An inservice process pipe should be classified as Class 1 when the % of H2S exceeds:

An inservice process pipe should be classified as Class 1 when the % of H2S exceeds:

• A. 1%.
• B. 2%.
• C. 5%.
• D. 3%.

Answer: (D)

H2S concentration in sour service drives how strictly piping is regulated. When hydrogen sulfide is present at more than three percent by volume, the environment is considered high risk for sour-related corrosion and sulfide stress cracking, so the piping is designated Class 1. This classification triggers more stringent design, materials selection, fabrication controls, corrosion allowances, and inspection/maintenance requirements to maintain integrity in a harsher environment. The boundary is three percent; any amount above that qualifies for Class 1. Lower values do not meet the threshold, while much higher levels still fall under Class 1, but the point used to decide the classification is the three-percent limit.

H2S concentration in sour service drives how strictly piping is regulated. When hydrogen sulfide is present at more than three percent by volume, the environment is considered high risk for sour-related corrosion and sulfide stress cracking, so the piping is designated Class 1. This classification triggers more stringent design, materials selection, fabrication controls, corrosion allowances, and inspection/maintenance requirements to maintain integrity in a harsher environment. The boundary is three percent; any amount above that qualifies for Class 1. Lower values do not meet the threshold, while much higher levels still fall under Class 1, but the point used to decide the classification is the three-percent limit.