What does the suffix 'S' in the designation '40S' indicate?

What does the suffix 'S' in the designation '40S' indicate?

• A. Stainless steel
• B. Schedule
• C. Steel
• D. Special

Answer: (A)

In pipe designations, the number shows the nominal pipe size and the trailing letter flags the material type. The suffix S is the shorthand used to indicate stainless steel, so 40S means a 40-inch nominal pipe size made of stainless steel. This matters because stainless steel has different corrosion resistance, weldability, and temperature behavior than carbon steel, so you’d verify the exact stainless grade (like 304 or 316) in the material spec. The suffix is not about schedule, nor does it imply plain steel or a nonstandard “special” designation.

In pipe designations, the number shows the nominal pipe size and the trailing letter flags the material type. The suffix S is the shorthand used to indicate stainless steel, so 40S means a 40-inch nominal pipe size made of stainless steel. This matters because stainless steel has different corrosion resistance, weldability, and temperature behavior than carbon steel, so you’d verify the exact stainless grade (like 304 or 316) in the material spec. The suffix is not about schedule, nor does it imply plain steel or a nonstandard “special” designation.