Interpretation Response #00-0190 ([Design Certifying Engineer] [Mr. David Fellows])
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Design Certifying Engineer
Individual Name: Mr. David Fellows
Location State: WI Country: US
View the Interpretation Document
Response text:
August 9, 2000
Mr. David Fellows Ref No. 00-0190
Design Certifying Engineer
904 Hawks Hollow
Delafield, Wisconsin 53018
Dear Mr. Fellows:
This responds to your letter, dated July 5, 2006, concerning cargo tank specification requirements in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you ask about a design modification to DOT 406 and 407 specification cargo tanks to equip them with an internal agitation system.
Your letter describes a design for an internal agitator that consists of a large rotating shaft installed through the rear bulkhead of a cargo tank. The design depends on a non-metallic packing gland, or seal, to guarantee lading retention capability of the cargo tank. In your opinion, the design does not conform to §178.345-9(h), which prohibits the use of non-metallic pipes, valves, or connections on DOT 406 and 407 cargo tanks unless they are outboard of the product retention system.
You are correct that the HMR do not specifically prohibit a design modification of the type you describe. It is difficult for us to evaluate the merits of the specific design in question without seeing a picture or design specification. However, as you describe it, it appears that the non-metallic seal is part of the tank wall. As defined in §178.320(a), "cargo tank wall means those parts of the cargo tank that make up the primary lading retention structure. Thus, under §178.345-9(h),,use of a nonmetallic seal or packing gland that is not as strong and heat resistant as the material used for construction of the cargo tank is prohibited. You are correct that one way to overcome this design deficiency is to provide a secondary containment device.
I hope this information is helpful. If you have further questions, please do not hesitate to contact this office.
Sincerely,
Thomas G. Allan
Senior Transportation Regulations Specialist
Office of Hazardous Materials Standards
178.345