What pressure is schedule 40 pipe

For gas, water, air, and industrial fluid systems, the rated pressure of a Schedule 40 pipe is one of the most important factors when selecting piping. This article will introduce the pressures that a Schedule 40 pipe can withstand, the factors that determine its rated pressure, and how the pressure varies with size and operating conditions.

What Is Schedule 40 Pipe?

Schedule 40 (SCH 40) refers to a standardized pipe wall thickness defined by ASME B36.10 (carbon steel) and ASME B36.19 (stainless steel). It does not represent pressure directly, but wall thickness plays a decisive role in determining pressure capacity.They are available in seamless and welded forms, with seamless pipes preferred for higher-pressure applications.

What Is the Pressure Rating of Schedule 40 Pipe?

The rated pressure of a Schedule 40 pipe is not a fixed value; it depends on four key engineering factors:

1. Pipe Size

Pipe size is the most important factor. Smaller pipes can withstand higher pressures, while larger pipes have lower rated pressures. For example:

A 1/2-inch Schedule 40 black pipe can withstand nearly 3000 PSI of pressure.
An 8-inch Schedule 40 black pipe can withstand approximately 700 PSI of pressure.
This difference arises because the rate of increase in wall thickness is much lower than the rate of increase in diameter.

2. Wall Thickness (Pipe Diameter Rating)

Pressure values shown below are calculated based on ASME design codes and typical allowable stress values for ASTM carbon steel pipes at ambient temperature.Pressure rating is typically calculated using the Barlow Formula:

P = (2 × S × t) / (D − t)

Where:

P = Working pressure;

S = Permissible stress of the pipe (Psi), e.g., S = 12,000–20,000 psi for ASTM A53 Grade B;
t = Wall thickness (in);
D = Outer diameter (in);

As wall thickness t increases, pressure P increases linearly;
With a constant outer diameter D, a thicker wall results in higher pressure resistance.

3. Material Grade

Pressure rating also depends on the grade of carbon steel and the manufacturing standard.

Common standards:

ASTM A53 Grade A/B
ASTM A106 Grade B

ASTM A500 Grade B/C

Higher steel grades generally offer better pressure resistance.

4. Operating Temperature

Temperature affects tensile strength; higher temperatures result in lower pressure resistance. For example, at 400°F (204°C), the pressure rating may decrease by 20% to 40%. Therefore, calculations must be performed based on actual temperature conditions.

Schedule 40 Pipe Pressure Rating Chart (PSI by Size)

Calculated based on ASME B31.3 allowable stress values：

Size (in)	Outside Diameter (in)	Wall Thickness (in)	Inside Diameter (in)	Schedule	Temperature (oF)
					100	200	300	400	500	600	650	700
					Allowable Stress (psi)
					20000	20000	20000	20000	18900	17300	17000	16500
1/2	0.840	0.109	0.622	40	4995	4995	4995	4995	4721	4321	4246	4121
3/4	1.050	0.113	0.824	40	4074	4074	4074	4074	3849	3524	3463	3361
1	1.315	0.133	1.049	40	3810	3810	3810	3810	3600	3295	3238	3143
1 1/4	1.660	0.14	1.38	40	3137	3137	3137	3137	2964	2714	2666	2588
1 1/2	1.900	0.145	1.61	40	2822	2822	2822	2822	2667	2441	2399	2328
2	2.375	0.154	2.067	40	2377	2377	2377	2377	2247	2056	2021	1961
2 1/2	2.875	0.203	2.469	40	2600	2600	2600	2600	2457	2249	2210	2145
3	3.500	0.216	3.068	40	2258	2258	2258	2258	2133	1953	1919	1862
3 1/2	4.000	0.226	3.548	40	2059	2059	2059	2059	1946	1781	1750	1699
4	4.500	0.237	4.026	40	1914	1914	1914	1914	1809	1656	1627	1579
5	5.563	0.258	5.047	40	1678	1678	1678	1678	1585	1451	1426	1384
6	6.625	0.28	6.065	40	1524	1524	1524	1524	1441	1319	1296	1258
8	8.625	0.322	7.981	40	1342	1342	1342	1342	1268	1161	1140	1107
10	10.75	0.365	10.02	40	1217	1217	1217	1217	1150	1053	1035	1004
12	12.75	0.406	11.938	40	1140	1140	1140	1140	1077	986	969	940
14	14.00	0.438	13.124	40	1120	1120	1120	1120	1058	968	952	924
16	16.00	0.5	15	40	1118	1118	1118	1118	1057	967	950	923
18	18.00	0.562	16.876	40	1117	1117	1117	1117	1056	966	950	922

Schedule 40 vs Schedule 80 Pipe Pressure Comparison

Item	Schedule 40	Schedule 80
Wall Thickness	Medium	Thick
Pressure Capacity	Medium	High
Weight	Lighter	Heavier
Cost	Lower	Higher
Typical Applications	Water, oil, gas, construction	High-pressure, high-temperature systems

Schedule 40 pipes are ideal for most medium-pressure systems, while Schedule 80 pipes are preferred when higher pressure or safety margins are required.

How to Select a Schedule 40 Pipe Based on Pressure

When selecting a Schedule 40 pipe, consider the following factors:

System Required Pressure: Gas pipelines, compressed air pipelines, and fire suppression systems have different pressure requirements.
Safety Factor: Industrial designs typically use a safety factor of 1.5 to 2.0.
Temperature of the Transported Medium: Higher temperatures require lower rated pressures.

Pipe Diameter: Smaller nominal diameters (NPS) can withstand higher pressure ratings (PSI).

Frequently Asked Questions About Schedule 40 Pipe Pressure（FAQ）

Is Schedule 40 pipe suitable for high-pressure applications?
Q: Schedule 40 pipe is suitable for medium-pressure applications. For high-pressure systems, Schedule 80 or thicker-wall pipes are recommended.

Does Schedule 40 pipe pressure rating vary by size?
Q: Yes. Larger pipe diameters generally have lower allowable pressure under the same schedule and material conditions.

Is Schedule 40 pipe pressure rating the same for all materials?
Q: No. Carbon steel, stainless steel, and alloy steel pipes all have different allowable stress values, which directly affect pressure rating.

Summary

The rated pressure of SCH40 piping varies depending on pipe size, material grade, and operating temperature. Typically, depending on pipe diameter and temperature, the reliable operating pressure of SCH40 piping can exceed 5000 psi. In practical applications, operating temperature, media characteristics, and safety regulations must be considered. It is recommended that pressure verification be performed according to ASME B31.3 and a material measurement report be provided during the project design phase.

Read more：Schedule 80 steel pipe pressure rating