TS-148
Vibration Monitoring for Wear Condition of Cylinder Liner and Piston Ring in Marine Diesel Engine
Sen-ichi SASAKI*
ABSTRACT
The cylinder liner and piston rings of present large marine diesel engines are in severe lubricating condition with the trend of higher engine output. Sometimes their abnormal wear due to scuffing appears in the earlier stage of the voyage despite manufacturer's effort in the structural and metallurgical modification. In such situation many researchers are studying the method of the lubricating condition monitoring from viewpoint of Condition Based Maintenance (CBM).
The purpose of this study is to establish the technique for wear condition monitoring of cylinder liner and piston rings based on liner vibration signals. This paper describes the results of preliminary test carried out in shop trial of a 2-stroke cycle engine, and examines the effectiveness of the monitoring method by the analysis of vibration data measured in the period of running-in of the engine.
Key Words: Condition Based Maintenance, Condition Monitoring, Vibration Measurement
1. INTRODUCTION
Recent large marine diesel engines are operated in the condition of increased maximum pressure and longer piston stroke. As a consequense of these trends, the problem of abnormal wear of cylinder liner and piston rings (hereafter cited as liner/rings) is increasingly raised, and for early detection of the abnormal wear not a few studies have been done on the lubricating condition monitoring.
Among the monitoring methods, measurement of oil-film thickness or oil sampling through a hole made in liner wall [1] has high sensitivity in the detection of abnormal condition. However these methods are not so popular because of the expensiveness of the equipment and the difficulties in employment for ships in service.
On the other hand there is an attempt to evaluate the wear condition of liner/rings by vibration measurements [2]. Vibration monitoring as a method of condition monitoring is usually applied to general rotational machines such as steam turbines, turbo compressors, pumps and so on, but application to reciprocating machines such as diesel engines is rare. This is because vibrations of diesel engines are induced by several kinds of exciting forces and the relationship between vibration responses and abnormal conditions is not known in detail.
While the goal of this study is to establish the technique for wear condition monitoring using vibration data, at the beginning it is to be examined whether vibration signal is effective or not as a signal for diagnosis. Because vibration signals include several kinds of signals irrelevant to friction, rubbing vibrations induced by the friction of liner/rings are to be distinguished from other vibrations and the availability of vibration measurements must be estimated.
This paper describes the results of preliminary test which was carried out in shop trial of a 2-stroke cycle crosshead engine (uni-flow scavenging, rated output: 9,156kW, rated speed: 114 rpm). Based on the vibration data measured in the period of running-in of the engine, the effectiveness of the method is examined.
Fig. 1 Outline of measuring system
