GE Infrastructure

Oil & GasExhaust ducts

Stig InstanesSales Manager, Services

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GE

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Six businesses, each with a number of business units aligned for growth.

Commercial Finance

Healthcare

Infrastructure

NBC Universal

Consumer Finance

Industrial

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Oil & Gas

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Focus on Oil & Gas Market

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From Nuovo Pignone to GE InfrastructureOil & Gas – 160 Years of Experience

Nuovo Pignone Established in Florence as a Cast Iron Foundry

Design and Production of Compressors

Production of Energy Related Equipment

Production of Turbocompressors

GE Buys Nuovo Pignone Majority Share

Global Services Business Formed

GE Acquires Gemini, Rotoflow, Thermodyn, Odessa, A-C Compressor, CONMEC and PII

1842

1901

1954

1960

1994

1997

1999to

2004

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Nuovo Pignone• Centrifugal & Reciprocating

Compressors• Gas & Steam Turbines• Reactors• Air-Coolers• Pumps - Valves• Metering Systems

Gemini• High Speed Recips.

Rotoflow• TurboExpanders

Odessa• Multi-Vendor Gas Turbine

Services

A-C Compressor• Screw Compressors• Centrifugal Compressors

Conmec• Multi-Vendor

Compressor Services

PII• Pipeline Solutions

Thermodyn• Low & Medium Pressure

Centrifugal Compressors• Low & Medium Power

Steam Turbines

GE Infrastructure’s Oil & Gas centers of excellence

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GE Infrastructure’s Oil & Gas global presence

Oil & GasBusinesses

Sales Offices

Service Shops

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Turbines

Gas Turbines• Over 1,700 Units• 5-124 MW• Aero and Heavy Duty• On and Off-shore

Norwegian fleet• Hydro (PGT16, PGT25 and PGT25+): 16 units • Statoil (PGT25 and LM6000): 9 units• COP (PGT25): 5 units• Marathon (LM2500): 2 units

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Exhaust ducts

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Exhaust ducts

• GE Oil & Gas scope of supply are ranging from– only flange at GT exhaust plenum to…– complete exhaust system including Silencers and WHRU.

• Detail design, engineering and fabrication are performed by GE’s approved duct/WHRU vendors following Customer and GE specifications.

• Mechanical design are considering the following factors– Torsional effects – due to friction forces and support eccentricities– Localized stresses – at flanges and duct supports – Thermal stresses – due to uneven temperature distribution and support design– Natural frequencies – due to external wind loads– Flow induced vibration – that may lead to fatigue failure

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Exhaust ducts - Design

GE’s “Best practice” for exhaust duct design. #1

• Incorporate expansion joints at supply limits, i.e between different vendors– To avoid transfer of “unaccounted” loads.– Minimize installation errors

• Symmetry of duct supports, preferably at a common elevation– minimize eccentric loads, also during intermediate load conditions

• Flow induced vibration– Avoid boundary layer separation. (CFD simulations to be performed for complex flow

patterns designs)– Keep gas velocities below 30-35 m/s– Keep angle of divergence in duct transitions below 30 degrees.

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Exhaust ducts - Design

GE’s “Best practice” for exhaust duct design. #2

• “Hot ducts”– Cylindrical elements to be used to avoid local stress in corners– Stiffners and support structures will add thermal loads to the hotter duct and needs to be

accounted for during design.– Flange bolts and nuts to be carefully chosen to keep torque after multiple thermal cycles.

> Bolts and nuts normally need Re-torque after first start-up

• Damper– Dampers should be placed upstream expansion joints.

> This design will structurally isolate the hot damper from the cold inactive cold duct; minimizing potential thermal stress.

– Avoid “dead legs” when using shut off dampers.> The cooling effect on trapped exhaust gases may introduce thermal stress.

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Alternative: Square insulated stacksAlternative: Square insulated stacks

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Exhaust ducts - Design

GE’s “Best practice” for exhaust duct design. #3

• “Cold duct” - Duct Casing with internal insulation > Reduces thermal cycle stresses and overall duct casing temperature> Reduces thermal expansion induced problems as well

– Minimum duct plate thickness 6+1.5 mm for carbon steel (ASTM A36) and 5 mm for SS steel (AISI321).

– Minimum flange thickness 10mm – Minimum 150mm basalt wool approved insulation (100 mm if out of reach of personnel)– Minimum Insulation lagging sheet thickness 2.5 mm. (ASTM A240 Tp409). – Max distance between studs 300mm – Nuts and washers to be welded to Studs.

Cold casing design is “proven” technology and are incorporated in the majority of GE Oil&Gas turbine packages.

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Exhaust ducts - Maintenance

- Expansion joints- Normally the week point in a duct configuration- Even “proven” design EJ need regular inspection and replacement.- Accessibility for maintenance shall always be foreseen

- Bolts and nuts in flanged connections- For “hot ducts” re-torque after first start up is normally needed- Regular Visual inspection followed up by re-torque