How to reduce maintenance impacts on natural gas transmission? Ing. Rastislav Ňukovič EFG2008, Bratislava, 18.9.2008 Content of the presentation • Introduction of eustream • Description of eustream‘s pipeline system • New challenges for maintenance and how to tackle with them • Possibilities for maintenance of pipelines - preparatory phase • Possibilities for maintenance of pipelines - performance phase • Conclusions Description of eustream´s transmission system Lengths of Pipelines: Diameter of Pipelines: Transport Capacity: Maximum Daily Capacity: Installed Power: Over 2200 km Mostly 1 200, 1 400 mm Over 93 bcm/Year Over 290 mcm Almost 1 050 MW New challenges for maintenance • new trends in the gas business environment – – – – – increasing competition increasing number of short-term contracts increasing number of customers pressure to shorten maintenance periods pressure on costs • need to respond to new legislation – – gas legislation packages new environmental legislation transmissionflow Changing nature of transmission environment 2004 2007 I II III IV V VI VII VIII IX X XI XII month 2004 2005 2006 2007 Average Difference [Nm3/day] 4 419 573 6 005 701 6 753 148 8 240 272 Max/Min Transportation Ratio 1,59 1,96 2,52 2,35 Year Consequences: • Increased number of starts of turbo-compressors and auxiliary technology • Increased number of manipulations with technological devices • Higher probability of failures • Limited time for maintenance activities How to tackle the new challenges ? • to shorten the maintenance periods – – preparatory phase (safe stopping and depressurizing of transmission network technology) performance phase • to introduce new maintenance technologies – – improving effectiveness of performance reducing maintenance impacts on operation - minimizing of disruptions to the system Possibilities for maintenance of pipelines The preparatory phase of the work : • depressurizing – entire gas discharge to the air • use of Stopple fittings to isolate the affected section • using the mobile pumping compressor – flaring of waste gas – pre-boosting of the pumping compressor The performance phase of the work (new technologies): • orbital welding technology • non destructive defectoscopy - ultrasonic girth weld inspection system Entire gas discharge to the atmosphere Advantages: • the quickest way to depressurise the pipeline • minimal direct costs (personnel, material, services) Disadvantages: • large indirect costs (loss of the discharged natural gas) • large environmental impact • safety risks – possible dangerous concentration of the natural gas • high noise Conclusions: • the method is used only in case of emergency when other methods are not feasible Use of Stopple fittings • to isolate the affected pipeline section without flow stoppage • to build pipeline branch or pipeline looping without flow stoppage Hot tapping Stoppling Plugging Closed fitting Example – works schedule for the Stopple fitting DN1200: Fitting position selection – 1 day Welding on of the fitting: longitudinal welds – 3 days girth welds – 4 days Hot tapping Stoppling Plugging – 3 days – 2 days – 3 days Use of Stopple fittings Use of Stopple fittings Advantages: • low losses of discharged gas • very low environmental impact – minimum amount of gas discharged into the atmosphere • time for maintenance is shortened – hot tapping can be performed in advance under full operation • fittings can be re-used for Stoppling in the future Disadvantages: • high demands for positioning of fittings (e.g. problems with existing welds in the pipeline) • the need to stop the gas flow during the welding phase • expensive technology • limited application during emergencies Use of mobile pumping compressor Technical parameters KOA2 – older type CFA34 – new type CATERPILLAR CAT 3412 CATERPILLAR CAT G3412 TA 130 75 Nm3/hod., 150 Nm3/hod., DRESSER RAND USA RVM KOA2 CAMERON USA C-FORCE 34 Technical design two-stage, double-acting two-stage, double-acting Working pistons 1 x 5,25“ a 1 x 7“, 2 x 3,75“ a 2 x 4,125“ Suction pressure 0,7 – 7 MPa 0,5 – 7,5 MPa 7,24 MPa 7,3 MPa 2500 – 24000 Nm3/h 2500 – 38000 Nm3/h 40 t FLOOR 40 t SVAN Gas engine Fuel consumption (gas) Compressor Max. discharge pressure Power output (Dependent on the level and the ratio of suction / discharge pressure) chassis Use of mobile pumping compressor Dresser Rand KOA2 Cameron C-Force 34 Use of mobile pumping compressor Comparison of mobile compressors: 7 KOA 6 CFA KOA+CFA Pressure [MPa] 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 Length of repumping [Days] Evacuation of the pipeline DN1200: L= 22 000 m ; Psuction= 6,5 MPa; Pdischarge= 6,5Mpa 11 Flaring of waste gas Advantages: • environmentally-friendly solution – reduction of CH4 emissions • no luminous flame, no heat radiation • low noise Disadvantages: • prolongation of the preparatory phase • additional cost CEB4500 Capacity 100 000 Nm3/day Power 45 MW Footprint and Height 3 x 2,6 x 6,2 m Weight 7500 kg Inlet pressure 0.8 barg - 8 barg Electrical power consumption 5 kW Battery limit 3’’ ANSI 150 lbs RF Operating Temperature 900 - 1200°C Ground Temperature Ambient during operation Example: • pipeline DN1200; L= 22 000 m • start pressure flaring: 8 bar(g) • stop pressure flaring: 1 bar(g) Flaring configuration: 2 x CEB4500 3 x CEB4500 Flare time: 41 hours 28 hours Use of mobile pumping compressor Pre-boosting of the mobile compressor: Objectives: • to shorten evacuation period • to achieve lower suction pressures MC – mobile compressor BC – boosting compressor PV – pressure vessel Reasons: • to improve effectiveness of the mobile pumping compressor • to develop environmentally-friendly solution Use of mobile pumping compressor Advantages: • relatively low direct costs (price of the compressor rent, personnel, average consumption – 75 m3/h) • low environmental impact (only a small amount of the gas is discharged) • possible solutions for further decrease of the environmental impacts Disadvantages: • length of pumping time – prolongation of the maintenance activity • technical limit - minimal suction pressure 0,7/0,5 MPa – below this limit operation is not possible • high initial investment to buy the mobile pumping compressor Performance phase - Orbital welding Objective: • to speed up the welding works Features: • automated solution • about 50% time reduction compared to the manual welding • difficulties to use the technology in complex conditions Performance phase – Non Destructive Defectoscopy NDT – ultrasonic girth weld inspection system Objective: • to speed up the defectoscopy works Features: • comparable method to X-ray • about 30%-50% time reduction compared to X-ray • difficulties with welds on pipelines with different wall thickness Summary Maintenance of pipelines – preparatory phase: Impact on the length of maintenance Safety risks Environmen tal impacts Used technology Direct costs Indirect costs Discharge to the atmosphere minimal high low high high Mobile pumping compressor medium low high medium medium Stopple fittings high minimal medium medium minimal Maintenance of pipelines – performance phase: • orbital welding technology – to speed up the welding works by 50% • non-destructive defectoscopy – ultrasonic girth weld inspection system Thank you for your attention