Pressure Rating Chart for ERW Steel Pipes

Pressure rating chart for ERW (Electric Resistance Welded) steel pipes are commonly used to estimate the internal pressure that a pipe can withstand, based on factors such as pipe diameter, outer diameter, wall thickness, wall thickness schedule, and material strength.

For steel pipes of the same material and nominal diameter, a greater wall thickness generally results in a higher resistance to internal pressure. This is why, for a given nominal size, a Schedule 80 pipe typically has a higher pressure-bearing capacity than a Schedule 40 pipe.

The pressure-bearing capacity of a steel pipe is generally related to its wall thickness and diameter through the thin-walled pressure vessel formula, for example:

P ≈ 2St / D

Where:

P = Internal pressure-bearing capacity
S = Allowable stress of the pipe material
t = Nominal wall thickness

D = Outer diameter

The maximum operating pressure for A53 steel pipe at 400°F is calculated using the Barlow formula. This applies to A53 Grade B welded steel pipe, which has a yield strength of 35,000 psi and a design factor of 0.7.
The allowable stress used in the Barlow formula is calculated as follows:

(35,000 psi) × 0.7 = 24,500 psi

Dimensions—pipe outside diameter (OD) and wall thickness—comply with the ANSI B36.10 standard.

ASTM A53 Grade B Carbon Steel Pipe: Relationship Between Allowable Pressure, Wall Thickness, and Pipe Dimensions

ASTM A53 B Carbon Steel Pipes - Allowable Pressure vs. Schedule and Size
NPS (in)	Outside Diameter (in)	Maximum Allowable Pressure (psi)
		Schedule
		10	20	30	STD	40	60	XS	80	100	120	140	160	XXS
1/4	0.54				7985	7985		10798	10798
3/8	0.675				6606	6606		9147	9147
1/2	0.84				6358	6358		8575	8575				10908	17150
3/4	1.05				5273	5273		7187	7187				10220	14373
1	1.315				4956	4956		6670	6670				9316	13340
1 1/4	1.66				4133	4133		5638	5638				7380	11276
1 1/2	1.9				3739	3739		5158	5158				7247	10316
2	2.375				3177	3177		4498	4498				7097	8995
2 1/2	2.875				3460	3460		4704	4704				6391	9408
3	3.5				3024	3024		4200	4200				6132	8400
3 1/2	4				2769	2769		3896	3896
4	4.5				2581	2581		3670	3670		4769		5782	7339
5	5.563				2273	2273		3303	3303		4404		5505	6606
6	6.625				2071	2071		3195	3195		4157		5318	6390
8	8.625		1420	1574	1829	1829	2307	2841	2841	3375	4085	4613	5147	4971
10	10.75		1140	1399	1664	1664	2279	2279	2708	3277	3847	4558	5128	4558
12	12.75		961	1268	1441	1560	2160	1922	2644	3244	3843	4324	5042	3843
14	14	875	1092	1313	1313	1533	2079	1750	2625	3283	3829	4375	4921
16	16	766	956	1148	1148	1531	2009	1531	2585	3157	3733	4404	4882
18	18	681	849	1192	1021	1530	2042	1361	2553	3147	3743	4252	4848
20	20	613	919	1225	919	1455	1989	1225	2526	3138	3675	4288	4824
22	22	557	835	1114	835		1949	1114	2506	3063	3619	4176	4733
24	24	510	766	1147	766	1405	1978	1021	2489	3126	3700	4210	4786
30	30	510	817	1021	613			817
32	32	478	766	957	574	1054
34	34	450	721	901	540	992
36	36	425	681	851	510	1021
42	42		583	729	438	875

1 inch = 25.4 mm
1 psi (lb/in²) = 6,894.8 Pa (N/m²) = 6.895 × 10⁻² bar

What factors influence the pressure rating of ERW steel pipe?

The pressure rating of ERW steel pipe is not determined solely by the manufacturing process; rather, the allowable operating pressure is established by considering several factors:

1. Pipe Diameter and Outside Diameter (OD)
Given the same wall thickness and material, a larger outside diameter generally results in a lower pressure-bearing capacity, as internal pressure generates greater hoop stress (circumferential stress) within the pipe wall.

For example, a 2-inch pipe and an 8-inch pipe made from the same A53 Grade B material—even if they share the same wall thickness specification—cannot simply be assigned the same pressure rating.

2. Wall Thickness
Wall thickness is one of the most critical factors affecting the pressure-bearing capacity of ERW steel pipe.

A greater wall thickness provides more metal, which more effectively resists the hoop stress generated by internal pressure. Therefore, given the same nominal pipe size (NPS) and material:

NPS 80 > NPS 40 > NPS 10

3. Material Grade
The material grade determines the mechanical property parameters used in pressure calculations.

For example, the ASTM A53 standard covers Electric Resistance Welded (ERW) steel pipe in Grades A and B. Grade B has higher specified tensile and yield strengths than Grade A; thus, material properties are a critical factor in calculating pressure-bearing capacity.

4. Operating Temperature
As the operating temperature increases, the pressure-bearing capacity may decrease, because the allowable stress of the material often declines at higher temperatures.

5. Corrosion Allowance
If internal or external corrosion is expected over the service life of the pipeline, the remaining wall thickness must be accounted for during the design phase. Consequently, for a new pipe with a nominal wall thickness of 6 mm, one should not assume that it will maintain its full 6 mm thickness throughout its entire service life.

6. Pipe Connections and Fittings
While the pipe itself may possess a certain pressure-bearing capacity, the allowable pressure for the entire piping system may be lower due to the presence of fittings, flanges, valves, threaded connections, welded joints, or other components.

Therefore, the pressure rating of a system is determined by its weakest component—the component with the lowest pressure-bearing capacity—rather than by the pipe alone.

FAQ About Pressure Rating Chart for ERW Steel Pipes

1. What is the pressure rating of ERW steel pipe?

There is no single, universal pressure rating for ERW steel pipe. Its pressure-bearing capacity depends on factors such as pipe diameter, wall thickness, material grade, operating temperature, corrosion allowance, and specific design requirements.

2. How is the pressure-bearing capacity of ERW pipe calculated?

A simplified relationship for thin-walled pipes is:

P ≈ 2St/D

Where P is pressure, S is allowable stress, t is wall thickness, and D is the outer diameter. For actual piping systems, one should follow the applicable design codes and design conditions, rather than relying solely on this simplified formula.

3. Is ERW steel pipe suitable for high-pressure applications?

ERW (Electric Resistance Welded) steel pipes can be used in pressure-bearing applications, provided that the selected specifications, steel grades, wall thicknesses, manufacturing quality, inspection criteria, and design conditions all meet project requirements. For instance, ASTM A53 Type E ERW steel pipes are specifically designed for pressure-bearing service and can be used to transport media such as steam, water, gas, and air.

Conclusion

Pressure rating tables for ERW steel pipes serve as an essential reference for understanding how pipe diameter, wall thickness, material grade, and operating conditions influence pressure-bearing capacity. These tables facilitate the comparison of steel pipes across different schedules and sizes. However, the values provided in general-purpose tables should not be taken directly as the final working pressure ratings. In engineering practice, the maximum allowable pressure must be verified by accounting for applicable design codes, material properties, operating temperatures, corrosion allowances, and the specific requirements of the entire piping system.