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| NESC® and OSHA Newsletter | January 12, 2010 |
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Marne and Associates NESC and OSHA Newsletter addresses issues relevant to power and communication utilities.
In This Issue:
"K" Factor (additive constant)
The change proposals for the 2012 NESC have been published to gather industry comments. Comments are due by May 1, 2010.
Change proposal CP3454 applies to two NESC rules, NESC Rule 230B (in the clearance section) and NESC Rule 251B (in the loadings section). Both rules contain values for an additive constant which is commonly referred to as a "K" factor. The change proposal involves deleting the additive constant and using a greater wind pressure. For example, for the Medium Loading District (Clearance Zone 2) instead of 15°F, 0.25 in of ice, 4 lb/ft² of wind, and an additive constant of 0.20 lb/ft, the constant of 0.20 lb/ft would be deleted and the wind would increase to 8 lb/ft². An example of how the "K" factor is currently applied is shown in the figure below.
 Industry comment is needed to review this proposed change. To get your voice heard, the first step is to purchase the Preprint Proposals for the 2012 Edition of the NESC (unfortunately this document is not available for free). The second step is to follow the electronic revision process to submit your comments to the Code committees.
To order a copy of the Preprint Proposals for the 2012 Edition of the NESC click here. We only have two (2) left in stock!
60' Extreme Wind Exemption
The change proposals for the 2012 NESC have been published to gather industry comments. Comments are due by May 1, 2010.
Change proposal CP3423 applies to NESC Rules 250C (extreme wind loading) and 250D (extreme ice with concurrent wind loading) which contain an exclusion for structures or supported facilities less than 60 feet above ground or water level. The change proposal is to eliminate the 60 ft exclusion (therefore requiring all poles to meet extreme wind and extreme ice with concurrent wind loading). This change proposal was rejected but continues to be a source of controversy.
Industry comment is needed to review this proposed change (in this case, rejection of the proposed change). To get your voice heard, the first step is to purchase the Preprint Proposals for the 2012 Edition of the NESC (unfortunately this document is not available for free). The second step is to follow the electronic revision process to submit your comments to the Code committees.
To order a copy of the Preprint Proposals for the 2012 Edition of the NESC® click here. We only have two (2) left in stock!
Marne and Associates new cycle of NESC live web seminars begins again on January 20, 2010.
This is a great low cost, no travel, and easy way to get NESC training for your engineering or operations personnel. More Info.
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 Books & References
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If you have a question for our newsletter, please send an email to kirstin@marneassociates.com with a concise description of your NESC or OSHA question. We attempt to answer every question received, but the volume and type of questions limits us.
Disclaimer: The content of this newsletter should be considered general information only. It is not intended to be consulting engineering advice, legal advice, or an official interpretation of the NESC® or OSHA requirements.
Information and diagrams contained in this document attempt to show common situation where the 2007 NESC Code applies. Diagrams and photos are intended to be used as visual aids to the reader of the Code and are not intended to be a replacement for the comprehensive nature of the Code as it is written.
Any figures and/or photos used in this document derived from McGraw-Hill's NESC® Handbook were used with permission from the publisher, McGraw-Hill Companies, Inc.
Copyright © 2009 Marne and Associates, Inc.
Information and diagrams contained in this document attempt to show common situation where the 2007 NESC Code applies. Diagrams and photos are intended to be used as visual aids to the reader of the Code and are not intended to be a replacement for the comprehensive nature of the Code as it is written.
Any figures and/or photos used in this document derived from McGraw-Hill's NESC® Handbook were used with permission from the publisher, McGraw-Hill Companies, Inc.
Copyright © 2009 Marne and Associates, Inc.
