Slow Strain Rate Testing
Slow Strain Rate Test (SSRT) method for Screening Corrosion Resistant Alloys (CRAs) such as material grade SM2535-110 for stress corrosion cracking in sour oilfield service and in accordance with API 5CT Specification and also NACE Specification TM0198-2004; that the Slow Strain Rate Testing of these materials is supported by Decundi Inspection Services. Slow Strain Rate Testing of these materials is carried out at Accredited Laboratories. The narrative below is a truncated overview regarding some of the parameters associated with Slow Strain Rate Testing of materials which are witnessed by Decundi inspectors.
Decundi Inspection Service has several inspectors who are highly trained and experienced and are fully capable of carrying out witness inspection during SSRT of materials referenced herein. Slow Strain Rate Testing of material grade SM2535-110 for stress corrosion cracking in sour oilfield service is generally carried out where the number of tests is noted to be three (3); one (1) test in an Inert environment and two (2) tests in a Hostile environment in special circumstances and as may be required by clients to crosscheck between a certain type of Hostile environments; that a fourth (4th) Slow Strain Rate Test is carried out by adding a concentrated amount of Elemental Sulfur to the mixing solution which is added directly to the containment vessels.
Decundi inspection personnel witnessing the Slow Strain Rate Testing of materials carry out inspections for dimensional inspection and etching of the SSRT specimens (material grade SM2535-110) prior to placement of the specimens in the containment vessels where testing of these materials is carried out.
In addition, the scope of inspection activities includes inspection for the current calibration of the measuring scales and witnessing the weighing (in grams) of the Reagents used for the Mixing Solution where these Reagents are noted to be Deionized Water (H2O), Salt (NaCL), Sodium Acetate (NaCH3COO) and Hydrochloric Acid (HCI) and are added in grams as per scope. As stated above that, in special cases, Elemental Sulfur is added for Hostile environment testing.
Decundi inspection personnel witnessing the SSRT of materials also carry out inspections for mixing of the solution where a 3-part pH buffer solution consisting of 4 pH, 7 pH, and 10 pH is generally used, following which, Deaeration of the solution is carried out using an inert gas.
Determining the Nature of Failure
After the completion of these tests, Decundi inspection personnel carry out inspections for the nature of the failure of the SSRT specimen as to whether the nature of the failure is at the middle of the SSRT specimen or at the threads and also for the duration that the SSRT specimen took to fail. After Slow Strain Rate Testing, a detailed inspection report is always provided by the inspector. Not pictured, Decundi inspection personnel also carry out witness testing for Tensile testing of materials in the transverse and longitudinal direction, Charpy Impact Testing (CVN), and Hydrogen Induced Cracking (H.I.C.) test of materials at Accredited Laboratories.
