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How to choose SCH 40 carbon steel pipe, and what is its pressure rating? Pressure rating corresponds to size, material, and wall thickness; different ratings have different pressures. Specifications and pressure rating are crucial when selecting steel pipes.
The pressure rating represented by SCH 40 carbon steel pipe is related to different sizes and is not a uniform pressure rating. Smaller sizes and thicker walls generally have higher pressure ratings.
The following is an introduction to SCH 40 carbon steel pipe.
What Does SCH 40 Mean for Carbon Steel Pipe?
SCH 40 refers to Schedule 40, indicating the wall thickness of the carbon steel pipe, not a fixed pressure rating.
A complete carbon steel pipe specification usually includes dimensions, specifications, and wall thickness. The outer diameter is usually the nominal diameter. Wall thickness also depends on the specific specification.
Is the SCH 40 Carbon Steel Pipe Pressure Rating a Fixed Number?
No, it is not fixed.
The pressure ratings of 1-inch and 6-inch pipes are different. This is because pressure depends not only on size but also on wall thickness. Size increases, but wall thickness does not. Therefore, the pressure they can withstand will differ. Of course, for the same wall thickness, smaller sizes can withstand higher pressures.
However, when choosing SCH 40 carbon steel pipes, you must consider their size, pressure rating, operating temperature, and wall thickness.
SCH 40 Carbon Steel Pipe Pressure Rating Chart
The following is a table of SCH 40 carbon steel pipe size and pressure specifications under different environments and temperatures:
| Nominal Pipe Size | Outside Diameter | SCH 40 Wall Thickness | Approx. Pressure Rating | Approx. bar | Approx. MPa |
|---|---|---|---|---|---|
| 1/2 in | 0.840 in | 0.109 in | 5,190 psi | 358 bar | 35.8 MPa |
| 1 in | 1.315 in | 0.133 in | 4,050 psi | 279 bar | 27.9 MPa |
| 2 in | 2.375 in | 0.154 in | 2,590 psi | 179 bar | 17.9 MPa |
| 3 in | 3.500 in | 0.216 in | 2,470 psi | 170 bar | 17.0 MPa |
| 4 in | 4.500 in | 0.237 in | 2,110 psi | 145 bar | 14.5 MPa |
| 6 in | 6.625 in | 0.280 in | 1,690 psi | 117 bar | 11.7 MPa |
| 8 in | 8.625 in | 0.322 in | 1,490 psi | 103 bar | 10.3 MPa |
| 10 in | 10.750 in | 0.365 in | 1,360 psi | 94 bar | 9.4 MPa |
| 12 in | 12.750 in | 0.406 in | 1,270 psi | 88 bar | 8.8 MPa |
The data in the table above can help you make a selection.
Why Do Smaller SCH 40 Pipes Usually Have Higher Pressure Ratings?
Because pressure depends not only on size but also on wall thickness. Smaller sizes have a relatively larger wall thickness relative to the outer diameter.
Here is a simple calculation formula:
P=2×S×t/D
P: Internal pressure
S: Allowable pressure of raw material
T: Wall thickness
D: Outer diameter
Therefore, as the pipe diameter increases, the effect of wall thickness on internal pressure decreases. Therefore, 1-inch SCH40 steel pipe has a higher pressure rating than 8-inch SCH40 steel pipe.
What Factors Affect SCH 40 Carbon Steel Pipe Pressure Rating?
Here are some factors that affect the pressure rating:
| Factor | Why It Matters |
|---|---|
| Nominal pipe size | Larger diameter usually reduces allowable pressure |
| Wall thickness | Thicker wall increases pressure capacity |
| Material grade | Higher-strength steel allows higher pressure |
| Temperature | Higher temperature reduces allowable stress |
| Corrosion allowance | Internal corrosion reduces effective wall thickness |
| Seamless or welded pipe | Joint efficiency may affect design calculation |
| Design code | ASME B31.3, ASME B31.1, or project code may change allowable values |
| Fluid type | Gas, steam, water, and hazardous media require different safety considerations |
ASTM A53, ASTM A106, and API 5L: Do Standards Affect Pressure Rating?
Yes. Different standards do affect the pressure rating.
SCH 40 defines the wall thickness, but the raw materials define the chemical composition, mechanical properties, and manufacturing processes, etc., all of which affect the pressure.
ASTM A53 standard is mostly used for carbon steel pipes.
ASTM A106 standard is mostly used for seamless steel pipes used in high-temperature environments.
API 5L standard is mostly used for line pipe production.
SCH 40 vs SCH 80 vs SCH 160: How Do Pressure Ratings Compare?
SCH 160 has the thickest wall thickness, followed by SCH 80, and then SCH 40.
Of course, when choosing a pipe, you can’t just look at the wall thickness; you also need to consider the dimensions, raw materials, and manufacturing process.
How Temperature Reduces Carbon Steel Pipe Pressure Rating
The pressure rating of steel pipes is usually based on a reference temperature. As the temperature rises, the allowable stress of carbon steel decreases.
Therefore, this must be considered in some piping systems that require heat treatment.
For more detailed data, refer to ASME B31.3 Process Piping Tables.
SCH 40 Carbon Steel Pipe for General Industrial Use
SCH 40 carbon steel pipe is commonly used in some common industrial piping systems because of its good strength, usability, and weldability.
The following are some common applications:
- Water supply systems
- Cooling water piping systems
- Compressed air systems
- Fire protection systems
- Prefabricated pipe sections
- General utility piping
- Non-corrosive process fluids
One important point to note about carbon steel pipes is that their corrosion resistance is generally low. They cannot be used in highly corrosive environments.
What Should Distributors and Construction Buyers Check Before Ordering?
The dimensions, specifications, wall thickness, and raw materials need to be checked.
Here is a detailed inspection reference table:
| Procurement Item | What to Confirm |
|---|---|
| Size and schedule | NPS and SCH 40 wall thickness |
| Standard and grade | ASTM A53, ASTM A106, API 5L, or project requirement |
| Manufacturing type | Seamless, ERW, or welded |
| End finish | Plain end, beveled end, threaded end |
| Surface treatment | Black painting, anti-rust oil, galvanized, coated |
| Testing | Hydrostatic test, NDT if required |
| Documents | Mill test certificate, packing list, inspection report |
| Packing | Bundles, caps, marking, export packing |
| Delivery | Quantity, lead time, loading plan |
In addition to the above, it’s also necessary to determine if it has a coating and what the manufacturing process is.
Can Buyers Use Online SCH 40 Pressure Rating PDF Charts Directly?
Of course, this is a relatively intuitive, globally applicable data reference table. It’s essential for beginners.
However, before making specific determinations, actual calculations by an engineer are required.
After purchase, the actual product needs to be inspected upon delivery by the manufacturer.
How to Choose the Right SCH 40 Carbon Steel Pipe
The following points can be considered when selecting steel pipes:
1. Confirm the medium.
2. Confirm the design pressure and temperature.
3. Confirm the nominal pipe size and required flow rate.
4. Confirm the SCH 40 wall thickness.
5. Confirm the material standard and grade.
6. Confirm the corrosion allowance or coating.
7. Confirm the end finish and installation method.
8. Confirm the testing, marking, and documentation.
9. Confirm the delivery schedule and packaging.
10. Confirm supplier technical support.
Summary
The above is an introduction to SCH 40 carbon steel pipe. The specific pressure rating of this specification of carbon steel pipe is related to its size, wall thickness, material grade, temperature, and production standards. An engineer should confirm these data before purchasing.
