IEC 60601-1 - Medical Electrical Equipment Safety 8.9: Creepage distances and air clearances

What does 8.9 require?

Creepage distances and air clearances are at least the values of Tables 12 to 16: insulation between the mains part's opposite polarities ahead of a fuse (on its supply side) provides one means of operator protection per Tables 13, 14 and 16, and insulation providing a means of protection follows Table 12 for patient protection (both distances set by the working voltage, r.m.s. or d.c.) and Tables 13 to 16 for operator protection (clearance related to peak voltage, creepage to r.m.s.), with the exceptions of 8.9.1.2 to 8.9.1.15: operator-protection distances meeting IEC 60950-1 insulation coordination under the conditions tested are exempt; for glass, mica, ceramic and comparable materials, minimum creepage equals minimum clearance; a creepage below the applicable clearance is raised to it; equipment is rated to 2,000 m unless declared otherwise and clearances (not creepages, which stay at least as large) are multiplied by the Table 8 factor for higher or pressurised altitudes; working voltages between table values are interpolated linearly to the next 0.1 mm for creepage and for clearance above 2,800 V peak, the higher value applying below; material groups follow the comparative tracking index of Table 9 with IIIb assumed where unknown; pollution degree 1 (sealed), 2 (non-conductive with occasional condensation), 3 (conductive or condensation-prone) apply and degree 4 is never acceptable for a means of protection; mains transient voltage follows the overvoltage category and nominal voltage of Table 10; mains part clearance up to 300 V is the Table 13 value plus the Table 14 addition for the peak working voltage; on overvoltage category III supplies the next transient column up is used; secondary circuits earthed or internally powered use Table 15, unearthed mains-derived secondaries use the primary Tables 13 and 14 unless screened or attenuated, and the no-transient column covers reliably earthed d.c. with ripple under 10 percent and internally powered circuits; above 1,400 V peak the Table 15 values may be replaced by at least 5 mm clearance passing a dielectric test at 1.06 times peak working voltage across a path through air or material group I; two means of operator protection double the Table 16 creepage; and defibrillation-proof applied parts keep at least 4 mm. Mains part distances between opposite polarities are not required where shorting each in turn causes no hazardous situation of 13.1; grooves and gaps under 1 mm contribute only their width; clearances used as a means of protection are held by rigid, moulded or otherwise fixed parts allowing for likely movement. Where spaces are filled with insulating compound (potting, encapsulation, vacuum impregnation, cemented joints, inner layers of multilayer boards) only the solid insulation requirements apply, checked by sample tests: one finished sample through ten thermal cycles, 48 hours humidity and dielectric strength at 1.6 times the voltage with no cracks or voids on sectioning, or for cemented joints three samples, one cycled and tested hot and two humidity-treated and tested at 1.6 times. Measurement follows the rules of Figures 22 to 31 with transverse-groove minimum widths by pollution degree (0.25, 1.0, 1.5 mm for operator protection at 3 mm clearance or more, one third of the clearance below; 1 mm and 1.5 mm for patient protection), corners under 80 degrees bridged by a 1 mm link, moving parts in the least favourable position, varnish, enamel and oxide ignored, floating conductive parts summed ignoring sections under 1 mm, barriers counted only where sealed against dust and moisture, appliance inlets measured with a connector inserted, cords with the largest specified conductors and without, 2 N on bare conductors and 30 N on metal enclosures with the test finger, and paths through openings measured to the test finger.