Finding the Mettle to Persevere
Apr 1, 1998 12:00 PM, Charles E Wilson
CARBON steel and 316 and 316L stainless steel are the most common materials used in the construction of hazardous waste transport equipment. These metals have served the industry well over the years, and they do a good job in general.
However, it's possible that hazardous waste equipment manufacturers and users are overlooking alternatives that might lead to better products with reduced life-cycle costs. These are key factors in today's very competitive hazardous waste transport marketplace.
Certainly, aluminum and fiberglass have been available for years for use in vacuum tanks and such. Some hazardous waste handlers have found that they are excellent alternatives in certain applications. They seem to be carving out their own niches.
It's other steels that are being overlooked, and these are the materials that deserve more attention. Some have been around for a number of years, while others are relatively new. The steels were discussed during Corrosion 98 March 22-27 in San Diego, California. Corrosion 98 is the annual conference of the National Association of Corrosion Engineers.
Richard R Staebler, Heil Trailer International, said that duplex stainless steel has been available for cargo tanks since the mid-1980s and holds considerable potential. Three physical characteristics make 2205 duplex superior to 316L: higher yield strength, lower coefficient of thermal expansion, and higher thermal conductivity.
The higher yield point, combined with greater corrosion resistance, offers the possibility of building vacuum and other cargo tanks with thinner shells. Safety would not be compromised, but tare weight would be lowered, offering the potential for higher payloads.
Duplex steel tanks would cost more. Staebler speculated that duplex steel tanks would be competitive if the selling price was kept within $10,000 or less of those constructed of 316 stainless steel.
One of the newest entries to the transportation industry is Cr12 stainless steels. They are being suggested as a replacement in applications that favored carbon steel in the past.
Cr12 is a new-generation ferritic stainless steel with 11% to 12% chromium. Within the transportation industry in general, Cr12 is displacing mild steels, galvanized and painted steels, abrasion resisting steels, and certain stainless grades.
This family of ferritic stainless steels has 200 to 300 times the atmospheric corrosion resistance of carbon steels. It also has higher tensile and yield strengths. Cr12 stainless steels have been designed to match the fabrication, forming, and weldability of carbon steels. The combined factors make them a cost-effective alternative in the right applications.
Cr12 is being used in coal hopper cars for the railroads and dry bulk and dump trailers. It would seem to be a material well suited to rolloff containers, vacuum loader debris boxes, and other related waste handling equipment.
It is probably important at this point to explain that we are not recommending a wholesale shift to the materials described in this editorial. These steels may fit certain hazardous waste handling applications, but more study is needed.
We do want to suggest that hazardous waste haulers need to be open to alternatives of any sort that will make their operations more efficient and cost-effective. This business has become incredibly competitive, and operators continue to fall by the wayside.
Even the mighty are falling. Allwaste Environmental Services Inc was acquired by Philip Services Corp last year, and Philip recently vied with Laidlaw Environmental Services for Safety-Kleen Corp. Laidlaw was the victor in that contest, which is detailed on page 38 of this issue of Modern Bulk Transporter.
Managers at one environmental services company say that many of their vacuum truck subcontractors have shut down. Less transport work is available, and many companies are working with rates that are at the same level as in 1991.
None of this means that the hazardous waste handling industry is going away. Despite all of the consolidation, opportunities still exist. Companies just have to be more adaptable.
Nothing can be taken for granted, including the materials used in the transport vehicles.
© 2013 Penton Media Inc.
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