If you’re looking to know more about deflected pipes, read on. This article will look at the material characteristics that allow pipes to deflect without damage. We’ll also discuss the methods used to deflect flexible pipes and their limits on repairing deflected pipes. Deflection is a crucial safety measure in pipe installations, and the right way to use it depends on the circumstances. So here’s an overview of deflected pipes.
Deflected Pipes
Deflected pipes occur when a horizontal pipe bends under the weight of an external object. This type of pipe is best used in structures that support the weight. It turns the maximum number of inches before it becomes straight again. Deflection is also a safety concern. Here are some ways to test your pipe’s load-bearing capacity. Deflected lines are easy to recognize, but you must be sure to test them before they are used.
The force of lift acting from below a pipe causes an upward deflection. It must be greater than the lift resistance acting from above to prevent pipe deflection. Excessive deflection causes a pipe to rupture. Before you backfill your pipes, ensure that they are supported and appropriately compacted. Remember to use pipe supports in areas with reactive clay soil. The moisture content of soil can vary dramatically. You should always measure pipe deflection with a caliper before deciding on how to backfill.
Material Characteristics
Pipes with a flexible design can withstand two percent deflection without sustaining any structural damage. However, most standards only allow a maximum of five percent deflection. Loose pipes can be constructed from ductile iron, high-density polyethylene, and vitrified clay. The following material characteristics allow deflected pipes to bend without sustaining damage. For more information, check the pipe manufacturer’s specifications.
The flexural modulus of elasticity measures the piping material’s ability to resist changes in length due to temperature changes. The greater the modulus, the longer the pipe will need to be spanned before it can deflect the same distance. The smaller the area to spread the force, the greater the pipe’s ability to deflect without damaging the piping system.
Methods of Deflection
Various methods have been used to analyze the deflection of pipes. One of these is the finite-element analysis (FEA) method. This method was developed from an experimental study of small corrugated steel pipes. While deflection is a normal property of piping, small diameter pipes can cause local excess stress. For these reasons, strict pipe deflection management is necessary. The FEA deflection was compared to field measurements and was close to the actual value.
Pipes embedded underground are subject to upward pipe deflection. This occurs when the buoyancy force exceeds the total downward weight of the pipe. As a result, the soil loses moisture content during dry spells and regains it during wet spells. The resulting pressure exerted on the pipe may result in its rupture. This is why a proper geotechnical investigation is necessary before installing a pipe in a sensitive area.
Limit of Deflection
The conventional tolerable deflection limit for flexible pipes is 5% of pipe diameter, with a safety factor of four. In this paper, we consider the influence of in-situ uncertainties on the calculation of pipe deflection. We also present a reliability assessment method using the point estimate method and the central safety factor. Finally, we discuss the use of safety margins in flexible pipe design.
For a buried pipeline system, the Limit of Deflection for Flexible Pipes is evaluated by comparing the load-carrying capacity of the pipe with the soil surrounding it. CCTV inspections are not sufficient to determine the deflection of a pipe. In addition, a laser profile report helps measure changes in deflection. By analyzing the deflection of a pipe’s internal surface, the engineers can decide whether it is safe or not.
Impact of Soil Compaction
The Modulus of Soil Reaction (E’) is an empirical value that describes the stiffness of the embedded soil. The value is essential in predicting the deflection of flexible pipes. When trenching a pipeline, the stiffness of the pipe’s material must be considered. The soil surrounding it adds additional support to the pipe. Excessive deflection will cause the line to fail.
The stiffness of the pipe and the soil around it in a deflected pipe determine its resistance to long-term deflection. But the contribution of each element is not equal. The line and the soil embankment have greater influence than each other. A pipe with a stiffness of 15 will deflect 1% more than one that is stiffer than 75. Using a good-quality fill, however, will minimize the influence of pipe stiffness.
