Detection of Misalignment from Vibration Data

Case StudyOn a boiler feed pump driven by a motor running close to 3600 rpm, a horizontal misalignment issue was suspected by examining orbit plots besides shaft centerline plots. The follow-up inspection did uncover large parallel misalignment of 0.012 inch along the horizontal direction between the pump and the motor. The root-cause of changes in alignment indicates piping strain as evidenced by loose bolts between the pump and the foundation. The unit was then re-aligned to below 0.001 inch in parallel alignment, followed by correct re-assembly of the coupling. Shaft vibration was successfully reduced to below 2 mil pp and with a normal orbit orientatio

Successful 2 planes balancing confirm by rotordynamics calculation

Case StudyThis historical case is focus on the vibration behavior of a generator. After a short circuit issue on the grid, the machine train trip. At this time the level of vibration of the generator was acceptable and well below the level of alarm. However, 10 days after the restart of the unit the level of vibration started to increase. The analysis of the data pointed out an increase of the 1X component. There were no signs of rub or other malfunctions. The analysis of the data concluded on an increase of unbalance or a decrease of the dynamic stiffness. Even if, It is unusual to observe such increase of vibration on a generator, the full inspection of the generator was rejected. In order to operate, even if the root cause was not identified, it was decided to balance the generator. The balancing activity was a success using a modal method. Since the root cause was not determined and in order to be sure that the dynamic behavior of the generator was as expected compare to its design, a lateral analysis was done on site using basic information available on site. Comparing the vibration data recording on site with the result of the lateral analysis, it was concluded that the dynamic stiffness of the machine was almost as expected. The increase of vibration could have been due to a real modification of the unbalance or a potential increase of the bearing clearances. The customer could be confident to continue to operate the unit until the next overall

Conversion of Influence Coefficients among Static-Couple and Multiplane Formats On Two-Plane Balancing

TutorialThe influence coefficient (IC) method is typically used in balancing, especially on-site. For a two-bearing machine, there are basically two approaches to apply this method. The first one is to treat it as a multiplane balance problem involving a 2x2 matrix of complex ICs. In this approach, two direct ICs along with two cross-effect ICs are generated so that correction weights at one or two balance planes can be determined. The second one is to apply a static pare (in-phase) and/or couple pair (180 degrees out-of-phase) weights to reduce the vibration. The latter approach has been used extensively in the field, especially on steam turbine and generator rotors. Dependent on vibration mode shapes and combinations as well as balance plane accessibility, sometimes applying static or couple pair weights can be a wise choice; other times weights at one or two end planes are needed. There are totally 4 possible sets of IC data due to weights at plane 1, plane 2, static pair, and couple pair. Influence coefficient data would typically be obtained by applying trial weights followed by trial weight runs. It is found, however, that these IC data can be converted easily without trial weight runs once any two of 4 sets are known. The above findings and conversion equations have been obtained analytically and verified by experimental results. This paper presents all available IC conversion equations together for the first time. Experimental verification is also provided by a rotor kit to demonstrate their accuracy. Four real cases are presented to demonstrate their applications. The first case is to show the necessity of applying a couple pair weight by obtaining its IC converted from plane 1 and plane 2 ICs. The second case is to show a one-trial weight run method on symmetric Copyright© 2021 by Turbomachinery Laboratory, Texas A&M Engineering Experiment Station rotor. The third case is to show the necessity of applying individual weights each at plane 1 and plane 2 by obtaining their ICs converted from static and couple pair ICs. And the fourth case is to apply individual weights each at plane 1 and plane 2 after having one trial weight run only, with previously known static pair IC data

Optimization of a city logistics transportation system with mixed passengers and goods

International audienceIn this paper, we propose a mathematical model and an adaptive large neighborhood search to solve a two{tiered transportation problem arising in the distribution of goods in congested city cores. In the rst tier, goods are transported in city buses from a consolidation and distribution center to a set of bus stops. The main idea is to use the buses spare capacity to drive the goods in the city core. In the second tier, nal customers are distributed by a eet of near{zero emissions city freighters. This system requires transferring the goods from buses to city freighters at the bus stops. We model the corresponding optimization problem as a variant of the pickup and delivery problem with transfers and solve it with an adaptive large neighborhood search. To evaluate its results, lower bounds are calculated with a column generation approach. The algorithm is assessed on data sets derived from a eld study in the medium-sized city of La Rochelle in France

A shared " passengers & goods " city logistics system

International audienceMany strategic planning models have been developed to help decision making in city logistics. Such models do not take into account, or very few, the flow of passengers because the considered unit does not have the same nature (a person is active and a good is passive). However, it seems fundamental to gather the goods and the passengers in one model when their respective transports interact with each other. In this context, we suggest assessing a shared passengers & goods city logistics system where the spare capacity of public transport is used to distribute goods toward the city core. We model the problem as a vehicle routing problem with transfers and give a mathematical formulation. Then we propose an Adaptive Large Neighborhood Search (ALNS) to solve it. This approach is evaluated on data sets generated following a field study in the city of La Rochelle in France

Balancing with the presence of a rub

During commissioning of a cogeneration plant the air cooled generator cannot be run up to synchronization speed because of high 1X vibration during startup. Several attempts were done by the commissioning team to balance the rotor but proven ineffective. This paper presents the vibration analysis performed by GE MDS Engineer. As a result of the analysis it was concluded the high levels of synchronous vibration are caused by thermally induced bow because of rub in the new type of seals installed in generator casing. The seals were removed for test and the generator was started successfully. The next part of the paper discusses the differences between Newkirk and Morton type thermally induced bows as they can be observed in the machinery diagnostics during field analysis

Lube Oil Carbonisation

Case StudyCarbonized particles can get deposited in housing oil seal clearances causing a partial rub like phenomenon. Friction caused due to reduced clearances because of accumulation of carbonized particles leads to shaft thermal bow inducing 1X vibration. When the accumulated particles are abraded due to increase in vibration, the clearance opens up which reduces the thermal bow causing the vibration levels to drop to normal levels and this cycle repeats.This presentation outlines a case where a similar phenomenon wasobserved causing the unit to trip after a few hours of operation. Successful diagnosis was carried out using vibration data which is presented in this case study

Optimisation d'un système de transport urbain mixte passagers/marchandises

National audienceNous considérons ici un système de transport mixte où la capacité résiduelle de bus urbains est utilisée pour transporter des biens à destination d'un centre ville. Nous proposons deux approches pour optimiser un tel système et les évaluons sur un cas d'étude situé à La Rochelle

Optimization of a shared passengers and goods urban transportation network

International audienceOptimizing passengers and goods flows reduces the costs and ecological footprint of transportation systems, as well as congestion in cities. Since passengers and goods do not have the same nature (a person is active and a good is passive), modeling each flow separately seems natural. But local authorities need to consider passenger and freight transport together as a single logistic system. In this paper, we assess the efficiency of an existing transportation system where the spare capacity of public transport is used to distribute goods toward the city core. We propose two optimization approaches. The first one considers the problem as a multidepot VRPTW followed by an assignment problem. The second one solves the whole model as a pickup and delivery problem with transfers (PDPT). These approaches are evaluated on data sets generated following a field study in the medium-sized city of La Rochelle in France

Identification of proteins involved in the anti-inflammatory properties of Propionibacterium freudenreichii by means of a multi-strain study

Propionibacterium freudenreichii, a dairy starter, can reach a population of almost 109 propionibacteriaper gram in Swiss-type cheese at the time of consumption. Also consumed as a probiotic, it displaysstrain-dependent anti-inflammatory properties mediated by surface proteins that induce IL-10 inleukocytes. We selected 23 strains with varied anti-inflammatory potentials in order to identify theprotein(s) involved. After comparative genomic analysis, 12 of these strains were further analysed bysurface proteomics, eight of them being further submitted to transcriptomics. The omics data werethen correlated to the anti-inflammatory potential evaluated by IL-10 induction. This comparativeomics strategy highlighted candidate genes that were further subjected to gene-inactivationvalidation. This validation confirmed the contribution of surface proteins, including SlpB and SlpE, twoproteins with SLH domains known to mediate non-covalent anchorage to the cell-wall. Interestingly,HsdM3, predicted as cytoplasmic and involved in DNA modification, was shown to contribute toanti-inflammatory activity. Finally, we demonstrated that a single protein cannot explain the antiinflammatoryproperties of a strain. These properties therefore result from different combinationsof surface and cytoplasmic proteins, depending on the strain. Our enhanced understanding of themolecular bases for immunomodulation will enable the relevant screening for bacterial resources withanti-inflammatory properties