The PETRONAS LNG Complex inBintulu, Malaysia covers a land areaof 276 hectares and with a com-

bined production capacity of about 23 mil-lion tonnes per annum (Mtpa), it is theworld's largest LNG export facility in asingle location. It is made up of three LNGplants (see Figure 1):

Malaysia LNG Sdn Bhd (Trains 1, 2 and 3), which began operation in 1983. Malaysia LNG Dua Sdn Bhd (Trains 4, 5, and 6), which began operation in 1994Malaysia LNG Tiga Sdn Bhd (Trains 7 and 8), which began operation in 2003.

The MLNG Tiga project has a totalannual capacity of 7.8 Mtpa for twotrains, which are among the largest everbuilt. The application of several signifi-cant innovative ideas makes this projectone of the most significant achievementsin the LNG industry. A fire at the MLNGTiga plant in August 2003, however,forced a temporary shutdown for repairs.This article provides a thorough analysisof the incident and the enhanced modifi-cations instigated in resolving the prob-

lems encountered. In accordance with therecovery plan, the facility managed toresume its normal operation in April2004, three weeks ahead of the originaltarget of seven months.

Overview of the Train 7Fire Incident

In March 2003, Train 7 of MLNG Tigaplant had started its operation. It had suc-cessfully passed its performance test inJune 2003 and was soon to be offered forprovisional acceptance to the owner. Twomonths later, the Propane CompressorGas Turbine (C3 GT) exhaust system of

Train 7 was involved in a fire incident(Figure 2). It occurred on 16 August 2003at 22:21 hours and led to a temporaryshutdown of the train. After thoroughinvestigation and analysis, appointedteams identified the specific damagesthat had occurred and developed a step-by-step recovery process to ensure thatthe Train 7 could resume operationquickly and safely.

The design utilised within the MLNGTiga plant seeks to recover the heat from

the exhausts of the main turbine driversof the refrigeration compressors. Hot oilfor general heating duties and hot naturalgas for regeneration of dryers recover theexhaust heat with the use of heatexchanger coils. The exhaust gas from theC3 GT passes through an exhaust plenumand then splits in a Y piece to enter thetwo halves of the Waste Heat RecoveryUnit (WHRU). Each half contains aregeneration gas coil and 5 hot oil coils. Aschematic of the arrangement is shown in Figure 3.

The regeneration coil has an inlet andoutlet header with 32 tubes connectingthem, each tube with a U bend at the top.The entire regeneration coil, including theheaders, is housed within the WHRUduct. Under normal operation, the duct,which is refractory lined, reaches temper-atures in excess of 500 °C.

Prior to the incident, unbeknown tothe operations personnel, a crack haddeveloped in the joint between the tubeand header of the regeneration gas coil.This leakage was not obvious to theOperator from the instrumentationarrangement but could be detected on theinstrument records during subsequentinvestigations.

The propane compressor and turbineexperienced a trip that was unrelated tothe gas leakage. This resulted in fuel gas to the turbine shutting off and theturbine speed running down before stopping. The procedure was then forthe turbine to go into a slow rotation of 6 rpm using the barring motor, whichsuccessfully occurred. Because of therotation of the turbine blades and thechimney effect of the turbine exhauststack, air was drawn in through the tur-bine and into the exhaust duct. Duringslowing down (about 14 minutes), theoxygen (O2) content rose from 14% innormal operation to 21% by the intake offresh air through the gas turbine airintake compressor

The natural gas escaping from theregeneration coil mixed with the air insidethe WHRU that was still at a very hightemperature, near the normal operatingexhaust temperature of 570 °C. Highpressure leaking gas, mostly methane(CH4+), only required 4% volume in air toreach its lower flammability limit and autoignition temperature of 537 °C. This wasachieved and led to an explosion insidethe WHRU.

Damages OccurredThe WHRU ducting was damaged beyond repairThe hot oil coils were damaged beyond repairThe regeneration coils were recoverableThe gas turbine plenum was extensive-ly damagedThe housing around the compressor / turbine was extensively damagedThe compressor was undamaged but needed to be stripped down for examinationThe turbine moved on its base but only sustained damage to ancillary equip-ment. It required disassembly for internal inspectionsThe building suffered superficial damageNo injury occurred to any personnel.

Recovery ProcessIn an effort to recover production safely inthe quickest possible time, it was decidedto establish multiple teams to tackle thevarious challenges. The teams included:

Initial Investigation Team to find theroot cause

Business Recovery TeamInterim Production Study TeamDemolition TeamEngineering Team to develop a safe redesignReconstruction TeamRe-HAZOP TeamInsurance Claim Group

PLANT SAFETY

LNG journal July/August 2005 page 12

The Train 7 Fire at PETRONAS’ LNG Complex, Bintulu, Malaysia

A major fire occurred in 2003 in the exhaust system of the propane compressor gas turbine in the first train(train 7) of the MLNG Tiga project. The authors describe the consequences of the accident, the analysis

of the causes, the management of the plant recovery process, and the re-design of the system in both train 7 and train 8 to ensure enhanced integrity and increased safety.

Norrazak Hj. Ismail, MLNG Tiga Sdn Bhd, PETRONAS and Thomas Roy Stuart, Foster Wheeler Energy Ltd, Malaysia

Figure 1: Overview of the PETRONAS LNG complex

Figure 3: Side View of MLNG Tiga C3 GT, WHRU, Exhaust System, and Incinerator

Figure 2: Top View of MLNG Tiga C3 GT Exhaust Plenum Damage

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LNGjournal

LNG journal July/August 2005 page 13

The participating personnel were fromthe following:

Owner : MLNG TigaOperator: MLNGEPCC Contractor: JGC / KBR / SIMEProject Management Consultant: Foster Wheeler / OGP Technical ServicesTechnical Services: Shell Global Solu-tions InternationalWhilst the plant had

commenced operation, contractually it stillremained the EPCC Con-tractor's responsibility to repair the damage. However, the majority of the costs were recover-able against the owner'sConstruction All RisksInsurance.

As soon as access waspossible to the regenerationcoil, the crack between thetube and header wasobserved and extensive stud-ies conducted into the designof the coil. During normaloperation the coil undergoesseveral heating and coolingcycles per day and highstresses occur. However, thearea where the failure hap-pened has relatively lowstress factors.

A section of the coil wassent to The Welding Insti-tute in the United Kingdomfor analysis. The tube toheader joint was section-alised and examined. Itcould be clearly seen from aconnection adjacent to thefailed weld that the rootpass had not been carriedout correctly. Several othersuch joints were examinedand found to be poorlywelded. The failed weldconnection was maintainedby a very small section ofweld that was sufficient towithstand hydrostatic pres-sure test but not the cyclicstresses induced duringoperation as shown in Fig-ure 4. This type of weldcannot be fully tested usingradiographs, whilst Ultra-sonic Testing (UT) is notsuitable for use with incol-loy material. The inadequa-cy of the weld could havebeen determined during theinspection of the root weld.

The redesign team select-ed the use of nipoletsbetween the header andtubes to allow easier weldingand full radiographic testingof each joint. The originaldesign of welding is shownin Figure 5 and the newdesign is shown in Figure 6.Additional springs wereadded to the coil supports toeliminate the high stressesexperienced elsewhere in thecoil (the U bend at the top ofthe coil).

The original estimated

duration for reconstruction of Train 7WHRU section was twelve months, main-ly due to the long delivery of the replace-ment hot oil coils. The original coils couldnot be reused due to the extensive dam-age. Analysis by the Interim ProductionTeam concluded that by sharing hot oilfrom Train 8, Train 7 could operate nearto its full capacity. Piping modifications

to allow this operating mode were imple-mented and the revised target for interimproduction was set at seven months.

A large number of equipment itemswere associated with the GE / NuovoPignone compressor turbine arrange-ment, particularly the exhaust arrange-ment on the turbine outlet. NuovoPignone established a special task force

team to place and expedite orders forreplacement parts. Critical items wereregularly air freighted. The purchaseorder for WHRU ducting was placedwith Ishikawa Heavy Industries (IHI)within a very short schedule as agreed.The WHRU ducting was completed ontime and was transported by a speciallychartered ship travelling non-stop from

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Japan to Bintulu. Owner's spare partswere utilised within the rebuild wherev-er they were available.

The co-operation of all parties wasessential to complete the project and thesuccess was measured by an efficient andsafe start-up three weeks ahead of thetarget.

The Re-Hazop AnalysisThe MLNG Tiga LNG liquefaction traindesign utilises Propane Compressor GasTurbine (C3 GT) Exhaust Gas duty toregenerate the Drier Beds. C3 GTExhaust Gas passes through a WHRU,which contains the Regeneration Coil(heat exchanger used to provide the nec-essary heat input for regenerating the dri-er beds). When the C3 GT trips and thereis a Regeneration Coil tube leak an explo-sive mixture can form in the WHRU. TheRe-HAZOP team recommended a newsafeguarding system such that, in theevent of a hazardous situation arising,the regeneration gas in the coil should beisolated (using existing motorised valves)and then vented from the coil (via a newrelief system). Depressurisation of theregeneration coil was initiated by a C3GT trip or shutdown; or by high differen-tial flow between the inlet and the outletof the regeneration coil; or by the loss ofpressure in the regeneration coil. Thenew system employed the existingprocess instrumentation around theregeneration coil.

These modifications were immediatelyincorporated into the adjacent Train 8 thatwas ready to enter service in two monthstime and later made to Train 7 prior to itsrestart. For future designs, the Re-

HAZOP team recommended that consid-eration should be given to locating the coilheader and connection outside the wasteheat recovery duct.

C3 GT Trip or shutdown: With refer-ence to Figure 7, when the C3 GT trips orshuts down the new safeguarding sys-tem automatically closes valves A to D,thus preventing further RegenerationGas and Purge Gas entering the regener-ation coil. Next valve E is opened, allow-ing the regeneration coil to fully depres-surise to flare. Extra isolation is provid-ed as inlet valves FC1 and FC2 are alsoclosed. The check valve provides suffi-cient extra isolation on the regenerationcoil outlet.

High flow differential: Figure 7 shows aflow differential instrument (FD), whichmeasures the difference between regener-ation coil inlet and outlet mass flowrate. Ifthe differential exceeds approximately15% the new safeguarding system auto-matically initiates the closure of valves Ato D as per the C3 GT trip or shutdownscenario where extra isolation is providedby inlet valves FC1 and FC2 and the outletcheck valve.

However, in this case valve E remainsclosed unless the operator chooses to man-ually depressurise the regeneration coil.The operator monitors the new regenera-tion coil inlet pressure instrument (P1); ifit indicates falling pressure, hence a leak-ing regeneration coil, manual depressuri-sation would then follow.

As the Drier Bed sequence proceeds,transitions between certain steps allow

the mass flowrate through the regenera-tion coil to vary quickly between approx-imately 0-1400 tonnes/day. For this reason the mass flow differential input to the new safeguarding system is tem-porarily inhibited until steady flowresumes. This inhibition only lasts for a few minutes of the 8-hour Drier Bed cycle.

Low pressure: Once the pressure dropsto a low enough level (approximately 70%of the normal operating pressure, as meas-ured by P1) the new safeguarding systeminitiates the same response as flow differ-ential instrument (FD). Again, if P1 con-tinues to indicate falling pressure, hence aleaking regeneration coil, manual depres-

surisation would then follow.Start up/Shutdown: The question of

when to pressurise the regeneration coilhad to be addressed as part of the newsafeguarding system design. This is

because the regeneration coil will alwaysbe depressurised during a C3 GT trip orshutdown.

When the C3 GT is starting up anexplosive mixture can form if a fully pres-surised Regeneration Coil is leaking. Thisis due to lower C3 GT Exhaust Gas flowand higher oxygen content in the WHRU.For this reason a permissive is providedwhereby the regeneration coil can only bepressurised once the C3 GT reaches 95% ofits full operating speed.

ConclusionThe inspection plan for the regenerationcoil was adequate but due to the complex-ity of the weld details and the criticalnature of the equipment, additional sur-veillance should have been carried out inthe fabrication workshop. The redesign ofthe tube to header connection is vastlysuperior to the original design and facili-tates the application of Non DestructiveExamination (NDE) reducing the need forday-to-day surveillance.

The damages of the Train 7 fire inci-dent at the Petronas LNG Complex wererepaired successfully. Instead of the esti-mated twelve months of the recoveryprocess, Train 7 managed to be broughtback into production within sevenmonths. The multiple teams establishedin the recovery process shared the common objective of getting the plantonto line quickly and safely again. These teams, who were made up ofthe best members from each organisa-tion, worked together in an environmentwhere information was shared freelywith an excellent spirit of co-operation.It saved a lot of time, energy and costas duplication of effort was appropriate-ly avoided. Decisions were made quick-ly and followed up with the most suit-able actions.

The outcome of the investigations pro-vided an improved welding design of theregeneration coil and also a new safe-guarding system that not only is usefulfor rebuilding of Train 7, but was also ofuse for Train 8. These modifications wereimmediately incorporated into the adja-cent Train 8 that was ready to enter serv-ice and later made to Train 7 prior to itsrestart. Besides the long hours of work,the teams also took ownership of theproblem. This helped to expedite therecovery of Train 7 and the facility man-aged to resume its normal operation safe-ly three weeks ahead of the original tar-get of seven months. Currently, bothTrain 7 and 8 are in operation producinga total annual capacity of 7.8 Mtpa as thedesign intends.

PLANT SAFETY

LNG journal July/August 2005 page 14

Norrazak Hj. Ismail is the General Man-ager for PETRONAS Malaysia LNG TigaSdn. Bhd. He has a Bachelor of Science inChemical Engineering from the Universityof East London, England. He has beenwith PETRONAS for 20 years in the gasbusiness and for the last 13 years in LNGProjects as Process/Commissioning andStart-up Manager for Malaysia LNG DuaPlant Project. In 1995 he was appointedGeneral Manager for Malaysia LNG TigaProject.

Roy Stuart is a Senior Project Managerwith Foster Wheeler. He has an HonoursDegree in Mechanical Engineering fromLoughborough University, England and is aChartered Engineer and Member of the Insti-tution of Mechanical Engineers. He has 20years experience in the Oil and Gas Con-tracting Industry, completing projects formany of the major oil companies. From 2002until 2004, he resided in Bintulu, Malaysiawhere he was the Project Manager of theProject Management Consultant for the con-struction of Train 7 and Train 8 of theMalaysia LNG Tiga Project.

Figure 6: Improved Welding Design thatuse Nipolets between the Header and

Tubes

Figure 7: Regeneration Coil Isolation and Depressurising

Figure 4: Cross Sectionalised between the Tube and Header of theOriginal Weld Figure 5: Original Welding Design between the Header and Tubes

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