Chemical industry
Alloys like chromium ( Cr ), nickel ( Ni ), molybdenum ( Mo ), manganese ( Mn ), and silicon ( Si ), stainless steel can attain higher degrees of corrosion resistance , durability , high temperature and pressure tolerance , and versatility .
However , the testing and inspection conditions are unlikely to meet the same requirements as the working conditions ; international and domestic valve test standards are close to room temperature conditions , and gas or water are used for testing . This is one of the most fundamental pitfalls of factory testing , as harsh conditions may arise in the client ’ s working environment due to material selection , casting quality , sealing damage , and other issues , in addition to accidents .
Stainless steel valves
Valve bodies of stainless steel are manufactured by casting and forging . Investment cast products are corrosion- and heat-resistant but suffer from low formability , low strength , and brittleness . Investment casting is only suitable for geometrically complex shapes . Forged valves are more durable and have a high degree of dimensional accuracy with uniform wall thickness , a longer lifecycle and can be used in a wider range of applications . Cost , quality , and the area of application should be considered for forged valves . Their most desirable properties are high strength , durability , heat and corrosion resistance . Clear rules and regulations should be established to standardise suitable working temperatures for the valve body material . Additionally , from the technical , production management , and procurement aspects , steel grades should be chosen based on performance to ensure they withstand high pressure and fluid flow rates to increase the valve ’ s lifespan and reliability . Industries need not be worried about rust or corrosion . For this reason , stainless steel valves have become the top choice for most industrial applications where other metals are susceptible to corrosion .
Characteristics of stainless valves
Grade 304 is the most common and widely used valve material in the 300 series as it has excellent resistance to corrosion in most applications . Grade 316 is more resistant to sulfuric acid and sulfurous acids , acetic acid , iodides , bromides , chlorides , and fatty acids at higher temperatures and has good resistance to pitting corrosion . The most commonly used steel grades in the austenitic family for stainless steel valves are 304 , 304L , 316 , and 316L . Moreover , 304 is especially suited for high-temperature applications such as forging , stamping , and bending without hardening in heat treatment . It is non-magnetic and is safe to work with up to temperatures of 196 - 800 ° C . As a low-carbon stainless steel , 304L ’ s corrosion resistance is similar to that of 304 under normal conditions , but it has excellent resistance to intergranular corrosion after welding or stress relief . After that , it can operate in the same range of temperatures . Grade 316 stainless steel has excellent pitting corrosion resistance , atmospheric corrosion resistance and high-temperature strength . It can be used in very severe conditions because of the addition of molybdenum , making it suitable for use in seawater . 316L stainless steel ( low carbon ) has excellent resistance to intergranular and grain-boundary corrosion and has the same characteristics as 316 steel . Chemical valve selection requires special consideration of the scientific nature of the valve material . Usually , there is a misunderstanding that stainless steel is a ‘ universal material ,’ regardless of the media and environmental conditions present .
Conclusion
As mechanical devices , valves are fitted in pipelines in chemical and other industries to control the movement and flow of liquids , fluids , powders , and gases . Generally , stainless steel valves have various applications due to their excellent performance in terms of temperature limits , corrosion resistance , and high-pressure tolerance . Considering the total cost of stainless steel for valves , it is the most cost-efficient material in terms of lifecycle cost as well as the direct and indirect costs of replacements , maintenance , and performance .
44 Valve World February 2024 www . valve-world . net