Compresor+Tech+ +May+2011

www.compressortech2.com

May 2011

Status of African Oil and Gas Development

Ambient Air Standards Explained Part I

New Pump from Sundyne

On the Back

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HOERBIGER Engine Solutions

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C O M P R E S S O R S n T U R B I N E S n G L O B A L S E R V I C E

EBARA CORPORATIONwww.elliott-turbo.com

n Customer: Ethylene plant, Saudi Arabia.

n Challenge: Overhaul and repair four critical steam turbines in 12 days.

n Result: Elliott coordinated six months of pre-planning and completed the project four days early.

They turned to Elliottfor planning and execution.The customer turned to Elliott because they understood that planning is everything and that few companies can match Elliott in turnaround planning and execution. Who will you turn to?

The world turns to Elliott.

SEE DIRECTLINK AT WWW.COMPRESSORTECH2.COM

Elliott.indd 1 4/21/11 2:47:47 PM

UNDERSTANDING CATALYSTS A Handbook for the User Part 3 Building a Catalyst, Step 1 Forming a Substrate

Catalyst Emissions EduCation Program

A scheduled series from Catalytic Combustions Catalyst 101

substrateThe substrate is more than just the framework that supports everything else so exhaust gases can come in contact with the catalytically active layer. The majority of substrates used for industrial engines are an Iron-Chrome-Aluminum alloy that has been rolled into a .002 inch thick foil strip. Foil is preferred for industrial engines, instead of the ceramic substrates typical in automobiles, because of the vibration, duty cycle changes and misfires it must endure.

Before substrate manufacturing begins, choices have to be made regarding the shape needed, the size of the cells (cell density), the cells longitudinal pattern and the inclusion of brazing materials or mechanical locks. Housings for round, rectangular, and other multi-sided shapes are in use and each shape has its pros and cons regarding installation and sealing effectiveness. Cell density is expressed as the number of cells per square inch, or cpsi. The most common cell densities are 200-400 cpsi, but they can range from 100-1,000 cpsi. The longitudinal pattern of the substrate can be straight, herringbone (zig-zag), or angled from one face to the other. The combination of cell pattern and cell density provides a balance between maximizing the contact between the exhaust and the surface of the catalyst, which directly affects the performance of the catalyst while minimizing the backpressure on the engine.

The foil arrives on coils containing several thousand feet of foil already slit to the desired flow depth of the pattern. The cell structure is achieved by corrugating the foil with special gear forms, progressive die forming or a pleating process. Then the foil can either be formed into the substrate shape or it begins the coating process, depending upon the manufacturers process. For this discussion, we will follow the

QuAlITy CATAlysTs sInCe 1950

IN THE NEXT ISSUE Building a Catalyst, step 2 -

The Wonderful World of Washcoat

For your catalyst questions, contact:John W. Robinson Jr., V.P. Catalyst Group

[email protected]: 715-568-2882 Ext. 127 Fax: 715-568-2884

www.Catalyt icCombustion.com

The structured monolith has emerged as the clear choice for the catalyst form used in industrial engines. Its three layers - substrate, washcoat and catalytically active materials - all play vital roles in the performance of the catalyst. Lets begin with the substrate.

first path and assume that a round element is being made.

To make a round substrate the corrugated foil is combined with a layer of flat foil and is wound around a hub or mandrel. Winding is done under tension to keep the substrate flat and resist deformation from its own weight. substrate size is limited by the catalyst manufacturers downstream coating equipment, but elements as large as 72 inches have been produced.

Over the years many solutions to prevent the commonly seen sagging or telescoping failure mode have been implemented. Inserting rods through the foil across the diameter of the substrate, using retaining bars either laid across or placed flush with the faces of the substrate, and incorporating a lock and key pattern into the foil corrugation pattern have been tried with various degrees of success. By far the most robust method applies a brazing alloy or compound during the winding operation, which after being processed at high temperatures and vacuum levels approaching that of outer space, weld the layers together into a unified whole.

At this point our wound, brazed substrate is complete and ready for the coating process.

Straight Cell Pattern

Herringbone Cell Pattern

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We borrow from nature everyday. It doesnt take much imagination to see the intricate vein structure of a simple leaf, routing life to a plant, engineered as the runs and traces of a circuit board, pulsing with countless electronic signals from the very heart of products like the EPC-110 Air/Fuel Ratio Controller from Altronic.

Its all in the family.The EPC-110 is one of many Altronic products that help operators to cost-effectively increase the efficiency and reliability of their natural gas-fired industrial engines, while reducing emissions in the process. Fewer emissions, greener planet. We call this combination of features Greenability and, just like Altronics legendary product quality, its built right innot added on.

When you borrow from Mother Nature, its always a good idea to pay her back.

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Be good to yourself and kind to your Mother.Contact an Altronic Distributor for more information about the EPC-110 and to find out how you can apply the benefits of Greenability to your application. You can find one at www.altronicinc.com.


When you borrow from Mother Nature, its always a good idea to pay her back.

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4 CompressorTechTwo

PUBLICATION STAFFCTTwo Founder ........................ Joseph M. KaneEditor and Publisher ..........D. Phillip BurnsideAssociate Publisher .............. Roberto ChelliniManaging Editor ..........................Patrick CrowSenior Editor .......................... Brent D. HaightSenior Editor .................. Michael J. BrezonickRegional Manager/Editor ........... Ian CameronSenior Editor ..........................Dawn M. GeskeFeature Editor .....................Amanda M. KlempAssociate Editor ..........................Kyle KopplinAssociate Editor ...............................DJ SlaterField Editor/ Business Manager ...................... Bo SvenssonAdvertising Manager .......... Christa L. JohnsonProduction Manager ............. Marisa J. RobertsGraphic Artist ........................Brenda L. BurbachGraphic Artist .............................Carla D. LemkeGraphic Artist ...........................Amanda J. RyanGraphic Artist ................................Alyssa LoopeCopy Editor ...........................Melissa C. McNultyCirculation Manager ...................Sheila Lizdas

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According to a recent editorial in The Wall Street Journal, more Ameri-cans work for the government than in manufacturing, farming, fishing, for-estry, mining and utilities combined. Much has to do with the burden of regulations imposed by various agen-cies. For every regulation, a regulating body must be formed. To err is hu-man, so Ive heard. It seems as though every time someone makes a mistake, no matter how trivial, someone else decides we need a regulation to either prevent the mistake in the future or to penalize the offender.

Weve Become a Nation of Tak-ers, Not Makers, is the title of this observation by Stephen Moore, se-nior economics writer for the Journal. Some 22.5 million people work for the government. All of manufacturing employs approximately 11.5 million just about half. This is compared to 1960 when 15 million worked in manufacturing and 8.7 million for gov-ernment. Nearly half of the US$2.2 trillion cost to run state and local gov-ernments is the US$1 trillion/yr tab for pay and benefits of state and local employees. This is one major reason why the locals cant pay their bills.

While productivity in the private sector accounts for some of the dis-crepancy, government propensity to-ward hiring more and more employees to do less and less is by any measure a contributor to negative productivity. More alarming are surveys of college graduates that find that more and more

bright graduates want to work for the government. This is because only gov-ernment agencies have been hiring lately, and because they offer near life-time security for young college gradu-ates who are not willing to take career risks. This constitutes a real problem.

In a 2009 research report, David Keating of the National Taxpayers Union said, The income-tax indus-try employed more workers than are employed at the five largest employ-ers among Fortune 500 companies more than all United Parcel Service, McDonalds, International Business Machines and Citigroup combined. These produce nothing except tax compliance. Enough of that stuff.

Something of interest, Chuck Leavell and Carlton Owen, both connected with forestry in one form or another, wrote an editorial, Save a Forest: Print Your Emails. The reality is that the notice that appears on many emails to not print, may hasten the conver-sion of forests to other uses like strip malls, parking lots and housing devel-opments. This is because the nations forest landowners cant keep growing trees without markets for this natural, organic and renewable product.

Growing and harvesting trees pro-vides jobs for millions of Americans. With modern and improved forest management, the United States has more trees today than it had 100 years ago. The editorial authors say, More forests are dying of insect infestation and disease or being paved over across this country right now than could be converted to an email print-out in a thousand years.

With all this going on, may the Lord hold you in the hollow of His hand. A

Joe Kane

Volume XVI: Issue IVCheck These Numbers

and Weep

www.compressortech2.com

Follow compressortech2 on

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DCL.indd 1 10/27/10 2:20:35 PM

n Volume XVI: Issue IV ................................................................................ 4n Global Perspective Coalbed Methane to Supplement Asia-Pacific LNG Resource ....................................................................... 8

n Market Talk Oil, Gas Firms to Boost Capital Investments During 2011 ....................................................................... 10

n Oil and Gas in the African Continent....................................................... 12n MAN Introduces Irds Monitoring for Turbomachinery .............................. 20n TECHCorner Centrifugal Compressor Train in Coal Seam Gas Application .................................................................... 22

n Troubleshooting Capacity Reduction of Critical Process Gas Compressors ......................................................... 30

n Telvents SCADA Systems Dominate Northern Hemisphere Pipeline Scene ..................................................... 34

n Atlantic Offshore Gas Continues to Gain Prominence .............................. 38n Cummins Shifts Gears ........................................................................... 42n Compressor Installation Specialist Strikes Right Balance ........................ 44n The Relevance of the National Ambient Air Quality Standards, Part 1 ...... 46n Howden Buying Thomassen Compression for E100 Million ..................... 54n Leap in Smart Actuators Research ........................................................ 56n Miratech Hires Staff for Tulsa Headquarters .......................................... 57n sgard Subsea Compression System Going Ahead ................................. 58n Sundyne Adds to High-Pressure Centrifugal Pump Line .......................... 70

n Dateline ................................................................................................ 11n Featured Products ................................................................................ 33n Industry News ....................................................................................... 45n Planning Ahead ..................................................................................... 55n Scheduled Downtime ............................................................................. 62n Recent Orders ...................................................................................... 63n Advertisers Index ................................................................................. 64n Marketplace ......................................................................................... 65n Product Information Center ................................................................... 66n About the Business ................................................................................... 72

p. 38

p. 54

MAy 2011

p. 20

May 2011 6 CompressorTechTwo

CompressorTechTwo (ISSN 1085-2468) Volume 16, No. 4 Published 10 issues/year (January-February, March, April, May, June, July, August-September, October, November, December) by Diesel & Gas Turbine Publications, 20855 Watertown Road, Waukesha, WI 53186-1873, U.S.A. Subscription rates are $85.00 per year/$10.00 per copy worldwide. Periodicals postage paid at Waukesha, WI 53186 and at additional mailing offices. Copyright 2011 DIESEL & GAS TURBINE PUBLICATIONS. Canadian Publication Mail Agreement # 40035419.

Return Undeliverable Canadian Addresses to: P.O. Box 456, Niagra Falls, ON L2E 6V2, Canada. E-mail: [email protected].

POSTMASTER: Send address changes to: Circulation Man ager, COMPRESSORTECHTWO, 20855 Watertown Road, Suite 220, Waukesha, WI 53186-1873 U.S.A.

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p. 42

Member of...

CT May TOC.indd 1 4/27/11 1:12:58 PM

not just one...

> H i - F l o > r a d i u s e d d i s c > r i n g t y p e

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> r e c o n d i t i o n i n g > r e p l a c e m e n t s p a r e p a r t s

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CPI valves are designed, manufactured and reconditioned

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The Asia-Pacific LNG export mar-ket with Japan, South Korea, and now China and India as main consumers has always been lucrative. The recent nuclear disaster in Japan will make it even more lucrative in the future.

For many years, Australia and Indo-nesia have been among the main sup-pliers of LNG to these consumer mar-kets. Both countries, while possessing substantial conventional natural gas reserves, also feature extensive coal re-serves and thus unconventional natu-ral gas in the form of coalbed methane (CBM). While Australian natural gas reserves are still on the rise, Indonesia, after many years of extraction, is facing a decline in its reserves.

With the rise in gas price, CBM, which is more costly to produce, be-comes a viable source of energy in Aus-tralia. It will lead to development of the energy industry in the eastern part of the continent (natural gas reserves are concentrated in the west/northwest of the country). Indonesia is going to sup-plement the natural gas declining pro-duction to make full use of the existing LNG production facilities.

The total amount of CBM in place reserves worldwide is estimated to be between 3500 and 9500 Tcf (100 x 1012

and 272 x 1012 m3). CBM is considered one of the worlds largest sources of fossil fuel. Australia has total CBM re-serves of about 300 to 500 Tcf (8.6 x 1012 to 14.3 x 1012 m3). Many Austra-lian coal seams contain high volumes of methane gas up to 880 cu.ft. (25 m3) per tonne. Australia began produc-ing CBM in 1988 but it was not until 1996 that commercial CBM produc-tion started in the state of Queensland. It is now rapidly developing both in Queensland and South Australia.

Australias Icon Energy recently an-

nounced signing of an LNG sales agree-ment with Chinas Shantou SinoEnergy, concluding a deal to supply 44 MMtpy (40 x 106 T/yr) of LNG, equivalent to a total of 2.0 Tcf (52 x 109 m3), or 92 Bcf (2.6 x 109 m3) annually, over a 20-year period to Shantou SinoEnergy. First deliveries are envisioned in 2016. Icon Energys tenements are in east-ern Queenslands Surat Basin as well as in the Cooper Basin, which extends across western Queensland into South Australia. Icon said it is looking at liq-uefaction options in both Queensland and South Australia.

However, its development focus is presently on its Surat Basin acreage, with its close proximity of these to sev-eral proposed Gladstone-area LNG ex-port terminals. This strongly suggests that Icon will look to Queensland for its export route. Other Australian inde-pendent explorers, such as Beach En-

ergy, similarly look to Gladstone-area terminals for access to the Asia-Pacific LNG export market.

On the other side of the Pacific Ocean, Shantou SinoEnergy has joined forces with Chinese state-run utility China Guodian to build an LNG receiv-ing terminal and regasification facility at Nanao Island, near the city of Shan-tou in Guangdong Province.

With some of the worlds largest coal reserves, Indonesia is believed to hold significant reserves of CBM, estimated at around 452 Tcf (12.8 x 1012 m3) by the government. In early April, BP an-nounced that it had signed production-sharing contracts for four CBM blocks in the Barito Basin in Indonesias South Kalimantan. This is one more than the three CBM blocks it was awarded in March. This demonstrates the extent to which the company is expanding in In-donesias upstream segment. BP is no stranger to Indonesias CBM sector. The company was awarded study rights for the West Sanga CBM block in June 2010. The award of the study secured match-ing rights for BP and its local partner over the 1351 sq.mi. (3500 km2) block.

Exploration of CBM blocks enables increasing production by 18% between 2010 and 2017 to 3.2 Tcf (90 x 109 m3). Following years of stagnating output, Indonesia is turning to CBM to boost gas production. BP has also been ex-panding in Indonesias conventional upstream segment, winning a 100% in-terest in the North Arafura oil and gas production-sharing contract onshore West Papua in November 2010. The U.K. company is involved in a joint venture with Italys Eni at the Sanga Sanga gas field and also operates the Tangguh LNG export plant. The future sees CBM joining natural gas in the production of LNG. A

may 2011 8 CompressorTechTwo

Roberto Chellini

Coalbed Methane to SuppleMent aSia-paCifiC lnG ReSouRCe

Both Australia and Indonesia are Blessed with Major Resources of Coalbed Methane

By Roberto Chellini, Associate Publisher

CT697.indd 1 4/26/11 11:18:36 AM

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Growing confidence in the United States and global economies is spur-ring companies to increase their capital investments in 2011. This is particular-ly true in the oil and gas sector where, according to the Oil & Gas Journals annual spending report, companies plan to invest US$258.9 billion in up-stream projects compared with US$245 billion last year. Of this US$258.9 bil-lion, 84% would be spent on drilling and exploration, with the balance on production. The production expendi-tures alone are expected to increase to US$41.3 billion, up 6.2% over 2010.

The bigger question is how many of these wells will be natural gas, as com-pared to oil. Reports from traditional domestic natural gas exploration and production companies have indicated their intent to pursue oil plays, rather than natural gas, during 2011. This re-allocation will likely slash the number of gas wells drilled. According to the U.S. Energy Information Administration (EIA), over the past 10 years the ratio of gas to oil wells has averaged 2.24:1. This ratio peaked in 2004 when 2.75 natural gas wells were drilled to that of each oil well. Since then the ratio has been declining. In 2010 it was parity at 1:1, when 19,054 gas and 19,386 oil wells were drilled. In the first two months of 2011, according to EIA, a monthly aver-age of 4105 natural gas and oil wells were drilled. But the gas:oil ratio has declined and now stands at 0.68:1, clearly reflecting producers preference to seek higher-priced oil. Assuming that the first two months are indicative of the upcoming year, it would mean that 49,260 wells would be drilled in the United States in 2011, with about 20,010 being natural gas. While this is a marginal increase over 2010, it is well

below levels of 2004-2008, when gas wells averaged 30,374 per year. That being said, one could conclude that gas production in 2011 will continue at lev-els seen during 2009-2010.

Canadian investments are also ex-pected to increase, but at about half the rate seen in the United States. The spending survey found that invest-ment in Canada will increase by 3.1% to Can$33.5 billion, of which 70% will be spent for drilling and exploration and the balance of Can$9.8 billion on production. Currently, the Canadian Association of Oilwell Drilling Contrac-tors is forecasting 11,811 wells will be drilled in 2011. Over the past several years about 47% of the wells drilled have been natural gas. If that holds true for this year, about 5500 wells will be drilled in Canada. Yet current year-to-date rig activity in Canada, according

to Baker Hughes, shows only 32% of the rigs drilling in Canada are seeking natural gas.

On a brighter note, natural gas pipe-line projects in the United States are expected to see a 75% increase from 2010 with a total capital investment of US$5.3 billion, including costs for pump stations and compressors, according to the report. Conversely, Canadian natu-ral gas pipeline investments are pro-jected to decline 81% to Can$434 mil-lion in 2011.

There has been some strengthening in the futures markets for natural gas, with the 12-month strip increasing to US$4.48/MMbtu, a gain of 14% from the previous report.

While the U.S. economic recovery seems to be gathering traction, the over-all market remains concerned about the potential for an oversupply of natural gas. EIA reported that dry gas produc-tion in January 2011 was 1.883 Tcf (53 x 109 m3). This was 6.4% above the level in January 2010. Currently, production is running 16% above the 10-year av-erage and at levels not seen since EIA started collecting data in 1973.

The availability and price of natural gas may actually be getting some at-tention in the nations capital. Federal tax incentives to encourage natural gas engines for trucking fleets are being discussed. While public policies can be beneficial, it seems that their best in-tentions can ultimately lead to market disruptions that in the long term could prove adverse to the industry. A

Oil, Gas Firms tO BOOst Capital investments DurinG 2011

But Decline in Gas Drilling Expected to ContinueBy Harold Lampe


Harold Lampe

Harold Lampe is principal of Energy Re-search Services of Tulsa, Oklahoma, U.S.A., which provides a range of marketing serv ices for the energy industry. He can be reached at [email protected].

CT684.indd 1 4/26/11 11:19:53 AM


*May 2-5, Offshore Technology Confer-ence - Reliant Park, Houston, Texas, U.S.A.; Tel: (972) 952-9494; Web: www.otcnet.org

May 3, Permian Basin Gas Processors Asso-ciation Annual Meeting - MCM Elegante Hotel & Conference Center, Odessa, Texas, U.S.A.; Tel: (915) 490-9033; Web: www.gpaglobal.org/chapters/permian

*May 10-12, Eastern Gas Compression Roundtable (EGCR) - Robert Morris Universi-ty, Moon Township, Pennsylvania, U.S.A.; Tel: (412) 372-4301; Web: www.egcr.org

May 10-12, Intergas VI: 6th Intl Conference & Exhibition - CICC, Cairo, Egypt; Tel: +44 20 7978 0078; Web: www.intergasegypt.com

May 17-19, OGU 2011: 15th Uzbekistan Intl Oil & Gas Exhibition & Conference - Uzexpo-center, Tashkent, Uzbekistan; Tel: +44 207 596 5233; Web: www.ogu.com

May 23-27, Applied Principles of En-gines and Compressors - Hilton Shreveport, Shreveport, Louisiana, U.S.A.; Tel: (972) 620-4026; Web: www.gmrc.org/events/ap_ engines_compressors.html

May 24-25, 2011 Core Symposium: Magnolia Hotel, Houston, Texas, U.S.A.; Tel: (800) 524-1620 x4; Web: www.coresymposium.com

May 25, Reciprocating Compressors: Opera-tional Reliability - Institution of Mechanical En-gineers, London, England; Tel: +44 (0) 20 7973 1258; E-mail: [email protected]

May 25-27, Foundation Design & Repair/The Bolted Joint - Hilton Shreveport, Shreveport, Louisiana, U.S.A.; Tel: (972) 620-4026; Web: http://gmrc.org/events/bolted_joint.html

*June 6-10, ASME Turbo Expo 2011 - Van-couver Convention & Exhibition Centre, Van-couver, BC, Canada; Tel: (404) 847-0072; Web: www.asmeconferences.org

*June 7-9, Sensor+Test 2011 - Nuremberg Exhibition Centre, Nuremberg, Germany; Tel: +49 5033 9639-0; Web: www.sensorfairs.com

*June 7-9, Power-Gen Europe - Fiera Mila-no, Milan, Italy; Tel: +44 1992 656 617; Web: www.powergeneurope.com

*June 7-9, Gas & Oil Expo & Conference 2011 - Stampede Park, Calgary, Alberta, Cana-da; Tel: (403) 209-3555; Web: www.gasandoi-lexpo.com

June 7-10, Caspian Oil & Gas 2011 - Hyatt, Baku, Azerbaijan; Tel: +44 207 596 5000; Web: www.ite-exhibitions.com

June 8-10, The 58th Annual Corrosion Con-trol Course - University of Oklahoma, Norman, Oklahoma, U.S.A., Tel: (405) 325-3891; Web: www.engr.outreach.ou.edu/corrosion

*June 15-16, Energy Exposition - Cam-Plex convention center, Gillette, Wyoming, U.S.A.; Tel: (307) 234-1868; Web: www. energyexposition.com

*Sept 12-15, International Pump Users Symposium - George R. Brown Convention Center, Houston, Texas, U.S.A.; Tel: (979) 845-2924; Fax: (979) 845-1835

*Sept 12-15, Turbomachinery Symposium - George R. Brown Convention Center, Hous-ton, Texas, U.S.A.; Tel: (979) 845-7417; Web: www.turbolab.tamu.edu/

*Sept 14-16, Wyoming Gas Fair 2011 - Snow King Center, Jackson Hole, Wyoming, U.S.A.; Tel: (307) 234-7147; Web: www.wyo-gasfair.org

Sept 18-20, Arab Oil and Gas - Dubai Inter-national Convention and Exhibition Centre,

United Arab Emirates; Tel: +971 4 3355001; Web: www.ogsonline.com

Sept 20-22, Asia Pacific Oil & Gas Conference & Exhibition - Jakarta Convention Center, Ja-karta, Indonesia; Tel: +60 3 2288 1233; Web: www.spe.org/events/apogce/2011

*Sept 27-29, Gas Compression Conference - University of Oklahoma, Norman, Oklahoma, U.S.A.; Tel: (405) 325-3891; Web: www.engr.outreach.ou.edu/gascompressor

Dateline

*Indicates shows and conferences in which CompressorTechTwo is participating.

For a complete listing of upcoming events, please visit our website at www.compressortech2.com

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May Dateline.indd 1 4/26/11 11:21:24 AM

Today, Africa is split into some 50 free states or more with a total popula-tion estimated at 842 million. All these states have been formed after the end of the colonization era and the politi-cal situation today is still fluid (a recent referendum has indicated that in July 2011 Sudan will be divided into two states, North and South Sudan.) With the exception of South Africa the word democracy is more or less unknown. The majority of African states are ruled

Oil and Gas in the african cOntinentAfrica Has Great Energy Production Potential,

but Political Unrest Impedes ProgressBy Roberto Chellini


The illustrations accompanying this article are based upon information compiled from a wide range of sources by ECOWAS SWAC/OECD and presented in the Oil and Gas in West Africa chapter of the At-las on Regional Integration in West Africa, May 2007 and available online on the website of the Organisation for Economic Co-operation and Development at http://www.oecd.org/dataoecd/28/34/38798400.pdf and http://www.oecd.org/dataoecd/28/34/38798400.pdf.

Oil production has been growing in Africa since 1980.

by dictators in a military or tribal form. From the geographic, ethnic and cul-tural point of view the continent can be divided into two parts: North Africa and sub-Saharan Africa.

North Africa compris-es Mauritania, Mali, Mo-rocco, Algeria, Tunisia, Libya, Egypt and North Sudan. The population and culture is Arab. The Maghreb which means sunset in Arabic groups the eastern Arab states including Libya and excluding Egypt and Sudan (North Sudan). Sub-Saharan Africa is also called Black Africa and is completely differ-ent from the ethnic and cultural point of view.

This report, intended for the readers of Compressor-

TechTwo, will focus on the energy resourc-es of this continent rich in both oil and natural gas.

African oil represents some 9.6%

Africas share of world energy production has been growing, but exports have been static.

CT695.indd 1 4/27/11 1:19:57 PM

share of the whole world, and natural gas represents 7.9%. This means con-siderable quantities of compressors and pumps will be required for up-stream and midstream activities. Data, referring to the end of 2009, is taken from the BP statistic Review of World Energy, June 2010.

Statistical data for the main ener-gy- producing countries will give the reader an idea of the size, popula-tion, nominal GDP per capita and amount of oil and gas reserves. How-ever, keep in mind that the GDP and the population are not evenly distrib-uted because of political and geo-logical reasons characteristic of this large continent.

AlgeriaPopulation: 32 millionArea: 918,923 sq.mi. (2.38 x 106 km2)GDP per capita: US$3816 (estimated 2009)Proved gas reserves: 159.1 Tcf (4.5 x 1012 m3)Proved oil reserves: 12.2 Bbbl

Algeria is a main producer and ex-porter of natural gas to Europe, cover-ing 20% of its consumption.

The country enjoys a vast internal network of oil and gas pipelines. The natural gas hub is in Hassi RMel where a giant gas field is located. Many other gas fields located in the

Sahara Desert convey their produc-tion to Hassi RMel from where inter-national pipelines start.

The first pipeline connection to Europe was the Transmed pipeline that crosses Tunisia, the Mediter-ranean Sea to Sicily and Italy. The Maghreb-Europe pipeline connects Algeria, through Morocco, to Spain and Portugal. Recently, the Medgaz pipeline connecting Algeria with Spain has started pumping gas to the European continent. A proposed fourth pipeline should connect Alge-ria with Sardinia and Italy.

But Algeria is known to pioneer LNG. The first refrigeration trains in-stalled in Arzew started to produce 88,185 tpy (80,000 T/yr) of LNG back in 1964. Presently, Sonatrach oper-ates three LNG trains in Arzew and one in Skikda with a total production of 26.5 MMtpy (24 x 106 T/yr).

LibyaPopulation: 5.4 millionExtension: 679,540 sq.mi. (1.76 x 106 km2)GDP per capita: US$9570 (estimated 2009)Proved gas reserves: 54.4 Tcf (1.54 x 1012 m3)Proved oil reserves: 44.3 Bbbl

Libya is a major oil producer. Lib-yas main oil reserves are concentrat-ed in the eastern part of the country,

Cyrenaica Province, with some other fields in the west, near the border with Tunisia and Algeria. Natural gas has always been considered a by-product of low interest. The lack of infrastructure is a result of the politi-cal situation that, in the last 40 years, has made international oil compa-nies cautious in allocating major in-vestments in the country. Production of the more remunerative oil has led to massive flaring of natural gas.

Although Libya started production of LNG in 1970 in Marsa el Brega, the third nation in the world, after Algeria and the United States, lack of investments have, in practice, killed this activity. The first year of produc-tion (1970) shows a mere 44,092 tpy (40,000 T/yr) of LNG which, howev-er, is in line with the other pioneer-ing countries (Algeria, 88,185 tpy (80,000 T/yr); United States, 55,116 tpy (50,000 T/yr) while recent fig-ures show that the system has nev-er reached industrial production (584,225 tpy [530,000 T/yr] in 2006) and operation of a first-generation LNG plant if not definitively closed must be noncompetitive.

The only link to export natural gas to Europe is the Greenstream, a 32


OECD issued this summary of proven oil and gas reserves in Africa at the end of 2005.

continued on page 14

CT695.indd 2 4/26/11 11:25:05 AM


py (5.5 x 106 T/yr) train; its produc-tion is delivered to the Segunto re-ceiving terminal in Spain. A second train of the same size is planned to double production.

NigeriaPopulation: 130 millionArea: 356,669 sq.mi. (0.92 x 106 km2)GDP per capita: US$1089 (estimated 2009)Proved gas reserves: 185.4 Tcf (5.25 x 1012 m3)Proved oil reserves: 37.2 Bbbl

Nigeria is a major producer of both oil and gas. Because of its geo-graphical position, far away from the consumer markets, the country has implemented its LNG capabilities becoming one of the major LNG pro-ducers in the world. A Trans-Sahara pipeline to transport Nigerian gas to Hassi RMel and from there to Europe is planned, but the size of the invest-ment, the technical problems and the political/security risk are hold-ing back the project. The distance to cover from the Warri region to Hassi RMel is 2580 mi. (4128 km).

In the meantime, the natural gas reserves concentrated in the eastern part of the Niger Delta are processed at the Bonny Island LNG facilities situated at the southern edge of the Rivers State. This plant is enjoying a continuous increase in the number of refrigerating trains in operation.

The six LNG trains in operation have a delivery capacity of 24.3 MMt-py (22 x 106 T/yr), which will rise to 33.1 MMtpy (30 x 106 T/yr) with the commissioning of the seventh train presently under construction and to 41.9 MMtpy (38 x 106 T/yr) with the planned eight liquefaction train. The majority of Nigerian LNG is ex-ported to Europe and North America. In spite of several delays and cost raises, the present gap between gas and oil prices will make the Escravos GTL plant (EGTL) very profitable.

Chevrons own EGTL plant is now 70% complete and will come on-stream in 2013. The EGTL project is designed to convert 325 MMcfd (9.2 x 109 m3/d) of gas into 33,000 Bbbl/d of diesel, naphtha and liquefied pe-troleum gas. The plant is located next to the Escravos gas plant (EGP) in a swamp 60 mi. (100 km) southeast of Nigerias largest city, Lagos. The EGTL facility will be supplied with gas from the EGP, where Chevron completed its latest, Phase 3a, expan-sion in 2009.

Equatorial GuineaPopulation: 0.5 millionExtension: 10,831 sq.mi. (28,051 km2)GDP per capita: US$8759 (estimated 2009)

transit land for Hassi RMel gas ex-ported to Spain and Portugal.

EgyptPopulation: 70.7 millionArea: 386,102 sq.mi. (1.0 x 106 km2)GDP per capita: US$1450 (estimated 2009)Proved gas reserves: 77.3 Tcf (2.19 x 1012 m3)Proved oil reserves: 4.4 Bbbl

Egypt claims considerable oil and gas reserves located in the Gulf of Suez, the Sinai Peninsula, the Nile Delta, in deep waters of the Mediter-ranean Sea and in the Western Des-ert near the Libyan border. Main gas reserves are located onshore and off-shore the Nile Delta and in the West-ern Desert. A pipeline exports Egyp-tian natural gas to Israel and Jordan, and plans are to extend the route to Syria and possibly join the planned Nabucco pipeline to Europe.

For the time being, gas is exported to Europe as LNG. The liquefaction plants are located in Idku, east of Alexandria and Damietta, 38 mi. (60 km) from Port Said.

The Egyptian LNG plant of Idku features two 3.97 MMtpy (3.6 x 106 T/yr) trains. LNG production of train 1 is taken under a 20-year contract, by GDF-Suez while train 2 has a similar 20-year contract with the BG Group. Plans are to increase LNG output by installing more liquefaction trains (up to six).

The Spain Egyptian Gas (SEGAS) plant of Damietta features a 6.1 MMt-

in. (813 mm), 223 mi. (520 km) long sealine crossing the Mediterranean Sea from Mellitah, west of Tripoli, to Gela, Sicily. This pipeline has trans-ported up to 283 Bcfy (8 x 109 m3/yr) of Libyan gas to Italy since 2004. The turmoil in Libya at the time of writ-ing will certainly lead to a change in the oil and gas business and hope-fully a more intensive and rational use of Libyan natural gas reserves.

Other Maghreb CountriesMauritania, Mali, Morocco and Tuni-

sia do not have developed oil and gas industries. Tunisia is a small country one-tenth the size of Libya and has proven oil reserves of 0.6 Bbbl. Its position makes it strategically important as a transit country for Algerian natu-ral gas to Europe. From the Hassi RMel gas hub, two lines cross the Algerian and Tunisian Sahara Desert to reach Cape Bon. From this point the gas is conveyed at high pressure through five parallel lines to Mazara del Vallo in Sic-ily and through the Italian Peninsula to the European natural gas net.

Morocco has very limited gas re-serves. Circle Oil, an independent U.K. oil company with exploration interest in Morocco, announced last February its third gas discovery in its Sebon permit. However, the amount of gas available is only sufficient to be piped to the consumer markets along the Morocco coast line. As is Tunisia, Morocco is important as a

0

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Other

West Africa

North Africa

200520001995199019851980197519701965

North African nations consistently have produced most of the continents oil.


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KBdelta.indd 1 9/21/10 9:16:03 AM

Proved Reserves:Gas: 1.4 Tcf (0.04 x 1012 m3), May 2010Oil: 1.1 Bbbl, Jan. 2011

This small state in the Gulf of Guinea features significant offshore oil and natural gas reserves.

The LNG plant of Bioko Island, Punta Europa, has started operations in 2007 when its first LNG train with a capacity of 3.7 MMtpy (3.4 x 106 T/yr) was commissioned. A second LNG train with a 4.9 MMtpy (4.4 x 106 T/yr) capacity is planned to start opera-tions in 2016.

AngolaPopulation: 1.2 millionExtension: 4.09 million sq.mi. (10.6 x 106 km2)GDP per capita: US$4027 (estimated 2009)Proved Reserves:Gas: 10.6 Tcf (0.30 x 1012 m3), May 2010Oil: 13.5 Bbbl, Jan 2011

Angola is mainly known for its oil reserves, the great majority of which are located offshore on the continen-tal shelf as well as in deep waters of some 4921 ft. (1500 m).

Natural gas is also abundant, mainly as associated gas connected with oil production. The lack of more accu-rate knowledge of natural gas reserves is because of, in part, the absence of dedicated investment and non-exis-tence of a legal contractual framework that promotes the exploration and de-velopment of natural gas as a primary energy source.

Annual production of natural gas is presently estimated at 24 Bcf (680 x 106 m3). A part of this gas will be used locally and the major part ex-ported. Export activities are planned to start in 2012 after completion of the 5.7 MMtpy (5.2 x 106 T/yr) Soyo LNG plant. All the LNG is due to be shipped to a Mississippi, U.S.A., re-gasification terminal.

South AfricaPopulation: 1.2 millionExtension: 16.8 million sq.mi. (43.6 x 106 km2)GDP per capita: US$5635 (estimated 2009)

South Africa is known to be very poor in hydrocarbons, while it has extensive coal deposits. However, the development of shale gas is chang-ing the perspective. After a year of studying the shale gas potential of South Africas Karoo Basin, Shell has applied for exploration rights at three contiguous blocks covering about 34,749 sq.mi. (90,000 km2), roughly the size of Portugal, in the vast basin in the center of the country. The Ka-roo Basin has emerged as one of the more prospective shale gas plays in Africa, and with its exploration ap-plication Shell is positioning itself as an important player in the region.

16 CompressorTechTwo

ConclusionsFrom what is reported, the major

African hydrocarbon reserves of both oil and gas are concentrated in North Africa and the Gulf of Guinea. East Africa only has small spots of oil and gas used for local consumption. Con-sider that most of the African acre-age is still to be explored and im-portant discoveries may happen any time. However, keep in mind that several factors prevent large interna-tional oil companies to invest heavily in the continent. Political instability and security, and in many cases the absence of clear legislation, restrict exploration to small companies pre-pared to face high risk with limited investments in order to eventually enjoy high profits.

Local tribal fights and major events like the ones under way in North Africa at the time of writing are a normal happening from the Ivory Coast to Nigeria, from Congo to Ruanda, from Somalia to Eritrea, just to name a few. The latest news from Egypt and Libya is monopoliz-ing newspaper headlines, but in the oil and gas sector uncertainty seems to be the rule. After years of discus-sion, only in March 2011 Cameroon and Nigeria have reportedly agreed to explore the Bakassi peninsula together for oil and gas resources. Reports indicate that both coun-tries support joint exploration. The two countries have agreed that joint exploration of the area would be cheaper, better and faster for both countries. After years of conflict be-tween Nigeria and Cameroon, the International Court of Justice ruled in 2002 that the Bakassi peninsula belongs to Cameroon, but the rul-ing did not see the end to conflicting ownership claims by the two coun-tries and its inhabitants, and the se-curity situation in the peninsula re-mains tense.

In January 2011, after a referen-dum, agreement was reached that on July 9 South Sudan will become officially independent from North Sudan. The official border line is yet to be defined. While produc-tion activities are concentrated in the South, all export infrastructure is in the North. The newly formed government of the South has en-sured that it will honor contracts the government of the North has signed with exploration and production companies before the 2005 Compre-hensive Peace Agreement. However, many questions remain over what shape the states oil industry will take and what role foreign compa-nies will play. A

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MAN PrimeServ, the aftersales brand of MAN Diesel & Turbo, is offering an intelligent remote diagnostic system (irds) for the companys turbomachin-ery products to improve reliability and availability via a condition-based main-tenance approach.

The system can process data from measuring points in and around the tur-bomachinery installation, so that MAN Diesel & Turbo can remotely monitor equipment at the customers facility.

The collected raw data is automati-cally evaluated by adams plus, the companys software that allows auto-matic or manual analysis, to spot de-viations and changes in parameters.

Those deviations are analyzed via trend presentations that make it pos-sible to recognize impending faults at an early stage and thus help to reduce outages, the company said.

MAN PrimeServ said an irds system has been installed at a globally known oil platform, which was a prime can-didate for qualified remote monitor-ing. The continuous data evaluation helps to optimize the operations and maintenance, and the facility is always checked. If there are any uncertainties regarding the MAN turbomachinery products, the manufacturer is always up to date, which also helps its prod-uct enhancements and research and development activities.

Regular reports are made available to customers in order to optimize plant operation and plan mainte-nance measures.

In addition to preventive main-tenance, condition analysis enables pre-planning work with a high level of precision, and then implementing those plans when needed. The avail-

ability and reliability of the installa-tions are significantly increased and spare parts management is improved, said MAN PrimeServ.

The irds monitoring system is modu-lar in design. An industrial computer with a real-time operating system col-lects process data via direct links with the open-loop/closed-loop control sys-tem of the machine installation.

The long-term data is acquired as streams via Profibus-DP, Modbus-RTU or Modbus-TCP/IP, written to a ring buffer and automatically transferred at intervals to the central database of MAN PrimeServ.

Furthermore, high-resolution ring buffers with a sampling rate of 10 ms can be used to get process data or alarm messages from the control sys-tem of the machine. This data is event triggered, stored on the local computer

MAN INtroduces Irds MoNItorINg for turboMAchINery

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The MAN PrimeServ irds monitoring system collects operating data from turbomachinery installations. The data is transmitted through a local VPN box via Internet LAN, ISDN, DSL or even satellite to the MAN control center for analysis.


CT683.indd 1 4/26/11 3:55:08 PM

and transferred if necessary. Remote data transmission is through ISDN, DSL (broadband) or customers LAN via the Internet using a local VPN box that es-tablishes an SSH connection for high security. Transmission via satellite is also possible.

MAN PrimeServ said operating data transmitted by each individual ma-chine is automatically examined by adams plus software. If a limit value infringement is found by the auto-matic analysis, the system saves this result in the database in the form of graphic and text information. Adams plus makes these messages available for further processing. Expected con-ditions are calculated using physi-cal and experience-based equations, which are influenced by several differ-ent parameters. As these parameters and influences vary under different operating conditions, the automated data analysis distinguishes possible operating states of a machine.

The system determines whether ma-chines are operating free of disruption and will automatically flag possible faults for the MAN PrimeServ service engineer responsible for the machine.

Over time, the system accumulates the specific operating behavior of each machine. This individual history pro-vides a basis for regular reports includ-ing measures and recommendations for preventive maintenance.

With the introduction of irds, the company said that it has been possible not only to optimize plant operation but also to significantly increase plant availability. Malfunctions and causes of failure can be analyzed and rectified

within a minimum of time. Spare parts stocking for the machines in question is directly related to evaluation of the operating data. For example, special spare parts can be ordered in advance so that they arrive at the facility in time for preventive replacement during the next scheduled shutdown.

All the turbomachinery products of MAN Diesel & Turbo are manufactured irds-ready, but are fully equipped with irds functionality only on the cus-tomers request. On the other hand, if MAN Diesel & Turbo sells a machine in combination with a service contract, then irds is a prerequisite.

The company said an increasing number of customers are asking for the irds feature.

While irds is the monitoring sys-tem for all turbomachinery products of MAN Diesel & Turbo, the company also recently launched its PrimeServ Online Service, which is a similar monitoring solution dedicated to low- and medium-speed engines, gen-sets and turbochargers.

The Online Service is based on the companys existing engine diagnosis sys-tem, CoCoS EDS, which monitors all en-gine operating data and shows it at the engines installation for the operator.

MAN Diesel & Turbo said Online Service has been an integral part of all medium-speed engine man-agement contracts since early 2010. Subsequently, the company decided to include it as a standard free-of-charge feature for all new engines warranty period. A



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IntroductionFor coal seam gas (CSG) compression, centrifugal compres-

sors have been applied in an approximate range of 211,900 cfh to 10.6 MMcfh (6000 to 300,000 m3/hr). Above 10.6 MMcfh (300,000 m3/hr), CSG compressor trains are not applicable, however, if any are required, axial compressors may be used. Below 211,900 cfh (6000 m3/hr) oil-flooded screw compres-sors are more efficient and cheaper. Full allowance is needed for the untreated and water-saturated nature of the CSG, which may contain coal fines and corrosive agents. A CSG centrifugal compressor train design and arrangement is often complex, and optimization must be made between the various process requirements. These include mechanical needs, aerodynamic limits, reliability issues and commercial situations of centrifu-gal compressor and gas turbine driver.

CSG can be converted more efficiently to electricity in large central generating power stations. For CSG fields near electric power grids or major power stations, the costs of electrical en-ergy may displace gas turbine drivers. Large electric-motor driv-ers using variable frequency conversion are very attractive but not for remote CSG fields. Gas turbine drivers are common in remote CSG projects. The speed of gas turbine is standard for a given frame. Gas turbine main components are not custom engineered to the specific application for a power and speed match. In many applications, a speed matching gear must be included. If exhaust heat recovery or regeneration is used, the efficiency of the gas turbine is quite attractive. Gas turbines have always been tolerant of a wide variation of fuel conditions (an important consideration for CSG).

Centrifugal CompressorMultistage arrangement centrifugal compressors are the

most common of any found in process service [1-5]. They are the most common compressors in CSG service. For relatively


Centrifugal Compressor train in Coal seam gas appliCation

Many of the Usual Guidelines Apply in Coal Seam Gas Application for Centrifugal Compressors, but This Application Presents Additional

Conditions That Should be ConsideredBy Amin Almasi

Amin Almasi is lead rotating equipment engineer in Worley Parsons Services Pty Ltd., Brisbane, Australia. He previously worked at Technicas Reunidas (Madrid, Spain) and Fluor (vari-ous offices). He holds chartered professional engineer license from Engineers Australia (MIEAust CPEng Mechanical), chartered engineer certificate from IMechE (CEng MIMechE), Registered Professional Engineer in Queensland (RPEQ) and he also holds MS and BS in Mechanical Engineering. He specializes in rotating machines including centrifugal, screw and reciprocating com-pressors, gas and steam turbines, pumps, condition monitoring and reliability. Almasi is an active member of Engineers Austra-lia, IMechE, ASME, CMVI, Vibration Institute, SPE, IEEE, SMRP and IDGTE. He has authored more than 40 papers and articles dealing with rotating machines. For additional information or answers to questions, contact the author via his e-mail addresses: [email protected] or [email protected].

low pressure, horizontally split compressors are used (for high capacity below 1810 psig [25 barg] and for low capacity be-low 1960 psig [35 barg] or even 2030 psig [40 barg]. Above these limits, the common arrangement for a CSG compressor is vertically split with bolted head. Figure 1 shows a vertically split centrifugal compressor with bolted-on head for medium-pressure applications including CSG.

Figure 1. Vertically split centrifugal compressor with bolted-on head for medium-pressure appli-cations (Picture from H. P. Bloch, A Practical Guide to Compressor Technol-ogy, 2nd edition, 2006).

Figure 2 shows a vertically split centrifugal compressor with shear ring head. This is not a common arrangement for CSG applications, but may be used in special high-pressure cases, depending on type of downstream CSG consumer.

Figure 2. Vertically split centrifugal com-pressor with shear ring (Picture from H. P. Bloch, Compressor and Modern Process Application, 2006).

In CSG applications, the flow out of each section of the compressor is taken through an intercooler and back to the compressor. Usually, cooling water is not available in CSG remote project locations and air-cooled heat exchangers are provided as intercooler and aftercooler. Provision to remove and scrub condensed liquid is usually required because CSG is generally saturated.

Multistage centrifugal compressors generally operate at a pressure ratio of less than or around two per impeller (closed


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impellers) [6, 7]. In multicasing trains, the first casing, because it has the highest suction volume, will dictate the train speed. This will lead to increasingly sub-optimum designs as the suc-tion volume of the later stages decreases. An optimum solu-tion is a gear unit between casings for large pressure ratios.

Capacity control may be accomplished by suction throt-tling, speed variation, a cooled bypass from discharge to suction, or discharge throttling. For CSG compressors, the best and more efficient method is speed variation. It alters the characteristic curve of the compressor, and a separate curve for each speed is required. Variable guide vane capac-ity control is not common since single-stage or integrally geared machines are not common in CSG fields. Suction or discharge throttling are not efficient and only used for very small centrifugal compressors.

Net forward flow from a CSG centrifugal compressor pack-age is generally controlled from zero to 100% using a combi-nation of speed control and recycle control (turndown with maximum use of speed control). Compressor control allows operating at points below the characteristic curve and to the right of the surge curve (speed control). Bypassing is needed when operating to the left of the surge line [3]. Generally, several trains will work in parallel and a load-sharing control system is required.

The most common seal arrangement with a CSG compres-sor is a tandem dry gas seal with intermediate labyrinth. A suitable seal system is required for specified variations in seal operating conditions that may prevail during start-up, shutdown or settling out, and during any other special op-eration specified. Also, a wide range of CSG condition varia-tion should be considered. For CSG, a primary gas seal is from the compressor discharge. Additional supply (second-ary seal gas) from downstream of the plant gas dehydration unit is usually provided. Separation gas will be backed up by bottled nitrogen. For gas turbine-driven CSG compres-sor units, rotation at low speed may be needed for certain periods to avoid shaft thermal distortion during start-up or immediately following a shutdown. The dry gas seals must be reliable and not be damaged by such operation. Specify special precautions that must be taken.

Anti-surge systems are required to prevent operating in unstable regions that may cause damage. The reaction time of the anti-surge system should be rapid, and the volume seen by the compressor at the delivery should be kept to a minimum by mounting a fast-acting nonreturn valve near the delivery connection, immediately downstream of the recycle line (sometimes hot gas bypass is required). Reverse rotation of the compressor following a trip should be avoided.

A rule of thumb is that the energy of the gas entrained between compressor and check valve should be less than 50% of the kinetic energy stored in the rotating masses [8, 9]. Coupling of the limited end float type is always pre-ferred (best selection is a diaphragm type). CSG compres-sor packages are generally transported with instrumenta-tion in place. As online gas composition measurements for CSG compressors may not be available, provision for the manual input of the gas characteristics for performance cal-culations is necessary.

Gas Turbine DriverFigures 3 and 4 show examples of heavy frame industrial

and aeroderivative gas turbines, respectively. There are dif-ferences between the aeroderivative and heavy industrial gas turbines including weight, combustor design, turbine design, bearing design and lube oil system.

Heavy frame industrial compared to aeroderivative gas tur-bines are slower speed, have higher air flow and need more time and spares for maintenance. Heavy industrial gas tur-bines use hydrodynamic bearings but aeroderivative gas tur-bines use anti-friction bearings. The advanced aircraft engine and space technologies have been used to provide maintain-able, flexible, lightweight and compact aeroderivative gas turbines. The key to maintainability is the modular concept, which provides for removal of components and replacement without removing the gas turbine from its support mounts. The heavy industrial units, by contrast, require more effort to remove and replace components (especially combustor parts) and more effort to inspect or repair the sections.

The user must weigh needs and requirements against the variety of gas turbines offered. The preference has been to place the aeroderivative units in remotely located applica-tions (such as CSG remote fields) and to place heavy frame industrial units in easily accessible applications. The heavy industrial gas turbine consumes more fuel and approximately 50% more air than the aeroderivative units. The large cross-sectional area of blades and vanes in heavy industrial turbines are under more corrosion attack and contamination impact, but can tolerate more corrosion than the thin and high aspect ratio turbine blades of the aeroderivative gas turbines.

In hot-end drive configurations, the output shaft is at the turbine end where exhaust gas can reach high temperatures that affect bearing operation and life. Also, service is more difficult because the assembly must be fitted through the exhaust duct. Constraints include output shaft length, high temperature, exhaust duct turbulence, pressure drop and maintenance accessibility. Insufficient attention to any of these details often results in power loss, vibration, shaft or coupling failure and increased downtime for maintenance.

In the cold-end drive configuration, the output shaft ex-tends out the front of the compressor. Here, the compressor is accessible, relatively easy to service and exposed to ambi-ent temperature only. Drawbacks include: turbine compressor of inlet must be configured to accommodate the output shaft and the CSG compressor. This inlet duct must be turbulent free and provide uniform, vortex-free flow throughout its operating speed range. The problem resulting from a poor design can be catastrophic. For example, inlet turbulence can induce surge in the turbine compressor resulting in complete destruction of the unit. Inlet duct turbulence is of major concern, however, it can often be eliminated at the expense of pressure drop.

An integral shaft gas turbine is uncommon for compres-sor drive applications [10,11,12]. The high torque required to start compressors under full pressure results in high turbine temperature during the start-up cycle when cooling air flow is low or non-existent. A single-spool split output shaft gas turbine is a single-spool gas turbine driving a free power turbine. The air compressor and turbine component shaft is not physically connected to the power turbine shaft but is

Figure 3. An example of a heavy frame industrial gas turbine [10].

Figure 4. An example of an aeroderivative gas turbine [10].



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coupled aerodynamically, which makes starting easier (cooler) in mechanical drive. This usually is referred to as a split shaft mechanical drive gas turbine and attains self-sustaining opera-tion before picking up the load of the driven equipment.

In a dual spool split output shaft gas turbine, indepen-dent low- and high-pressure air compressors and turbines generate the hot gases that drive the free turbine. (There are three shafts, each operating at different speeds, for higher power applications.)

Optimum over-rating includes 5% as tolerance to meet the CSG compressors additional 2% for gearbox (if appli-cable), additional 2% for fouling and erosion and finally an additional 5% for long-term gas turbine deterioration (totally around 12 to 14%).

The preferred starting device is electrohydraulic (electric motor drives a hydraulic pump, which in turn transmits hy-draulic power to start the gas turbine) rated to supply a mini-mum 110% of the starting and acceleration torque in a worst case. Helper drivers are not recommended. The gas turbine should be capable of an immediate hot-start at any time af-ter trip for three consecutive start attempts. Cold-start and hot-start restrictions are very important (finalized in bidding stage). Igniters should not remain in the primary combustion zone during operation. The rotating blades and the labyrinths of shrouded rotating blades are designed to start up without rubbing. Renewable sealing components (such as labyrinths, honeycombs or abradable surfaces) are required at all inter-nal close-clearance points between the rotating and stationary parts and all external points where shafts pass through the casings. For variable speed mechanical drive applications, the speed ranges for single-shaft gas turbine and two (or more) shaft gas turbines are recommended 25% (80 to 105% of rated speed) and 55% (50 to 105%), respectively.

Air compressors of the gas turbine are either axial design (up to 19 stages) or centrifugal design (one or two impel-lers). Increase in compressor ratio is the prime contributor in the overall increase in simple-cycle thermal efficiency to above 35% (especially for aeroderivative). Combustor de-sign is a complex task, often referred to as a black art. The combustor design took two distinct configurations fairly early in the evolution of the gas turbine. These are the can-annular combustor and the annular section. There are two types of can-annular combustors: 1. More efficient straight flow through. 2. Reverse flow combustor. The advantage of the reverse flow combustor, as used in the heavy industrial gas turbine, is in use of regenerator, which improves over-all thermal efficiency. A further distinctive design approach within the can-annular concept is a single fuel nozzle and multifuel nozzle per combustion chamber.

Present gas turbines use impulse-reaction turbine design. Aeroderivative units use high aspect ratio (long and thin) blades incorporating tip shrouds to dampen vibration and improve blade tip sealing characteristics. The heavy frame industrial gas turbines incorporate a low aspect ratio (short and thick) blade with no shroud. Where long thin airfoils have been used, lacing wire may be used to dampen vi-bration. Improvements in metallurgy and casting techniques have allowed eliminating midspan shrouds and lacing wires. Turbine blades are subject to stresses resulting from high temperature, high centrifugal forces and thermal cycling. Figure 5 shows structure of high-pressure turbine blades with cooling distribution.

Required gas turbine performance curves: net output, net heat rate, exhaust temperature, exhaust flow versus ambient temperature for the CSG fuel at site conditions.

Auxiliaries and AccessoriesFor aeroderivative gas turbines (anti-friction bearings, use

synthetic lubrication oil), the turbine lubricating oil system is

usually separate from the CSG compressor lubricating oil system and includes instrumented metal chip detection an online me-tallic debris monitoring system, which is strongly recommended. Industrial gas turbines (hydrodynamic bearings, usually use min-eral-based lubricating oil) generally have one integral lubricating oil system per train. In a common oil system, the lubricant is usually hydrocarbon oil and corresponds to the ISO Grade 32 or similar. Anyway, ensuring that the proposed oil is compatible with all lubricated components is necessary. As a rule of thumb, the rise in oil temperature (through the bearing and housing), bearing outlet oil temperature and bearing metal temperature measured (with embedded temperature detectors) should not exceed 80F (30C), 185F (85C) and around 203 to 239F (95 to 115C) (depending on oil temperature), respectively.

Lubrication oil systems should include at least two pumps each [1, 13, 14]. API 661 air coolers with spare fan (for oil cooling), double filters with removable element and stainless- steel piping and valves should also be provided. The lubri-cation system is one of the major sources of trouble. Neces-sary lubrication points and lubrication spare points should be provided. Oil supply line to critical components should be monitored (mainly oil pressure). For oil reservoir volume, retention time more than eight minutes is recommended.

Auxiliaries and accessories (such as air filter system, exhaust system, etc.) should be provided with proper supports since they are in the vicinity of rotating machines, subjected to vi-bration. Corrosion protection of the gas turbine filter, ducting and silencer is necessary. Filter house (mounted on top of the gas turbine enclosure) and silencers include inlet silencer per-forated plate element, exhaust plenum and exhaust silencer usually fabricated from suitable grades of stainless steel.

Silencers need rigid structure. They are designed consid-ering acoustical or mechanical resonances and differential thermal expansion. The air inlet and exhaust systems for gas turbines are designed for a minimum practical pressure drop. Air filters for 100% removal of particle sizes down to 3 mi-crons are generally necessary [10]. Filter systems require: an entrance screen to prevent debris from entering, proper ori-entation of the air inlet, a louver or cowling to minimize the entry of driving rain (snow or sand), proper access to facili-tate maintenance, differential-pressure alarm for each stage of filtration, modular construction (fully factory-assembled modules) and clean-air side completely free of objects that can become loose during operation. Some of the worst ef-fects of turbine hot-section corrosion are experienced in CSG applications where saltwater pond or brine water pond of reverse osmosis systems are nearby. (A very large volume of salty and contaminated water is pumped from CSG wells.)

The prevention or reduction of corrosion should be addressed in the design of the inlet air filter system, selection of turbine material and material coatings. For an optimum duct system,

Figure 5. Internal structure of high-pressure turbine blades showing the cooling distribution throughout the core of the blade airfoil and root [10]. Note: Figures 3, 4 and 5 from T. Giampaolo, Gas Turbine Hand-book Principles and Practices, 3rd Edition, 2006.


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ed because of the possibility of damage from water carryover or poor quality of water. Liquid-to-air heat exchangers to cool the inlet air (for performance enhancement) and steam or water injected for emission control purposes are not pro-posed because of significant maintenance problems.

Casing vibration monitoring (minimum of two sets for each machine casing) are always recommended both velocity measurements for low-speed vibrations up to 2 kHz and ac-celerometers for high-speed vibrations and for hot sections. Noncontacting probes are used for axial and radial vibra-tion monitoring (journal bearings, noncontacting X-Y probes mounted at a 45 angle from the vertical centerline, in addi-tion to velocity seismic transducer for bearing housings and dual probes axial position for thrust bearings). Monitoring of pressure (discharge pressure against a reference) is the opti-mum way to monitor performance and degradation both for centrifugal compressor and gas turbines. (Flow is usually not as easily monitored compared to pressure.)

Temperature monitoring, including temperature monitor-ing of strategic locations of rotating machines, oil tempera-ture and gas flow temperature monitoring, is important. Over-temperature protection shall be independent from the turbine combustion temperature control. Six thermocouples usually are placed around the turbine exhaust gas frame to measure exhaust gas temperatures for alarm and trip.

Heavy-duty industrial turbines usually have two wheel space thermocouples (thermocouples are replaceable during opera-tion). Aeroderivative turbines usually have two wheel space thermocouples located downstream of the last turbine wheel (thermocouples and conduits as small as possible). Electronic governors are required to prevent gas turbine speed increase beyond the specified over-speed limit upon any case of malfunction, such as loss of rated load (coupling failure). Each shaft should have its own over-speed trip protection system,

requirements are a minimum number of direction changes in-cluding proper turning vanes (to ensure uniform flow distribu-tion and avoid resonance); air velocity limit of 66 ft./s (20 m/s) and 98 ft./s (30 m/s) for the inlet and exhaust respectively; ducts sufficiently rigid to avoid vibration (plate 0.2 to 0.4 in. [5 to 10 mm] thick is generally used); and appropriate required man-ways for cleaning and inspection. Ducting and casing design should permit field balancing in the end planes of the rotors without requiring the removal of major casing components.

Layout of the inlet and exhaust system should be designed with great care. The air inlet should be upstream of the exhaust stack during prevailing wind conditions. Relative position should avoid recirculation of exhaust gases because of any conceivable potential wind conditions (minimum horizontal separation of 320 ft. [97.5 m]). The air inlet (minimum 16.4 ft. [5 m] elevation) and gas turbine exhaust should be outside a three-dimensional fire hazardous zone and outside any classified electrical area. Support, ducting and piping should be designed with respect to operation and maintenance also to facilitate piping spool and ducting module removal and avoid support removal [11].

The CSG fuel system is critical and needs special attention. A fuel strainer (Y-type strainer with stainless-steel internals) and a blow-down system for purging and warming up the fuel system for approximately 20 minutes prior to starting (manual valve closed around two minutes after starting) should be provided (also consider safety shutdown valve). The pilot limit valve (fail safe) for trip on primary gas knockout drum high liquid level, preceded by a high level alarm (also capable of manual trip), is required. To prevent condensate mist carryover or hydrate formation, if required, a super-heater designed to deliver 104F (40C) fuel gas (CSG) should be included.

Train Reliability Evaporative coolers (for gas turbine) are not recommend-

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[2] Bloch, H. P., Compressor and Modern Process Applica-tion, 2006 (John Wiley, New Jersey, U.S.A.).

[3] Davidson, J.; Bertele, O., Process Fan and Compressor Selection, pp 47-68, 1996 (Mechanical Engineering Publica-tions Limited, London, England).

[4] API 617, Axial and Centrifugal Compressors and Ex-pander-compressors for Petroleum, Chemical and Gas Indus-try Services, 7th Edition, July 2002, (American Petroleum Insti-tute Publishing, Washington, District of Columbia, U.S.A.).

[5] Brown, R. N., Compressors Selection and Sizing, 3rd edition, pp 120-220, 2005 (Gulf Publishing Company, Hous-ton, Texas, U.S.A.).

[6] Bloch, H. P.; Soares, C., Process Plant Machinery, 2nd edition, 1998 (Butterworth Heinemann, Oxford, U.K.).

[7] Forsthoffer, W. E., Forsthoffers Rotating Equipment Handbooks Volume 3: Compressor, 1st edition, 2005 (Elsevier, Oxford, U.K.).

[8] Rangwala, R. S., Turbo-machinery Dynamics Design and Operation, 2005 (McGraw-Hill, U.S.A.).

[9] Walker, D. N., Torsional Vibration of Turbomachinery, 2004 (McGraw-Hill, U.S.A.).

[10] Giampaolo, T., Gas Turbine Handbook Principles and Practices, 3rd Edition, 2006 (The Fairmont Press Inc., U.S.A.).

[11] Kulikov, G. G.; and Thompson, H. A., Dynamic Mod-eling of Gas Turbine: Identification, Simulation, Condition Monitoring and Optimal Control, 2005 (Springer, England).

[12] Han, J. C.; Dutta, S.; and Ekkad, S. V., Gas Turbine Heat Transfer and Cooling Technology, 2000 (Taylor & Fran-cis, New York, U.S.A.).

[13] Davey, N., The Gas Turbine Theory and Practice, 2006 (Merchant Books, Berks, U.K.).

[14] Saravanamuttoo, H. I. H.; Rogers, G. F. C.; Cohen, H.; and Straznicky, P. V., Gas Turbine Theory, 6th Edition, 2009 (Pearson Education Limited, Essex, England).

which allows online testing without over-speeding the turbine (over-speed trip system independent of the governor). All shut-down functions are two out of three voting to avoid unnecessary trip. Recommended shutdowns include: over-speed, low fuel supply, flame out gas temperature, low lube oil pressure and radial and axial shaft vibration.

The purge period should displace the minimum six times of the exhaust system volume (including turbine, exhaust duct, waste recovery device, exhaust stack, etc.) before firing the unit. Gas turbine surface temperatures should be lower than the ignition temperature of the CSG. The fuel control system should include a shutoff valve (separate from the fuel control valve) that stops all fuel flow to the turbine on any shutdown condition (local and remote tripping) and can-not open until all permissive firing conditions are satisfied. Fuel shutoff valves should have a remote shutdown actuator device and a partial stroke feature to permit checking the operability of the shutoff valve during normal operation of the gas turbine.

ConclusionThis study allows the optimization of centrifugal compressor

with gas turbine driver arrangement for CSG applications. The optimum figure described here offers the advantages to integrate all different aspects of compressor, gas turbine driver and en-ables correctly specifying and purchasing centrifugal compressor trains. Proper design and selection of various train components, together with proper maintenance and operating practices, can affect the level of performance significantly, along with environ-mental impact and thus time between repairs or overhauls. A

References[1] Bloch, H. P., A Practical Guide to Compressor Technol-

ogy, 2nd edition, 2006 (John Wiley, New Jersey, U.S.A.).

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The cracked gas compressor train in a world-scale ethylene plant had been exhibiting performance impair-ment for some time. The daily plant production level of 2250 tons was not being achieved. Performance degra-dation of the cracked gas compressor was evident from various symptoms, such as a need to increase first-stage suction pressure in order to maintain discharge pressure (fractionation col-umn overhead) and increase in the steam turbine driver speed; the train was operating at its maximum con-tinuous speed of 4124 rpm as com-pared with the rated speed of 3927 rpm and the turbine governor valves

were full open, i.e., the steam rate had gone up.

The machine could not be run in this condition for a prolonged duration, as it significantly impacted ethylene pro-duction revenues. To confirm the initial analysis that the output was reduced most likely because of fouling inside the casings, a Six Sigma approach was used to define the problem, assess condition, analyze the findings, recom-mend corrective measures, and monitor and control performance thereafter.

As a starting step, the compres-sor first-stage suction conditions were maintained in close proxim-ity to the original normal case. At

steady state, gas samples were de-rived from each of the six-stage in-lets from which the gas properties were determined and thermody-namic calculations of the compres-sion train were performed (Table 1). These calculations substantiated the initial analysis that because of fouling inside the compressor cas-ings and possibly the rotors, poly-tropic efficiency was lower and the machine was delivering a reduced throughput.

In the weeks following the analy-sis, a number of discussions were held with the plant operations, maintenance and warehousing de-partments to plan for the outage of the compressor, disassembly of the casings, carrying out internal inspection and implementing reme-dial measures. Compressor suction knock-out drums were also included in the turnaround inspection to ex-amine internal demisters because of reported liquids in compressor suc-tion lines.

A detailed turnaround plan was de-veloped that consisted of step-by-step instructions for disassembly, check-ing, cleaning, measurements and reas-sembly. All required spare parts were identified and the ones that were not available in the warehouse were or-dered from the manufacturer. Spare compressor rotors in the warehouse were cleaned and balance checked. The decision was made to replace the installed rotors with spare rotors to fa-cilitate quicker turnaround. The rotors that were removed would be subjected to a thorough inspection after start-up of the plant.

The compressor was shut down

This is a sectional view of a centrifugal com-pressor typical of those discussed in the cracked gas compressor train in a world-scale ethylene plant.


Neetin Ghaisas is director of Design Engineering in Fluor Canadas Calgary office. He has a masters degree in Mechanical Engineering and is a registered practicing Profes-sional

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Compresor+Tech+ +May+2011