Konsta Karioja

• Master of Science (Technology)
• Researcher at University of Oulu

Various methods are used in the field of machine diagnostics for recognizing cyclostationarity in signals. The real order derivatives of vibration signals, however, have been rarely reported from the perspective of their effect on the performance of cyclostationarity detection methods. In this paper, we use real order derivatives together with spec...

Stress monitoring systems are not always included in machinery, and this might create a need for a retrofitted system. Programmable Logic Controller (PLC) units, mini PCs and other similar hardware are nowadays widely available at a reasonable price, which makes this type of hardware an interesting choice for retrofitted monitoring systems. However...

Fault diagnosis can utilise signal processing in various ways: informative time domain signals are separated or transformed from the source signals and used in feature extraction to find useful fault indicators. Frequency domain analyses focus on identifying interesting signal components. This research integrates different solutions together: diffe...

Spectral analysis is a very common tool in vibration monitoring. While useful in machine diagnostics, spectral analysis can be rather time consuming. Tasks that require an extensive amount of time are often considered too expensive, especially in modern industry. To achieve an automatic monitoring system of some kind, different features, such as th...

This study is focused on the application of automated techniques on low-speed bearing diagnostics. The diagnosis in low-speed conditions is hampered by the long periods between defect-related impulses and the high level of noise relative to the magnitude of the impulses. To detect a localised defect in such conditions, a new approach that uses vibr...

Liquid steel is typically stirred in a vacuum tank using argon gas injection to achieve a homogeneous composition and high‐purity steel. The aim of this work is to study the effect of vessel vibration on the operational state monitoring of the gas stirring in a vacuum tank degasser. Following an extensive analysis of vibration features, the root me...

The continuous development of steel products generates new challenges for the maintenance of manufacturing machines in steel mills. Substantial mechanical stress is inflicted on the machines during the processing of modern high-strength steels. This increases the risks of damage and flaws in the processed material may appear if the capability of a...

Periodically repeating shocks are a quite common indication of certain defect in machinery. Detecting these shocks in early stage, before the defect is severe enough to cause failure, can provide a huge advantage in maintenance planning. The earliest possible warning of a defect may be highly important, especially in targets where failure can lead...

Manufacturing of modern high-strength steels generates new challenges for the maintenance of equipment at steel mills. Harsher conditions than previously need to be tolerated during the manufacturing processes. These conditions increase the risk of machine failure and the product quality may deteriorate if the machine capability is exceeded. Theref...

The objective of this work was to develop a mechanical vibration-based objective indicator, which can be used for monitoring of the stirring intensity, detection of gas leakage during the stirring process, and condition monitoring of ladles.

Roller bearing faults are a common fault type in machines. There are several condition monitoring handbooks which describe ways of detecting these faults by means of vibration measurements. Handbooks on neither condition monitoring nor vibration analysis usually mention real order derivatives or cyclostationary technique. These methods have rarely...

Upsampling is a pretty commonly used term in field of signal processing. It may be necessary e.g. when processing a signal sampled at fairly low frequency to be played by a sound board. In field of machine diagnostics, applications of upsam-pling techniques are very rare, and when there is a need for high number of samples oversampling is used inst...

Ladle treatments are employed for adjusting the composition and temperature of molten steel before casting. For this aim, gas stirring is employed in order to improve mixing and to promote chemical reactions. Gas leakages decrease the intensity of gas stirring and constitute a common problem in the melt shops. Various methods have been proposed for...

In condition monitoring, detecting changes in measured signals is often desired. Another crucial piece of information is the frequency, which shows the change. In industrial applications today, it is quite common to monitor some features, for example RMS value, and visually analyse the frequency spectrum for information about the frequency content....

In condition monitoring detecting changes in measured signals is often desired. Another crucial piece of information is the frequency which shows the change. In industrial applications today, it is quite common to monitor some feature e.g. RMS value, and for information about the frequency content the frequency spectrum is visually analysed. The RM...

Development of high-strength steels has been rapid in recent times. This has created huge commercial potential, but some maintenance problems as well. Materials of high-strength obviously impose a higher stress on machinery than the conventional materials. However, the machinery available is often designed for processing steels from the past, and i...

This paper presents an approach to real time condition monitoring of an epicyclic gearbox in a hydroelectric power plant. Early and reliable change and fault detection in an epicyclic gearbox is important, because a failure may cause long out-of-service time. The hydroelectric power plant is used to provide load following power to the electrical gr...

The dimensionless MIT index is a new method of stress evaluation of guillotine-type steel cutters. The S surface is utilised in order to determine suitable features for the index. The S surfaces are obtained using real-order derivatives and weighted lp norms. In this paper, it is shown that these methods can provide easily understandable informatio...

Machine diagnostics is usually based on measurements and monitoring changes in signals obtained. It is crucial to reliably determine if there have been changes in signals, as this is usually considered a sign of deteriorating condition of the machine. When correctly applied, generalised norms can provide a very good estimate about the changes in si...

Frequency spectrum is widely used to determine frequencies present in a signal, but it fails to extract information regarding deviations from Gaussianity and presence of phase relations. Higher order spectra, on the other hand, contain such information and have shown large potential in numerous disciplines including vibration based diagnostics. In...

Misalignment is a common problem, and several handbooks on condition monitoring provide instructions on how it can be detected. Very often monitoring the component of rotational frequency and some of its harmonics in the frequency domain are considered a solution to this problem. This can indeed be a suitable method in many cases, but when misalign...

Cavitation is a somewhat common and well-known phenomenon and can cause erosion in machines, such as water turbines and pumps. The detection of cavitation in different machines has been quite widely investigated. However, when cavitation occurs simultaneously with different types of mechanical faults, the task is slightly more complicated. This pap...

Mechanical cutting is an old, effective method for steel cutting. The variety of steels available in the market has changed considerably over the last few years, and new demands for mechanical cutting have been set. The shearing force is of course a very important factor in the stress evaluation of a cutter, but also vibrations should be considered...

Acquiring signals without disturbance is a crucial part of condition monitoring. This paper discusses some observations concerning disturbance in signals caused by two different frequency converters when measuring acoustic emission and acceleration. Signals are acquired by means of two acoustic emission and acceleration sensors. The test rig includ...