Refresher course provides information about government cargo tank regulations

Feb. 1, 2005
FOR PEOPLE new to the tank truck industry, as well as those looking for refresher information, the National Tank Truck Carriers (NTTC) Cargo Tank Maintenance

FOR PEOPLE new to the tank truck industry, as well as those looking for refresher information, the National Tank Truck Carriers (NTTC) Cargo Tank Maintenance seminar provided an introduction to federal cargo tank regulations.

Presenting the information at the October 18-20 meeting in Chicago, Illinois, were John Cannon, Brenner Tank LLC; Danny Shelton, Federal Motor Carrier Safety Administration; John Barrett, Brenner Tank Services; and John Conley, NTTC.

The panel focused on continuing qualification and maintenance of cargo tanks in accordance with Part 180 of Title 49 Code of Federal Regulations.

They pointed out that certain people, including hazmat carrier maintenance specialists, repair facility employees, owners of hazmat cargo tanks, and shippers of hazardous materials, must have knowledge of Part 180.

Until 1985, the few regulations that existed on cargo tank continuing qualification and maintenance were vague, but with the Docket HM-183 publication, the Department of Transportation endeavored to strengthen the minimum requirements for cargo tank tests, inspections, repair, and much more, Cannon said.

In 1991, Part 180 began to take effect. It included definitions; qualifications; tests and inspections; inspector and tester qualifications; and acceptable results, said Shelton.

Other parts addressed repair, modification, stretching and rebarrelling, test and inspection markings, and reporting and record retention.

The regulation offers definitions:

  • Corroded or abraded: visible reduction in the material thickness of the cargo tank.

  • Corrosive to the tank or valve: the lading being transported has been shown to reduce the material thickness of the cargo tank wall or valve. The regulation did not say that the material had to meet the definition of a corrosive material.

  • Delivery hose assembly: liquid delivery hose and its attached coupling.

  • Modification: any change to the original design and construction of a cargo tank or cargo tank motor vehicle (CTMV) effecting structural integrity or lading retention capability.

  • Piping system: any component of a cargo tank delivery system, other than a delivery hose assembly, that contains product during loading or unloading.

  • Rebarrelling: replacing more than 50% of the combined shell and head material of a cargo tank.

  • Stretching: any change in length, width, or diameter of the cargo tank or any change to a cargo tank motor vehicle's undercarriage that may affect the structural integrity.

The regulation requires that the external inspection must be performed every year. The tank shell, tank heads, all piping, valves, and gaskets must be inspected for corroded, pitted, or abraded areas, dents, distortions, defects in welds, and other conditions, including leakage, that might render the tank unsafe for operation.

Barrett discussed testing and inspections that include external visual efforts. All devices for tightening domelid covers must be operative and there must be no evidence of leakage. All emergency devices and all valves must be free from corrosion, distortion, erosion, and any damage that will prevent safe operation, and must be functioned to demonstrate proper operation.

In addition, missing bolts, nuts, and fusible links or elements must be replaced, and loose bolts and nuts must be tightened. All markings on the cargo tank required by Part 180 must be correct and legible, or removed. Insulated trailers must be given an internal inspection.

If the trailer has no domelid or inspection lid, or has a lining, it must be pressure tested. All tank framing and sub-framing, and attachments must be inspected for corrosion, holes, cracks, or damage, which might prevent safe operation.

All re-closing pressure-relief valves carrying lading corrosive to the valve must be removed and bench tested to open at the required set pressure and reseat to a leak-tight condition at 90% of the set-to-discharge pressure or the pressure prescribed for the applicable cargo tank specification.

Fifth-wheel plates must be dropped and inspected every two years if the trailer is hauling a corrosive product. Most MC307 tanks with three-inch venting must have two three-inch fusibles along with the three-inch vent.

All corroded or abraded areas of the outside of the cargo tank wall must be thickness tested.

If the cargo tank is constructed of steel with steel reinforcing rings, the rings must be thickness tested in four symmetrical positions around the circumference. If any reading varies from the average by more than 10%, a thickness test is required for the shell internally, in the area covered by the ring.

Each on-vehicle, manually-activated, remote shutoff device for closure of the internal self-closing stop valve must be identified by marking “emergency shutoff” in letters at least 0.75 inch in height, in a color that contrasts with its background, and is located in an area immediately adjacent to the means of the closure.

Recorded results

Inspectors must record results of the external visual examination on the inspection/test report, and the proper decals applied to the front jacket head or the roadside front jacket sheet.

Turning to internal visual test and inspections, the rule requires inspections every year on all insulated MC307 and DOT407 cargo tanks, and on all cargo tanks transporting a corrosive product.

The inner shell and heads must be inspected for corroded and abraded areas, pits, dents, distortions, defects, welds, and any other corrosion that might render the tank unsafe for transportation service. If there are corroded, pitted, or abraded areas, a thickness test must be conducted in those areas to meet the manufacturer's minimum thickness.

If the corroded, pitted, or abraded areas fall under the minimum thickness, the areas must be repaired or replaced. Inspect internal fittings, emergency valves, stand pipes, and internal vapor lines. If dents are discovered in the shell or the inner heads that include a weld, the maximum allowable depth is one-half inch.

If dents are found in the shell or in the inner head away from welds, the maximum allowable depth is one-tenth of the greatest dimension of the dent, but in no case may the depth exceed one inch.

The results of the internal inspection must be recorded on the inspection/test report and the proper decals applied to the front head or the roadside front jacket sheet.

Leakage tests

Leakage tests and inspections must be performed every year on all MC307 and DOT407 cargo tanks. The leakage test must be performed with all valves, accessories, and vents in place and operative. Product piping must be tested. All internal or external self-closing stop valves must be tested for leak tightness.

The leakage test pressure is at 80% of the cargo tank maximum allowable working pressure (MAWP) and held for a minimum of five minutes. If the cargo tank is compartmental, each compartment shall be tested with the adjacent compartment empty and at atmospheric pressure.

The inspector doing the leakage testing and inspections must record results on the inspection/test report and the proper decals applied to the front jacket head or the roadside front jacket sheet.

Thickness testing of unlined MC307 and DOT407 cargo tanks must be done every two years if the cargo tank has transported materials corrosive to the tank, or shows any corrosion or pitting present. Cargo tanks measuring less than the sum of the minimum prescribed thickness, plus one-fifth of the original corrosion allowance, must be thickness tested annually. The person doing the thickness test must be using a device capable of accurately measuring thickness to within plus or minus 0.002 inch, and be trained on how to use the thickness testing device.

Ultrasonic testing requires coverage of the following:

  • Areas of the tank shell and tank heads.

  • Areas around any piping that retains lading.

  • Areas of high shell stress, such as the bottom center of the tank, or front and rear support structures.

  • Areas around all openings, nozzles, liquid level lines, shell reinforcements, and weld joints.

  • Areas near upper coupler and suspension assembly attachments, and areas around any appurtenance attachments.

Thickness results must be within specified manufacturers minimum thickness. (For more information, see the specification plate on DOT400 series tanks.) If the shell or heads measure below the allowable minimum thickness, those areas must be repaired or replaced, or the tank downgraded to a non-spec tank, or have its service limits lowered per a design certified engineer.

A trailer with a shell that is below minimum thickness may be transported as long as the specification plate is covered, and the inspection/test stickers are removed or covered, and the tank is transporting a non-hazmat product.

The inspector must record the results on the inspection/test report and the proper decals applied to the front jacket head or the roadside front jacket sheet.

Pressure testing

All MC307 and DOT407 tanks must undergo a pressure retest at least once every 5 years. As part of the pressure test, the inspector must perform an external and internal visual inspection.

The test pressure is 40 psi or 1.5 times the design pressure or MAWP (whichever is greater). The tank should be hydrostatically tested, which includes filling the tank and dome lids with water that does not exceed the temperature of 100° F. The tank must hold this pressure for a minimum of 10 minutes, while at which time the tank is being inspected for leakage, bulging, or other defects.

All re-closing pressure-relief valves must be removed, inspected, and bench tested to open at the required set pressure and to re-seat to a leak tight condition at 90% of the set to discharge pressure. (The vent's PSI rating must match the cargo tank specification plate MAWP.) Operation of all vents must be restored after testing and before the tank is returned to service.

If the trailer is not hauling a corrosive material, the fifth-wheel plate needs to be dropped and the tank needs to be inspected above the fifth-wheel plate for abraded area, dents, distortions, and defects in welds.

Heat systems

All heat systems need to be pressure tested at least once every five years by at least the maximum system design operating pressure, and this pressure must be held for a minimum of five minutes. Heating systems that leak must be repaired or marked out of service. Any leak into the shell must be fixed.

Inspectors must record results of the pressure test onto the inspection/test report and the proper decals need to be applied to the front jacket head or the front roadside jacket sheet.

There are certain functions where registration is required. They include:

  • Manufacturing a DOT specification cargo tank or a tank built to an exemption (FRP Trailer) assembly.

  • Mounting specification tanks to a chassis.

  • Installation of equipment or components (eliminate specification shortages).

  • Installation of linings, coatings or other material to the inside of a cargo tank wall.

  • Certification that a cargo tank complies with the specification requirements (design certifying engineer).

  • Inspection and testing.

  • External Visual

  • Internal Visual

  • Leakage Test

  • Pressure Test

  • Lining Inspection

  • Thickness Test

  • Repair is defined as welding to the cargo tank wall to return a cargo tank motor vehicle to its original design or to an equivalent specification in effect at the time of repair.

  • Repairs on ASME Code Tanks must have an R stamp.

  • Repairs on Non-ASME Code Tanks may have either an R stamp or a U stamp.

As for recordkeeping, owners of specification cargo tanks must have a manufacturer's certificate, ASME U1A data report, related papers that certified that tank was manufactured and tested.

Motor carriers that use a specified CTMV must have a manufacturer's certificate, related papers, alternative report authorized by 180.417(a)(3)(i) or (ii).

Test and inspection reports must include the owner's and manufacturer's serial number, cargo tank manufacturer, specification number, MAWP, minimum thickness (when thickness testing is required), indication of lined, insulated or both, and indication of special services.

Some of the specific information that is required includes the type of test or inspection, date of test or inspection (month and year), listing of items tested or inspected, location of defects and method of repair, minimum thickness (when thickness testing is required), name, address of person performing test, and CT number of person or facility performing test.

There also must be a continued qualification statement, registration number of the registered inspector, and dated signature of the registered inspector and cargo tank owner.

Owners and motor carriers must retain the inspection report until the next test or inspection is successfully completed. This is not applicable to a motor carrier leasing a cargo tank for less than 30 days.