**1. What is the formula for thickness of metal pipe?**
The most common formula used to *calculate the required minimum thickness* for a pipe under internal pressure is derived from **Barlow's Formula**:
`t = (P * D) / (2 * S)`
Where:
* `t` = minimum wall thickness
* `P` = internal design pressure
* `D` = outside diameter of the pipe
* `S` = allowable stress of the pipe material
This formula is used in design and engineering to ensure the pipe can safely handle a specific pressure.
**2. What is the thickness of the wall of 30 steel pipe?**
The term "30 steel pipe" is ambiguous. If you are referring to a **Nominal Pipe Size (NPS) 30** pipe, then its wall thickness is not defined by the number "30" alone. The thickness is determined by its **schedule number** (e.g., Schedule 40, Schedule 80).
For a common NPS 30 pipe:
* **NPS 30, Schedule 40** has an approximate wall thickness of **0.312 inches** (7.92 mm).
* **NPS 30, Schedule 80** has an approximate wall thickness of **0.500 inches** (12.70 mm).
You must know the schedule to determine the exact thickness.
**3. What is the outer diameter of a pipe?**
The Outer Diameter (OD) is the measurement of the pipe's width from one outer edge to the opposite outer edge, passing directly through the center. It includes the pipe's wall on both sides. For many standard pipes, especially those covered by the ASME B36.10 and B36.19 standards, the OD is a fixed and standardized value for a given Nominal Pipe Size (NPS).
**4. Is steel pipe measured by ID or OD?**
This depends on the type of steel pipe:
* **For structural steel tubing** (e.g., used in construction, frames), it is typically specified and measured by its **Outside Diameter (OD)** and wall thickness.
* **For pressure piping** (e.g., used in plumbing, oil and gas), the standard system uses **Nominal Pipe Size (NPS)**. For NPS 12 (DN 300) and smaller, the OD is not exactly equal to the nominal size but is a standardized value. For NPS 14 (DN 350) and larger, the OD is exactly equal to the nominal size in inches.
The Inside Diameter (ID) is then a calculated value based on the OD and the wall thickness.
**5. How to calculate OD from ID and wall thickness?**
You can calculate the Outside Diameter (OD) if you know the Inside Diameter (ID) and the wall thickness (t) using this simple formula:
`OD = ID + (2 * t)`
This is because the wall thickness is added twice to the inside diameter (once on each side of the pipe) to get the full outside diameter.
