Vladimir Shlyomin

Pipe insulation section at the Volzhsky Pipe Plant

    Today about 230,000 km of trunk pipelines constructed in Russia for different purposes are currently in operation. They are used for transporting oil, oil products, condensate, ethylene and liquid ammonia. But over two thirds of this gigantic network consist of gas pipelines.

The considerable part of the gas transportation system created in the Soviet era is obsolete. For example, the age of gas pipelines averages 22 years and the share of those, which have been in service for more than 30 years, amounts to 16 %. Many sections were repeatedly repaired but they still remain accident-prone. The accident ratio (an average number of cases a year per 1,000 km) has been quickly increasing: from between 0.18 and 0.21 in 1996 through 1999 to between 0.24 and 0.26 in 2000 and further on. What is more, if one is to trust statistics accumulated from 1992 to 2000, most accidents were the result of negligence:
– external damaging effect on pipelines mainly by excavation and caterpillar machinery (34.7 %);
– breaking of standards and rules for construction works and maintenance (24.7 %);
– corrosive damage to pipelines as well as to stopping and control valves (23.5 %);
– violations of technical requirements at pipe-producing plants (12.4 %);
– faults of maintenance and operating personnel (4.7 %).
Annually about 30,000 leakages (from 50 to 70 daily) are officially registered at Russia’s field pipelines. The analysis shows that in the first years of operating, mainly construction defects become apparent, then, pipelines start working properly for a certain period of time but after 14 to 16 years there are breakdowns due to aging of structures.
On the basis of accident data it is possible to group in certain order factors, which determine the reliability of hydrocarbon transport.
Let us start with pipe quality. Russia has been constructing trunk pipelines for over seventy years. During this period both materials and technologies underwent significant changes.
In the 1930s and 1940s oil and oil products were not playing a determining role yet in the country’s economy and there was mainly a local transport servicing terminals and oil-filling plants. That is why pipes of the first generation were made of plastic steels with low strength.
As new fields were developed in the country’s remote regions, which lacked infrastructures, the direct transporting of hydrocarbons was started. That made additional transfer tank farms unnecessary. There was a need to increase diameters and strength of pipelines, which should withstand high pressure. Strengthening of pipe steel was initiated and it seemed to be an optimal decision. But it was soon discovered that along with higher strength properties of the steel structure itself was becoming more sensitive to different external factors. What is more, it is true not only for pipelines. Every industry sets its own norms of reliability for systems and structures with an individual ultimate strength.
The leading expert in welding, professor of the Gubkin Oil and Gas University, president of the Russian Scientific and Engineering Society of Welding Oleg Steklov singles out three regularities. First, the stronger the material, the more sensitive it gets to stress concentrators. Second, the stronger the material, the more it reacts to technological factors: impacts, deformations and, particularly, welding because it radically changes properties of material in the weld zone. Third, a high-strength material reacts more sharply to destroying factors of the environment: corrosion, temperature, etc.
As everywhere in the world, steel-makers in Russia are constantly working to create qualitatively new materials. Modern pipe-producing enterprises widely use controlled rolling and microalloying that permit to include carbonitride strengthening and refined structures in steels. As a result of such a processing, quality of materials improves in two aspects: strength and plasticity. What is more, they are better welded because the content of carbon is very low. At the same time the existing methods of controlled rolling require some adjustment so as to get a steel structure capable of withstanding corrosion cracking.
Trunk pipes are welded. Future operation of a pipeline much depends on the quality of steel welding at pipemakers. Nowadays technologies used in Russia are as good as those in the West. Modern methods are employed by such major enterprises as the Chelyabinsk Tube-Rolling and Volzhsky Pipe Plants.
However, in the opinion of Oleg Steklov, high-strength materials require new welding methods that imply different physical solutions. He cites an example from another sphere: when there was a need in the aircraft industry for welding high-strength aluminum sheet, a method of plasma-arc impulse welding was developed that prevented structure distortion. In other words, structural requirements dictated the choice of methods. This logic is applicable to pipelines as well. Studies show that as far as pipe production is concerned, plasma-arc and laser welding methods are the most pressing today. They are being mastered at Russian enterprises with assistance of such consumers as Gazprom and leading oil companies, which are interested in their products.
If enterprises are already using new methods of welding in mall-lot production, the manual welding still remains the principal one in constructing pipelines. And as is always the case with using manual labor, the quality depends on random factors, such as, for example, change in air humidity and the psychological state of the worker himself.
The manual welding accounts for 30 % of welding operations globally. The figure is much higher for Russia: during pipeline erection over two thirds of welding works are done manually. Western companies are actively switching to semiautomatic welding, machine welding, welding with gas mixtures (with argon, carbon dioxid acid with nitrogen and argon), powder wire welding, metal-arc welding wire with gas mixture. Russian construction workers are still learning to use these methods.
The rather high accident rate at Russian trunk large-diameter pipelines is the result of the evolving corrosion cracking process. This was the cause of 26 accidents in 1991 to 1995 and of 54 accidents in 1996 to 2000, 14 of them happening in 2000 alone. Today this process, which is often called stress corrosion, is among major causes of failures at trunk pipelines not only in Russia but also in the U.S., Canada and a number of other countries.
There are even more complications with operating oil field pipelines. Russian oil wells are considerably flooded: up to 9 tons of water saturated with salts have to be pumped out with every ton of oil. At most fields in West Siberia, the principal oil production region, the volume of highly mineralized water containing hydrogen sulfide, oxygen, carbon dioxide and other corrosion agents amounts to 70 % to 80 %. As a result, steel pipes are usually out of service in two to three years.
It might be a cause of 95 % of accidents at oil field pipelines, Oleg Steklov believes. He proposes to divide all accidents of this kind into two groups: accidents connected with main cracks and accidents without them. The first group includes: general corrosion of structural components, pitting with honeycombs, condensate corrosion. The second one consists of stress corrosion cracking (SCC) of two main types: sulfide stress corrosion cracking (SSCC) and hydrogen-induced cracking (HIC) as well as stress corrosion cracking due to anodic, deformation and sorption processes linked by time and place.
The analysis of all operational factors suggests a number of options to provide pipe internal protection. In the opinion of professor Steklov, «The most acceptable one is to use inorganic enameled coating and vitrifying. The peculiar properties of enamels minimize friction during hydrocarbons’ pumping permitting to reduce pressure by 1.5 times so as to pump over the same volumes. Deposition of hazardous substances on walls is also reduced».

However, it is more important to secure external damage protection of trunk pipelines transporting purer hydrocarbons. The quality of protective coatings depends on conditions, in which they are applied. For a long time this important work was done in Russia directly on the route. Simple technologies and materials – first, bituminous and, later, film coatings – were used. These coatings were designed for only 10 to 15 years of life and now they are losing their protective properties on a large scale. Not long ago plants have started to make pipes with high-quality coatings. In the last two to three years modern coating sections were constructed at all enterprises, which supply pipes for trunk pipelines. Among them are the Volzhsky Pipe Plant, Vyksa Steel Works and Chelyabinsk Tube-Rolling Plant.

P    R    O    F    I    L    E  Oleg Steklov Professor of the Gubkin Oil and Gas University (Moscow). Holds the chair of welding and corrosion protection. President of the Russian Scientific and Engineering Society of Welding. In 1957 graduated from the Bauman Moscow Engineering Institute, mechanical engineer in welding by speciality. Has a practical experience. Was a scientific intern at the Rhine-Westphalia Engineering School (Aachen, Germany). In 1972 received a doctor degree. Leading expert in strength and reliability of materials and welded structures. Author of 56 inventions and patents. Published over 350 scientific works. Winner of the science and engineering prize of the Russian government. Member of the New York Academy of Sciences. Chairman of specialized councils on technology, welding equipment and corrosion. Holds responsible positions at a number of other scientific organizations. His hobby is skiing and he has been many-times champion of Moscow, Russian as well as world-wide senior citizen ski racing.

Experts pay attention to not only pipe quality but also to geophysical aspects of construction projects. By the available data, about 80 % of all accidents at trunk pipelines happened in areas that were crossing tectonically disturbed zones. What is more, accidents often recur at the same sites. The typical example is a 40-kilometer section of the trunk 9-line gas pipeline near the city of Krasnoturiensk in the northern part of the Sverdlovsk region. From 1990 through 1995 there were 45 accidents there or about 90 % of all accidents in the system of Gazprom, a company that has a monopoly on production and transportation of Russian gas.
During the investigation it was established that technological characteristics (quality of steel, reinforced concrete structures, welded seams, insulation, etc.) conformed to the project’s requirements. Construction defects, if any, became apparent in the first year of operation. The real cause of numerous tears and failures was external factors that led to reduction of fatigue characteristics of pipe steel and reinforced concrete structures. Thus, surface motions along edges of tectonic blocks of the different hierarchical level might become such factors.

R    E    F    E    R    E    N    C    E  «Today it can be stated with confidence that Russia’s pipe-insulation complexes based on the use of extruded polyethylene, including the Penza pipe-insulation complex and installations at the Volzhsky Pipe Plant, Chelyabinsk Tube-Rolling Plant and Vyksa Steel Works, completely free us of the need to import pipes with insulation of up to 1200 mm in diameter». Valery Potapov, the chairman of the «Pipeline Protection from Corrosion» section of the Scientific and Engineering Council, Rosneftegazstroi JSC.

So as to check this hypothesis researchers from the Institute of Mining examined the section by vertical electric sounding and electric profiling. They discovered the principal tectonic break, which was crossing the route of the gas pipeline at the acute angle, and several transversal breaks of the lower rank. Unfortunately, further studies were canceled. For reasons unknown operating organizations did not show any interest in them and refused to provide funds.
It is assumed that there was a trivial unscrupulousness on the part of some mid-level managers, who personally profited from servicing accident-prone sections: the cost of repairing 1 kilometer of trunk gas pipeline amounts to hundreds of thousands of US dollars and with frequent accidents it is much easier to justify increased expenses. However, such an opinion may be regarded as an emotional reaction since there are no proven facts of corruption so far.
There is another opinion that seems more prudent. In Russia the state was and remains the owner of the gas transportation system. The state is obliged to support its functioning with funds from the federal budget. Stating this fact Evgeny Leontiev, the deputy director of the institute VNIIGAZ, says that limited finances give no choice other than to concentrate mainly on detecting and eliminating the most serious dangers, such as major stress corrosion defects. «The backlog of necessary works was accumulating for many years and today we are just unable to do preventative maintenance to the full», Leontiev stresses.
Now it is important to diagnose pipelines of all types and destinations. Determining potentially dangerous sections of the route can be done by geophysical methods. An in-pipe diagnostics is another possibility. There are special gears for this. Oilmen have finished inspection practically all pipelines. In the gas industry, on the contrary, only one third of pipelines has been inspected. The completion is hampered by errors made at the construction designing stage – there were just a few experts then, who gave thought to the need of controlling the suitability of trunk lines. That is why because of different barriers (transfer stations and other installations) most of the country’s gas pipelines are not subject to internal inspection and diagnosing. Furthermore, there is the lack of necessary equipment and use of technologically non-adjusted control programs.
Under these conditions the operational monitoring can be done by stages: at first to use aerospace systems capable of tracing the slightest changes on the routes of oil and gas pipelines and, then, to conduct a local steel analysis so as to take necessary steps on the basis of its generalized results.
Experts propose to work out a single complex program of controlling the most hazardous facilities. Pipelines are among them. This program would unite designers and steelmakers with pipe-rollers and construction people. It would be supervised by state bodies, such as the Ministry for Emergency Situations. All large companies, which produce as well as transport oil and gas, should participate in this program because the situation at pipelines is becoming literally explosive.