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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #11-0002 ([Thompson Tank Inc.] [Mr. David Thompson])

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name: Thompson Tank Inc.

Individual Name: Mr. David Thompson

Location State: CA Country: US

View the Interpretation Document

Response text:

May 11, 2011





Mr. David Thompson

Thompson Tank Inc.

8029 Phlox Street

Downey, CA 90241

Ref. No.: 11-0002

Dear Mr. Thompson:

This is in response to your December 28, 2010, letter requesting further clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) based on a letter issued by this office (Ref. No. 10-0219) regarding inspection and use of non-DOT specification cargo tank motor vehicles constructed from glass fiber reinforced plastics (GFRP) authorized by Department of Transportation Special Permit, (DOT-SP) 11903. Your questions are restated and answered below:

Q1. Does DOT-SP 11903 require compliance with § 178.347-1(c)?

A1. No, § 178.347-1(c) does not apply to non-DOT specification glass fiber reinforced plastic (GFRP) cargo tanks manufactured in accordance with DOT SP-11903 paragraph 7.b(viii). Section VIII of the American Society of Mechanical Engineers (ASME Code) referenced in § 178.347-1(c) contains design and manufacturing rules applicable to metallic pressure vessels and is not applicable to GFRP cargo tanks manufactured in accordance with DOT-SP 11903.

Q2. If § 178.347-1(c) does not apply, is the internal maximum allowable working pressure (MAWP) unlimited?

A2. DOT-SP 11903 paragrph7.a states that the cargo tank must have a design pressure of 35 psig. For the purposes of DOT-SP 11903, the design pressure is the same as the MAWP.

Q3. Is vacuum loading permissible without ASME certification?

A3. ASME certification ("U" stamp) is not required for vacuum loaded non-DOT specification GFRP cargo tanks manufactured in accordance with DOT-SP 11903.

Q4. Will the DOT correct the applicable special permits that specifically require compliance with § 178.347-1(c)?

A4. As stated in the response to Question 1, no currently active DOT special permits that authorize the manufacture, marking and sale of non-DOT specification GFRP cargo tanks require compliance with Section VIII of the ASME Code referenced in § 178.347-1(c).

Q5. Are GFRP cargo tank motor vehicles manufactured in accordance with DOT-SP 11903 required to meet § 180.407(f)(3), which requires thickness testing of the tank wall if affected by a lining or resin rich corrosion barrier failure?

A5. As specified in DOT-SP 11903 paragraph 7.c, non-DOT specification GFRP cargo tank motor vehicles must meet the requirements in Subpart E of Part 180 for the periodic testing and inspection of DOT 407 and DOT 412 specification cargo tank motor vehicles. In our December 21, 2010 letter to you, we stated that the lining inspection requirements of § 180.407(f) do not apply since these cargo tanks do not have a liner. Instead, the cargo tank motor vehicles authorized by DOT-SP 11903 are fabricated with a resin rich corrosion barrier that is part of the GFRP construction.

The certificate of compliance you supplied with your letter states this particular non-DOT specification GFRP cargo tank is equipped with a "Durakane 510A 40 BPO" lining material. Durakane 510A 40 BPO is an epoxy vinyl ester resin. This material comprises the corrosion barrier and not lining material as used in § 178.345-2.

Q6. Must we verify the minimum shell and head thickness specified on the DOT specification plate and in the manufacturer"s certificate of compliance?

A6. Yes, in accordance with DOT-SP 11903 paragraph 7.c, during periodic inspection, the shell and head thickness must be measured in accordance with § 180.407(i).

Q7. Can this cargo tank comply with both DOT-SP 11903 and TC 412?

A7. If the TC 412 specification allows cargo tanks to be manufactured of GFRP, it is possible that a cargo tank can comply with both DOT-SP 11903 and TC 412. DOT- SP 11903 requires conformance with all regulations applicable to a DOT 407 or DOT 412 cargo tank except as specified. DOT specification cargo tanks made in the United States are generally recognized for use in Canada as equivalents to the corresponding Transport Canada specifications. Provided Transport Canada recognizes the DOT special permit, this cargo tank would be suitable for use in Canada.

Q8. Please define what the DOT considers to be the specific differences between an interior lining and a corrosion barrier.

A8. The application of a lining material is one option to protect a DOT specification cargo tank motor vehicle from corrosion or abrasion. Typical lining materials applied to the cargo tank wall are rubber, Kynar or polytetrafluoroethylene. A corrosion barrier serves the same purpose as a liner (i.e. protect the cargo tank from attack by the lading). In the case of DOT-SP 11903 and other GFRP cargo tanks, the corrosion barrier is a thin resin rich area which is part of the cargo tank wall. The requirements of § 178.345-2(c)(2) do not apply to cargo tanks manufactured in accordance with DOT-SP 11903 (see DOT-SP 11903, paragraphs 4 and 7.b(ii)). While some persons may use the phrases "lining material" and "corrosion barrier" interchangeably, for the purposes of the HMR, non-DOT specification GFRP cargo tanks manufactured in accordance with DOT-SP 11903 are considered unlined cargo tanks.

Q9. Can the visual examination only, as recommended by the cargo tank manufacturers, satisfy the DOT requirements that the "structural integrity of the GFRP cargo tank must be determined prior to the repair or the replacement of the corrosion barrier." Are we correct to assume that this requirement also applies to an interior lining?

A9. The non-DOT specification cargo tanks manufactured in accordance with DOT-SP 11903 are subject to all requirements of Subpart E of Part 180 including an external and an internal visual inspection, a pressure test, and a leakage test (see DOT-SP 11903 paragraph 7.c). In accordance with the table in § 180.407(c), Iif the cargo tank is equipped with a liner, the lining must be inspected as required by § 180.407(f), and for unlined cargo tanks, the shell and head thickness must be measured in accordance with paragraph § 180.407(i).

Q10. When will the DOT inform the manufacturers of the GFRP cargo tanks of their responsibilities and enforce compliance?

A10. The Pipeline and Hazardous Materials Safety Administration independently reviews and evaluates the information provided in each special permit application and application for renewal. This review includes a technical analysis, an evaluation of the past compliance history of the applicant (including incident history and enforcement actions) and coordination with the other modal administrations to gather additional relevant information. If you are aware of a manufacturer or inspection facility that does not comply with the HMR or the terms of a DOT special permit, you may file a complaint at or contact our enforcement office directly at (202) 366-4700.

I hope this answers your inquiry. If you need additional assistance, please contact the Standards and Rulemaking Division at (202) 366-8553.


Ben Supko

Acting Chief, Standards Development

Standards and Rulemaking Division

178.347-1, 180.407

Regulation Sections

Section Subject
178.345-2 Material and material thickness
178.347-1 General requirements
180.407 Requirements for test and inspection of specification cargo tanks