The Research and Special Programs Administration (RSPA) issued an interpretation on June 30 regarding the attachment of an appurtenance to an MC331 cargo tank. This interpretation identifies situations when mounting pads are required and the minimum qualifications required for repair facilities to attach an appurtenance to the cargo tank wall. 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 appurtenances are ladders, light brackets, hose trays, conduit clips, brake line clips, and placard holders.
Cargo Tanks manufactured prior to September 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 September 1, 1995, are required to meet the following criteria:
Appurtenances and other accessories should be attached to structural members, the sub-frame, accident protection and ring stiffeners when practicable (178.337-3(g) (1)).
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 the “half-moon” gauge protection devices that are illustrated above, unless those devices meet the definition of a lightweight attachment described in 178.337-3(g)(2).
Attachments meeting the definition of a lightweight attachment do not require a welding pad. A lightweight attachment is any attachment to the cargo tank wall where the measurement of the thickness of the attachment is less than or equal to 72 percent of the minimum thickness of the cargo tank shell or head material to which it is attached. NOTE: Lightweight attachments are not authorized under part UHT in Section VIII, Division 1 of the ASME code.
An MC-331 cargo tank manufactured after September 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 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 applicable specification. Any tank that is discovered not in compliance with the specification requirements shall be removed from specification service until appropriate repairs or modifications have been completed. Please contact Danny Shelton, hazardous materials specialist at the Federal Motor Carrier Safety Administration at 202-366-0476, for additional information.