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Carbon Steel Pipe Schedule: ش 40 vs Sch 80 سمك الحائط
Carbon Steel Pipe Schedule: ش 40 vs Sch 80 سمك الحائط
Steel pipe “جدول” (ش 40, ش 80, ش 160) defines the wall thickness for a given nominal diameter, and it is one of the most frequently mis-specified parameters in piping. This guide explains what the numbers mean, how Sch 40 compares to Sch 80, and how to choose the right schedule for pressure service.
What Schedule Means
Schedule is a dimensionless number that determines wall thickness. For a given nominal pipe size (مصادر القدرة النووية), higher schedule means thicker wall and smaller inside diameter. ش 40 is the standard wall for general plumbing, HVAC and low-pressure process piping. ش 80 has roughly twice the wall thickness, used for higher pressure or corrosive service. ش 160 is the extra-heavy wall for very high pressure. The outside diameter stays the same across schedules — only the inside diameter changes. انظر لدينا Q345D seamless pipe.
| مصادر القدرة النووية | ش 40 حائط (مم) | ش 80 حائط (مم) | ش 160 حائط (مم) |
|---|---|---|---|
| 1/2″ | 3.91 | 5.54 | 7.47 |
| 1″ | 4.55 | 6.35 | 8.38 |
| 2″ | 5.54 | 7.62 | 11.07 |
| 4″ | 6.02 | 9.53 | 13.49 |
| 6″ | 7.11 | 10.97 | 14.27 |
Why Wall Thickness Matters
Thicker wall handles higher internal pressure. For a given material, pressure rating scales with wall thickness divided by outside diameter. ش 80 pipe handles roughly 1.5× the pressure of Sch 40 at the same size. The trade-off is that thicker wall reduces inside diameter, which reduces flow capacity — a 2″ ش 80 pipe has about 15 % less internal flow area than a 2″ ش 40. For gravity flow or low-pressure water, ش 40 is sufficient; for steam, high-pressure oil or gas, ش 80 or higher is required by code.
Buying Advice
Never specify “1 أنبوب بوصة” without the schedule — suppliers default to Sch 40, which may not meet your pressure rating. For structural pipe (الدرابزين, مشاركات السياج), ش 40 or even STD is fine because pressure is not a concern. For process piping, always run the pressure calculation per ASME B31.3 and specify the schedule accordingly. Also note that “يضخ” و “أنبوب” are different: pipe is specified by nominal diameter and schedule, while tube is specified by exact outside diameter and wall thickness.
