# Safety Analysis and Emergency Response of Suspended Oil and Gas Pipelines Triggered by Natural Disasters

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

^{3}. The internal pressure is 4 MPa. The pipe is produced by API X52 pipeline steel. This pipeline steel is always applied in low-medium pressure transport of oil and gas. Figure 2 shows the nonlinear relationship between the stress and strain of the pipeline steel. The yield strength σ

_{y}is 375 MPa, and the other mechanical parameters are shown in Table 1.

## 3. FEM Analysis Results

#### 3.1. The Effects of Suspended Lengths

#### 3.2. The Effects of D/t

#### 3.3. The Effects of Operating Pressure

_{max}is obtained as 15 MPa when the design factor is equal to the maximum (0.72).

#### 3.4. The Effects of the Fluid Gravity

## 4. Emergency Response to Suspended Pipelines Caused by Natural Disasters

#### 4.1. Emergency Decision Criteria

_{a}is obtained:

_{a}is the axial normal stress, MPa; A is the metal area of the nominal pipeline cross-section, mm

^{2}; D is the diameter of the pipeline, mm; F

_{a}is the axial force, N; and i is the component stress intensification. For a straight pipeline, i = 1.0. M is the bending moment across the nominal pipe cross-section due to weight or seismic inertia loading, N m; P is the pressure, MPa; and t is the thickness of the pipeline, mm. The bending moment M of a suspended pipeline is calculated:

_{a}= 0), the maximum allowable suspended length can be obtained.

#### 4.2. Emergency Levels and Treatment Measures

## 5. Conclusions

- (1)
- The finite element results show that the case pipeline with 320 m suspended length is in a high-risk status with a 447 MPa equivalent stress and 1.8% total strain at the critical locations.
- (2)
- The stress, strain, and deflection are symmetrical along the perpendicular bisector of the pipeline. Both the maximum stress and strain appear at the ends of the suspended section, which are defined as critical locations, and the safety of suspended pipelines depends on the locations.
- (3)
- The factors of suspended length, the ratio of diameter to thickness, the internal pressure, and the fluid inside the pipe influence the safety of suspended pipelines. The pipeline stress, strain, and deflection increase with increasing these factors. The suspended length is the most critical factor for the safety of the suspended pipeline.
- (4)
- The irreversible plastic strain occur if the suspended length exceeds 50 m and becomes dominant when the length exceeds 150 m, and the total strain reaches 2% when the suspended length is 340 m.
- (5)
- An emergency plan with four emergency levels based on plastic strain and suspended length is developed to deal with different suspended pipelines caused by natural disasters.
- (6)
- This study only considers the X52 steel, and thus, other steels such as x70 and x80 may be considered in the future. Additionally, the coupling effects of different natural disasters and hazardous scenarios may also be considered to improve the application of this study. In addition, this study may be extended to analyze submarine pipelines by changing the model parameters such as loads and boundary conditions.

## Author Contributions

## Funding

## Conflicts of Interest

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**Figure 7.**(

**a**) The MES and the ANS versus the suspended length (

**b**) the maximum EES and the maximum EPS versus the suspended length.

**Figure 10.**(

**a**) The MES and the MAS versus D/t and (

**b**) the elastic strain and the plastic strain versus D/t.

**Figure 11.**Total strain contours of the location of the maximum strain versus the ratio of diameter to thickness (D/t).

**Figure 13.**(

**a**) The MES and the MAS versus the operating pressure and (

**b**) the elastic strain and the plastic strain versus the operating pressure.

**Figure 16.**(

**a**) The equivalent stress along axial and (

**b**) the maximum equivalent stress under different values of the suspended length versus the fluid gravity.

**Figure 17.**(

**a**) The maximum total strain and (

**b**) the maximum deflection under different values of the suspended length versus the fluid gravity.

Parameters (Units) | Values |
---|---|

Soil length (m) | 80 |

Soil depth (m) | 2 |

Suspended length (m) | 320 |

Pipeline diameter (mm) | 219.1 |

Internal pressure (MPa) | 4 |

Oil density (kg/m^{3}) | 840 |

Pipeline material | X52 steel (API) |

Yield strength (MPa) | 375 |

Poisson’s ratio | 0.3 |

Elastic modulus (E) | 203 |

Ρ_{s} (kg/m^{3}) | E_{s} (Mpa) | υ_{s} | c (kPa) | φ (°) | ψ (°) |
---|---|---|---|---|---|

1450 | 40 | 0.4 | 30 | 12.3 | 0 |

Emergency Levels | Descriptions | Treatment Measures |
---|---|---|

I l < 50 m | Low risk, no plastic strain. | Normal transportation operations, refill the soil in the suspended section. |

II 50 m≤ l < 150 m | Medium risk, there are elastic strain and plastic strain, while mainly elastic deformation. | Stop transportation operations and refill the soil in the suspended section as soon as possible. |

III 150 m≤ l < 340 m | High-risk, plastic strain is dominant but the strain is less than 2%. | Stop transportation operations, replace the suspended pipe, and refill the soil in the suspended section. |

IV l ≥ 340 m | Very high risk, with a strain larger than 2%, and even causes oil leakage, fire, and explosion. | Stop transportation operations, evacuate surrounding people, prepare for leakage rescue, fill the soil in the suspended section, and replace the suspended pipe. |

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**MDPI and ACS Style**

Yu, J.; Chen, C.; Li, C.
Safety Analysis and Emergency Response of Suspended Oil and Gas Pipelines Triggered by Natural Disasters. *Sustainability* **2022**, *14*, 17045.
https://doi.org/10.3390/su142417045

**AMA Style**

Yu J, Chen C, Li C.
Safety Analysis and Emergency Response of Suspended Oil and Gas Pipelines Triggered by Natural Disasters. *Sustainability*. 2022; 14(24):17045.
https://doi.org/10.3390/su142417045

**Chicago/Turabian Style**

Yu, Jin, Chao Chen, and Changjun Li.
2022. "Safety Analysis and Emergency Response of Suspended Oil and Gas Pipelines Triggered by Natural Disasters" *Sustainability* 14, no. 24: 17045.
https://doi.org/10.3390/su142417045