Stainless steel pipe is the desired material for process piping systems due to ease of maintaining sanitary conditions and corrosion resistant properties. It is the material of choice for food conveying applications which require conformance to FDA requirements. A standard benefit of the stainless steel family of materials is that it covers materials of much different chemistry, permitting economical alternatives to higher end materials and providing greater corrosion resistance to a wide variety of chemical services and environments, as well as providing increased strength.
The internal pressure capabilities make stainless steel pipe suitable for use in many heavy duty applications.
Process piping fluids cover a wide range of applications from water to chemical services. For high pressure applications or highly corrosive environments, it may be necessary to utilize a duplex or super duplex stainless steel because of its high physical properties and greater corrosion resistance.
Duplex stainless steel differs from austenitic stainless steel in chemical make-up; it has higher quantities of chromium and molybdenum and lower quantities of nickel. Duplex stainless steel can be referred to as 2205, and super duplex 2507 because of the percentages of chromium and nickel in their composition. All stainless steels contain a varying percentage of chromium, molybdenum and nickel.
The most common stainless steel is austenitic, which includes the stainless steel pipes made to the specifications of ASTM A312 in Types 304/304L and 316/316L. Types 304/304L are for general corrosion applications such as process cooling water. Types 316/316L have a higher corrosion resistance to chlorides and may be desired based upon the chemical composition of the process fluid. The “L” designation means that the stainless steel contains less than 0.03% carbon. This is beneficial if the pipe needs to be welded.
Stainless steel pipe is generally available in diameters up to 36 inches with dimensions ranging from Schedule 5S to 160S with Schedule 10S being the most readily available.
The system working pressure and pipe joining method will determine the required pipe wall thickness for each application.
Stainless steel pipe may be installed using a variety of joining methods including grooved, welded, flanged, and threaded.