Turbomachinery for the world's largest nitrogen plant - MAN Diesel ...

of mechanical and thermodynamictrials are precisely stipulated invarious internationally approved acceptancecodes for the respectivemachine types. Customers andthose they commission to carry outacceptance therefore devote particularattention to these test runs.Fig. 10: Nitrogen Compressor LoopOne example of using this simulationsystem is shown in Fig. 10, showingthe system design of the nitrogencompressors. To avoid “surging” ofindividual stages or stage groups intransient processes, recycle valvesare provided for certain stagegroups, which open automaticallywhen required. Fig.11 shows as theresult of such simulation how thetransient effects of a shutdown process– in this case by means of turbinetripping – can be traced in theperformance map of the 6th stagegroup of the nitrogen compressor set.The turbomachinery and relatedunits are controlled and monitoredby the proven turbolog DSP machinecontrol and protection system, whichwas developed in-house. Linked tothe digital control and monitoringsystem of the overall plant,turbolog DSP protects the air andnitrogen compressors against surging,controls the position of thevariable stator vanes of the axialflow compressors, the speed of thesteam turbines, monitors and controlsall the other components, andlast but not least handles the visualizationof the operating data requiredfor smooth, uninterrupted production.Workshop trialsWorkshop trials of the compressorsand their drivers serve to demonstratethe guaranteed mechanicalintegrity of the finished product aswell as the guaranteed thermodynamicproperties prior to dispatch tothe site as it has long been recognisedthat it is easier and more costeffective to fix a problem in the factoryrather than in the field. For suchlarge units the cost of one weeksdelay can result in over $1 million inlost revenue. These test runs areto be regarded as a comprehensivequality assurance measure at theend of the design and manufacturingprocess. The procedure and contentFig. 11: Result of Dynamic SimulationMAN GHH BORSIG has met thegrowing market demand for test runsto be carried out by continuouslyexpanding the number of test standsavailable for such tests [4]. Driveoutputs of 14 MW (electric motors),16 MW (steam turbines) and 25 MW(gas turbines) are now available inthe plant for works test purposes,along with an open-air area for compressortrials involving combustiblegases. The following programme oftrials was conducted for the turbomachinesdescribed in Chapter 3:Mechanical testing of all– compressors as per API 617,– steam turbines as per API 612 and– gear boxes as per API 613,and thermodynamic test runs eachinvolving one axial flow compressor,one LP centrifugal compressor andone HP centrifugal compressor asper ASME PTC-10.8