Optimising stainless steel design

While the need for minerals processing equipment in stainless steel is not a daily activity, there are instances when stainless steel is the optimum, if not the only, choice. Although it is relatively expensive at the outset, the return on investment in terms of performance and longevity is soon realised. Given the challenges of the global recession, it is particularly important to consider all options in stainless steel. There could be significant financial implications if an optimum selection has not been made. Although the decision behind integrating a stainless steel design is process-driven and cannot be avoided, deciding on what type of stainless steel offers quite a few choices. Necessity for stainless steel Taking thickening as an example, a stainless steel design is required when the slurry is chemically corrosive (low pH). Generally, stainless steel is used only for the wetted components as the non-wet components can be made of cheaper structural carbon steel. Basic groups There are two main categories of stainless steel for mineral processing applications, each of which has a myriad of variations within. Austenitic steel (304, 316) is the more ''traditional'' type, while duplex steel (LDX, SAF) is more ''contemporary.'' Duplex is made of two phases: austenite and ferrite. The physical properties of duplex steel are a mixture of the austenitic and ferritic grades. Generally, duplex steel offers the same or better corrosion properties than their austenitic counterparts. Also, because duplex has roughly twice the yield strength of its counterpart, less steel is required, resulting in a more cost-effective solution. In terms of chloride stress corrosion cracking (CSCC), all duplex alloys have better CSCC resistance than their 304L, 316L, or 317L austenitic counterparts. Pitting is the most common form of corrosion in SS and again duplex outperforms its counterpart in this case. However, there are some cases where the ferrite phase of duplex is targeted, so a comprehensive understanding of the process slurry is necessary. With all key purchase decisions, it is vital to work closely with your suppliers, ensure they are involved early and that fully comprehensive on-site test work is performed before any final decisions. Pre-design requisites The purchase of equipment, whether stainless steel or not, is a task that should be reviewed with a complete plant design. Considering this early in the design process can have a significant impact on the plant economics. Changes to issues, such as tank arrangements, support structures and piping can cost significantly more if not properly specified and subsequent modifications need to be made in the initial detail design. If further amendments to the size and quantity are necessary, project lead-time can be severely affected, particularly if the materials are in short supply. Other factors like site ground conditions and horizontal loads, including wind and seismicity, must also be correctly specified at an early stage. Design process The capital cost of a stainless steel design is not the only element that needs to be checked. When working with your technology provider, they should outline all the elements that will make up the total cost of a design. Elements include fabrication or the forming, machining and welding of plates. Thinner plates can take less time and cost less money. However, depending on the type of steel used, contamination is one issue that needs to be carefully monitored. Transportation is when duplex steel weighs less (as less is often required than austenitic). Another factor to consider is the selection of sheet size to optimise transport costs. If the mass of steel is high compared to the mass limitation of a standard container, then consider half height contaiSaldos - Entrega gratuita