1. Q: What does a "PSL 2" designation mean in API 5L pipe specifications?
A: PSL stands for Product Specification Level. PSL 1 is the basic requirement. PSL 2 imposes more stringent requirements, including tougher impact testing (Charpy), higher maximum yield and tensile strength, stricter chemistry control (e.g., lower carbon equivalent for better weldability), and additional non-destructive testing (NDT).
2. Q: What is the purpose of a Hydrostatic Test?
A: It is a non-destructive test where the pipe is filled with water and pressurized to a specified level (a percentage of its minimum yield strength) to verify its structural integrity and leak-tightness under pressure.
3. Q: What is measured by a Hardness Test (e.g., Brinell, Rockwell) on a pipe?
A: Hardness testing provides a quick, indirect measurement of the pipe's strength and wear resistance. It correlates to tensile strength and ensures the material has been heat-treated correctly. For example, Grade 4140 in a quenched and tempered condition will have a high Rockwell C hardness.
4. Q: What is an NDE Ultrasonic Test (UT) used for?
A: Ultrasonic Testing uses high-frequency sound waves to detect internal and subsurface flaws such as laminations, inclusions, or voids within the pipe wall. It is a critical quality control step for pipes used in critical service.
Category 4: Application-Specific Issues
5. Q: Why is Sulfur content a critical factor in pipes for OCTG (Oil Country Tubular Goods)?
A: High Sulfur (S) content can lead to Hydrogen-Induced Cracking (HIC) or Sulfide Stress Cracking (SSC) in the sour (H₂S-containing) environments common in oil and gas production. Standards like API 5CT for sour service have very low maximum sulfur limits.
