Jacinto Delgado, Schlumberger Rod Lift
Non-API rods use a Tensile/2.8, also known as T/2.8, calculation to determine the maximum loading that should be applied to a rodstring. API grades use T/4 which limits the loading that can be applied to these rods compared to their high strength counterparts. In addition, API and design software recommend that a service factor as low as 0.7 be applied to any rodstring that is operating in a corrosive environment. This forces the use of a high strength rod in many applications where an API grade would outlast it due to the higher corrosion tolerance of the API grade. When designing a rodstring, T/2.8 should be used for all rod grades with a service factor of 1.0 and the rod should be loaded to 100% allowable stress before a higher grade rod is selected. This will reduce the use of high strength rods in corrosive environments that are detrimental to high strength rods. This will prove to reduce rod failures and save the operator money by recommending a less expensive rodstring.