Numerous systems of rating the strength of building materials exist, from the durability of concrete to the tensile strength of steel. Determining the yield strength of a length of schedule 80 galvanized steel pipe requires information about the particular pipe in question, including its exact compositional material. Understanding what you need to know for this process and why you need to know it requires a look at the nature of pipe schedules, strength measurements and more.
The American National Standards Institute, or ANSI, allied with the International Standards Organization, or ISO, creates, maintains and distributes standards on everything from environmental management to steel pipes. ANSI divides its standards for steel pipes into charts known as schedules. These schedules provide minimum weight and wall thickness requirements for steel pipes based on the inside and outside diameter of the pipe. Schedule 80 provides information for heavy pipes formerly known as "Extra Heavy." ANSI schedules provide no information regarding yield strength.
Pipe strength is generally measured in tensile strength, or the maximum amount of weight a pipe can support before it breaks. Yield strength comprises a type of tensile strength; it denotes how much a pipe can hold before it suffers permanent deformation -- or, the maximum weight a pipe can hold before it bends. Manufacturers and engineers measure yield strength in units such as pounds per square inch (PSI), kilopounds per square inch (KSI) and megapascals (MPa). The yield strength of a pipe depends upon the material used to make the pipe.
Types of Steel
Numerous types of steel exist, including galvanized steel. Within this general heading, various materials exist because the galvanization process can assume different forms. Hot dip galvanization, for instance, occurs when a manufacturer dips a piece of steel in molten zinc. The zinc coats the steel while melting its top layer. When the zinc and steel cool, the top layer of steel forms an alloy with the zinc. Some manufacturers, however, create galvanized steel by simply binding an outer layer of zinc to a piece of steel without melting the two together. ASTM International, an organization like ANSI, provides classes for numerous types of steel in the same way ANSI provides schedules for types of pipe.
Schedule 80 Yield Strength
Yield strength on schedule 80 pipes runs a wide gamut depending upon the manufacturer and type of galvanized steel used. For instance, schedule 80 pipes produced by Wheatland Tubes exhibit a minimum yield strength of 30,000 PSI or 205 MPa, while One Steel produces schedule 80 pipes with a minimum yield strength of 250 MPa, or about 36,260 PSI. Rocky Mountain Steel Peering, meanwhile, produces schedule 80 piping with a minimum yield strength range of 35 KSI to 42 KSI, or 35,000 to 42,000 PSI. According to ASTM A653 standards, mild hot-dip galvanized steel must have a minimum yield strength of 36,300 PSI. To find the actual yield strength of your pipe, contact the manufacturer or an engineer.