﻿ Code checks: API RP 1111

# Code checks: API RP 1111

## Data

### Allowable load factor, $\boldsymbol{F_\mathrm{a}}$

Not explicitly defined in the standard, this factor represents the value chosen for the right-hand side of the inequality used in the combined load design, see API RP 1111, section 4.3.1.2, equation 8.

### Collapse factor, $\boldsymbol{F_\mathrm{c}}$

The collapse factor for use with combined bending and external pressure, see API RP 1111, section 4.3.2.2.

### Bending safety factor, $\boldsymbol{F_\mathrm{bs}}$

Not uniquely defined in the standard, this is the bending safety factor for use with combined bending and external pressure. API RP 1111, section 4.3.2.2, defines $f_1$ for installation bending and $f_2$ for in-place bending.

### Strain amplification factor, $\boldsymbol{\SAF}$

For use with combined bending and external pressure, see API RP 1111, section 4.3.2.2.

### Young's modulus, $\boldsymbol{E}$

The modulus of elasticity, used in calculating the elastic collapse pressure, $P_\mathrm{c}$, see API RP 1111, section 4.3.2.1. Even if you have specified, separately, the line type Young's modulus, you must also supply a (non-zero) value here.

### SMYS, $\boldsymbol{S}$

The material minimum yield strength, used to determine the burst pressure $P_\mathrm{b}$, yield tension $T_\mathrm{y}$, and elastic collapse pressure $P_\mathrm{c}$. See API RP 1111, section 4.3

### SMTS, $\boldsymbol{U}$

The specified minimum ultimate tensile strength of pipe, used in determining the burst pressure, $P_\mathrm{b}$, see API RP 1111, section 4.3.1.

### Ovality, $\boldsymbol{\delta}$

Used in determining the collapse reduction factor, $g$, see API RP 1111, section 4.3.2.2.

## Results

 Note: The effective tension, $T_\mathrm{e}$, is influenced by the stress loading factors or by homogeneous pipe additional bending stiffness before being used in the calculations below.

### API RP 1111 LLD (longitudinal load design)

This result represents equation 6, section 4.3.1.1, API RP 1111, rewritten as a unity check: inequality 6 in API RP 1111 is satisfied if the value reported is no greater than one. The value is $$\frac{\max(T_\mathrm{e}, 0)}{0.6\,T_\mathrm{y}}$$ where \begin{eqnarray} T_\mathrm{y} & = & SA \\ A & = & \frac{\pi}{4}\left(\ODs^2 - \IDs^2\right) \end{eqnarray}

### API RP 1111 CLD (combined load design)

Equation 8, section 4.3.1.2, API RP 1111, in the form of a unity check. Inequality 8 in API RP 1111 is satisfied if the value reported is no greater than one. It is given by $$\frac{\sqrt{\{(p_\mathrm{i} - p_\mathrm{o})/P_\mathrm{b}\}^2 + (T_\mathrm{e}/T_\mathrm{y})^2}}{F_\mathrm{a}}$$ where $$P_\mathrm{b} = 0.45\,(S + U) \log_e\left(\frac{\ODs}{\IDs}\right)$$

### API RP 1111 BEP (bending and external pressure)

This result combines inequalities 13, 14, and 15, section 4.3.2.2, API RP 1111, and casts them as a unity check. These inequalities in API RP 1111 are satisfied if the reported value is no greater than one. The result is $$\frac{F_\mathrm{bs}\SAF\epsilon}{\epsilon_\mathrm{b}g} + \frac{\max(p_\mathrm{o} - p_\mathrm{i}, 0)}{F_\mathrm{c}P_\mathrm{c}g}$$ where $\epsilon$ is the max bending strain and \begin{eqnarray} \epsilon_\mathrm{b} & = & \frac{t}{2\,\ODs} \\ g & = & \frac{1}{1 + 20\delta} \\ P_\mathrm{c} & = & \frac{P_\mathrm{y}P_\mathrm{e}}{\sqrt{P_\mathrm{y}^2 + P_\mathrm{e}^2}} \\ P_\mathrm{y} & = & 2S\left(t/\ODs\right) \\ P_\mathrm{e} & = & 2E\frac{\left(t/\ODs\right)^3}{1-\nu^2} \\ \nu & = & \href{LineTypes,StructureData.htm#PoissonRatio}{\text{Poisson ratio}} \\ t & = & \frac{\ODs - \IDs}{2} \end{eqnarray}

### API RP 1111 max combined

This combined result is calculated as the maximum value of the API RP 1111 LLD, CLD, and BEP code check results.