Lateral and Upheaval Buckling of Pipelines: Overview & Prevention

We know that the piping systems are the integral component of a plant facility. In industries such as oil & gas, petrochemicals and more, engineers maximize the use of onshore and offshore pipelines. It helps for easy moving of liquid or gas from one place to another.

Sometimes, the pipes expand because of the high temperature and pressure of the fluid flow. It results in the buckling of pipelines.

In this article, we will highlight the two types of pipeline buckling:

1. Upheaval buckling
2. Lateral buckling

It covers their introduction, causes, prevention & some guidelines that you can consider for them.

Overview

Lateral buckling takes place when the pipeline laid on the seabed or sand bands sideways. It happens due to the high pressure and high temperature of the material.

If we talk about upheaval buckling, it occurs when a pipeline in a trench or buried under the surface buckles vertically.

Both these types of pipeline buckling are usually bound to happen in environments with low soil cohesion. They can occur at offshore pipelines as well as onshore pipelines. Also, they can be global or local in type. A global buckling affects the complete section of the pipeline. In comparison, the local buckling stays within the specific areas of the pipe.

Causes of Upheaval and Lateral Buckling

The primary reason for pipeline buckling is the difference in temperature and pressure in the pipes than the surroundings. When it reaches higher values, tubes try to expand. If there is no space to enlarge, pipes create an axial expansion force.

The friction between the ambient soil and pipe surface resists the expansion of the pipe. It results in a restraining force in the overall pipe section. Based on the type of installation of the piping system, it tends to move upward or sideways.

How to Calculate & Prevent Lateral and Upheaval Buckling

There are a couple of ways to calculate upheaval buckling in the pipeline that helps prevent it.

Many engineers follow the calculations shown in the technical paper released by Dr. K. Peters for the underground piping. It is available with the name "About Upheaval and Lateral Buckling of embedded pipelines" (International third edition 2006).

Software such as Hexagon and more also helps calculate the maximum allowable over-bend angle and other parameters.

You might know about the SABKHA area, a.k.a. flat area in a desert or coastal surface where the lateral buckling mostly occurs. You can calculate the sideways force needed to resists lateral buckling as per the guidelines provided at the end of the article. Your pipe stress analysis consultant should also provide how much change in direction would be allowed for a lateral bend angle based on the geography.

One of the precautions to prevent upheaval buckling is to use extra soil cover at the pipeline route. To avoid lateral buckling, you may also need to keep berm reinforcement in check.

A Few Vital Guidelines

1. The alignment sheets should also have notes about maximum allowable over-bend angle calculations. You should also check the details of the minimum elastic bend radius in sheets and relevant drawings.
2. Engineers should ensure that the angle variation is within the allowed limits for the specific soil cover. They can also increase the soil resistance to maximize the over-bend angle. It helps control the upheaval buckling in pipes.
3. You need to verify the as-built data during the analysis & installation of the pipes and compare them with the requirement sheets.
4. If the angle exceeds the limit when routing the piping system, you can do suitable grading to control it.
5. Engineers should also define the maximum allowable over-bend angle per 12-meter pipe length based on buckling calculations. It helps update the rise of the system within permissible limits.
6. For common geographical areas, engineers can carry out the calculations for a sufficient height of 1.9-meter. It covers the 1-meter standard cover depth and 0.9-meter soil cover.
7. During the design and construction phases, the contractor should also focus on the pipeline route's rough sections. It helps them finalize the buckling checks and make changes in design if required.

Conclusion

To summarize, buckling in pipelines can occur in areas with less vertical or horizontal resistance to an axial compressive force. It includes sections between road crossings, interfaces between non-sabkha and sabkha locations & more.

You can consult an engineering services provider having experience of long and various types of projects. They can help you with the flexibility analysis of piping systems using modern tools while adhering to industry standards. It will help you implement cost-effective mitigation measures and make your engineering project a success.