In case of doubt, supplementary insulation and reinforced insulation are subjected to the electric strength test of 16.3.
) B8 v: [, t" F+ q- O# \9 N( ]NOTE 3 Damage to the finish, small dents that do not reduce clearances or creepage distances below the values specified in clause 29, and small chips that do not adversely affect protection against access to live parts or moisture, are ignored., E# O, ]4 G) K; W ~
NOTE 4 If a decorative cover is protected by an inner cover, fracture of the decorative cover is ignored if the inner cover itself withstands the test.
! s6 ^0 H7 W8 fIf there is doubt as to whether a defect has occurred by the application of the preceding blows, this defect is neglected and the group of three blows is applied to the same place on a new sample which shall then withstand the test.
- K2 D0 L4 b% MNOTE 5 Cracks not visible to the naked eye and surface cracks in fibre-reinforced mouldings and similar materials are ignored.
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