Selection of steel pipe wall thickness for high pressure and large diameter oil and gas pipeline
In the oil and gas pipeline transportation system, the reasonable selection of steel pipes for the pipeline can not only ensure the safety of pipeline transportation, but also save the capital investment in pipeline construction to a certain extent, because if the wall thickness and corrosion resistance can be selected reasonably, the final effective operation can be guaranteed and the corresponding investment will be reduced. Through the specific research on the selection of steel pipe wall thickness for high pressure and large diameter oil and gas pipelines, this paper promotes the relevant departments to be more scientific and reasonable in the selection of steel pipe wall thickness for high pressure and large diameter oil and gas pipelines.
With the continuous development of the economy, in ordinary production, life, more and more places can not do without the use of oil and gas, oil and gas pipeline because of its special characteristics, most of the buried, once the leakage or pipeline cracking problems, not only will have an impact on the environment along the pipeline, and even the threat to the personal safety of nearby personnel, therefore, the selection of the wall thickness of steel pipes in the oil and gas pipeline must be in accordance with the corresponding Therefore, the selection of wall thickness of oil and gas pipelines must be in accordance with the corresponding standards, so that the safe operation of the pipeline is guaranteed, better for people’s production and life to provide energy.
1. High pressure large diameter oil and gas pipeline wall thickness selection criteria
Usually, in the less densely populated areas for the construction of oil and gas pipelines, the design factor can be calculated using 0.8 (0.72 for oil pipelines), in the process of pipeline construction, in order to ensure the safety of the pipeline on the basis of the minimum construction costs, it is necessary to consider all aspects of the impact factors . First of all, the difference in the performance of the pipe should be analyzed, because the same design factor of the pipe contains different steel grades, in the actual selection should be based on the mechanical properties of the scientific selection; secondly, from the inspection standards. In the construction of oil and gas pipelines, the choice of steel pipe, whether from its own structure or weld hardness are certain standards; third, the choice of steel pipe, and the construction of oil and gas pipelines along the topography of the landscape also has a certain relationship. Because of the different topography, may cause subsidence or landslide problems, thus affecting the integrity of the pipeline; fourth, after the selection of steel pipe, construction should be carried out in strict accordance with the corresponding construction standards; fifth, the welding of the pipeline, if welding problems, then even if the steel pipe thickness, quality and other aspects of no problem, the final operational safety can not be guaranteed . Therefore, in the welding process, first of all, we must pay attention to the preheating problem of welding, followed by a comprehensive consideration of the residual height limit and grinding treatment, the actual minimum thickness of steel pipe parts should be kept at about 5 mm; finally, the choice of anti-corrosion layer inside the pipe, we must ensure that it has a good corrosion resistance, so as to avoid corrosion inside the pipe.
2. Research on the fracture mechanics of pipelines
The choice of wall thickness of high pressure large diameter oil and gas pipeline is mainly to avoid the problem of pipe fracture, and then to promote its safe and stable operation. The following study on the fracture mechanics of the pipeline.
The wall thickness of oil and gas pipeline in a certain range, in order to well balance its various aspects of the force, the fundamental element of this reasonable wall thickness is the toughness of the material. In addition, this issue also has a direct relationship with the yield strength of steel. When in a state of triaxial stress, and in the time of stress, that is, when the material is in a plane strain state, this state, the material itself is good toughness, the possibility of brittle damage is also quite large, because in this state, the toughness of the material does not play effectively, to effectively avoid the phenomenon, through the relevant experiments found that if the thickness of the steel pipe to 25mm, the steel pipe will be in a triaxial stress state, therefore, in the actual selection, should be effective control of its thickness . In addition, the factors affecting the occurrence of fracture are the chemical composition of the steel pipe, the organizational form and other factors related to the mechanics of the choice, according to the actual situation to weigh the specific factors affecting the comparison, so as to effectively have a clear grasp of the performance of the steel pipe, and then achieve effective control of it, to avoid the occurrence of steel pipe fracture problems.
If the pipe once fractured, you can deal with the following ways: First, the problem of brittle fracture occurs from the development of small cracks on the surface of the pipe. In general, the phenomenon of brittle fracture, are due to the case of pipe pressure, the steel tough brittle transition temperature higher than the working temperature of the pipe and lead to. However, in today’s steel manufacturing process has been improved, the toughness of the pipe has been effectively enhanced, in the operation of the pipe, the probability of this problem has been reduced, but then, the frequency of ductile fracture accidents has increased. Ductile fracture occurs through the slow expansion of cracks, which are initially manifested by the formation and continuous merging of cavities in the pipeline, the shape of the fracture is generally fibrous and lusterless, and the problem occurs mainly due to the increasing pressure and caliber of oil and gas pipelines. This problem is mainly due to the increasing pressure and diameter of the pipeline. The problem is dealt with by effectively controlling the occurring phenomenon and preventing its further expansion.
In summary, high pressure large diameter oil and gas pipeline wall thickness in the selection of reasonable, the normal operation of the pipeline later has a direct impact, once the problem, not only will affect the normal production, life, and oil and gas leakage in the ground, but also on the ecological environment, water and personal safety threats, therefore, in the construction of oil and gas pipeline, must be reasonable for its wall thickness Therefore, when building oil and gas pipelines, it is necessary to make a reasonable choice of wall thickness, especially the high pressure and large diameter oil and gas pipelines, because of its high pressure and large volume, if a leak occurs, the consequences are unimaginable. Although the current selection of this issue is not perfect, I believe that in the future, the construction quality of oil and gas pipelines will be gradually improved.
Authors: BoBo Liu, Jianfeng Chen
Source: China Oil and Gas Pipeline Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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