ISSN 10618309, Russian Journal of Nondestructive Testing, 2010, Vol. 46, No. 9, pp. 698–703. © Pleiades Publishing, Ltd., 2010. Original Russian Text © V.A. Popov, G.S. Korzunin, 2010, published in Defektoskopiya, 2010, Vol. 46, No. 9, pp. 90–96.

TECHNOGENIC SAFETY

The Corrosion Protection System Used at OOO Gazprom Transgas Yekaterinburg V. A. Popova, *, and G. S. Korzuninb ,** a

b

OOO Gazprom Transgas Yekaternburg, Yekaterinburg, 620000 Russia Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620041 Russia * email: [email protected] ** email: korzunin.uran.ru Received July 29, 2010

Abstract—The work of the corrosion protection system used at OOO Gazprom Transgas Yekaterin burg is considered, mainly for the period of 2008. It is noted that the passive corrosion protection com ponent, which consists of different pipeline wrappings, requires repair and replacement. The active (electrochemical) corrosion protection component achieves a high level of corrosion protection of gas pipelines via the application of different technical processes. Their work is exemplified by the main gas pipelines of the Nev’yansk Regional Gas Pipeline Operation Center. Keywords: gas transportation system, corrosion protection, electrochemical protection, main gas pipeline, wrapping. DOI: 10.1134/S106183091009010X

The total length of the main gas pipelines (MGPs) of OAO Gazprom has reached 120000 km, among which 60% is accounted for by gas pipelines 1020–1040 mm in diameter. The average age of the gas pipe lines of OAO Gazprom is almost 25 years, and 20% of them have been in operation for more than 35 years [1–3]. In this connection, the importance of developing efficient MGP corrosion protection facilities is obvious, as the corrosion of pipe metal is the main factor that influences the operational reliability of gas pipelines [4–7]. In this article, the work of the corrosion protection system (CPS) used at OAO Gazprom Transgas Yekaterinburg is considered for the period of 2008. The gas transportation system (GTS) of OOO Gazprom Transgas Yekaterinburg has been in place for 45 years and is a complex branched structure, which consists of pipelines of different ages that extend nearly 1000 km in the latitudinal and meridional directions in four regions (Fig. 1). As the pipelines have numerous sections arranged in parallel to electrified railways and a significant length of branches directed to industrial centers, they are strongly subjected to hazardous technogenic actions produced, first of all, by stray currents (at nearly half of the total pipeline length and pipeline maintenance depots). According to the data from annual nondestructive inspections, the passive CPS component (pipeline wrappings) (Fig. 2) requires repair, or, more precisely, replacement, as its basic protective properties, Earth currents

50% of the entire linear part

Soil resistances

2–10000 Ωm (up to 100000 Ωm for rocks)

Crosscountry terrain

Elevation difference up to 300 m, hilly, flat and mountainous terrain

Distributed pipeline network

Nearly 3900 km of pipeline branches, and 4000 km of MGPs

Industrially developed regions

Nearly 1000 crossings with highways and railways

Fig. 1. Operational conditions of the gas transportation system at OOO Gazprom Transgas Yekaterinburg.

698

THE CORROSION PROTECTION SYSTEM USED AT OOO GAZPROM

699

(a) 2% 1%

1% 1%

Combined, polymer tape and extruded polyolefin based

10% 1%

Combined, mastic and polymer tape based Tape Rubberbitumen Threelayer polymer Masticpolymer reinforced

84%

Heatshrink material based (plant/basic)

(b) After 2000 1990–2000 1980–1990

Threelayer polymer

Rubberbitumen

Heatshrink material based (plant/basic)

Masticpolymer reinforced

Tape polymerbitumen (reinforced)

Tape

Combined, mastic and polymer tape based

before 1980

Combined, polymer tape and extruded polyolefin based

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Fig. 2. Passive CPS component at OOO Gazprom Transgas Yekaterinburg: (a) distribution in % and (b) service life of pipeline wrappings.

which were taken into account when designing the active CPS component are worse than those specified by normative requirements on the major part of the pipeline. Owing to the these facts, the active CPS component (electrochemical protection) differs appreciably from the state, which is usually called the designed state, along the entire pipeline length. The corrosion protection is still successfully maintained within the framework of normative requirements, mainly via electrochemical protection (ECP). In 2008, the corrosion protection was at the 99.7% level and it was maintained by the following technical facilities: (1) 1110 cathodic protection station (SCPs) including 111 inspection stations (ISs) and 8 Pulsar cor rosion monitoring system (CMS) dispatch stations (DS); (2) 78 drainage protection units (DPUs); (3) 7351 protectors; (4) 936 insulating flanges (IFs); (5) 262 electrical insulating joints (EIJs); (6) 3070 km of electric power transmission lines (EPTLs); RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING

Vol. 46

No. 9

2010

700

POPOV, KORZUNIN 140 120

IS number

100

Projected Implemented

80 60 40

Maloistokskoe

Mednogorsk

Buzuluk

Orenburg

Magnitogorsk

Alekseevsk

Krasnogorsk

Shadrinsk

Chelyabinsk

Kartalinsk

Dalmatovsk

Nev’yansk

0

Dombarovsk

20

Fig. 3. Application of Pulsar CMSs at the RGPOCs of OOO Gazprom Transgas Yekaterinburg.

Number of inspections

3000 2500 2000 1500 1000 500 0 2002

2003

2004

2005

2006

2007

2008

2009 Years

Fig. 4. Electrometric inspection dynamics.

(7) 817 transformer station (TSs); and (8) 42 independent current sources (ICSs). The CPS technical state and protection are monitored at 12 531 inspection and measurement stations (IMS). At seven regional gas pipeline operation centers (RGPOCs), the total protected zone of nearly 1800 km is monitored by 111 ISs and 8 DSs of Pulsar CMSs (Fig. 3). The discrete monitoring of pipelines is conducted electrometrically (Fig. 4). In 2008, thirdparty com panies performed electrometric work on 1000 km of pipeline, and 450 km were inspected by specialists of the Engineering and Technical Center (ETC) of OOO Gazprom Transgas Yekaterinburg. The total length of pipelines inspected in 2008 was 935 km and 44000 corrosion defects were detected. The maintenance and repair of CPS equipment fit into the established system for planning the repairs and diagnostics of the linear part of the MGP and are performed mainly by specialists of RGPOCs (30 engineers and 141 workers). To succeed in preventing the corrosion of pipelines, it is necessary to perform the continuous and pro found analysis of all adverse factors combined in time and space for the purpose of ascertaining corrosion RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING

Vol. 46

No. 9

2010

THE CORROSION PROTECTION SYSTEM USED AT OOO GAZPROM % 100

701

100

100

99.8

99.8

99.8 99.6

99 99 98.6

98.6

2006

2007 Years

Main gas pipelines Pipeline branches Others

98

97 2008

Fig. 5. Protection dynamics, %.

mechanisms and developing the recommendations for efficient corrosion protection. The results of the diagnostics are collected, systematized, and analyzed in a laboratory organized on the basis of ETC at OOO Gazprom Transgas Yekaterinburg. Pipeline sections are ranked by their corrosion danger. The mea sures for improving and maintaining the protection of the linear part of the MPG are planned in cooper ation with the Nev’yansk RGPOC and the Production Departments (PDs). Correspondingly, within the assigned monetary limits, some elements of CPS (ECP facilities) and aerial pipelines (APs), namely, 92 anodic grounds, 623 IMSs, and 116.3 km of APs were repaired, and 31 cathodic protection transformers, 18 electric power meters, and 526 protectors were replaced. An increase in the protection characteristics was observed for the period from 2006 to 2008 (Fig. 5). First of all, this is connected with the introduction of Pulsar CMSs, and, correspondingly, with the reduc tion of losses from theft and vandalism (54, 52, 10, and 13 incidents in 2005, 2006, 2007, and 2008, respec tively). However, the number of service specialists’ visits to the pipeline route increased due to the imper fection of equipment and its low reliability. The service maintenance of pipelines, especially the repair of blocks, is also inefficiently organized. As shown by ten years of work experience, the main problem in operating Pulsar CMSs at OOO Gaz prom Transgas Yekaterinburg is the unreliability of CMS equipment, and the frequent failures of its indi vidual components. OOO Gazprom Transgas Yekaterinburg has succeeded in attaining the maximum development of CMSs at the Nev’yansk RGPOC. Owing to a number of organizational and technical measures conducted purposefully in accordance with a special program since 1999, the main protection characteristics have improved. At the Nev’yansk RGPOC, the protection of pipelines was increased at the expense of introducing the latest achievements in the field of electrochemical protection, namely, 27 EIJs, 9 thermogeneratorbased ICSs, extended flexible elastomeric anodes, earth polarized drainage elements, galvanic elements, and corrosion monitoring, and by restoring disabled ECP facilities and repairing the wrapping of some sec tions on the basis of intube inspection results. As mentioned above, the CMSs have proved to make up a very viable system, whose application gives a positive effect. However, the system has some disadvantages, among which are the low power of SCPs, the low maintainability and reliability of transformers, the complexity in organizing the repair of CMS components, the impossibility of attaching transformers produced by other manufacturers to the system, the absence of a common DS, and also the fact that DPUs are not incorporated into the CMS. Over the last 10 years, the main factors that hamper the efficient work of the CPS have been revealed and systematized. Owing to the fact that the range of ECP facilities was actually created and operates on such a complicated pipeline route (Fig. 6), we have a unique experience in operating the linear part of MGPs with some electrical sectioning elements. The EIJs used at the Nev’yansk RGPOC allowed us to reduce the influence of the earth currents of electrified railways. However, this effect proved to be negligi ble because of the insufficient number of insulating joints. RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING

Vol. 46

No. 9

2010

702

POPOV, KORZUNIN

Nizhnii Tagil

Verkhnyaya Salda

Nev’yansk

Fig. 6. Route of the main gas pipeline of the Nev’yansk RGPOC.

The recent studies performed at the ETC of OOO Gazprom Transgas Yekaterinburg are aimed at revealing the patterns in the distribution of defects in pipeline metal on the basis of intube inspection data in the regions of highway and railway bed crossings. The work has just begun, but it can already be sup posed that the excess of defects near crossings within the limits of 4.1–57.0 km can be explained by either failures or imperfections of drainage protection. The presence of a pipeline section with an increased defect density at a distance of 3 km can be preliminarily explained by the limited influence of DPUs. In any case, after receiving the average currents from several DPUs, the longitudinal resistances of corre sponding pipelines experienced a voltage drop of 0.5 V at a distance of 2.7–3.8 km. When the potential of steel is shifted by 0.4–0.5 V from the stationary one towards positive values, the increase in the corrosion rate is maximal. One of the feasible methods for the prevention of increased corrosion of electrified railway bed cross ings may be the installation of EIJs at a distance of 4.5–5.0 km from them. However, this question requires further studies. ICSs still remain important for society as a whole and for the Nev’yansk RGPOC in particular, as the design, building, and, most importantly, the maintenance of EPTLs in the operational mode is very expensive, and often not feasible in principle because of severe environmental and geological conditions, thefts, and the absence (remoteness) of electrical power supply sources. The operation of ICSs (Pravdinsk plant) at the Nev’yansk RGPOC of OOO Gazprom Transgas Yeka terinburg shows that more than a half of them failed at the period shorter than their lifetime as declared by the manufacturer. This seems to be connected with the imperfection of the covers that are used and the active influence of earth currents. The Pravdinsk plant was closed and the search for other repair plants has not been successful. Therefore, it is necessary to make a decision on the replacement of the existing ICSs with units produced by other manufacturers or to build APs along the transportation route. The results of many years of work allow us to reveal the basic problems that must be solved to attain 100% protection of the linear part of the MGPs at the Nev’yansk RGPOC and OOO Gazprom Transgas Yekaterinburg as a whole. To make a reasonable decision on the application of the experience gained while operating CPSs at the Nev’yansk RGPOC and to provide 100%protection of pipelines, it is necessary to comprehensively discuss the CPS technology in Yekaterinburg with the participation of OOO Gazprom VNIIGAZ, DOAO Orgenergogaz, OAO Giprospetsgaz, and OOO Gazprom Gaznadzor. RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING

Vol. 46

No. 9

2010

THE CORROSION PROTECTION SYSTEM USED AT OOO GAZPROM

703

REFERENCES 1. Dolganov, M.L., Analysis of the State of the Corrosion Protection of Main Gas Pipelines and Gasfield Industry Objects, and Basic Results of Their Electrometric Diagnostics, Materialy mezhotraslevogo soveshchaniya po problemam zashchity ot korrozii (Proc. of Interbranch Conf. on Corrosion Protection Problems), Nebug, 2009; Moscow: OOO Gazprom Ekspo, 2009, pp. 3–15. 2. Kanaikin, V.A., Vnutritrubnaya magnitnaya defektoskopiya magistral’nykh gazoprovodov (InTube Magnetic Inspection of Main Gas Pipelines), Matvienko, A.F., Ed., Yekaterinburg: Ural. Otd. Ross. Akad. Nauk, 2009. 3. Shafikov, R.R., Monitoring and Predicting the Propagation of Corrosion Defects, Territoriya Neftegaz, 2009, no. 5, pp. 56–58. 4. Alfeev, V.N., Buzulyak, B.V., Zaval’nyi, P.N., et al., System for the Industrial Predictive and Corrosion Moni toring of Main Gas Pipelines, Gas. Prom., 2002, no. 9, pp. 43–47. 5. Glazov, N.P., Problems in Developing Technical Devices for the Diagnostics of the Corrosion State of Pipelines, Materialy otraslevogo soveshchaniya po problemam zashchity ot korrozii (Proc. of Branch Conf. on Corrosion Protection Problems), Moscow, 2008, pp. 33–40. 6. Miroshnichenko, B.I. and Varlamov, D.P., Evaluating the State and Safety Operation Time of Gas Pipelines, Gas. Prom., 2006, no. 2, pp. 48–50. 7. Steklov, O.I., Integrated Technical Diagnostics of Main Gas Pipelines, Territoriya Neftegaz, 2006, no. 4, pp. 20–26.

RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING

Vol. 46

No. 9

2010