Design of a reliable pipe-lay system for a deepwater construction vessel 2009.TEL.7337
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SUMMARY
Heerema Marine Contractors performs the installation of offshore platforms and infrastructures with their deepwater construction vessel the ‘Balder’. The vessel can install large structures with two cranes (heavy lift operation) and, since an upgrade in 2002, it is also able to install pipeline infrastructures with a J-lay tower. Because the demand for this type of projects is still growing, it is likely that the Balder will perform a large number of pipe-lay projects in the future and a start has been made for the development of a new vessel.
While a heavy lift project is a one-time operation with a lot of preparation time, pipe-lay projects require the set up of a continuous production process. It is important that these projects are executed in the scheduled timeframe to prevent extra costs when the project is delayed. A first estimate was made about the performance of the Balder pipe-lay system, which indicated a high amount of downtime. For the development of effective measures to reduce these delays, it is required to analyze these delays in more detail.
This study is split into two separate parts: a detailed analysis of the performance of the Balder pipe-lay system and development of possible improvements for this system. The goal of the first part is to determine the main sources and causes of the delays. The goal of the second part is to find effective measures to reduce these delays.
Performance Balder pipe-lay system
For the analysis of the vessels pipe-lay system the availability, which reflects the proportion of up- and downtime, was selected as the key performance indicator. The analysis is based on data from all pipe-lay projects during the years 2003-2007. Because the tower was assumed to be the bottleneck, this is the only part of the system for which data was recorded. During these years 337 days were spent on pipe-lay operations of which a total of 70 days were lost due to delays. This results in a total technical availability of 79% for the combination of all pipe-lay projects in those years.
The availability is determined for every single project to determine whether the characteristics of the project, like the type and diameter of the pipe, have influence on the performance. This revealed that the projects with a low availability (below 75%) are all short (<15km) and complex projects. Since this type of projects is where a J-lay vessel can distinguish from other vessels (S-lay or reeling), they are and will be an important part of the vessels portfolio. It is therefore of major importance to reduce downtime for such projects.
From the distinction between the different sources of the delays the most remarkable result is the high amount of waiting on pipe (16% of all delay time), which means that the tower cannot continue production, because no pipe sections are available. The assumption of the tower being the bottleneck of the system therefore does not hold true. Two other important sources of downtime occur during the
Design of a reliable pipe-lay system for a deepwater construction vessel 2009.TEL.7337
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process of welding the pipe sections together; process failures resulting in rejected welds (27% of delay time) and breakdown of equipment used during welding (15% of delay time). The fourth source of downtime is breakdown of the tower equipment, which transports and handles the pipe sections in the tower (23% of delay time). The root causes for these delays could not be identified because not enough data was available; no data about the performance of processes on deck resulting in waiting on pipe and no data about why equipment broke down, why welds were rejected or which measures were taken to solve the problems.
Opportunities for improvement
A large number of opportunities are determined with which the performance of the pipe-lay system can be increased significantly. The focus for these improvements has been on an improved flow of pipe sections through the system, reducing equipment breakdown and improvement of the quality of the weld, test and coating processes.
The measures derived to reduce these delays can increase the availability with 7% (from 79% to 86%), which means an elimination of approximately 40% of the total delay time. The most recommended improvements can be traced back to one central conclusion: the pipe-lay system should be treated more like a production system instead of a traditional offshore installation system. Three main focus areas are determined which need attention for this reason; equipment design, buffer function and maintenance.
• Equipment should be designed for the repeatable use to reduce equipment breakdowns, increase product quality (reduction of process failures) and reduce set-up times.
• More focus is required on the pipe handling & multi joint and buffer subsystems to reduce waiting on pipe and to prevent further increase in the future.
• A maintenance program needs to be developed to decrease repair times, increase the reliability and get more insight on the failure modes and causes. Within this program, procedures for the operators can be developed for regular tests of the equipment.
An investment of 30 million dollar to impement the proposed improvements could reduce the delays with 15 days per year, resulting in a payback time of 2 years.
Conclusion
The main conclusion of the study is that an integral approach of the complete pipe-lay operation is required to obtain a system with much less downtime. Many different departments are dealing with different parts of the pipe-lay system and a coordinating role is missing. This has a number of consequences for the systems performance.
Design of a reliable pipe-lay system for a deepwater construction vessel 2009.TEL.7337
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• The total systems performance was never analyzed. Therefore it was unknown which sources are causing the high amount of downtime, resulting in neglecting the waiting on pipe phenomena. • Relations between different processes are not clear. This makes it hard to find the root causes of
delays, because these are often situated in preceding processes.
• The design aspects concerning the system performance are overlooked. Equipment is developed to perform the required processes, but not to contribute to a smooth overall production.
Recommendations
Based on the results of the performed study a number of recommendations can be given to implement the most promising improvement proposals.
• Assign one department or team to be responsible for the performance of the complete pipe-lay system. This team should coordinate between the different departments and keep tracking the performance in the future to constantly improve the performance, resulting in lower costs. • Initiate a project to reduce waiting on pipe; the project should start with measurements to
determine the causes of this delay and further determine effective measures to reduce them based on these measurements.
• Start a maintenance program in which the maintenance need for all equipment is determined and use this as a base to develop a maintenance policy. From this policy, the (preventive) maintenance tasks can be determined for every part of the system. Additionally, start a maintenance measurement program, by reporting all performed maintenance tasks to be able to analyze the maintenance policy’s efficiency and determine possible future improvements.
