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IMPROVING SAFETY OF OPERATION OF THE SHIP'S PROPULSION PLANT
Maksym Stetsenko
Engineer of the Fleet Technical Operation Department, Odesa National Maritime Academy Yuriy Lukashuk
Head of the Laboratory of the Fleet Technical Operation Department,
Odesa National Maritime Academy
П1ДВИЩЕННЯ БЕЗПЕКИ ЕКСПЛУА ТАЦП СУДНОВО1ПРОПУЛЬСИВНОI УСТАНОВКИ
ПОВЫШЕНИЕ БЕЗОПАСНОСТИ ЭКСПЛУАТАЦИИ СУДОВОЙПРОПУЛЬСИВНОЙ УСТАНОВКИ
Стеценко Максим Сергтович
¡нженер кафедри «Техн1чно'1 експлуатацИ флоту»,
Одеська нацгональна морська академ1я
Лукашук Юр1й Васильович
Завгдуючий лабораторгею кафедри «Техн1чноХ експлуатацИ флоту», Одеська нацгональна морська академ1я
Absract: In this paper we introduce an approach to modernize technical diagnostics of thrust bearings of low speed diesel engines, in order to improve the safety of their operation. The problem is solved by supplementing the existing system of technical diagnostics with new electronic devices that provide continuous and highly accurate measurement of radial clearance of the thrust bearing of the crankshaft of a diesel engine. Key words: thrust bearing, axial clearance, inductive distance probe
Анотацгя: У статт1 запропоновано удосконалення техн1чно'1 дгагностики упорних пгдшипниюв малообертових дизелгв з метою пгдвищення безпеки i'x експлуатацИ. Задача виршуються шляхом доповнення 1снуючоХ системи техтчно'1 дгагностики новими електронними приладами, що забезпечують непереривтсть та високу точнкть вимгрювання радгального зазору упорного пгдшипника колтчатого валу дизеля. Ключовi слова: упорний пгдшипник, осьовий зазор, iндуктивний датчик вгдстанг
Аннотация: В статье предложено усовершенствование технической диагностики упорных подшипников малооборотных дизелей с целью повышения безопасности их эксплуатации. Задача решается путем дополнения существующей системы технической диагностики новыми электронными приборами, которые обеспечивают непрерывность и высокую точность измерения радиального зазора упорного подшипника коленчатого вала дизеля.
Ключевые слова: упорный подшипник, осевой зазор, индуктивный датчик расстояния
Statement of a problem.
It is known that the most vulnerable points of marine diesel engines are bearings of the both crankshaft and connecting rods [1]. To those belong: main bearings, thrust bearing, crankpin bearings and crosshead bearings. These bearings are perceived significant loads which are made up of gas pressure forces and the forces of inertia. The sum of these forces is very complex, and has a significant impact on the operation of bearings. The bearings can be divided into working under a constant load, and under a variable load.
The special position is occupied by the thrust bearing, since it is designed to take not only those kinds
of loads mentioned above, but also to perceive the thrust of the propeller. The trust bearing is mounted at the driving end of the engine. The thrust created by the ship's propulsion is transmitted by the thrust flange of a crankshaft via the thrust pads into a bedplate [2].
Arbor support prevents the thrust pads from being turned out. Depending on the sense of rotation of the crankshaft or propeller, thrust pads forward or aft take up the axial thrust forces.
Such working condition requires constant monitoring of the bearing temperature and periodic maintenance which consists in visual inspections and clearances measurement.
Fig. 1. Thrust bearing of Sulzer RT-flex diesel engine:
1) Coupling flange;
2) Oil baffle, upper part;
3) Oil baffle, lower part; 4, 4a) Holder;
5) Thrust flange;
6) Crankshaft;
7) Thrust bearing pads ASTERN; 7a) Thrust bearing pads AHEAD;
8) Cover
Analysis of recent research and publications.
A systematic destruction of babbit layer in all types of bearings has been reported on engines of various types while in operation. There was no direct connection observed between defects formation and service time [1]. Destruction of babbit layer depends on the variety of structural, technological and operational factors. The main damage to the bearings is due to malfunction of the lubrication (reduce the amount and the decline in the quality of oil). One of the major causes of cracking and
galling white metal is a deformation of the bearings and crankshaft journals. Deformation of the bearings arises from a lack of rigidity of the crankshaft bearings beds and fundamental frame that easily reacts to the change of the hull.
Malfunction of a bearing will result in temperature rise of a bearing shell. This is highly critical for the thrust bearing. Therefore, this type of bearing is normally equipped with appropriate instruments to provide an
automatic slow down and shut down functions of diesel engine.
To prevent any defects formation, it is very important to regularly measure and record the thrust bearing radial and axial clearances. This requirement is specially stressed out in diesel engines maker's instruction manuals [2, 3], since any malfunction of this part will affect the safe operation of main engine and vessel itself.
Readers may consult literature [4] for comprehensive theoretical background of how thrust bearing defects influent on the rotating system. Our concern in this case is the safe operation of the ship's propulsion plant. Behind the term "safe operation" it is understood appropriate repairs, tests and maintenance of the machinery coupled with constant monitoring and control. A low quality of any aspect of this complex term may result in loss of property, and even life. For instance, a malfunctioning thrust bearing may result in grounding or collision while operating in port or narrow waters.
Unsolved aspects of the problem. The procedure for checking radial bearing clearance is rather simple and requires using a filler gauge only. Radial clearance will correspond to the size of a filler gauge inserted between the bearing shell and a journal. However, axial clearance measurement is more challenging and does not have any standard procedure [2, 3].
This is so due to the thrust bearing construction properties and principle of operation. Thus, one engine maker does not require any measurement at all. Only visual confirmation of the white metal absence under the bearing is needed. Another maker demands dismantling some of bearing parts and performing the measurement while pushing pads with a crow bar.
Marine engineers, who work on board a ship, have developed their own methods of performing this task. For example, one of them is to make two scratches on the propeller shaft while engine is going ahead and astern. Then distance between scratches will correspond to the axial clearance and it can be measured with a Vernier calliper.
All this points out on a significant gap in the diesel engine thrust bearing technical diagnostics. Thus, this is of high importance to eliminate that deficiency by developing utilizing modern methods of clearance measurement.
The aim of the research. The aim of this paper is to propose an approach to improve safety of ship's propulsion plant operation by means of modernization an existing electronic technical diagnostics system related to the diesel engine thrust bearing.
Method of measurement.
We have introduced rather simple dynamic method of checking main engine thrust bearing axial clearance. Measurement of this clearance is done by simple electronic system, which consists of inductive displacement sensor mounted close to the flywheel, signal amplifier and portable scope meter.
Measuring systems with eddy current transducers serve the measurement of mechanical quantities, such as shaft vibration and shaft displacement. Applications with such systems can be found in different industrial areas and laboratories.
Due to the contactless measuring principle, small dimensions, a rugged construction and the endurance against aggressive media, this type of sensor is optimally suitable for the use at all kind of engines [5].
Inductive proximity sensors determine the distance to the conductive metal objects, such as steel, aluminum, brass. Since the principle of operation of the inductive sensor is based on determining the mutual induction currents, such sensors are very resistant to non-metallic objects influence and other interferences, such as dust or the engine oil. Modern technologies allow creating an inductive sensor with analogue output having a diameter of 6 mm and a measuring distance of 2 mm. Such sensors with high resolution and quick response time are used in most high speed applications. The transducer may be formed by a single circuit, on a transformer circuit, a differential circuit and differential transformer circuit. As it can be seen in Fig. 2, in a single circuit changing of magnetic flux causes a change of inductance and the impedance of the coil [5].
d\\f d<& • . = Z = Rl+ JOL,
L =
dt
dl
where y and ® are the flux linkage and the magnetic flux of the coil, correspondently, W is the number of turns of the coil, I is the current in the coil, RL is the equivalent resistance of the coil and ra is the angular frequency of the current. The main problem of the theory of the inverter is the determination of magnetic flux in the magnetic circuit and its relationship to the input signal.
Fig. 2. Eddy current transducer model
Eddy current transducer is characterized in that the external source field which is interacting with the magnetic coil field originates from eddy currents induced by the alternating field of the coil in the electromagnetic masses (in special screens or controlled conductive products). Despite the fact that the structural element in the form of additional excitation coil in such a converter is not exist, the principle of transformation should be still regarded as inductive [5].
Experiment.
Field experiments have been performed on board container vessel Ebba Maersk operated by the Maersk Line company . The vessel equipped with Sulzer 14RT-
flex96C main engine. The engine designed maximum power is 80080 kW at 102 rev/min.
There was measuring unit developed and built on the engine. It consists of inductive displacement transducer (type PR6424), amplifier and portable scope meter (Fig. 3). Inductive sensors require an amplifier as they need a DC power supply for operation and original signal generated is very low.
Displacement sensor has to be mounted as close as possible to the engine flywheel as shown in Fig. 4. This is to ensure that total displacement will remain in a sensor's working range.
Fig. 3. Measuring unit:
1) Inductive displacement transducer;
2) Amplifier;
3) Scope meter
Displacement sensor c°nnected in series with k = 4,75 V/mm. Such accuracy allows detecting amplifier provides highly accurate measuring of the
.. even a very small wear of bearing metal.
flywheel displacement with ratio of
Fig. 4. Displacement sensor mounting
Axial clearance of the thrust bearing is best determined when ship is going astern and ahead in turns. The propeller thrust will move shaft in forward and aft direction, respectively. Then clearance is calculated as the sum of these two movements of the shaft. This is done by analyzing the output voltage trend logged in to a scope meter memory.
Results and discussion.
The experiment post processing was done by using software provided by the Fluke Company for its scope
meters, as a standard. Software allows analysing the data massive saved in a devise memory.
There were a number of experiments performed during one year period. The vessel locations were both at sea and in harbour waters. As it can be seen in Figs. 5 and 6, output voltage trend contains a lot of noise. This is due to the fact that flywheel does not create exactly 90 deg. with a shaft. However, voltage readings can be taken then between two highest or two lowest values of respective part of the trend, as it is shown in Figs 5 and 6.
Name Date Time Y Scale YAt 50% X Scale XAt OX X Size Maximum Minimum
- Datablock — = Input A = 01/01/1995 = 00:46:50 = 1.5V/Div = 6.5 V = 20 s/Div = 00:03:00 ■ 100 (240) = 9.2 V = 2.2 V
-Cursor Values —
00:04:24 (00:51:14) 00:06:12(00:53:02] 00:01:48 6.4 S- 9.0 V^ 2.3 [ 4.8 V -4.1 V -4.2 V
Fig. 5. Trend logged during harbour transit
Finally, actual values can be calculated simply by dividing resulted voltage from cursor measurement by conversion ratio k. An example of calculation is given in Table 1. It can be seen that values obtained in one year
period are the same. This is an indication that the thrust bearing remains in a good condition and no wear detected.
Table 1.
Calculation and evaluation for Sulzer 14RT-flex 96C
Parameter Value, mm Voltage difference, V
Minimum designed clearance 0,8 -
Maximum allowable clearance 2,5 -
Actual clearance 0,884 4,2
Name Date Time
Y Scale
Y At 505; X Scale XAt 0i XSize MaHimum Minimum
- Datablock-
= Input A
- 02/01/1995 = 19:24:00
= 1.5 V/DIv = 6.00 V = 100 s/Div = 00:00:00
- 240 (240)
- 9.60 V = 2.20 V
- Cursor Values — 12:49(19:36:48] 05:56(19:29:56] 06:52
25 4.90 V
35 9.10
10 4.ar
logged during trials in open sea
Conclusions.
Installation of industrial system for main engine thrust crankshaft and camshaft bearings axial clearances surveillance system (or upgrading existing one, if any) would be beneficial to the ship's propulsion plant safe operation, since the method introduced has proved to be accurate and simple.
Obviously, accuracy can be improved by creating a proper measuring point as the flywheel is not primary designed for this kind of measurements. Therefore, output signal requires careful post processing.
References.
1. Судовой механик [Текст]. Справочник в 3 т. Т. 1 / под ред. А. А. ФОКА. - Одесса: Феникс, 2008. - 1036 с.
2. Electronic instruction manual for HSD-Sulzer 14RT-flex96C diesel engine [Electronic resource] -Changwon-City, Doosan Engine Co., Ltd., 2006. - 1 electron. opt. disc (CD-ROM).
3. Electronic instruction manual for 50-98 ME/ME-C Engines [Electronic resource] - Ulsan, Hyundai Heavy Industries Co., Ltd., 2006. - 1 electron. opt. disc (CD-ROM).
4. Berger, S. Influence of axial thrust bearing defects on the dynamic behavior of an elastic shaft [Text] / S. Berger, O. Bonneau, J. Frêne // Tribology International. - 2000. - Vol. 33. - № 3-4. - P. 153-160.
5. Федотов, А. В. Теория и расчет индуктивных датчиков перемещений для систем автоматического контроля: монография [Текст] / А. В. Федотов. - Омск: Изд-во ОмГТУ, 2011. - 176 с.
ПРО МОДЕЛЮВАННЯ ПЕРЕНЕСЕННЯ ДОМ1ШКОВИХ АТОМ1В У НЕОДНОР1ДНОМУ ПОЛ1
М1КРОНАПРУЖЕНЬ ПОЛ1КРИСТАЛ1В
Скачков В. О.,
кандидат технгчних наук, доцент кафедри металургИ чорних металгв, Запоргзька державна Iнженерна академ1я
1ванов В.1. науковий ствробтник кафедри металургИ чорних металгв, Запоргзька державна Iнженерна академ1я
Критська Т. В., доктор технгчних наук процесор кафедри електронних систем Запоргзька державна Iнженерна академ1я
Мосейко Ю.В. кандидат технгчних наук, доцент кафедри металургИ чорних металгв, Запоргзька державна Iнженерна академ1я
ABOUT MODELING FOR TRANSFER OF ADMIXTURE ATOMS IN HETEROGENEOUS PAUL OF MICROSTRESSES FOR POLYCRYSTALS Skachcov V.A.
candidate of technique, assistant professor, Department of black metals, Zaporozhe state engineering academy
Ivanov V.I.
scientific worker Department of black metals, Zaporozhe state engineering academy Kritskaya T. V. doctor of technique, Department of electronic systems, Zaporozhe state engineering academy Mosejko Yu.V.
candidate of technique, assistant professor, Department of black metals, Zaporozhe state engineering academy
Анотацш: З позицп виргшення статистично'1 крайово'1 задачi мтромехатки неоднор1дних середовищ виконано спробу створення математично'1 моделi дифузшного перенесення домшок у неоднорiдному полi мiкронапружень. Розглянуто дифузшне перенесення атомiв у полi градieнта мехатчного напруження. Модель дифузшного перенесення атомiв у неоднорiдному полi макронапружень може бути використаною для оцтки особливостей дифузшних проце^в для дефектних кристалiв, тд час розробки технологт дифузИ домшок до конкретних областей кристала або очищення ïx вiд небажаних домшок.
Ключовi слова: кристалти, домiшковi атоми, кристалографiчнi та лабораторш ой координат,
