Schedule 40 vs Schedule 80 Steel Pipe

What is a Pipe Schedule?

A pipe schedule (SCH) is a measure of a steel pipe’s nominal wall thickness.

In the past, metal fabricators used three pipe dimensions — standard, extra strong, and double extra strong. Just having these three undetermined dimensions wasn’t helpful, though. So today, there are currently about 10 standardized SCH grades for steel pipes (such as SCH 5S, 10S, 10, 40, 80, 120, 160, XXS, etc.). While there may be more on the list, many are not commonly used (such as SCH 20, 30, 60, 100, 140). They are not suitable for all pipe diameters. The most commonly used in engineering selections are schedule 40 and schedule 80.

Numbers with the suffix "S," such as 10S and 40S, are specifically used for stainless steel pipe standards (ANSI B36.19). For small-diameter pipes, their wall thickness may be the same as that of carbon steel pipes with the same number (ANSI B36.10); however, for large-diameter pipes, the wall thickness is usually thinner to optimize material usage and economy. STD and XS are older designations, now generally equivalent to SCH 40 and SCH 80 in standards, respectively.

What is Schedule 40?

Schedule 40 (SCH 40) steel pipe is a type of pipeline specification, which represents the wall thickness and pressure-bearing capacity of the pipeline. 

The wall thickness of SCH 40 pipe is: 40×1/1000=0.040 inches=1.016 mm.

According to the American pipeline standard ANSI/ASME B36.10M, the specific specifications of SCH 40 steel pipe are:
Outside diameter: 1/8 inch ~ 30 inches, wide range, covering various pipeline applications.
Wall thickness: 0.040 inches, approximately 1.016 mm.
Nominal diameter ratio: 0.85 (D/t).
The minimum yield strength specified by the standard: 35000PSI or 240Mpa.

Standard working pressure: up to 700PSI, about 48.3Bar.

What is Schedule 80?

Schedule 80 (SCH 80) steel pipe is also a type of pipe specification, which represents a thicker wall thickness and higher pressure-bearing capacity of the pipe.
The wall thickness of SCH 80 pipe is 80×1/1000=0.080 inches=2.032 mm, which is twice as thick as that of SCH 40.

According to the American pipeline standard ANSI/ASME B36.10M, the specific specifications of SCH 80 steel pipe are:
Outer diameter: 1/8 inch ~ 30 inches, the range is the same as SCH40, but also wider.
Wall thickness: 0.080 inches, about 2.032 mm, 2 times that of SCH40.
Nominal diameter ratio: 0.43 (D/t).
The minimum yield strength specified by the standard: 35000PSI or 240Mpa, the same as SCH 40.
Standard working pressure: up to 3000PSI, about 207Bar, much higher than SCH 40.

Schedule 40 vs Schedule 80 Pipe:

1. Wall Thickness - Schedule 80 pipes have a thicker wall than Schedule 40 pipes for the same NPS. The increased wall thickness makes Schedule 80 pipes more robust and able to handle higher pressure and heavier loads.
2. Weight - Schedule 40 pipe weight depends on its length and material composition, but it is less than Schedule 80 pipe weight due to the thinner wall.
3. Pressure Rating - Due to its comparatively thinner wall, Schedule 40 pipe has a lower pressure rating than Schedule 80 pipe.
4. Schedule 80 pipes can withstand higher pressure and are commonly used in heavy-duty applications.

5. Cost - When it comes to cost, Schedule 40 plumbing parts are typically more affordable than those made with Schedule 80. The reason behind the price difference is that Sch 80 has a thicker sidewall than Sch 40, which requires more material to manufacture. Additionally, Sch 80 pipes often come with colorant added, which also increases production costs.

Schedule 40 vs. Schedule 80: How to Choose?

1) Scenarios for Choosing Schedule 40 (SCH 40)

SCH 40 is an economical standard choice when your project meets the following characteristics:
1. Low-pressure fluid transport: chilled/hot water supply, drainage systems, low-pressure compressed air piping (typically < 1.6 MPa) within buildings.
2. General structural applications: guardrails, equipment supports, building framing.
3. Ventilation and Air Conditioning (HVAC): ventilation ducts, HVAC condensate drainage.
4. Budget-sensitive or temporary works: projects where cost is a primary consideration, or projects requiring only short-term use.

2) Scenarios for Choosing Schedule 80 (SCH 80)

SCH 80 is an essential choice to ensure safety and durability when your project involves the following demanding conditions:
1. Medium to high pressure systems: Oil and gas pipelines, plant process piping, boiler feedwater, high-pressure steam systems.
2. Corrosive or highly abrasive environments: Transporting chemical media, slurries, or operating in highly abrasive environments (such as mines).
3. High safety requirements: Compressed air trunk lines, fire sprinkler system main pipelines, and applications requiring a higher safety factor.
4. High mechanical stress environments: Applications susceptible to external impacts, vibrations, or requiring higher structural strength.
5. High-pressure applications with threaded connections: In high-pressure systems requiring threaded connections, the thicker wall of SCH 80 ensures thread strength and safety margin.

Conclusion: 

In low-pressure, non-corrosive, cost-effective, dry, or mild indoor environments, SCH 40 offers the best value for money. In applications involving high pressure, high temperature, corrosiveness, high wear, or where stringent requirements for safety and lifespan exist, SCH 80 is a more reliable and safer long-lasting option.

Read more: Carbon Steel Pipe Material and Classification or ANSI/ASME B36.10 & B36.19 Steel Pipe Dimensions