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December 2004

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Power-Gen International Orlando

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Some new products are borne ofgood luck and inspired technolog-ical breakthroughs. Others come

into being as creative new combinationsof well-proven, existing technologies.

Cooper Compressions introduction ofits new MSG Alpha integrally gearedcentrifugal process gas compressor earli-er this year definitely falls under the lat-ter category, according to its creators. Allthe technology applied to this new prod-uct has already matured in a range ofother Cooper Compression products.Whats new is the MSG Alphas specificcombination of design features thatmake it ideally suited to fuel gas boost-ing for even the largest high pressure

ratio gas turbines.According to John Bartos, Coopers

vice president, engineering and newproduct development, the MSG Alpha isthe most compact Cooper Compressionframe available for gas service and onethat offers more range in operating per-formance (higher flow capacity/high suc-tion pressure capability) than flooded oroil-free rotary screw compressors.

Significant to this compressor is itsexcellent efficiency, high reliability, low

maintenance cost and traditional Coop-er Compression quality, he said. It isavailable in one- through six-stage con-figurations. Its multistage, integrallygeared, inter-stage cooled, oil-free cen-trifugal design, combined with its abili-ty to handle power up to 932 kW andpressures up to 82 bar, its ability toaccommodate high suction pressuresand dual process capability, makes theMSG Alpha an excellent choice formany process gas applications and es-

pecially for fuel-boosting compressionneeds with medium natural gas-fueledturbines, such as the LM6000 from GE.

The MSG Alpha is a result of the natur-

al evolution of Cooper Compressionitself. In its consolidation with CooperEnergy Services, Cooper Turbocom-pressor became a complement to the nat-ural gas products and markets of CES. Asa consequence, the company evaluatedcentrifugal product solutions in applica-tions that once used primarily reciprocat-ing or oil-flooded screw compressors.

The MSG Alpha offers a number offeatures that make it ideal in demandingfuel-boosting applications, according to

Omar Kabir, Coopers senior principalengineer in new product developmentengineering. As a centrifugal compres-sor the MSG Alpha delivers high effi-ciency, high availability, dependabilityand minimal maintenance demands.

The MSG Alphas compression proc-ess is dynamic (as opposed to positivedisplacement) and results in no pulsa-tion within the gas stream. The result-ing forces and moments imposed onthe support structure are exceptionally

low, resulting in lowered overall costsfor foundation and support systems.Furthermore, it has a very small foot-print compared to alternative packages.

And because of the reliability andextremely high availability typical of inte-grally geared centrifugal compressors,theres no realistic need for backup com-pression. One MSG Alpha can oftenreplace up to three reciprocating or oil-flooded screw compressors, Kabir said.

One key benefit of the MSG Alpha toturbine operators, according to Kabir, isthat because the MSG Alpha compres-sion process is oil free the compres-sion process itself cannot contaminate

the process or fuel gas with lube oil.Coopers oil-free technology was

developed over years of experience withproven centrifugal compressor technol-ogy where oil separators and oil treat-ment are not required or permissible.By design, the compression process andentire gas stream in the MSG Alpha isisolated from the bearings and gearbox,eliminating the possibility of processgas and oil interaction. Downstreamscrubbers are not necessary since the

Gas Compression

by Joe Kane and Phil Burnside

New Centrifugal Compressorfor Fuel Boost Applications

Coopers MSG Alpha integrally geared compressor promises reliable service, contamination-free gas

Diesel & Gas Turbine Worldwide December 2004

Shown here is a three-stage configuration of

the MSG Alpha integrally geared centrifugal

compressor. It is available in one- through

six-stage configurations. Its multistage, inte-grally geared, inter-stage cooled, oil-free

centrifugal design is capable of handling

power up to 932 kW and pressures up to 82

bar.

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lube oil is not in contact with the proc-ess gas and does not become contami-nated. That can mean significantly lesserosion of turbine blades and otherinternal parts, Kabir said.

The MSG Alpha is a sister to the

proven TA 3000 centrifugal compressorthat has been on the market for over adecade in critical process air serviceapplications such as chemical and petro-chemical industries, said Kabir. He saidthat the complex combination of dryfaced seal and redundant labyrinth sealsthat assures containment of process gaswas introduced in 1994 and has beenused on much larger, high-pressuremachines with excellent success. Also,the physical atmospheric space between

the gearbox and the compressor hous-ing, which has been a classic design ofCooper Turbocompressor, guaranteesoil free process gas compression. Heemphasized that all rotating elements ofthe new compressor were transferredfrom totally proven technology.

The MSG Alpha was designed andanalyzed using the latest computationalengineering techniques including rotordynamic analysis, computational fluiddynamic (CFD) analysis, and finite ele-

ment analysis (FEA) to maximize theperformance and reliability of each de-sign. Another unique computer designapplication is the use of parametric solidmodeling for pre-engineered buildingblocks or modules. The parametric as-sembly forms the core of a new productdevelopment process that links and inte-grates marketing, design engineeringand manufacturing on a common plat-form for a unified and rapid design cycle.

The gearbox is a horizontally split

design. This permits easy access to inter-nal components for inspection andfuture upgrades. The central low-speedbullgear permits each pinion to operateat optimum speed to match the flow andpeak efficiency characteristics of theimpellers. The bullgear is connecteddirectly to the compressor driver by alow-speed coupling.

Sleeve bearings are used to supportthe bullgear journals. The high-per-formance pinions are supported byhydrostatic bearings. The patenteddesign of the squeezed film bearings andviscous damper results in long-life andvirtually vibration-free operation,according to the company. Thrust loadsare transferred, using tapered riderring thrust collars, to the low-speedbull gear thrust bearings. The rider rings

are a part of the pinion shaft and rideagainst the bullgear creating an oilwedge to carry the net thrust load whereit is absorbed by a simple low-speedthrust bearing. Each rotor assembly con-sists of a pinion shaft to which one ortwo impellers are attached. The piniongears are hardened and precisionground to AGMA 13 quality standards.Smooth, vibration-free operation isassured through precision componentbalancing of individual parts and then

the final assembly balancing. This de-sign minimizes power loss and maxi-mizes mechanical integrity of the rotat-ing components.

The design details mean that an MSGAlpha has no wearing parts requiringperiodic changes or replacement of thecompression elements, no contamina-tion of the gas stream with particulatematter or lubrication oil and no need ofdownstream treatment.

Aerodynamic performance is the key

to compression efficiency. To assure theoptimum performance for every applica-tion, the aerodynamic components aredesigned to meet each specific processneeds. Three-dimensional computation-al fluid dynamic (CFD) analysis usingreal gas properties is used to optimizethe compressible viscous flow througheach stage resulting in a matched high-efficiency impeller, inlet and diffusercombination.

After assembly, each unit undergoes

a complete aerodynamic and mechani-cal test in Cooper Compressions testfacility. Testing is performed by experi-enced engineers and technicians fol-lowing the guidelines set forth in the

ASME PTC 10 test code.Five individual test stands are avail-

able to test the units as complete pack-ages under customer-specific designconditions including design speed, gasproperties, as well as inlet and inter-cooler water temperatures. Each standis equipped with an electronic variablefrequency drive capable of supplyingeither 50 and 60 Hz and voltages rang-ing from 380 to 4160 V. The stands arealso capable of achieving over-speed to

ensure the mechanical integrity of thecompressor. Closed loop package test-ing is also available.

According to Bob Rajeski, president,Cooper Compression follows a well-defined product development processdriven by the voice of the customer.We believe in investing in new productdevelopment as we want to create thebest value for our customers as theirmarkets and needs change.

Gas Compression

A three-stage MSG Alpha compressor on one

of Cooper Compressions five test stands. Cutaway drawing of the impeller, shaft and

seals of the MSG Alpha compressor.

Exploded view of the MSG Alpha Compressor

in its three-stage configuration.

REPRINTED FROM DECEMBER 2004 DIESEL & GAS TURBINE WORLDWIDE Copyright Diesel & Gas Turbine PublicationsPrinted in U.S.A.

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THE EDGE IS INNOVATION

T H E E D G E I S Y O U R S

Oil free. Pulsation free. Vibration free.

And they practically take care

of themselves.

MSG fuel gas boosters. No matter what the application,

our portfolio offers the perfect multi-stage, integrally

geared centrifugal compressor solution. Theyre all 100%

oil free, pulsation free, and vibration free. They all take

advantage of proven Cooper Compression technology,

including our unique atmospheric air gap and superior

sealing arrangementsay goodbye to oil contamination

and our exclusive low-speed rider ring thrust collar, for

outstanding, long-lasting performance and extremely low

maintenance costs. Theyre US-built, so theyre readily

available, faster. And theyre backed by an unbeatable

warranty. Our latest, the MSG Alpha, is the only one in the

world made to run in the 850-1250 horsepower range,

with confidence. And its just one of a complete line of

MSG centrifugal engineering wonders. So, real ly, why not

centrifugal when Cooper Compression gives you such an

obvious edge? www.msgalpha.com

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