DSH 595 Requirement for the screws fixing internal parts

小米

广东安规检测
有限公司提供：

小型摆管淋雨试验机

IPX5X6X7喷水试验机

1000L恒温恒湿箱

各种试验指现货

可程式恒温恒湿试验箱

水平垂直燃烧机

自动卷线器试验机

耐划痕试验机

各种灯头量规现货

灼热丝试验机现货

GB1002插头量规

IPX1-X7淋雨现货

IEC61347/UL935镇流器热试验箱

灯具防风罩

IK冲击试验机

UL498插头插座量规

VDE0620插头插座量规

稳定性试验台

家电温升测试角

针焰试验机现货

热电偶焊机现货

家电125mm试验指

E12灯头量规

无绳壶无绳电熨斗插拔寿命试验机

IEC60335试验指甲

DSH 595 ; r; S4 a- }# z; A6 l* K* n

Requirement for the screws fixing internal parts & l/ U8 C) ?' t' h6 }7 x- G

17.3 2 h, o. l5 ~4 V; ?+ k" F

60065(ed.6) & 60065(ed.7) 8 e" ?# B/ \; W

5 Q3 k* F( J" s) K" DStandard(s):
! L! K1 e& b* r: J" B1 |IEC 60065 : 1998 6th edition
' R: \7 E; K4 _5 SIEC 60065 : 2001 7th edition
Sub clause(s):
9 C, `. E- w; b( R  M4 m. k0 \17.3
, _( I0 Z0 Y! {8 S4 X. JSheet n.
DSH 595
3 s" K7 a% J( P1 R9 KSubject:
! r( v' @) a* {8 U. S: X' s+ o! pRequirement for the screws fixing
2 _& D# u/ N3 B0 W/ T, Qinternal parts
Key words:
# }% c; E$ i2 O% [% C2 k; w; `: T- Screws
- Fixing internal parts
5 ]1 S! U7 G0 z/ K6 ^- y4 D8 ^# hDecision approved
0 V4 Y. b+ m8 y' `/ g. yduring the 44th CTL
" ^" P# ^; M) G2 V; X2 Smeeting 2007
Question: Should those screws, fixing internal parts, needed to be replaced for a service be captive or
( C9 V2 V! H3 V; q, i! }2 q$ |3 j# Vcomply with the insulation distance stated in clause 13 when replaced by screws having the same nominal
% L# F- x" o8 T' ~" ^diameter with a length of 10 times their nominal diameter? In the latter case, what insulation is required
: I7 _% q; ^( t' L$ [between the replaced screws and hazardous live parts?
- Situation
& `" u. }( D8 e! p- There is an amplifier which has an internal SMPS board encased by a metal enclosure.
# L. H5 v6 B, M- w$ g" C- 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.
2 n" C3 \7 N& i; k9 ?( T# l0 h4 Y, ]- 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.
4 a3 ~* _! M" ]! ADecision
It's not acceptable. In case of a PCB fixed by just screws without any enclosure, it's acceptable because the
2 q. B+ D5 f6 @; I6 N% U2 kservice 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
  |, O/ i1 y' S  U% B$ dwhether the screws are the right screws or not during a service due to the internal metal enclosure.
% K5 a) @  `3 P9 oIn the above case reinforced insulation is required because after the screws are replaced the amplifier can be
used without any malfunction.


. `6 ?0 }$ j% i* k; Y9 j+ I) h1 K" s