Tank Modifications Continue to Bewilder
Feb 1, 2000 12:00 PM, mbt staff
Complying with the federal rules that apply to cargo tank repairs may be one of the biggest challenges facing repair shops. Even 10 years after the current rules were adopted, there is still considerable confusion.
Dave Fellows, a consultant to the tank truck industry, addressed one area of concern during the 1999 Cargo Tank Maintenance Seminar October 25-27 in Chicago, Illinois. He discussed types of repairs that are classified as cargo tank modifications.
When Part 180 was adopted 10 years ago, it established a lot of new rules on repairs to specification cargo tanks. "For practical purposes, specification cargo tanks are only those that are designated MC306, 307,312, and 331 or DOT406, 407, or 412," Fellows said. "You may also run into some pre-1967 tanks or special permitted tanks that are covered under Part 180, but there are many cargo tanks in service that do not require Part 180 compliance."
For most of his presentation, Fellows concentrated on Part 180.403, which defines four kinds of work on cargo tanks-repairs, modifications, stretching, and rebarreling. "We have all struggled with getting a good handle on what work constitutes which of these categories," he said. "The most confusion, though, is caused by what constitutes a modification."
Original Design In the regulations, modification is defined as any change to the original design and construction of a cargo tank or cargo tank motor vehicle that affects its structural integrity or lading retention capability. Excluded is replacement of valves, vents, and fittings with a component of similar design and of the same size.
In discussions with industry experts and through reviews of Department of Transportation (DOT) audits, Fellows came up with the following list of tank changes that are considered modifications:
Adding more manholes, installing a Roto gage, adding cleanout openings, changing piping from individual lines to a manifolded system, changing a bulkhead into a baffle, converting a multicompartment tank to single compartment, adding or removing shell stiffeners, de-rating product density on an MC312 and adding MC307 venting, changing the type of manhole, installing a new sump, installing vapor-recovery fittings in the shell, converting a double head to a single bulkhead, changing compartment sizes, adding more overturn protection, modifying crossmembers for piping, and adding venting for a different code.
"If what is done is a modification, there are specific rules to follow," Fellows said. "It is necessary to add a small plate next to the cargo tank specification plate. The small plate will identify the company making the modifications, and will include the word "modified" and the date. The tank owner must receive a supplemental Certificate of Compliance describing the modification. The modification must be approved by a design certifying engineer.
"DOT has not been specific on the design of the certification document, just what it must convey. You can create your own. Just remember that you, as the registered repairer or registered inspector, have to certify the modification."
Design Certifying Engineer The biggest problem faced by many tank repair shops is that they also have to get the blessing of a design certifying engineer. The rub is that an engineer is not needed to determine whether the structural integrity has been changed with many modifications.
Many tank builders don't want to be bothered with the certifications, according to Fellows. That is a mistake. "I would encourage the service departments of tank manufacturers to work with management and engineers to develop a system to provide this service, particularly for simple tasks," he said.
It is common practice for tank builder service departments to advise on structural fixes, such as adding head stiffeners, crossmembers, shell stiffening devices, outriggers, and related components. It is not clear if these instructions constitute a design certifying engineer's approval or if a Supplemental Certificate should be issued. If a repair shop decides to add something without guidance from the manufacturer, it appears that the approval and certificate are required.
Some modifications require engineering, and a design certifying engineer must sign off. Fellows offered the following examples: Added fittings that extend beyond the original overturn protection, remounting of a truck tank, modification of structural components on truck tanks to clear underbody piping, adding axles even if the barrel length doesn't change, and bumper replacement.
Older Tanks When these changes are made to older specification tanks, the modification must comply with the applicable DOT400 requirement. Changes cannot be made in accordance with the specification under which the tank was built.
"I have seen some cases where extensive modification is being made to an older specification tank for some special purpose, but the proposed use doesn't really require a specification tank," Fellows said. "It may make more sense to decertify the tank. A specification tank can be returned to compliance later."
Cargo tank maintenance has gone through significant changes over the past 10 years, and the industry now keeps track of repairs on a cargo tank almost as if it were a Boeing 747 jet. Tank owners now expect good records, and so does the DOT.
If a tank repair shop is in doubt about documentation or whether a repair is a modification, management should pick up the phone and call someone for advice. Finding out during a DOT audit that a modification was performed but not documented can be embarrassing and costly.
Fellows recommended developing a good relationship with the DOT regional personnel. They are a good source of information, and it's better to ask than to be fined.
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