Enhanced Process EfficiencyHot gas expander replacement

With increasing operational problems and the declining reliability of a 30-year-old

expander, for which the OEM was no longer in a position to offer the necessary

technical support, the customer decided to have the work carried out by a qualified

third party. Following a competitive bid procedure, MAN PrimeServ was entrusted

with this demanding assignment.

Enhanced Process Efficiency Technical complexity and tight schedule

Project goals

Inordertokeepcostsaslowaspossiblebyeliminat-

ing costly alterations to pipework and foundations,

thenewunithad tobeadapted to theexistingpro-

cess and constructional infrastructure. Themachine

was required tobeupgraded to the latest technical

standards, with the focus on reliability in particular.

Process modifications performed by the operator

further required an increase in the unit thermal effi-

ciencytoallowtheretentionof theoriginal2,300kW

electricdrivemotor.Adeliveryperiod“nottoexceed

12months”withamaximumplantoutagetimeofsix

weekswasanabsoluterequirement.

The MAN PrimeServ solution

The original expander was a two-stage unit with a

separateaxialbearing.Thistypeofexpanderdesign

conceptwasnewtoMANPrimeServ.

Already the first preliminary investigations showed

thatitwouldbedifficulttomodifytheexistingcasing

toaccommodatethenewrotatingandstatorcompo-

nents.Thetimerequiredforsuchmodificationswould

alsofarexceedthespecifiedoutagetime.Thechosen

solution was, therefore, based on a new, cast cas-

ing.Thecasinginterfaceswiththeprocessequipment

and the foundation had to remain the same, which

presented a major design challenge. The original

two-stagedesignwith a separate axial bearingwas

retained,basedonasolidforgedrotorwithfour-seg-

mentradialbearings.

Additionallymoderninstrumentationforbearingtem-

perature,rotorvibrationandspeedmonitoringaswell

as online power measurement was to be installed.

The unit instrument rack was also mounted on the

base frame. In order to demonstrate the increased

efficiency, a torque meter was integrated into the

systembetween thenewexpanderand theexisting

aircompressor.

Project results and customer benefit

Customer'sspecificationsposedamajorengineering

challenge,whichhadtobesolvedwithinanextremely

tighttimeframe.Thetwo-stageconcept,usingstandard

aerodynamic technology (blading and flow channels)

wascomplexwithcorrespondinglyhigh risk factors,

especially considering the contractual efficiency

guarantees.Amajor factor inmaintaining thespeci-

fiedplantdowntimewasMANPrimeServ’s ability to

carry out high-speed balancing and mechanical

testing of the complete unit at the company-owned

facilitiespriortodelivery.Despitethetechnicalcom-

plexityandtheextremelytightschedule,thenewunit

was delivered on time, installed and commissioned

withinthespecifiedsix-weekplantdowntime.

The installationof thenewexpander,combinedwith

othersystemandprocessmodificationsnotincluded

intheMANPrimeServscopeofsupply,hasresulted

in major operational and economic benefits for the

user.Thecustomernowoperatesamodern,state-of-

the-artmachinewithsignificantly improvedefficiency

andhighreliability.Thecarefullyplannedretentionof

the interfaces with the existing process equipment

allowedallplantmodificationstobecarriedoutcost-

effectivelyandwithanabsoluteminimumofproduc-

tiondowntime.

New expander in operation

Original expander prior to the rebuild State-of-the-art production of expander blades

Works assembly of the new expander with the cast lower half casing and the newly designed two-stage expander rotor with separate axial bearing

Fully assembled new expander package with instrument rack, ready for dispatch

Technical Data

Inletpressure bar 3.47

Inlettemperature °C 460

Dischargepressure bar 1.02

Massflow kg/h 48,690

Gascomposition 92.7%N2,7.2%O2,0.05%SO2,tracesH2O,SO3,H2SO4

Withtheselectedbladestagedesignthenetpowerattheguaranteepointis2,300kWwithanisentropicefficiencyof79.9%.Thedischargetemperatureis298°C.

x /m

100,000

150,000

200,000

250,000

300,000

350,000

0 0.025 0.050 0.075 0.100 0.125 0.150 0.175

StaticpressurePs/Pa

Calculation of static pressure at stator and rotor blades

MAN Diesel & Turbo Schweiz

8005Zurich,Switzerland

Phone+41442782211

Fax +41442782261

mtprimeserv@man.eu

www.mandieselturbo.com

24/7Hotline:+492086929000

MANPrimeServ–aservicebrandofMANDiesel&Turbo

Alldataprovidedinthisdocum

entisnon-binding.Thisdataservesinformationalpurposesonlyandisespeciallynotguaranteedinanyw

ay.Dependingonthesubsequentspecificindividual

projects,therelevantdatamaybesubjecttochangesandw

illbeassessedanddeterminedindividuallyforeachproject.Thisw

illdependontheparticularcharacteristicsofeachindividual

project,especiallyspecificsiteandoperationalconditions·Copyright©

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