System dynamics and structural integrity challenges of UGS compressor installations Rene Peters, Jan Smeulers, André Eijk TNO Energy [email protected]

2 October 18, 2012

Content TNO Introduction UGS operations in The Netherlands Bergermeer UGS project TNO activities in Bergermeer UGS Integrity challenges in compressor operation Flow induced vibration and noise in centrifugal compressor systems Pulsations and vibrations in reciprocating compressor operations Flow dynamic impact on flow metering accuracy Showcase: RWE Essent EPE

3 October 18, 2012

TNO is the largest independent research and technology organization in Europe About TNO Founded by Dutch law in 1930 Mission: strengthen innovative power of industry & government Independent of public and private interests Focussed on application of scientific knowledge Key figures Annual turnover: EUR 600 M€ (1/3 government, 2/3 industry) 4500 Employees Not for profit Multi-disciplinary teams, no typical industry silos Strengthened by cross fertilization with other markets One-stop shop

4 October 18, 2012

Themes and innovation areas

5 October 18, 2012

TNO works cross discipline and cross markets Defense: main R&D contractor Dutch navy

Automotive: leading car crash testing Europe

High-end industries: main supplier equipment to leading chip lithography machine producer

Geological Survey of the Netherlands Space: design of satellites, telescopes, mars pathfinder NASA and ESA

6 October 18, 2012

TNO in The Netherlands

Den Helder

Groningen

Soesterberg Hoofddorp

Leiden

Rijswijk Enschede The Hague

Apeldoorn

Helmond Delft Utrecht Zeist Eindhoven

7 October 18, 2012

Collaboration models of TNO

•

Fundamental knowledge

Knowledge development

Knowledge application

Knowledge exploitation

With universities

With partners

With customers

Embedded in the market

Joint research

EU

• •

Co-investment Innovation contracts

• •

JIP

Contract research Consultancy

• • •

IP licensing Training Workshops

8 October 18, 2012 19/11/2012

TNO Worldwide Coventry

Shanghai Brussels

Livonia

Seoul

Delft

Boston

Tokyo

Yokohama

Nogent Marne

Frankfurt Stuttgart

Qatar Bangalore

Wheelers Hill

9 October 18, 2012

Gas Storage in The Netherlands Bergermeer WG: 5 BCM Depleted reservoir (H-gas) Operator TAQA

Zuidwending Salt caverns (G-gas) Operator Gasunie Grijpskerk (H-gas) Operator NAM Depleted reservoir Operational 1997 Norg/Langelo (Ggas) Operator NAM Depleted reservoir

10 October 18, 2012

Bergermeer Gas Storage Project Europe’s largest open access gas storage facility Operator TAQA Partners EBN and Gazprom Cushion Gas 4.3 BCM Working Gas 4.1 BCM Injection Capacity 41 MMCM/D Send-out Capacity 57 MMCM/D Total Investment 800 Meuro Start operation April 2014

www.bergermeergasstorage.com

11 October 18, 2012

TNO Involvement in the Bergermeer UGS project Geomechanical study to analyse the risk of fault reactivation and induced seismicity (2009) System Dynamics Study of the injection compressors (2011) Integrity study for the water injection pumps according to API674 (2012)

Bergermeer gas field

12 October 18, 2012

TNO references in UGS installations in Europe NAM, TAQA, Gasunie

Centrica

Fluxys

Carrico

In total 25 UGS references in Europe

RWE, E.on, Exxon Nuon, Essent

OMV, RAG

13 October 18, 2012

Process Flow Diagram of an UGS

Reciprocating compressor

Centrifugal compressor

Heart of the system: compressor

Typical suction pressures: between 30 - 85 bar Cavern (discharge) pressure: between 50-400 bar Typical flows: between 12.000 – 200.000 Nm3/hr.

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Compressors are the most critical part of complete installation Typical process parameters: Pipe line (suction) pressures: 30 - 85 bar Cavern (discharge) pressure: 50 – 400 bar Flow: 12.000 – 200.000 Nm3/hr

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Working Principles Compressors Turbo compressor: Reciprocating compressor:

Gas is compressed by moving pistons, driven by a crankshaft Positive displacement compressor: Volume is drawn in compression chamber where it is trapped, compressed and released Flow and pressure does not depend on system characteristics Wearing parts: Compressor valves Piston ring Rider rings Pressure packings Bearings

Gas is compressed by rotating impeller Dynamic compressor: Pressure is accomplished by transfer of dynamic (kinetic) energy from the rotor to the gas Flow and pressure depends on system characteristics Wearing parts Pressure packings Bearings

Reciprocating versus Turbo compressor

16

Criteria

Reciprocating compressor

Turbo compressor

Efficiency

approx. 90 %

approx. 80 %

Operation range and control range

High operation range and flow range

One operation point with a flow range from 70 to 105 %

Different types of gas

Not sensitive

Leads to changes in operation conditions, depending on density

Working and principles

Oscillation process; pulsations; Bigger footprint; lubrication of piston

Rotating process; Less friction; Higher rotations; Oil-free compressor

Maintenance and repair

Spare parts about 20% of contract value

Spare parts about 10% of contract value

Leakage

Few

Lost of gas with higher pressures

Availability

Little, depends on driving unit

More, depends on driving unit October 18, 2012

17 October 18, 2012

Compressors are a source of unsteady flow

Reciprocating compressors

Turbo compressors create high

create a pulsating flow

frequency dynamic flow

Relative low frequency

Relative high frequency

High amplitude

Low amplitude

Pulsation dampers are

In addition, flow separation can

required

generate dynamic flows

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Impact of dynamic flow on UGS installations Pulsation source

FluidStructure Interaction

Transmission Resonance • Compressor induced pulsations • Flow instabilities

Pulsation forces • Side branches • Pipe system • Vessels

Direct Mechanical exitation

Displacement, Vibration, Cyclic stresses • Noise • Dynamic stress

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Issues related to dynamic aspects of UGS operation Pulsating flow (near fiscal meters) Structural vibrations (near compressors) Cyclic stresses (on installation parts) Flow-induced noise (from valves and structures)

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Impact of dynamic aspects of UGS operation Dynamic loading of installation

Impeller failure

and subsurface can lead to: Structural integrity treats Flow metering errors Excessive maintenance costs

Valve failures

Valve failure Impeller failure Foundation failure Noise radiation Reduced compressor efficiency Increased pressure drop

Foundation failures

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Solve problems on the drawing board not in the field Quite some integrity and operating issues often related to compressors

Feasibility analysis

but mostly now well understood

Front End Engineering Design (FEED)

For both types of compressors the

Detailed design

issues differ in nature and origin Installation Design optimization analyses are essential for both type of compressors

Start-up, commissioning

Problems must be solved in an early stage of the design, NOT during operation

Trouble shooting

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Required Analyses for a Reciprocating Compressor according to API Standard 618 (5th edition) Pulsation analysis (dampers & pipe system)

Mechanical vibration analysis (piping & compressor)

Torsional analysis

Compressor valve dynamic analysis

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Required Analyses for a Reciprocating Compressor according to API Standard 618 (5th edition) Structure /air borne sound analysis

Vessel static and dynamic analysis (API 618, ISO 13707)

Foundation dynamic analysis

Piping flexibility (thermal) stress analysis (e.g. ASME B31.3)

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Required Analyses for a Turbo Compressor High frequency dynamic analysis: excitation of acoustic resonances inside compressor (FSI)

Rotor dynamic analysis (API 617:avoid shaft cracks)

Anti-surge Control

Structure /air borne sound analysis

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Required Analyses for a Turbo Compressor Flow induced pulsation analysis: vortex shedding in closed side branches excites pulsating flow similar to API 618 analysis for reciprocating compressors (pulsation and mechanical response analysis) Piping flexibility (stress) analysis

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Required Analyses for a Turbo Compressor System dynamic studies (piping/compressor interaction): Trip, emergency shut down, start-up -> surge/stonewall analysis Analyse stability and performance of operation during ESD Evaluate need for hot or cold bypass valve Analyse potential interaction between recips and turbo compressors Typical compressor map

Calculated compressor map during ESD 35

surge cycle

Surge Line Basic ASC 30

Hot Bypass (50%) Hot Bypass (100%)

Compressor control scheme

Cold Bypass (100% ) 25

Cold Bypass (200% ) HB (50% ) + CB (140%)

20

BV 3

PC (75% ), t=4.7 sec

PCV 2

EBV

Air Cooler

PC (50% ), t=10 sec PC (25% ), t=19 sec

15

Booster Compressor

EDV

HBPV

10

Hot Bypass

ASCV 2

Flare Header

PCV 1

5

Cold Bypass 0 0.0

0.2

0.4

0.6 Norm alised Flo w [-]

0.8

1.0

1.2

Flare Header

d p [b a r ]

PC (100% ), t=1.0 sec

BV 2

PCV 3

EQV 2

CBPV

BV 1

EQV 1

ASCV 1

Recompressor

= Check Valve = Control Valve = On/Off Valve

EDV EQV PCV EBV BV ASCV HBPV CBPV

= Emergency Depressurisation Valve = Pressure Equalisation Valve = Pressure Control Valve = Emergency Block Valve = Block Valve = Anti-Surge Control Valve = Hot Bypass Valve = Cold Bypass Valve

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Pressure versus Flow pulsations Pressure and flow disturbance are interrelated. For pressure pulsation issues: the absolute amplitude of the disturbance is most relevant to determine shaking forces. For flow pulsation issues: the relative amplitude of the disturbance is most relevant. In case of low mean flow (depletion), flow pulsation issues will be most relevant Many flowmeters have an error in reading in a pulsating flow Flow reversal

28 October 18, 2012

DP flow (Orifice) meter

∆p

Measurement principle: pressure drop over U

an orifice depends on the gas velocity Quadratic relation for pressure drop: Time-average of the recorded pressure drop does not correctly reconstruct the actual flow The offset is systematic: positive Error depends on (U’RMS/Umean)2, referred to as square-root error ISO/TR 3313:

 U RMS ET = 1 +   U mean

2  −1 

1 ∆p = K ⋅ ρU 2 2

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Acceptable dynamic performance of compressor installations Pressure pulsations should be within the allowable limits prescribed in the API618 standard for reciprocating compressors The vibrations on the compressor installation should be within the levels specified in the EFRC guideline (free download: www.recip.org) The flow pulsations should be within the acceptable level for the flow meter principle used (usually allowed maximum 5% of the mean flow)

30 October 18, 2012

Conclusions The compressor is the heart of the UGS installation, but can cause serious integrity threats to the installation Both reciprocating compressors and turbo compressors can generate dynamic forces which can cause vibrations, noise and flow metering errors Since large pressure and flow variations occur during UGS operation, acoustic and mechanical resonances are likely to be excited Fiscal metering can be impacted by unsteady flow causing significant flow metering errors Adequate dynamic analysis during the design stage can prevent unacceptable vibration and noise levels during operation Allowable pulsation and vibration levels for recips can be found in the EFRC vibration guideline (see www.recip.org)

31 October 18, 2012

Questions

Rene Peters TNO Energy Phone: +31 888 666 340 Mobile: +31 6 51551566 Email: [email protected]

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Example UGS Essent EPE, Germany 3

• Facility owner: Essent • Designed by HGC Hamburg Gas Consult • Technical consult TNO • Salt Cavern 130 m

90 m

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Case Study UGS RWE/Essent EPE Germany Two 6-throw ARIEL JGV 6 compressors of each 7.5 Mw Operation modes: 1-stage mode (gas withdrawal) 2-stage mode (gas storage) Cylinder operation: Serial mode for 2-stage Parallel mode for 1-stage Speed range: 400-750 rpm First gas fill: speed reduction up to 300 rpm Process data: Suction pressure: 40- 70 barg Discharge pressure: 80-220 barg Flow rate injection: 50.000-100.000 Nm3/hr Flow rate withdrawal: 100.000-200.000 Nm3/hr Flow rate first fill: 30.000-50.000 Nm3/hr

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Case Study UGS RWE/Essent EPE Germany Acoustic Analysis Pulsation Dampers

Optimised damper layout: Acoustic filter Acoustic Analysis Pipe System

Installation of orifice plates

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Case Study UGS RWE/Essent EPE Germany Mechanical Response Analysis Piping

FE model pipe system

Too high Vibrations

Advised pipe supports

Mechanical Response Analysis Compressor Manifold

FE model compressor

FE model complete manifold Too high Vibrations

Required Modifications

36 October 18, 2012

Case Study UGS RWE/Essent EPE Germany

Photo of the as built compressor system