Deniz altı boru hattı kaza analizi ve düşen nesnelere karşı boru hattı tasarımı
Subsea pipeline accidental analysis and pipeline design against falling objects
Yazar: MİKAİL RIZA ONAT
Danışman: DR. ÖĞR. ÜYESİ YALÇIN ÜNSAN
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Gemi İnşaatı ve Gemi Makineleri Mühendisliği Ana Bilim Dalı / Gemi İnşaatı ve Gemi Makineleri Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2023
Konu: Gemi Mühendisliği = Marine Engineering ; Mühendislik Bilimleri = Engineering Sciences
Dizin: Açık deniz = High sea ; Boru hatları = Pipelines ; Gemi inşaat sektörü = Shipbuilding sector ; Gemi inşaatı = Shipbuilding ; Kaza analizi = Accident analysis

Özet:
Son yıllarda artan teknoloji ile beraber deniz altı boru hatlarının uygulaması deniz teknolojisi mühendisliğinde oldukça önemli bir konumdadır. Farklı amaçlar için uygulamaları yapılan deniz altı boru hatlarının ekonomik ömürleri süresince dayanımlarının ve stabilitelirinin güvenli bir şekilde sürdürülmesi oldukça önemlidir. Deniz altı boru hatlarında meydana gelen arızalar, petrol sızıntılarına hatta büyük maddi ve çevresel zararı olan patlamalara neden olabilir. Petrol ve gaz endüstrisindeki ciddi çevresel felaketler ve insan ölümleri, boru hattı bütünlüğü yöntemini ekonomik, sosyal, çevresel ve daha birçok yönden çok önemli bir iş haline getirmiştir. Deniz altı boru hatlarının güvenli ve verimli işletilmesi, çevreye ve insanlara verilen zararı en aza indirir. Riskleri azaltmak ve boru hattı arızalarının nedenlerini ortadan kaldırmak için, boru hatları uluslararası kod ve standartlara göre güvenli ve uygun bir şekilde tasarlanmalı, inşa edilmeli ve yönetilmelidir. Yapılacak risk analizi sonucunda boru hattının işleyişine vereceği zararlar tahmin edilecek, böylece boru hattının zayıf noktaları ve yüksek riskli alanları belirlenecektir. Boru hattı bütünlüğü yönetimi; korozyon, çevresel etkiler, darbeler (çapalar, troller vb.), insan hatası gibi boru hattı operasyonuna zarar verebilecek birçok faktörü göz önünde bulundurur. Bütünlük yönetimi, dikkate alınması gereken boru hattı tasarımı ve işletimi, kaçak tespiti, acil durum yönetimi, iş sağlığı ve güvenliği vb. konuları içerir. Açık deniz petrol ve gaz endüstrisinde, çevre ve canlılar için telafisi zor olan büyük kazalar sonucunda bütünlük yönetiminin kullanımı artmıştır. Denizaltı sistemlerinin muayenesi, bakımı ve onarımı, genel bir bütünlük yönetim sisteminin temel bileşenleridir. Boru hattı sistemleri, birçok türde hasara maruz kalabilir. İstenmeyen olayları ve potansiyel tehlikeleri belirlemek ve analiz etmek için yaygın olarak kullanılan çeşitli uluslararası veri tabanları ve teknik raporlar vardır. Veriler farklı şekillerde analiz edilebilir ve bu analizin sonuçları planlama, tasarım, inşaat ve boru hattı yönetiminde çeşitli amaçlar için kullanılabilir. Bu çalışmada, gerekli risk değerlendirmesi sonucunda boru hattı tehditleri belirlenerek sınıflandırılmakta ve deniz altı boru hatlarına düşebilecek cisimlere karşı tasarım üzerinde durulmaktadır. Boru hatlarında oyulmaya ve darbeye karşı; boru hattını tamamen gömme, iri malzeme ile kaplama ve beton hasır serme gibi birtakım koruyucu yöntemler kullanılmaktadır. Deniz ve kıyı yapılarında kullanılan geotekstil tüplerin boru hatları için farklı bir uygulama metodolojisi üzerinde durulmaktadır. Genel olarak polyester veya polipropilen hammaddeden üretilen geosentetik tüpler, kıyı yapılarına koruma ve liman alanları için mendirek inşaasında kullanılan malzemelerdir. Geosentetik tüpe basılan su, kum karışımından su dışarı sızarken kum içerde kalır.

Abstract:
With the increasing technology in recent years, the application of submarine pipelines has a very important position in marine technology engineering. It is very important to safely maintain the strength and stability of submarine pipelines, which are applied for different purposes, during their economic life. Failures in submarine pipelines cause oil spills in the water and may even cause explosions with great material and environmental damage. Serious environmental disasters and human deaths in the oil and gas industry have made pipeline integrity method a very important business in economic, social, environmental and many more ways. The safe and efficient operation of submarine pipelines minimizes damage to the environment and humans. In order to reduce risks and eliminate the causes of pipeline failures, pipelines must be safely and appropriately designed, constructed and managed according to international codes and standards. As a result of the risk analysis to be made, the damages to the operation of the pipeline will be predicted, so that the weak points and high-risk areas of the pipeline will be determined. Pipeline integrity management considers many factors that can damage the pipeline operation, such as corrosion, environmental effects, impacts (anchors, trawls, etc.), human error. Integrity management includes pipeline design and operation, leak detection, emergency management, occupational health and safety, etc. issues to be taken into account. In the offshore oil and gas industry, the use of integrity management has increased as a result of major accidents that are difficult to compensate for the environment and living things. Inspection, maintenance and repair of submarine systems are essential components within an overall integrity management system. Pipeline systems can be subject to many types of damage that can compromise integrity. There are several international databases and technical reports that are widely used to identify and analyze undesirable events and potential hazards. Data can be analyzed in different ways and the results of this analysis can be used for various purposes in planning, design, construction and pipeline management. Statistical analysis of historical data is made for risk estimation 
and as a result of the analysis, the causes, consequences and distribution of failures are evaluated. Varying failure modes can be categorized according to time-independent and time-dependent damage situations. While erosion and corrosion cause time-dependent failures, damages caused by external forces as a result of impact and accident cause time-dependent failures. Risks that cause environmental and economic consequences are the combination of the probability and outcome of failure. Integrity management programs are risk management programs that involve continuous evaluation and improvement and sustainable activities. The integrity method organized in submarine structures is a process in which the system is carried out safely. The pipeline integrity program monitors and predicts defects, thus adjusting where, when, how, and what steps to take, such as inspection, maintenance, and repair. Good pipeline integrity management should ensure successful risk management, failure prevention, damage control and overall cost reduction. In the offshore oil and gas industry, the use of integrity management has increased as a result of major accidents that are difficult to compensate for the environment and living things. This use is a proactive approach not only for aging structures, but also to extend the life of the submarine project structures from the beginning of the system, to control the cost of use of the structure, and to ensure that the structure as a whole works properly. Programs for the inspection and maintenance of submarine structures are in high demand. When we do not inspect the structures in a comprehensive manner under the submarine, the physical condition of the structure loses its longevity. pipelines; corrosion, cracks, dents etc. may suffer a lot of damage. If damages are not properly managed and precautions are not taken, pipeline failures, including leakage or rupture, can result in environmental disasters and downtime. When the damage of any equipment cannot be observed directly, a costly and long repair failure may occur. Inspections must be done carefully, as submarine structures are not easy to access. It is necessary to be careful, especially since the corrosion cannot be observed directly and its measurements cannot be made. In this study, pipeline threats are identified and classified as a result of the necessary risk assessment, and the design against objects that may fall into submarine pipelines is emphasized. Against scouring and impact in pipelines; A number of protective methods are used, such as completely burying the pipeline, covering with coarse material and laying a concrete mat. A different application methodology for pipelines of geotextile tubes used in marine and coastal structures is discussed. Geosynthetic tubes, which are generally produced from polyester or polypropylene raw materials, are materials used in the construction of breakwaters for protection of coastal structures and port areas. The water pressed into the geosynthetic tube leaks out of the sand mixture, while the sand stays inside. In the study, ABAQUS software was used to simulate the impact process of submarine pipelines from object fall from situations that would cause pipeline failures. The calculation results show that the ability of the pipeline to withstand the anchoring effect increases with the increase of the wall thickness and slenderness ratio of the pipeline.
There are different methods as a protective structure against possible impacts to pipelines. Apart from the concrete coating, polymer coating, and gravel coating methods that protect the pipelines, a more economical, more energy-absorbing and longer-lasting design method can be developed.
Geosynthetic tubes used for coastal and port structures will be a long-lasting design that will absorb the impact energy that will stop the pipeline from working by being applied to concrete fixing kits for the protection of the pipeline. There is energy transfer to the pipeline, especially in protection methods with concrete mattress and gravel. Under the towers or piers where the objects are at risk of falling, geotextile tubes can be applied considering the thesis in the study in terms of the energy absorption properties of the pipelines. Taking into account the depth and tide calculations at the entrance of the pipeline to the sea, precautions will be taken against corrosion caused by waves thanks to the geotextile tube.
When designing submarine structures, it is necessary to avoid protruding parts in the design structures so that anchors, fishing nets do not get caught in parts of the submarine structure. When designing any structure, it is extremely important to anticipate possible scenarios and assess risks during the operation phase as well as during the construction phase. A safety system should be installed in offshore pipelines to prevent excessive pressure, leakage and pipeline damage or to reduce them to minimum hazard limits.
During the operation of the pipeline, the possibility of product release and pipeline explosion that will harm the aquatic ecosystem should be estimated and protective measures should be applied in the project documents for these situations.