An appurtenance is defined in 49 CFR §178.320(a) as any attachment to a cargo tank that has no lading retention or containment function and provides no structural support to the cargo tank. Some examples of an appurtenance include ladders, light brackets, hose trays, conduit clips, brake line clips, and placard holders.
The Research and Special Programs Administration (RSPA) issued an interpretation June 30, 2004, on the attachment of an appurtenance to an MC-331 cargo tank. This interpretation identifies situations when mounting pads are required and the minimum qualifications for repair facilities to attach an appurtenance to the cargo tank wall.
Cargo tanks manufactured before Sept 1, 1995, are not required to have pads, and there is no retrofit requirement for these tanks. These cargo tanks must be maintained in accordance with the specification in effect at the time of initial manufacture or in accordance with the current specification.
Cargo tanks manufactured after Sept 1, 1995, are required to meet these criteria:
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Appurtenances and other accessories should be attached to structural members, the subframe, accident protection and ring stiffeners when practicable (§178.337-3(g) (1)).
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When appurtenances cannot be attached in accordance with §178.337(g) (1), they must be attached to the cargo tank wall using a welding pad as specified in §178.337-3(g)(3). This includes devices such as lifting lugs and “half-moon” gauge protection devices, unless those devices meet the definition of a lightweight attachment described in § 178.337-3(g)(2).
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Attachments meeting the definition of a lightweight attachment do not require a welding pad. A lightweight attachment must be of a construction having lesser strength than cargo tank wall materials and any attachment to the cargo tank wall where the measurement of the thickness of the attachment is less than or equal to 72% of the thickness of the cargo tank shell or head material to which it is attached. Lightweight attachments are not authorized under part UHT in Section VIII, Division 1 of the ASME code.
An MC-331 cargo tank manufactured after Sept 1, 1995, that does not conform to these requirements must be repaired. Repairs involving welding on the cargo tank wall must be performed by a facility registered with the Department of Transportation and having a National Board Certificate of Authorization for the use of the “R” stamp. In addition, repairs must be performed in accordance with all applicable regulations, the National Board Inspection Code, and the American Society of Mechanical Engineers (ASME) code. A registered inspector is required to determine if the cargo tank complies with the specification.
Any tank discovered not in compliance with the requirements shall be removed from specification service until appropriate repairs or modifications have been completed. Phone Danny Shelton at 202-366-0476 for more details.