How to reduce maintenance

impacts on natural gas

transmission?

Ing. Rastislav ŇukovičEFG2008, 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: Over 2200 kmDiameter of Pipelines: Mostly 1 200, 1 400 mmTransport Capacity: Over 93 bcm/YearMaximum Daily Capacity: Over 290 mcmInstalled Power: 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

Changing nature of transmission environment

I II III IV V VI VII VIII IX X XI XII

month

trans

mission

flow

20042007

Year 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

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 Hot tapping – 3 daysWelding on of the fitting: Stoppling – 2 days longitudinal welds – 3 days Plugging – 3 daysgirth welds – 4 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

KOA2 – older type CFA34 – new type

Gas engine CATERPILLARCAT 3412

CATERPILLARCAT G3412 TA 130

Fuel consumption (gas) 75 Nm3/hod., 150 Nm3/hod.,

Compressor DRESSER RAND USARVM KOA2

CAMERON USAC-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

Max. discharge pressure 7,24 MPa 7,3 MPa

Power output(Dependent on the level and theratio of suction / dischargepressure)

2500 – 24000 Nm3/h 2500 – 38000 Nm3/h

chassis 40 t FLOOR 40 t SVAN

Technical parameters

Use of mobile pumping compressor

Dresser Rand KOA2

Cameron C-Force 34

Use of mobile pumping compressor

Comparison of mobile compressors:

0

1

2

3

4

5

6

7

Length of repumping [Days]

Pres

sure

[MPa

]

KOACFAKOA+CFA

1 2 3 4 5 6 7 8 9 10 11

Evacuation of the pipeline DN1200:L= 22 000 m ; Psuction= 6,5 MPa; Pdischarge= 6,5Mpa

Flaring of waste gas

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

CEB4500

Advantages:• environmentally-friendly solution –

reduction of CH4 emissions• no luminous flame, no heat radiation• low noiseDisadvantages:• prolongation of the preparatory

phase• additional cost

Example:• pipeline DN1200; L= 22 000 m• start pressure flaring: 8 bar(g)• stop pressure flaring: 1 bar(g)

Flaring configuration: Flare time:2 x CEB4500 41 hours3 x CEB4500 28 hours

Use of mobile pumping compressor

Pre-boosting of the mobile compressor:

Objectives:• to shorten evacuation period• to achieve lower suction pressures

Reasons:• to improve effectiveness of the

mobile pumping compressor• to develop environmentally-friendly

solution

MC – mobile compressorBC – boosting compressorPV – pressure vessel

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:

Used technology Direct costs Indirectcosts

Impact on the length of

maintenance

Safety risks

Environmental impacts

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