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| Temperature for ball pressure test
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Question:
$ v b$ ?3 D* jPlastic material used for e.g. insulation or enclosure must be subjected to ball pressure test. The temperature rise of the heating cabinet (where the test has to be conducted) is specified in most standards as e.g. 75°C, 125°C or (40K + the maximum temperature rise determined during the heating test in normal use)°C . The question now is: Where is the temperature rise to be measured? Is it the hottest spot of the material? Is it inside the enclosure? Or is it on the accessible surface of the material?
& W% y1 Y( H! ?7 W( s& U @) z8 oDecision :
$ {8 E2 M2 B0 y# j0 M1- The temperature should always be measured at the hottest accessible spot, which is usually on the inside of the enclosure.5 U1 G* H6 y) v. L, ^
2- The individual product standard should take precedence when determining where to measure the hottest spot. The enquiry identified a number of standards which vary in product types and require different considerations.
. @4 @2 U) E" q2 B( M6 T3- The 40K mentioned in the enquiry decision is not actually the safety margin between measurements inside and outside but a safety margin above normal operating conditions in order to anticipate abnormal conditions.7 I* F+ f( W1 R$ w( | a: N
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发表于 2012-9-5 10:48
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