# Pipe Strength Calculator

(mass, buoyancy & stress)

A pipe is normally taken to mean a tube with a wall thickness greater than 1/10th of the nominal radius.

Conversely, a tube is normally taken to mean a pipe with a wall thickness less than 1/10th of the nominal radius.

Whilst the stress calculations in pipe are valid for pipe and tube (i.e. any wall thickness), it is considered acceptable to use a short-hand formula for hoop stress in tube walls (hoop stress = pressure *x* nominal radius ÷ wall thickness) and to assume that radial stress is equal to the internal pressure and constant right through the wall. This, of course, is an approximation.

All the results from the pipe strength calculator are dependent upon the pipe material remaining within Hooke's law.

## Pipe Strength Calculator - Technical Help

The pipe strength calculator provides the facility for you to calculate as many (or as few) effects as you wish. You needn't enter the input data for the effects you don't need to include. For example:

### Mass pipe (empty)

You only enter the internal and external diameters of the pipe (Øᵢ and Øₒ) along with its material density ('ρ(pipe)')

### Added Mass (effects)

In addition to the data for **Mass pipe (empty)** (above), you will also need to enter a value for the added mass (Ca see Added Drag and Fluid Forces technical help pages). If Ca is not set to zero, 'm(pipe)' will include all the external displaced fluid (Ca+1) but does not include the mass of the internal fluid

### Mass internal fluid

You only enter the internal diameter of the pipe (Øᵢ) along with the internal fluid density (ρﬂᵢ)

### Buoyancy

In addition to the data for an empty and full pipes (above) you will need the external fluid density (ρﬂₒ). This value is the balance of forces from the pipe material, the internal fluid and the external fluid (it does not include any of the added mass effects)

### Internal pressure stresses (pipe strength)

You only need to enter the internal and external diameters of the pipe (Øᵢ and Øₒ) along with the internal pressure (pᵢ(pipe))

### External pressure stresses (pipe strength)

You only need to enter the internal and external diameters of the pipe (Øᵢ and Øₒ) along with the external pressure (pₒ(pipe))

### Bending stress (pipe strength)

You only need to enter internal and external diameters of the pipe (Øᵢ and Øₒ) along with the bending moment in the pipe (M)

A longitudinal shear stress τM will be present if you also enter an internal and/or external pressure as well as a bending moment

### Linear Shear stress (pipe strength)

You only need to enter internal and external diameters of the pipe (Øᵢ and Øₒ) along with the applied lateral force (Fτ)

### Torsional Shear stress (pipe strength)

You only need to enter the internal and external diameters of the pipe (Øᵢ and Øₒ) along with torque in the pipe (T)

### Longitudinal temperature stresses (pipe strength)

You only need to enter the internal and external diameters of the pipe (Øᵢ and Øₒ) along with the temperature variation ('δṮ(pipe)') and the pipe material's thermal coefficient of linear expansion ('α(pipe)')

### Your preferred stress result location

The hoop, radial, bending, pressure-shear and torsional-shear stresses (sh, sr, sM, τp, τT and τM) calculated will be at the radius (r) you specify.

Important: The axial forces from the effects of temperature are only valid if the pipe is constrained from any axial growth, whereas those from the effects of pressure in a closed pipe are valid whether or not growth is restricted.

### Reset to Default Data

By resetting the data to default, Pipe sets all loading conditions to zero in a steel pipe in air and filled with seawater. You simply modify or add the input data according to the material of your pipe and the results you're looking for, leaving the remainder at zero.

### Further Reading

You will find further reading on this subject in reference publications^{(1, 3 & 4)}

**Go to the calculator**