Bilgisayar destekli bakım yöntemleri ve gemilerde bakım yöntemi

Ayrancı, M. Mahir
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Fen Bilimleri Enstitüsü
Bu çalışmada bakım yöntemleri etraflıca incelenerek, bilgisayar destekli bakım yöntemleri ve gemilerde bakım yönetimi konusu ele alınmıştır. İkinci bölümde bakım işlevine gerekçe olan arızalar konusu işlenerek arıza çeşitleri tanımlanmıştır. Üçüncü bölümde ise bakım konusuna değinilerek bakım stratejilerinden söz edilmiştir. Dördüncü bölümde bakım yöntemleri sıralanmış ve arıza olduğunda bakım yöntemi açıklanmıştır. Beşinci bölümde ise önleyici bakım anlatılmış diğer bakım yöntemlerinden farkı üzerinde durularak uygulama sonuçlarına geniş yer verilmiştir.Önleyici bakımın ana hedeflerinden biri olan ve gemi makinaları işletme personelini yakından ilgilendiren yağlama yağı ve hidroliklerdeki kirlilik önlenmesinin önemi ve gerekleri üzerinde etraflıca durulmuştur. Altıncı bölümde gemilerde planlı koruyucu bakımın geleneksel uygulaması anlatılmış bölümün ilerleyen kısmında bilgisayar destekli planlı bakıma yer verilmiştir. Yedinci bölümde uyarıcı bakım anlatılmış ve arıza belirleme yöntemleri izah edilmiştir. Makina elemanlarının arıza, tanım ve teşhisinde en büyük ölçüm parametresi olan titreşim gözlemleme konusu geniş olarak açıklanmış, örnekler verilmiştir. Takip eden sekizinci bölümde de, incelenmiş olan bakım yöntemlerinin ışığında entegre bakım açıklanmış, sonuç ve öneriler ise dokuzuncu bölümde yer almıştır.
The maintenance applications are more important for the ships than it is for shore-installations. Because the malfunctions and their consequences on a ship is vital to the life of the crew, besides the economical side of it due to the time loss. That's why before going in to the maintenance, in the first chapter the malfunctions are investigated. Essentially the malfunction is an undesirable state operation of the systems or the machines, where they do not function properly. The malfunctions can be discussed in two groups as the functional and the potential malfunctions. In case of a functional malfunction, a system or a part cannot perform the predetermined standard operation. On the other hand, a potential malfunction can be seen in a system or a part as the symptom of a possible failure. The machines resist the failure in the beginning of the problem. But this resistance tends to decrease with the increasing operating time. In fact the decreasing resistance occurs due to the stresses in the operating part. When the stresses are more than the resistance, the failure occurs. If the systems are composed of a number of parts and machines, the failure takes place neither of one reason nor simultaneously. Because of this, in the ships, which use the high technology machinery, the precautions and the failure preventing methods must be considered precisely and attentively. In the second chapter, the maintenance and the maintenance methods are investigated. The maintenance should provide the longest operation time for the systems in the predetermined safety limits with the minimum cost. Today, in many marine vehicles, the maintenance is seen as an additional cost factor and only in case of a breakdown, repairing the failing part considered. The machines operate till the end of their limits and the systems are fixed if necessary by the crew who are not very knowledgeable. On the other hand the right thing to do would be to control all ttie appliances in the ship by a methodical maintenance technique. In order to provide a longer operational life to the systems, their best operational conditions must be preserved by the maintenance conducted before the lowest performance limits are reached. The most important problems can be faced during the maintenance programming are, first the arrangement when to conduct certain maintenance, and second the allocation of the financial support for the maintenance. Here the most vital duty of the person who plans the maintenance and the people who conduct it, is to estimate the required maintenance time correctly and to conduct maintenance with the less cost. The main maintenance costs are the following; 1. Protecting and warning maintenance costs 2. Fixing costs 3. Costs due to the not operating ship The insufficient or exceeding maintenance effects the system efficiency and profitableness negatively. Under the light of these facts, the maintenance of the xi systems must be programmed so that there is a balance between the maintenance operations and the maintenance investments and the profitableness of the system. The maintenance methods can be grouped into four main topics as follows: 1. Breakdown maintenance 2. Proactive maintenance 3. Preventive maintenance 4. Predictive maintenance These topics are discussed in the following part; BREAKDOWN MAINTENANCE This method is the least developed one among the others. In this method the function of the maintenance crew is to fix the malfunctions as they emerge. In other words, the duty of the maintenance crew is the repair. In case of a failure, if the system has a backup the backup system replaces the failed system otherwise the operation stops completely until the malfunction is removed. The advantages of the method;. there is no need for planning.. To repair some appliances may cost more than the new one.. The disadvantages of the method;. Unexpected malfunctions keeps the ship from sailing.. There is a need for the backup systems or the spare parts. This creates a financial burden on the firm and the stocking problems for the spare parts.. This is an unsafe method. Since the timing and the extend of the failure is totally unknown, this poses a danger for the crew. PROACTIVE MAINTENANCE This method suggests to remove the factors which may cause failure in the operating systems and provides a smoother operation. This method is the last one among the others which entered to the practical field. The proactive maintenance entered in the practical field in 1985 and it is quite different than the predictive maintenance. In the predictive maintenance the aim is to fix the failure after the malfunction emerges. On the contrary in the proactive maintenance method, the aim is to prevent the failures before happening. Thus in one method, the malfunction considered to be inevitable and no preventing precautions are taken and in the other method is completely design to prevent the failure. As the strategy goes, both methods must be applied together. By this application the failures in the ships and the repairing time, which keeps the ships away from sailing would decrease tremendously. PLANNED / PREVENTIVE MAINTENANCE In this method, the controls and the maintenance conducted on the systems in the time intervals as the manufacturing firm or the experienced crew suggest. The advantages of the method; Xll . With a simple program and minimum maintenance applications, the possible failures are investigated, prevented and the life of the machine is extended.. The time spent away from the sailing is reduced due to reduced failures.. This method increases the safety standards and decreases the dangers directed to the crew and the systems in case of a failure.. This method suggest to conduct the maintenance according to a program.. The complicated maintenance is expressed in simple procedure that the personnel can easily conduct the procedure.. Since the registration cards are filled during the maintenance, the personnel get familiar with the system. The disadvantages of the method; When the planned maintenance conducted as it should be, it provides 25% profit. If the maintenance intervals are not considered as programmed and some parts which are not worn out or not due replacement are changed with the new ones, the profit decreases. According to Forbes magazine in the US, one out of three dollars spend for the maintenance in the US is wasted. As an otfier example, in a large overhaul plant 60% of the hydraulic pumps are sent for maintenance when there is no need for it The reason of this loss in the efficiency is due to the maintenance requests according to a plan, regardless of the conditions of the working part The operations are to stop at the unexpected and undesired moments owing to the malfunctions. These sudden occurrences handicap the ship's sail plan, and discredit the maintenance crew. THE TRADITIONAL METHODS FOR MAINTENANCE APPLICATIONS IN THE SHIPS The following describes the installation of the planned maintenance application for the first time;. The systems in the ship are assembled in four groups as the ship systems, the systems, the auxiliary systems and the equipment.. The preparation of system/equipment cards.. The preparation of the maintenance list cards for machines/equipment.. The preparation of the equipment guidance lists.. The preparation of the equipment data lists.. The formation of the maintenance groups.. The preparation of the planed maintenance hand-book. THE MAINTENANCE PROGRAMMING For a better performing maintenance, one of the required preparations is the well organized maintenance programs. During the programming generally three phases are considered;. To prepare the general maintenance program between the two overhaul periods of the ship.. To prepare the three-month maintenance program.. To prepare the weekly programs. The general program based on the two main overhaul dates of the ship. The maintenance in the general program can be conducted by the ship's crew. But sometimes some special test apparatus can be required. In the ship the chief engineer prepares the general program. The maintenance other than the weekly and the daily ones are registered on the general program. Xlll The three-month maintenance programs includes the periods of sailing, harbor and repair. That's why this program is the most important one. Under the light of the general program, the three-month program is prepared by the second engineer. The weekly program is the last part of the planned maintenance which reaches the personnel who are going to conduct the maintenance. The personnel can check their names and see who is going to perform which maintenance. COMPUTER-AIDED PLANNED MAINTENANCE The traditional planned maintenance method which has been discussed in the previous part is replaced by computer-aided planned maintenance in many ships and the traditional method is going to be deserted totally in the future. Since 1980's the computers with their increasing data capacities and speeds and decreasing sizes are commonly implemented in the planned maintenance programs. Today the computer-aided maintenance programs like Administration of Maintenance, Operations and Spares-Data are still in use in many ships and can control up to 99 ships at a time. As an example these programs can store and manage the following;. 99 sections in a ship. Up to 3000 equipment for each section. Up to 999 spare parts for each equipment. For machinery and the equipment data up to 32.000 registration such as cards, addresses, etc. PREDICTIVE MAINTENANCE In this maintenance method the principle is to measure the machine performances during the operation and estimate the maintenance time. In the western countries this method, which depends on the performance data, became very common and proven to increase the profitability. The advantages of this method; With vibration measurements the future problems are estimated. Many problems are fixed before the damage becomes worse. The effect of the defective parts on the others are decreased. The time period between the stoppages because of the failure or maintenance increased. The sailing plans are realized more accurately. Which part to repair is known before hand decreases the maintenance period. The spare part stock is decreased. Since the malfunction is prevented the life of the machine is longer. Decreasing serious malfunctions, increases safety. Faster repair, increases personnel efficiency. The disadvantages of this method; The costs for the personnel who is going to gather and evaluate the data. Computer, hardware and software costs. In this method besides the vibrations, temperature, oil, leakage and noise levels are controlled and analyzed for estimation on the possible failures. XIV INTEGRAL MAINTENANCE The systems, which the ships and the plants use, are mainly high technology products. For these systems only one type of maintenance method cannot provide all the maintenance requirements. Besides the ship or the plant may suffer from the high losses due to ceased operation caused by the system failure. On the other hand, the unexpected malfunctions may occur even in the most contemporary systems and modem machines regardless of the maintenance method applied is up-to-date or not. Here the aim is to minimize the unexpected failures and the personnel risk. In a ship, a well planned maintenance procedure must be utilized and the personnel must be educated to the merits of the planned maintenance. Besides the methods for the prediction of the failures and the early warning systems must be used to their best advantage to the whole system. This kind of systematic work combined with the data from the failure prediction techniques contributes to the planned maintenance system. This procedure will decrease the use of the spare parts and the interruption of the operation, both of which may cause a lot of financial loss. An example for this type of maintenance program is given in the 8th chapter of this thesis. RESULTS AND SUGGESTIONS A good understanding and the application of the maintenance methods is vital to the ships. In the present time still in many ships, an organized and contemporary maintenance program is not exercised except for some upkeep maintenance for the main engines and the generator diesels. In an environment like a ship, where many complicated machines and systems gathered in a small volume, the importance of the maintenance programming is obvious. In the ships, most of the systems and machines are operational 24 hours a day and 7 days a week. This is a continuous process and during this uninterrupted operation the working elements of the systems get closer to a failure and the failures are encountered frequently. Under these circumstances, the maintenance procedure should be more than repairing the failing systems. Even though some maintenance procedures have some disadvantages, it is better than just waiting for a failure and repairing it when it happens. The predictive maintenance is the newest and the most attractive maintenance procedure. In a ship, where the systems are affected by the corrosion, humidity, and salt particles, the method of the predictive maintenance must be carefully considered in order to adapt the negative effects of ttie above mentioned factors. Especially the lubricating oil and the hydraulics are common in the ships and the predictive maintenance method states the importance of the cleanliness of these liquids. If the malfunctions are repaired as they appear, this will increase the repairing costs. Under these circumstances a planned maintenance must be put into effect in the ship. The traditional planned maintenance will decrease the costs and increase the personnel and system safety. The next step is to develop the traditional planned maintenance with computer support. With the computer support, more data can be put together and analyzed. This means better statistical results and more to the point maintenance. The other advantage of the computers in the planned maintenance is that the spare part flow and the storage can be controled more effectively. Another step would be to utilize the failure observation and diagnosis techniques. In the past 20 years the electronics and microchip technology have improved so that the vibrations of a machine can be used to determine the possible failures of the machine itself. The maintenance crew can identify the failing or worn XV out parts of the machine and can diagnose the possible failure without stopping the operation. The vibrations is the one of the methods to predict the possible failure. Other signs of the failures are the increasing temperatures or the increasing particles in the lubricating oil. But the vibration method gives more information and more failures can be detected with this parameter. The maintenance method of failure prediction with the vibration monitoring or with the other parameters is the most reliable and the most economical method. After 1980's with the decreasing size and weight, the computers and the electronic devices are much more practical and applicable for many field purposes as well as in the ships. Nowadays the maintenance methods in the ships must be totally computerized and supported by electronic devices. It is obvious that only one of the maintenance methods mentioned in this study cannot fulfill all the maintenance needs of a ship. As it has been stated before, all the methods have some advantages and some disadvantages. Because of this, the suggested methods must be inspected carefully and an optimized method must be applied to the ships. Here it is possible that a combined maintenance method, which is the integration of the planned maintenance and the predictive maintenance methods, can decrease the maintenance costs of the ship as well as increase the operation time, which will result in a net efficiency increase. In a short time, the combined maintenance method can yield a reliable system and amortize the personnel and the system costs.
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1997
Anahtar kelimeler
Bakım yönetim sistemi, Bilgisayar destekli bakım, Gemiler, Maintenance management system, Computerized maintenance, Ships