Code checks: API RP 1111
$\newcommand{\us}{_\textrm{stress}}$ $\newcommand{\IDs}{I\!D\us}$ $\newcommand{\ODs}{O\!D\us}$ $\newcommand{\SAF}{S\!A\!F}$

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 \begin{equation} \frac{\max(T_\mathrm{e}, 0)}{0.6\,T_\mathrm{y}} \end{equation} 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 \begin{equation} \frac{\sqrt{\{(p_\mathrm{i} - p_\mathrm{o})/P_\mathrm{b}\}^2 + (T_\mathrm{e}/T_\mathrm{y})^2}}{F_\mathrm{a}} \end{equation} where \begin{equation} P_\mathrm{b} = 0.45\,(S + U) \log_e\left(\frac{\ODs}{\IDs}\right) \end{equation}

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 \begin{equation} \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} \end{equation} 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.