Gas pipes types:

Compared with traditional energy sources such as coal and oil, natural gas not only has a high calorific value, but is also more environmentally friendly and low-carbon. In order to economically, efficiently, safely, and smoothly transport natural gas from distant production sites to end-user terminals, high-pressure pipeline transportation technology has developed rapidly in the past 40 years. Currently, the total length of natural gas pipelines worldwide has exceeded 1.5 million kilometers.

High-pressure natural gas is highly flammable and explosive, and when massively, long-distance, and uninterrupted transportation is required, the pipeline must withstand high internal pressure. In this case, any rupture or leak at any point could cause significant economic losses, or even public safety incidents. Therefore, in the design and operation of natural gas long-distance pipelines, measures must be taken to ensure the safety and economy of transportation, such as selecting the pipeline material reasonably and increasing the gas transportation volume. The material of the natural gas pipeline must be reliable and durable. Coated steel pipes are the most commonly used material for natural gas long-distance pipelines due to their high strength, good sealing and aging resistance, ability to withstand high pressure and temperature changes, etc. The durability of steel pipes mainly depends on the manufacturing process, anti-corrosion treatment, and construction quality. HDPE gas pipe can also be used for natural gas pipelines. HDPE gas pipe is lightweight, easy to install, and resistant to corrosion, but it can withstand a pressure of no more than 2.5 MPa and is not suitable as the main gas pipeline. Therefore, it is mainly used for low-pressure gas pipelines in gas supply branch lines.

The main characteristics of gas steel pipe:

To use high-strength pipeline steel or increase the wall thickness of pipeline steel can make natural gas pipelines capable of withstanding higher transmission pressure, thereby increasing natural gas throughput. Although the price of microalloyed high-strength steel pipes of the same diameter as ordinary steel is about 5% to 10% higher, it can reduce the weight of the steel pipe by about 1/3, making the manufacturing and welding process easier, and transportation and laying costs lower. Practice has proved that the cost of using high-strength pipeline steel pipes is only about one-half of the cost of the same pressure and diameter ordinary steel pipes, and the pipe wall thickness is reduced, and the possibility of pipe brittle fracture is reduced accordingly. Therefore, in general, the choice of increasing the strength of the steel pipe is made to increase the pipeline throughput, rather than increasing the wall thickness of the steel pipe.

The strength indicators of pipeline steel mainly include tensile strength and yield strength. The pipeline steel with higher yield strength can reduce the steel consumption of the gas pipeline, but the yield strength is too high will reduce the ductility of the steel pipe, causing the steel pipe to tear or burst, and causing safety accidents. In order to achieve high strength, the ratio of yield strength to tensile strength (yield-to-tensile strength ratio) must be considered comprehensively. The appropriate tensile strength-to-yield strength ratio ensures that the steel pipe can have sufficient strength and toughness, thereby improving the safety of the pipeline structure.

In the event of a rupture failure in a high-pressure gas pipeline, compressed gas will rapidly expand and release large amounts of energy, causing explosions, fires, and other serious consequences. To minimize the occurrence of such accidents, the pipeline design should carefully consider the fracture control scheme from two aspects: First, the steel pipe should always work in the ductile state, In recent years, as the development and exploitation of natural gas has extended to deserts, mountains, polar regions, and the ocean, long-distance pipelines often have to pass through geological and climatic conditions that are extremely complex, such as permafrost zones, landslide zones, and seismic zones. To prevent the steel pipes from deforming due to ground collapse and movement during service, gas pipelines located in earthquake and geological disaster-prone areas should use anti-large-deformation pipeline steel pipes based on strain design. Gas pipelines that cross overhead areas, permanent permafrost zones, high-altitude or high-latitude low-temperature areas, are subjected to long-term high-cold tests and should use pipeline steel pipes with excellent anti-low-temperature brittle fracture ability. Gas pipelines that are subjected to corrosion by groundwater and high-conductivity soil should strengthen the anti-corrosion treatment on both the inside and outside of the pipes.

Characteristics of HDPE Gas Pipes:

1. Corrosion resistance:

Polyethylene is an inert material and can withstand the corrosion of many chemical media except for a few strong oxidants. It has no electrochemical corrosion and is resistant to natural gas, liquefied petroleum gas, and artificial coal gas, etc. Chemical corrosion, so no anti-corrosion coating is needed and there is no need to worry about gas corrosion and leakage.

2. Sealing performance:

PE gas pipelines mainly use fusion connection (hot melt connection or electric fusion connection), which integrates the joint with the pipe material. The tensile strength and bursting strength of the interface are the same as the pipe body, ensuring the safety of the entire pipeline system.

3. Crack resistance: PE gas pipes are made of imported raw materials and have been tested by international institutions to have excellent resistance to environmental stress cracking.

4. Flexibility

PE gas pipes have a breaking elongation rate of over 500%, making them highly adaptable to uneven subsidence of the pipe foundation and an excellent earthquake-resistant pipe.

5. Scratch resistance

Scratches can cause stress concentration in pipes, leading to pipe failure. PE gas pipes have excellent scratch resistance.

6. Flexibility

PE pipes can easily be made into coils, allowing for longer lengths to be supplied and thus saving various connection fittings.

7. Long service life

PE gas pipes can have a service life of more than 50 years under normal working conditions.

Gas pipe fittings:

In the long-distance natural gas pipeline system, to meet the needs of medium distribution, direction change, and reducing the additional external force on the pipeline caused by geological movement, a large number of bends, three-way branches, etc. with matching performance to the main line pipe are needed to be installed on the pipeline route, valve chambers, and station fields.

At present, natural gas transmission pipeline bends are mostly manufactured by induction heating and water cooling using medium frequency, and large-diameter three-way branches are produced by hot-drawing technology using wide and thick plates. Unlike the manufacturing process of pipeline steel pipes, when manufacturing bends, elbows, and other fittings, pipeline steel materials need to be heated twice during the process, which causes significant changes in material properties. Therefore, the material composition design and heat treatment process require special attention.