DSH 595 Requirement for the screws fixing internal parts

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DSH 595

Requirement for the screws fixing internal parts # e- C2 E( a1 T5 x8 d& M

17.3 * I, P0 Z9 B) B  t  ]

60065(ed.6) & 60065(ed.7) 3 H* {! ]8 Q, w- a' U6 ]1 F+ [

5 q" ^1 b8 m/ X9 u" eStandard(s):
IEC 60065 : 1998 6th edition
- L; a& E" h) ?1 @+ D8 E: P" vIEC 60065 : 2001 7th edition
Sub clause(s):
17.3
Sheet n.
- S( T- ^0 V/ d' @- g+ h# [& MDSH 595
Subject:
Requirement for the screws fixing
internal parts
+ A: H! c- i# C2 U+ PKey words:
) m$ t; g0 W, @8 O: q- Screws
+ w9 m# ?# Y- J! H- Fixing internal parts
Decision approved
during the 44th CTL
/ d  p+ V. c+ s$ v3 r3 C( Smeeting 2007
Question: Should those screws, fixing internal parts, needed to be replaced for a service be captive or
comply with the insulation distance stated in clause 13 when replaced by screws having the same nominal
diameter with a length of 10 times their nominal diameter? In the latter case, what insulation is required
8 `3 r' Y, X) ?! Bbetween the replaced screws and hazardous live parts?
- Situation
$ x: U) P, e1 m/ |1 q" ]1 ]+ x- There is an amplifier which has an internal SMPS board encased by a metal enclosure.
) t# r8 Y3 o- ^$ I. F- The screws fixing the internal box should be unscrewed to get serviced.
- The screws are inserted from an exterior side or bottom of the amplifier but not fixing the cover of the
amplifier.
- The screws are not captive but don't comply with the insulation distance stated in clause 13 when replaced by
other screws having the same nominal diameter with a length of 10 times their nominal diameter.
Decision
6 _, d# R, L* }6 w& uIt's not acceptable. In case of a PCB fixed by just screws without any enclosure, it's acceptable because the
0 _: S1 ], ?0 Z9 x0 T$ Oservice personnel can make sure that the screws are the right screws during a service. However, in case of the
above SMPS board encased by a metal enclosure, it's not acceptable because the service personnel can't know
whether the screws are the right screws or not during a service due to the internal metal enclosure.
In the above case reinforced insulation is required because after the screws are replaced the amplifier can be
used without any malfunction.