DSH 595 Requirement for the screws fixing internal parts

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DSH 595

Requirement for the screws fixing internal parts

17.3 3 R8 U! w2 I8 K; `4 @1 h

60065(ed.6) & 60065(ed.7) 1 ~: e, R8 W" J* l

# w3 ]" K5 [& N0 }9 j7 a3 w/ O0 [Standard(s):
IEC 60065 : 1998 6th edition
& e/ R8 M0 Y+ |9 x5 ZIEC 60065 : 2001 7th edition
Sub clause(s):
17.3
, R/ P5 `" C; C, XSheet n.
" y% m6 G6 f8 t1 y2 t5 ~DSH 595
Subject:
Requirement for the screws fixing
internal parts
6 D/ G9 \( B* f+ ?7 zKey words:
; N# ]  p! {& E1 ?- Screws
- Fixing internal parts
Decision approved
during the 44th CTL
meeting 2007
0 P- @  s0 ~& O8 zQuestion: Should those screws, fixing internal parts, needed to be replaced for a service be captive or
7 T) I4 Y9 A/ [( lcomply 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
1 d& E8 v! c4 m$ {9 x: a" `between the replaced screws and hazardous live parts?
- Situation
. j% h2 }. g' q9 k- L+ H* ]; j( o! J- 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.
- The screws are inserted from an exterior side or bottom of the amplifier but not fixing the cover of the
2 O7 Y8 ?4 f' Z$ v" @amplifier.
- The screws are not captive but don't comply with the insulation distance stated in clause 13 when replaced by
, r& ]5 v; Y' _8 y9 hother screws having the same nominal diameter with a length of 10 times their nominal diameter.
& G1 u" Z9 v* j( d( s2 TDecision
* L/ q5 e6 i( l) [8 ^- S' K5 OIt's not acceptable. In case of a PCB fixed by just screws without any enclosure, it's acceptable because the
* w% [8 I2 O: x4 Iservice 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
$ p4 g- n" B$ F" s5 G) u# S& `whether the screws are the right screws or not during a service due to the internal metal enclosure.
7 ?4 C2 \1 ?: z: q9 X% qIn the above case reinforced insulation is required because after the screws are replaced the amplifier can be
' F1 y5 V& ^" ?- P3 E; [4 Q  Q6 Rused without any malfunction.
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