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Industries and residential areas rely on a continuous supply of energy therefore, transferring it from the source to the consumer is an exceedingly vital process.
Natural is one of the most commonly used fossil fuels. There are millions of miles-long distribution networks covering vast regions of the world to ensure consumers have access to an uninterrupted gas supply. Correct installation of infrastructure is crucial to ensure safe and steady energy transfer.
In this article, we’ll discuss how underground gas lines are built.
Basics
Underground gas networks use two types of piping, polyethylene, and steel. Polyethylene gas lines operate at 4-6 bars of pressure, while steel pipes can withstand up to 80 bars however, most local steel gas networks work at 19 bars.
Due to continuous flow and high operation pressure, gas pipes have a dynamic structure, meaning they move. The dynamic nature of the gas pipes can be harmful. If the moving gas pipe grinds against agitating material, the surface can get torn, causing gas leaks. To eliminate the risk of tear and wear, the gas pipes are padded and covered with fine sand.
Trench Specifications
The canal in which the gas pipe gets buried is called a trench. Different countries have different regulations about gas pipe trenches. The general rule of thumb is that the trench shouldn’t be too shallow to prevent damage but also shouldn’t be too deep to create difficulties reaching it in the future.
For local networks, the trench is usually 1-1.5 meters deep with 20-30 centimeters of padding material at the bottom. The bottom padding gets pressed down before the pipe is placed on top. After that, a covering layer of padding material is placed on top of the fine sand. The height between the top layer of the padding and the top of the pipe should be at least 20-30 centimeters. After the final layer of padding, a plastic warning band is laid on top in case a digger hits the gas line in the future. Sometimes the top layer of the padding materials gets covered with BIMS or another hardened protective layer to prevent accidental damage. In terms of the width of the trench, it’s preferred to be not narrower than a meter.
Corrosion Protection
Steel pipes when buried underground corrode over time. To prevent corrosion, steel gas pipes usually have a protective layer of polyethylene film on top however, in some circumstances even the protective layer may not be enough. In this case, cathodic protection systems are used.
Cathodic protection is the process of protecting metal pipes against corrosion via electrochemical reactions. The purpose of cathodic protection is to polarize the potential of the metal to be protected up to the open circuit potential of the anode. To achieve this, an external current is applied to the metal in the cathodic direction.
Cathodic protection, which started to be applied in the 1930s, has made great developments in recent years, and with the discovery of new high-performance anodes in parallel with technological developments, cathodic protection has become the most effective and economical method in combating corrosion. Cathodic protection is applied in two ways an external current source and a galvanic anode.
External current-induced cathodic protection is done by applying an external direct current to the metal. The direct current (-) end obtained from a transformer rectifier system is connected to the metal to be protected, and the (+) end is connected to an auxiliary anode. As an auxiliary anode in the external current source system; The most commonly used anode type in underground structures is silica-doped iron anodes. Apart from these anodes, graphite, and metal-oxide-coated titanium anodes imported from abroad are used.
In cathodic protection systems with a galvanic anode, a galvanic battery is formed by connecting a metal (anode) with a more negative potential than the metal structure to be protected. Thus, the metal structure becomes the cathode. Galvanic anodes dissolve on their own, producing current just like a battery. The electrons released as a result of the dissolution of the anode are transported from the outer junction to the cathode (protected metal structure), providing the electrons necessary for the cathodic reaction. Galvanic anodes lose their weight by dissolving at certain speeds during protection. By renewing them at appropriate time intervals, the protection function is given continuity.
Cathodic protection is also used by the maritime industry to protect components against corrosion by saltwater.
Summary
Energy transfer lines are what connect energy sources with industries and residential areas, therefore the way they are built is extremely important. Long-lasting and well-functioning energy lines are key to ensuring a steady flow of energy. In this article, we’ve curated detailed information about how energy lines are built and protected.
