Schedule 40 Vs 80 Steel Pipe: A Comprehensive Comparison And Engineering Selection Guide

In modern industrial piping systems, the choice of steel pipes affects the safety and stability of the entire project. Among them, the difference between Schedule 40 and Schedule 80 steel pipes is particularly significant. In order to help you understand the difference between the two pipes more deeply, this article will provide a comprehensive interpretation through parameter comparison, application scenarios, etc.

Core Differences

Why is wall thickness everything?

When faced with the choice between Schedule 40 steel pipe (Sch40) and Schedule 80 steel pipe (Sch80), it is actually a trade-off decision between wall thickness, pressure bearing capacity, and cost. According to the ASTM A53 standard (2 inches), the relationship between the three is analyzed in depth.
Sch40 wall thickness: 5.56mm
Sch80 wall thickness: 7.62mm
Thickness increase: 37%
The difference in wall thickness will lead to changes in the following core performance indicators:
Pressure bearing capacity: The thicker the wall thickness, the greater the pressure bearing capacity. The pressure bearing capacity of Sch80 steel pipe is greatly increased by 57% compared with Sch40. Under normal temperature working conditions, the maximum working pressure of Sch40 is 680psi, while Sch80 is as high as 1070psi.
Weight difference: The increase in wall thickness is bound to increase the weight. The weight of Sch80 is significantly higher than that of Sch40. Under the same size, Sch80 is 42% heavier than Sch40, and the cost of later installation, transportation, maintenance, etc. will be relatively high.
Material cost: As the wall thickness increases, more material is required. The material cost of Sch80 is usually 60% to 80% higher than that of Sch40.

9 indicators to quantify the basis for selection

Application scenarios: Selection logic for 7 typical working conditions

Scenarios where Sch40 is preferred

Building water supply and drainage system: When the municipal water supply pressure is 6 bar or less, the use of Sch4 can reduce costs by 15-20%, and the pressure is within the pressure range of Sch40.
Compressed air pipeline: In non-continuous air supply systems with a pressure of ≤10 bar, Sch40 pipes can also be used. Such systems usually do not need to withstand high pressure.
Steel structure support: In non-pressure scenarios such as warehouse shelves and scaffolding, Sch40 can fully cope with these scenarios and ensure the stability and safety of the structure.

Working conditions where Sch80 is mandatory

Steam transmission pipeline: The pressure in this scenario exceeds 10 bar or the temperature exceeds 150℃. The use of Sch80 steel pipes meets the requirements of ASME B31.3 standard.
Chemical corrosive media: Sch80 must be used in oil and gas pipelines containing H2S or CO2 because these media are corrosive. Sch80 has a given thickness of 2mm to resist erosion.
High-pressure hydraulic system: In the power pipeline of engineering machinery, when the working pressure reaches or exceeds 250 bar, Sch80 must be used.
Submarine pipeline outer layer: The pressure in this environment is about three times the pressure resistance of Sch40, so Sch80 must be selected to be competent.

Selection decision: 5 steps to lock in the right specifications

Confirm media properties‌: Corrosive media are automatically upgraded to Sch80
Calculate working pressure‌: Use the formula ‌P=(2ST)/(D-2YT)‌
(S=material yield strength, T=wall thickness, D=outer diameter, Y=material coefficient)
Evaluate impact risk‌: Sch80 is required for vehicle crushing/mechanical collision areas
Calculate life cycle cost‌: Sch80 installation cost increases by 25%, but maintenance cycle is extended by 40%
Verify standard compliance‌: Mandatory provisions of API 5L/ANSI B36.10

FAQs：

1.Thick-walled pipes are safer?

The risk of brittle fracture of Sch80 in low temperature environment is 30% higher than that of Sch40 (refer to Charpy impact test data)

2.Can different schedule pipe fittings be mixed?

ASME B31.3 explicitly prohibits the mixing of threaded connectors of different schedule grades

2.Is Sch80 suitable for all high-pressure scenarios?

When the medium temperature exceeds 200℃, Sch160 should be used instead of Sch80