December 16, 2005
Subject 1203 (698, 877, 886, 894, 1002, 1010)
TO: Listees of equipment covered by the following standards and
Subscribers to UL’s Standards Service for
Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, UL 1203
Industrial Control Equipment for Use in Hazardous (Classified) Locations, UL 698
Circuit Breakers and Circuit-Breaker Enclosures for Use in Hazardous (Classified)
Locations, UL 877
Outlet Boxes and Fittings for Use in Hazardous (Classified) Locations, UL 886
Switches for Use in Hazardous (Classified) Locations, UL 894
Electrically Operated Valves for Use in Hazardous (Classified) Locations, UL 1002
Receptacle-Plug Combinations for Use in Hazardous (Classified) Locations, UL
1010
SUBJECT: Revised effective date for the industry review of NPT male threaded explosionproof equipment covered by UL 1203
UL is actively working to process revisions to UL 1203 as a new 4th Edition that will incorporate the standards outlined above. This incorporation will extend the applicability of Pars. 12.1.1.4 and 12.1.1.14 of the current UL 1203, 3rd Edition regarding NPT threads to these products. The overall goal is to have a common set of requirements for construction and performance for the explosion-proof and dust-ignition-proof protection techniques where the type of product does not warrant a difference.
Pending successful publication of the new 4th Edition of UL 1203, UL anticipates proposing a future effective date for the NPT male thread requirements of December 30, 2009.
In order to harmonize the application of the requirements for products currently certified to the 3rd Edition UL 1203 with products currently certified to any of the affected standards, the effective date for the UL 1203 Industry Review for NPT male threads is being extended from April 30, 2006 to December 30, 2009.
Where UL has already found products to comply with the revised NPT male thread requirements of UL 1203, no future action will be necessary on those products. Those products not yet in compliance, and new products added to a UL file after the date of this letter will need to be determined to comply with the requirements before the future effective date.
UNDERWRITERS LABORATORIES INC.
Subject No. / 1203 / Page 2 of 2 / November 2, 2005Donald W. Ankele
Principal Engineer (PDE)
Hazardous Locations
tel: +1 847 664 2965
fax:+1 847 313 2965
email -
Paul T. Kelly
Operations Manager
Hazardous Locations, Gas & Oil
UL Conformity Assessment Services
tel: +1 847 664 2326
fax:+1 847 313 2326
e-mail: