650-748 - Removal of NFPA 780 Reference

650-748 - Removal of NFPA 780 Reference

Revision 0 - 02/09/2012

Page 1 of 2

K.L. Erdmann

Agenda Item: / 650-748
QUESTION / RESPONSE
May only the materials listed in API 620 Section 4 and Appendices Q, R, and S be used in API 650 F.7.3 roofs?
If materials other than those listed in API 620 are to be permitted, how are the design allowables to be established?
Are the maximum allowable stresses to be used in roof design those of API 620?
Must the joint efficiencies of API 620 Table 5-2 be applied to the roof?
May the radiography examinations of API 620 Section 5.26.4 be used for applicable roof butt joints to achieve a higher joint efficiency?
If the maximum design temperature is not limited to 250 degrees Fahrenheit and less as suggested by the response to the second question of Inquiry 650-I-39/00, how is one to modify the material properties in API 620?
API 650 F.7.3 mandates that self-supporting roof thickness be not less than that required by API 650 3.10.5 or 3.10.6. Does this mean that the potential non-compliance agreement of API 3.10.2.8 and the Notes located immediately after 3.10.5 and 3.10.6 are inapplicable in this particular usage?
Should the load combinations of API 620-228 be applied to F.7.3 roof calculations?
Must roofs subject to partial vacuum loading in excess of 1" water column and also subject to an internal design pressure of F.1.3 be designed according to API 620 for the external pressure loading as well?
Should design guidance be supplied for self-supported cone roofs subject to API 620 5.10.3.5?
Inquiry 620-I-17/02 indicates that the rules given in API 620 5.10.3.5 are inapplicable for self-supported cone roofs.
Should design guidance for umbrella roofs be provided in API 620?
Although umbrella roofs (API 650 3.10.1.d and V.7.3, among others) are permitted, Inquiry 620-I-05/02 says that there are no design rules given for umbrella roofs in API 620 and that such designs are covered by API 620 1.1. This may be too vague.
Do the requirements of API 650 F.7.2 for compliance with API 620 5.12.4 for dome and self-supporting cone roofs mean that the details of API 620 Figure 5-6 are to be followed for compression-ring roof junctures?
Agenda Item:
Title: /

Removal of NFPA 780

Date: / 02/09/2012
Contact: / Name: / Ken Erdmann
Company: / Matrix ServiceCompany
Phone: / 918-379-6434
E-mail: /
Purpose: / Current NFPA requirements for static drains introduce new hazards to drain dry tanks. Interim fix is editorial change to point NFPA to previous edition. This agenda item will remove reference to NFPA 780 from the standard.
Source: / SCAST direction to remove this reference as is the case in other Tank Standards in API.
Revision: / 0
Impact: / Addresses potential hazardous conditions in drain dry tanks..
Background: / Update to NFPA 780 introduced new hazard. Reference to 780 no longer was supported based on operational procedures in the standard.
Notes:

650-748 - Removal of NFPA 780 Reference

Revision 0 - 02/09/2012

Page 1 of 2

K.L. Erdmann

Current Standard Wording -

Excerpt from page 2-3...

NFPA14

NFPA 11 Standard for Low Expansion Foam

NFPA 30 Flammable and Combustible Liquids Code

NFPA 780 Standard for the Installation of Lightning Protection Systems

Proposed Standard Wording -

New excerpt from page 2-3...

NFPA14

NFPA 11 Standard for Low Expansion Foam

NFPA 30 Flammable and Combustible Liquids Code

NFPA 780 Standard for the Installation of Lightning Protection Systems

Current Standard Wording -

5.8.11.3 If required by the Purchaser, grounding lugs shall be provided in the quantity specified on the Data Sheet, Table 4, and comply with Figure 5-23. The lugs shall be equally spaced around the base of the tank. Provide a minimum of four lugs. The suggested maximum lug spacing is 30 m (100 ft).

Note: Tanks that rest directly on a foundation of soil, asphalt or concrete are inherently grounded for purposes of dissipation of electrostatic charges. The addition of grounding rods or similar devices will not reduce the hazard associated with electrostatic charges in the stored product. API RP 2003 and NFPA-780 contain additional information about tank grounding issues as well as comments about lightning protection.

C.3.1.6 All conductive parts of the external floating roof shall be electrically interconnected and bonded to the outer tank structure. Bonding (grounding) shunts shall be provided on the external floating roof and shall be located above the uppermost seal. Shunts shall be 50-mm (2-in.) wide by 28-gauge (0.4-mm [1/64-in.] thick) austenitic stainless steel as a minimum, or shall provide equivalent corrosion resistance and current carrying capacity as stated in NFPA 780 and API RP 2003. Shunt spacing shall be no more than 3 m (10 ft). All movable cover accessories (hatches, manholes, pressure relief devices, and other openings) on the external floating roof shall be electrically bonded to the external floating roof to prevent static electricity sparking when they are opened.

Proposed Standard Wording -

Note: Tanks that rest directly on a foundation of soil, asphalt or concrete are inherently grounded for purposes of dissipation of electrostatic charges. The addition of grounding rods or similar devices will not reduce the hazard associated with electrostatic charges in the stored product. API RP 2003 and NFPA-780 contains additional information about tank grounding issues as well as comments about lightning protection.