Clark Case – CSX

In 2017, a major sulfuric acid producer in the southeastern region of Brazil approached Clark Solutions to increase the reliability of its unit by improving production availability.

The interest in this change arose after maintenance shutdown studies were carried out over a one-year period, which were mapped and presented in a Pareto chart. The analyzed costs led to the search for safer alternatives.

The solution offered by Clark Solutions was the replacement of the existing cast iron piping with CSX™, a high-silicon austenitic stainless steel specially developed for use in piping for the transport of concentrated sulfuric and phosphoric acids. Developed more than 25 years ago, CSX™ offers several advantages when compared to nodular or ductile cast irons, significantly reducing failures and, consequently, production losses and maintenance costs.

The high corrosion resistance of CSX™ is mainly due to the strong affinity of chromium and silicon with oxygen. When these elements come into contact, they form very stable oxides and hydroxides that deposit along the surface, instantly forming a protective passive layer (Fig. 1).

In addition to superior corrosion resistance, this protective layer gives CSX™ another important characteristic absent in cast irons: greater resistance to erosion.

The austenitic structure allows the material to be welded, another important benefit both in piping design and maintenance.

The combination of these qualities brings a wide range of benefits to CSX™ users:

The possibility of manufacturing longer, welded piping sections reduces the number of flanged connections and, consequently, leaks, risks to personal and asset safety, as well as the weight and cost of the piping and its supports.
The higher erosion resistance makes it possible to operate with acid at much higher velocities—3 to 8 times higher than cast irons—reducing piping diameter, the inventory of retained acid, and the overall installation cost.

But it does not end there; because it is weldable, CSX™ allows for simple repairs. An eventual hole or crack can be repaired with simple welding and a short shutdown. Conventional cast iron piping requires the spool or fitting to be completely replaced, with the need for piping disassembly and cranes. The combination of qualities brings a wide range of benefits to CSX™ users: