which is the most frequently used test method for conducting SSC Test?

[zebmahar]

Hello everyone

NACE MR 0175 is the standard for the materials resistive to Sulfide Stress Cracking in H2S environment and for conducting SSC test there are many methods like proof ring type, four point bend type and four point deflection type methods. I would be really glade if some tell me which is the most frequently used method for conducting SSC test.

Kind Regards
Zebmahar

 

[unclesyd]

i don't think there is any test that can be said to cover all the bases. The type test to perform is usually determined by the end use and potential for SCC. As you stated Cracking by H2S is a given and is covered by certain type testing, again depending on the end use. Other test are recommended for testing for SCC caused by Chlorides, while others are for Caustic and Ammonia, etc. Who ever does the testing has to determine the appropriate test for the material and environment it will see. as far as the Petroleum Industry is concerned most testing labs have a very good handle on the requirements, while a chemical plant presents a whole new picture.

An example is for us, a large chemical plant, we we use bench scale testing to find a material that is suitable for the process. Once a material is determine we will run U-bend tests at various temperatures. At the same time we normally run heat-flux tests at the higher process temperature for corrosion and cracking on the test coupon. All these tests can only increase your confidence level but at time in-service cracking can still occur.

 

[redpicker]

In my experience, the Method A test is the most widely used, but the Medhod D test is gaining popularity. This experience is mainly with low-alloy steel tube. For other materials and product forms, other test methods may be more popular, I don't know.

Keep in mind, though, the test method says nothing about what test reuslts are needed for any particular service. There are test parameters and results that can mean that mean under one set of conditions, the material will pass while another set of conditions, the material will fail, even for the same test. The test method, test parameters, and results all need to be carefully evaluated when deciding on how to qualify a material for a specific application.

rp

 

[TVP]

My experience is similar to redpicker, Method A and Method D from NACE Standard TM0177-2005 are very common for evaluating low alloy steel tubes. Bent beam is sometimes used for evaluating materials used for flat springs, belleville springs/washers, etc.