• norsk
    • English
  • English 
    • norsk
    • English
  • Login
View Item 
  •   Home
  • Fakultet for ingeniørvitenskap (IV)
  • Institutt for maskinteknikk og produksjon
  • View Item
  •   Home
  • Fakultet for ingeniørvitenskap (IV)
  • Institutt for maskinteknikk og produksjon
  • View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.

Degradation Modelling for Predictive Maintenance - An Application to High Voltage Rotary Machines

Islam, Abu Md Ariful
Master thesis
Thumbnail
View/Open
16970_FULLTEXT.pdf (2.135Mb)
16970_COVER.pdf (1.556Mb)
URI
http://hdl.handle.net/11250/2454358
Date
2017
Metadata
Show full item record
Collections
  • Institutt for maskinteknikk og produksjon [4334]
Abstract
Large high voltage rotary machines are commonly utilized in gas processing plants for operations

such as dewatering and compression. The availability of these machines are very

critical as the operation down times are generally associated with expensive production

loss. Therefore this is no surprise that industries put a lot of effort in ensuring the maximum

availability of these machines. However accurate failure prediction of such machines

is challenging due to the complexity associated with technicality, data collection, testing

and condition monitoring, etc.

This project addresses such an issue regarding the high voltage motors in Kollsnes gas

processing plant that are currently in operation. It is operated by Gassco and Statoil serves

as technical service provider. Karsten Moholt AS conducts the condition monitoring and

ABB conducts the assessment of the conditions of these motors and claims to predict time

to failure of an individual machine with certain confidence level. However, this prediction

method is under the copyright of ABB and how the process works is not known by any

other party. Therefore it leaves some room for further investigations regarding estimation

of remaining useful life and in addition the current prognostics practice is limited to unit

level.

In this situation, Statoil is interested in estimating remaining useful life of the motors

due to ageing in order to reduce uncertainty regarding operation outage and to support

overall maintenance decisions. They are further interested in extending the boundary of

unit level prognostic to system level prognostic because the demand for motor operation

varies depending on the two seasonal periods- summer and winter. In addition, they would

like to explore the possibility of developing a simulator that is capable of estimate remaining

useful life of a motor (or possibly the system) under given current health condition,

previous history and future probable usage profile of the machine in order to further facilitate

maintenance decision making process.

Various approaches have been taken by researchers to address the issues in high voltage

rotary machine prognostic but there are still remaining many challenges that are making

the whole prognostic process complicated. The main focus of this thesis is to develop a

degradation model for the rotary machines in order to estimate remaining useful life under

the given current health condition and make a possible transition from unit level prognostic

to system level prognostic. The required preliminary task of prognostic estimation involves

finding a good indicator that describes the health condition of a motor reasonably well.

During the process, it s been observed that, failure due to ageing process in stator winding

insulation is the most critical failure mechanism in high voltage rotary machines and

the health of a motor basically depends on the condition of the stator winding insulation.

It s been noticed that, ageing processes can be influenced by multiple stresses acting in

synergistic fashion which makes any sort of life modeling or degradation modeling very

difficult. It s been further noticed that regardless of the stress acting most dominantly on a

failure process, the final failure usually occurs due to electrical ageing. Further progress in

the study leads to the conclusion that, partial discharge test is currently the most acceptable testing method for health condition indication of an insulation system among the available

methods.

Under the assumption that condition monitoring data is available, statistical approach

based on non-homogeneous Gamma process has been employed for the degradation modeling

in order to estimate remaining useful life of a given rotary machine. Important

properties of Gamma process has been discussed in correlation with the rotary machine

prognostic. Associated parameters have been calculated with a 95% confidence interval.

Quality of parameter estimation has been discussed for several inspection strategies. In

case of prognostic, current condition (actual degradation level) has been incorporated with

remaining useful life estimation. This is due to the fact that, condition-based prognostic

tends to be more accurate than traditional age-based prediction. Some relevant insights

have been discussed and a demonstration have been provided regarding possible transition

from unit level prognostic to system level prognostic.

Based on expert opinion provided by Statoil and literature surveys, non-homogeneous

Gamma process appears to be the most appropriate for degradation modeling of winding

insulation system utilizing partial discharge information. However reminding of the

famous quote by George E. P. Box, All models are wrong but some are useful ; proposed

model requires to go through some validation process with the help of useful field

data. Nevertheless the proposed model is full of possibilities for making transition from

a theoretical model to a more practical model as more information becomes available. In

addition, application of such degradation modeling is not only limited to this specific case.

Gamma process is already a popular choice for this purpose and non-homogeneous gamma

process have significant implications for civil engineering applications.

This thesis proposes an initial framework for prognostics of remaining useful life of

high voltage rotary machines under the assumption of non-linear degradation increment of

insulation system. It shows potential for further research leading to some interesting and

useful outcomes in this particular area of research.
Publisher
NTNU

Contact Us | Send Feedback

Privacy policy
DSpace software copyright © 2002-2019  DuraSpace

Service from  Unit
 

 

Browse

ArchiveCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsDocument TypesJournalsThis CollectionBy Issue DateAuthorsTitlesSubjectsDocument TypesJournals

My Account

Login

Statistics

View Usage Statistics

Contact Us | Send Feedback

Privacy policy
DSpace software copyright © 2002-2019  DuraSpace

Service from  Unit