DSH 595 Requirement for the screws fixing internal parts

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DSH 595 ) v5 W* A4 {! Z0 j# O8 R* K( C ( ~! [0 n% G- L  }. l7 S* y

Requirement for the screws fixing internal parts

17.3

60065(ed.6) & 60065(ed.7)

: L/ Y* a% h5 A2 M3 dStandard(s):
IEC 60065 : 1998 6th edition
IEC 60065 : 2001 7th edition
Sub clause(s):
17.3
" t+ G9 [% R, n- o" X, TSheet n.
DSH 595
Subject:
Requirement for the screws fixing
  {' O- J- T. Z6 f8 [internal parts
9 }! d9 p% y2 d  ^Key words:
- Screws
8 z6 A3 H! C6 H- Fixing internal parts
( w) K0 L/ J8 D$ d$ `Decision approved
during the 44th CTL
meeting 2007
( P  d  t) K$ h6 w2 D4 r' T& d: ]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
between the replaced screws and hazardous live parts?
7 M3 a2 F! m0 L- Situation
- There is an amplifier which has an internal SMPS board encased by a metal enclosure.
- The screws fixing the internal box should be unscrewed to get serviced.
+ f) x* v# d5 v  x; Y/ A; _- The screws are inserted from an exterior side or bottom of the amplifier but not fixing the cover of the
# g; }0 {0 G# z( Z2 O3 tamplifier.
- 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.
+ k/ r) {/ d2 h0 I( y: e# UDecision
7 }8 D: @# ~: {7 |* gIt's not acceptable. In case of a PCB fixed by just screws without any enclosure, it's acceptable because the
service 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.
  L- r/ O( h& ^; a" e; G: M" t