When it comes to gas road tankers, every extra ounce of weight can make a difference in terms of fuel consumption and payload capacity. The lighter the tanker, the more it can carry at lesser expense. For producers of transport vessels, the stainless grade chosen for the cylindrical tank thus merits careful consideration.
When Italian industrial vehicle specialist OMSP Macola chose Outokumpu Forta as the new material for their road tankers in 2010, they were positively surprised by the significant weight savings they gained. The improved tankers weighted 30% less than tankers fabricated from conventional steels.
Setting new standards
A lightweight design is particularly desirable with road tankers, as a lower tank weight translates into tangible cost benefits.
The chosen grade, Outokumpu Forta LDX 2101, is a lean duplex stainless steel grade that combines lightweight construction with high mechanical strength and excellent corrosion resistance. Carbon dioxide is typically transported as a liquid at elevated pressure in specially designed road tankers. Under codes for the transport of dangerous goods at the time of building, duplex grades could only be utilized in pressurized tanks. OMSP thus investigated the option of manufacturing the inner hull of its road tankers’ double hull from Forta LDX 2101.
Wider than the rest
At the time of the building there was no existing standard for Forta LDX 2101 in road tanker application, a Particular Material Appraisal (PMA) was required. After extensive microstructural and mechanical testing, the Italian Register of Shipping (RINA) approved the use of Forta LDX 2101 under IMO 8.
The secret to the 30% weight saving is the high internal pressure of the tanker, which enables full capitalization of the high strength of the stainless grade. Another special benefit from Outokumpu product is the greater width. With two-meter-wide coils supplied from Outokumpu Avesta in Sweden and 72 inch coils from Outokumpu Calvert, Alabama, US, the greater width reduces the number of welds, leading to cost savings in manufacturing. Welds are also the weakest points in a stainless structure; a wider coil thus reduces structural risks.