Catalogue - The basics of dust-explosion protection - STAHL - (Version JPG)

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3. Legal Basis and Standards

In the most important industrial countries, regulations and standards covering explosion protection in areas exposed to dust hazard were established early on. In the USA, standards have existed since 1929, in Germany since 1976.

However, it was a comparatively long time before the first international regulations at IEC level


Table 4: Dust Explosion Protection Standards			appeared - 1993. Work on these commenced in
	IEC	EN	the mid-70's, but the protective techniques used in the different countries were so different that it

General requirements	61241-0	prEN 61241-0	was very difficult to establish common standards.
Type of protection "tD"	61241-1	50281-1-1	The IEC 61241:1993 series of standards was still
	(61241-1-1)	in future EN 61241-1	based on the two zone concept.
Selection and installation	61241-14 (61241-1-2)	50281-1-2 in future EN 61241-14	Before the new European directives for explosion protection (94/9/EC and 1999/92/EC) came into force, explosion protection regulations in Europe
Inspection and maintenance	61241-17	prEN 61241-17	existed at the national level, based on the tow zone concept.
Testing methods:
> Min. ignition temperature	61241-20-1 (61241-2-1)	50281-2-1	In Germany the two zones were defined: Zone 10 and Zone 11, in Great Britan: Zone Z and Zone Y.
> Electrical resistivity	61241-20-2	61241-2-2	In Germany a special certification of design was
of a dust layer	(61241-2-2)	(50281-2-2)	not required.
> Min. ignition energy	61241-20-3	50281-2-3
	(61241-2-3)	in future at CEN	Although the special risk posed by dust explosions
> Lower explosion limit	61241-2-4	50281-2-4 in future at CEN	has long been known, due to devastating accidents in coal mines, the problem received
Classification of areas	61241-10 61241-3	50281-3	widespread attention in Germany only after
Classification of areas		50281-3	the flour dust explosion that completely destroyed
			the Rolands Mill in Bremen in 1978.
Protection by pressurization	61241-2		the Rolands Mill in Bremen in 1978.
"pD"	(61241-4)
Protection by intrinsic safety	61241-11
"iD"
Protection by encapsulation	61241-18
"mD"

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Alarm, Indicator, Enclosure, Circuit breaker, Control foot-switch