INTEGRITY MANAGEMENT OF PIPELINE SYSTEMS AT COMPRESSOR STATIONS OF EUSTREAM, A.S.

BACKGROUND Eustream (The Slovak Republic) is the largest gas transmission system operator in the countries of the European Union. Its transmission system is part of the system supplying natural gas to countries of western Europe from the Russian Federation. The annual transmission capacity is 90 billion Nm3 of natural gas which represents around 20% of the consumption of EU countries. The transmission system consists of 2, 260 km of pipes, mostly DN1200 and DN1400 and 4 compressor stations with overall installed output of 1,050 MW. The main mission of eustream is safe, reliable and cost-effective operation of the transmission network, its maintenance and development while respecting maximum safety and health protection at work and minimum negative impact upon ecology as well as keeping and improving quality of the provided service.

AIMS The transmission network of eustream consists of three main parts: Ø Transmission pipelines Ø Compressor technology Ø Pipeline systems of compressor stations

In the transmission pipeline area, huge effort has been taken in the prior years to establish a risk assessment syst em of the pipeline (Integrated Technical Information System) as part of integrity management. In compressor technology area, safety and reliability of operations is covered by the RCM system and its implementation in SAP/PM module. As the ITIS system is restricted to the transmission pipelines, quite an important part of the transmission network – the compressor station pipeline system remained without any safety or reliability monitoring system . Currently, more effort is being put especially to establishing an integrity management system in this part of the transmission network. The task is even more pressing as the compressor stations are unique due to its scale and total installed output of turbo compressors. On average, compressor stations are more than 900 m long and the gas technology establishes a complex web of aboveground and underground pipes crossing each other.

To assess safety and reliability, the following factors have further impact: Ø Due to strategic reasons, compressor stations were developed outside of

residential areas, mostly in marshes and damps Ø Due to safety reasons, pipes with excessively thick walls were designed and

used Ø Pipe insulation was applied in situ during the construction Ø The pipeline system of compressor stations was extended gradually, as the

transmission capacity was growing Ø No active corrosion protection was applied during the construction Ø The pipeline systems of compressor stations are nonpiggable Ø No „No pig“ method can be used for pipe diagnostics (thickness of walls,

number of crossings)

METHODS AND RESULTS

SAFETY AND RELIABILITY ACTIVITIES OF PIPELINE SYSTEMS IN COMPRESSOR STATIONS IN THE PAST 1 Corrosion Protection 1.1 Active corrosion protection (CP) A pilot CP project was implemented in 2002 on the pipeline system of compressor station 02. Based on the results of the pilot project, the active CP system wa s applied to all compressor stations. Various anodes have been used due to the complexity of pipeline systems – ferrosillicate, flexible, galvanic, rail anode. 1.2 Passive corrosion protection The ground-air junction has been identified as the point with increased corrosion risk level. In 2003 – 2008, all pipeline systems of compressor stations were excavated at ground-air junctions, after which they were treated with polyurethane insulation with high soil corrosion protection. Aboveground parts were treated against UV radiation . 2. Elasticity&Strength In the past, various tasks were undertaken to assess the residual life of the pipes due to various dynamic effects during the operation: Ø Stress test of pipes in pipeline systems through pressure impact upon the start

up of turbo machines (designing a model of gradual start up and line connection of turbo c ompressors)

Ø Experimental and numeric assessment of destruction pressure in corrosion damaged pipes and comparing the readings with semi -empiric values of ratios under DNV-RP-F101 or ASME B31G standards .

Ø Assessment of the impact of circumferential welding defects upon the load capacity of gas pipes.

Ø Assessment of life expectancy of pipes at compressor stations using numeric and experimental elasticity methods. Based on the results, elastic pipeline systems of compressor stations were commissioned anew or were relocated .

3. Diagnostics of pipeline system components 3.1 Check excavations were performed at selected locations, insulation condition was assessed and corrosion damage was investigated. 3.2 During the replacement of underground components of pipeline systems (valves, casings, fittings), diagnostics of pipes and insulation repairs were performed. During above activities, straightforward internal rules were missing that would unify and align measures, would propose evaluation of the conclusions under individual measures and would enable overall assessment of the total risk of pipeline systems at compressor stations.

DEVELOPING AN INTEGRITY MANAGEMENT SYSTEM OF PIPELINE SYSTEMS AT COMPRESSOR STATIONS With regards to above, a decision to develop internal rules for integrity management system of pipeline systems at compressor stations of eustream was adopted. Thorough mapping of pipeline systems at compressor stations and their components was an important step preceding such task. A unique combined technology of laser scanning of aboveground parts and locating underground parts was selected to do the job. The result of the project was: Ø Creation of a very precise 3D compressor station model in dgn format Ø Accurate incorporation of pipeline systems of compressor stations in GIS Ø Updating technology charts and importing them into an inte lligent browser

After the available nat ional and international legislation was reviewed, it was decided that the basis of the future inhouse regulations should derive from the NACE RP0502-2002 standard. I.e. to take over the ECDA (External Corrosion Direct Assessment) method described in the standard as the base for the future assessment of the condition of pipeline systems of compressor stations in terms of corrosion. The ECDA method is at the same time a structured process designed to improve safety and reliability of pipeline systems (nonpiggable pipelines). It identifies and handles corrosion activities, eliminates the cause, thus trying to proactively prevent increased cases of corrosion defects that can destroy pipeline integrity.

CONCLUSIONS eustream is currently establishing a methodology that will apply ECDA procedures described under the NACE RP0502-2002 standard together with their own know-how so as to fully account for the conditions of the operation of pipeline systems of

compressor stations. The results of the methodology shall be further described in our presentation delivered at the conference.