- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
PROPOSAL
Delete the current 501.15(B)(2) and replace with the following:
501.15(B)(2) Between Class I, Division 2 and Unclassified Locations
(a) Aboveground. In each aboveground conduit raceway between a Class I, Division 2 location and an unclassified location where, under normal conditions, there is a differential air pressure that may cause fluid flow from the Division 2 location to the unclassified location.
(1) Where a physical barrier, such has a wall or dike, creates the classified location boundary,
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(2) Where the classified location boundary is in open air and the conduit raceway penetrates a physical barrier, such has a wall or dike, into an unclassified location,
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(1) The sealing fitting shall be aboveground within 3.05 m (10 ft) of grade.
(2) A threaded connection shall be used at the sealing fitting.
(3) Except for listed explosionproof reducers, there shall be no union, coupling, box, or fitting between the conduit seal and grade.
SUBSTANTIATION
Since the 1990 cycle, there have been several Proposals accepted that relax the requirements for seals between Class I, Division 2 and unclassified locations ? almost to the point that they have become unnecessary. Under most conditions this is well justified since there is not supposed to be ignitible materials present in Division 2 under normal conditions.
A significant relaxation in the last cycle permits boundary seals to be non-explosionproof. I have come to the conclusion that they should be explosionproof - that is, if they are needed at all. Unlike the intrinsically safe circuits used to partially justify the relaxation, common circuits still have the ability to ignite flammable materials under abnormal conditions. That is, if the flammable materials are present at all ? which they should not be when the source is a Division 2 location.
I have reduced 501.15(B)(2) to the few conditions I believe seals between Division 2 and unclassified locations ARE necessary and they should be explosionproof.
Notes:
1.) 501.15(B)(2)(a)(1) and (2) do not apply unless the main rule applies; i.e., a differential air pressure exists under normal conditions.
2.) I have used the term "fluid flow" rather than "gasses" to emphasize the means of migration rather than the material that migrates.
[ August 04, 2005, 02:03 PM: Message edited by: rbalex ]
Delete the current 501.15(B)(2) and replace with the following:
501.15(B)(2) Between Class I, Division 2 and Unclassified Locations
(a) Aboveground. In each aboveground conduit raceway between a Class I, Division 2 location and an unclassified location where, under normal conditions, there is a differential air pressure that may cause fluid flow from the Division 2 location to the unclassified location.
(1) Where a physical barrier, such has a wall or dike, creates the classified location boundary,
</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(A) The sealing fitting shall be permitted on either side of the boundary within 3.05 m (10 ft) of the boundary.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(B) A threaded connection shall be used at the sealing fitting.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(C) Except for listed explosionproof reducers, there shall be no union, coupling, box, or fitting between the conduit seal and the boundary.</font>
(2) Where the classified location boundary is in open air and the conduit raceway penetrates a physical barrier, such has a wall or dike, into an unclassified location,
</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(A) The sealing fitting shall be within 3.05 m (10 ft) of the physical barrier.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(B) A threaded connection shall be used at the sealing fitting.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(C) Except for listed explosionproof reducers, there shall be no union, coupling, box, or fitting between the conduit seal and the boundary.</font>
(1) The sealing fitting shall be aboveground within 3.05 m (10 ft) of grade.
(2) A threaded connection shall be used at the sealing fitting.
(3) Except for listed explosionproof reducers, there shall be no union, coupling, box, or fitting between the conduit seal and grade.
SUBSTANTIATION
Since the 1990 cycle, there have been several Proposals accepted that relax the requirements for seals between Class I, Division 2 and unclassified locations ? almost to the point that they have become unnecessary. Under most conditions this is well justified since there is not supposed to be ignitible materials present in Division 2 under normal conditions.
A significant relaxation in the last cycle permits boundary seals to be non-explosionproof. I have come to the conclusion that they should be explosionproof - that is, if they are needed at all. Unlike the intrinsically safe circuits used to partially justify the relaxation, common circuits still have the ability to ignite flammable materials under abnormal conditions. That is, if the flammable materials are present at all ? which they should not be when the source is a Division 2 location.
I have reduced 501.15(B)(2) to the few conditions I believe seals between Division 2 and unclassified locations ARE necessary and they should be explosionproof.
Notes:
1.) 501.15(B)(2)(a)(1) and (2) do not apply unless the main rule applies; i.e., a differential air pressure exists under normal conditions.
2.) I have used the term "fluid flow" rather than "gasses" to emphasize the means of migration rather than the material that migrates.
[ August 04, 2005, 02:03 PM: Message edited by: rbalex ]