Does anyone know the rationale behind the change to Table 515.3 "Tank - Aboveground - Shell,Ends, or Roof and Dike Areas" The 1999 NEC stated that the space inside a dike to the level of the top of the dike was Class I, Div 2. The 2002 NEC states that the space insdie a dike to the level of the top of the tank is Class I, Div 2.
It would appear that this is a typo which occurred during the update of the table to add Zone classifications. However, there has been no proposal to change it back to the 1999 wording for the '05 code. I can see no technical justification at a Bulk Storage facility to classify an area which could be 50 feet above the top of the dike.
It would appear that this is a typo which occurred during the update of the table to add Zone classifications. However, there has been no proposal to change it back to the 1999 wording for the '05 code. I can see no technical justification at a Bulk Storage facility to classify an area which could be 50 feet above the top of the dike.