KEEPING drivers and mechanics off the tops of tank trailers has become increasingly critical from a safety standpoint. One of the latest developments in that effort was discussed during the Tank Trailer Manufacturers Association (TTMA) report delivered during National Tank Truck Carriers’ Tank Truck Week held October 28-30, 2013 in Houston, Texas.
Other topics discussed by TTMA representatives included chemical tank trailers constructed from lean duplex steel and disputable citations issued by enforcement personnel during roadside inspections of cargo tanks.
On the fall-protection side, carriers and members of the TTMA are doing field studies to test the effectiveness of the Hydraulically Actuated Sliding Cleanout Valve (HASCO) prototype, according to Dave Girard of Girard Equipment.
The HASCO Valve resulted from the Cargo Tank Risk Management Committee’s (CTRMC) efforts to limit driver falls from the top of trailers.
“We’re looking at this from the perspective of keeping drivers safe,” Girard said. “We have a manhole protected by an overturn, as well as on certain tanks, MC-307 and DOT-407, there may be a cleanout—an opening where a tank-cleaning facility would insert equipment to clean tanks, usually for difficult-to-clean products. Drivers are obligated to make sure a load is secure. So they’ll check the manhole cover and cleanout caps. Cleanouts tend to be at the end of the catwalk, so we ask drivers to go to the end of the cleanout and make sure the cap is set. Every year, there are falls. It’s just inevitable.
“The beauty of the HASCO Valve is it keeps drivers from having to make that climb because it’s operated from the ground. Typically, a cleanout cap has a seven- to 10-inch diameter. That’s a small space to work within.”
Girard said TTMA feedback would provide a better idea of how to write a Recommended Practice.
“This would enable any manufacturer to come out with an idea like this,” he said. “I strongly encourage anyone—fleet carriers, tank facilities, shop facilities—to seek out TTMA members.”
Stainless steel in the 300 series has been the go-to material in the industry for decades, but because of its limitations, stainless steel manufacturers have developed new cost-competitive grades of stainless steel—lean duplex and duplex barrel materials—that offer advantages over 300 stainless, according to Peter Weis, chief engineer for Polar Tank Trailer .
He said austenitic steel is a typical T316/T304 material, with high toughness (fracture resistance), good weldability, good formability, higher thermal expansion, and non-magnetic properties. Ferritic steel—used in kitchen appliances and mufflers—has low toughness and limited weldability, is stress-corrosion-cracking resistant, has higher thermal conductivity, and is magnetic.
“Add the two together and you get duplex,” Weis said. “Like chocolate and peanut butter, they’re better mixed together. This is dramatic oversimplification of the material-making process but you end up with duplex class stainless steel: 2101, 2205, and other grades.”
They’re characterized by high toughness, high strength, acceptable weldability, acceptable formability, and lower thermal expansion. Lean duplex (LDX 2101) is 21% chrome and 1% nickel, while duplex (2205) is 22% chrome and 5% nickel. He said this structure can be preserved in a welded joint, with a microstructure of 50% ferrite and 50% austenite.
Weis said 2205 duplex is a “standard duplex” that emerged in the 1980s and is the most common duplex material.
“2205 duplex was used on some tankers in the 1980s for its thermal properties, but is uncommon in our industry—you’re talking handfuls of trailers,” Weis said.
Lean duplex has a lower level of nickel and molybdenum than duplex and was developed to be a competitor to T304 and T316 in cost and corrosion resistance. It’s commonly used in stationary pressure vessels, including API 650, and ASME Code products. He said several lean duplex tankers have been built under DOT Special Permit.
Weis said duplex is relevant to this industry because:
• It’s a higher strength material. “That means in some cases the trailer can be made thinner and lighter. 2101 and 2205 are about 25% stronger than T316.”
• It has increased corrosion resistance. “For increased corrosion resistance, increase chromium, increase molybdenum, and increase nitrogen. 2205 duplex is significantly more resistant to pitting than T316L—about 50%. It’s not a material you can guarantee will never pit, but it will be lot more resistant. Both duplex types are more resistant to crevice corrosion, which can occur in a poorly finished surface, a poorly penetrated weld, or entrapment of a product due to poor design.”
• It has better thermal stability. “Both types of duplex have less thermal expansion and are less likely to buckle due to heat or thermal shock, and they are less likely to warp during welding, partly due to higher strength.”
• It has a lower price. “Duplex price fluctuations differ versus T316 due to differences in composition. 2101 lean duplex can be cheaper than T316, but is not currently. 2205 duplex is more expensive than T316. During periods of fluctuating commodity prices, lean duplex can be cheaper than T316.”
He said DOT Special Permits for duplex materials allow for materials that are not otherwise authorized in the regulations. They allow these materials to be thinner due to higher strength, and they are granted to each manufacturer individually. They are necessary because some materials aren’t ASME-recognized in the 1998 A99 ASME Code. Many of these materials have been newly developed since 1998.
Weis said DOT Special Permit documents can be easily obtained with a Google search of “Polar DOT-SP 14573” or “Brenner DOT-SP 14467.”
Testing per Section 180 requirements is the same as any 400 series tank. Training is required for each “hazmat employee,” and they must be able to calibrate the thickness tester, etc. Marking must be marked on both sides with the permit number, and repair requires a qualified weld procedure, he said.
Recent disputable citations
Jack Rademacher of Brenner Tank Services provided an update on citations issued during roadside inspections by state and federal inspectors:
• Placard visibility. “It’s required to be seen from the direction it faces and kept at least three inches from anything that could affect visibility. FMCSA has interpreted that differently and says it has to be visible at 45 degrees. So basically, what’s happened in quite a number of cases is the placard on the fender is set back and you would not be able to see it at 45 degrees. The interesting thing is that in one particular case, someone put another placard holder on the other side. The interpretation from FMCSA is that, ‘No, now you have two of them.’ This is not a manufacturer’s requirement; this is a carrier’s requirement. We always recommend putting placards up front so they’re always visible at 45 degrees, roadside and curbside.”
• Bumpers. “The FMCSA bumper is a rear-end accident damage protection or a NHTSA, which is an underride guard. The NHTSA guard has to be within 22 inches of the ground. You’re allowed to have a split of up to 24 inches. A non-specification cargo tank is not required to have an FMCSA bumper. People are getting cited because there is no underride bumper. If you have no less than 12 inches from the back of the tire itself to the rear-wall structure, which is the FMCSA bumper, you are not required to have the underride bumper.”
• Certificate of compliance for a trailer. What do you do if you don’t have one? The Federal Highway Administration (FHWA) Cargo Tank Technical Advisory Committee document explains what happens if the manufacturer is no longer in business.
“If you have no way of getting a certificate of compliance, you can do inspections and make sure it meets all requirements, then make a copy of the DOT dataplate. The owner is taking ownership of this certification. You have the dataplate on the side of the trailer, which is actually a certificate that the tank was built correctly. What I have told people to do is make your own certificate of compliance. I actually take a picture of that dataplate and paste it right on the certificate, and down at the bottom, it has to be signed off by a registered inspector and by the cargo tank owner.” ♦
Find the Cargo Tank Maintenance Seminar archive with articles from 2010 to 2013