Introduction:

In the offshore piping design, deep water projects are playing a vital role in the recent years. Ever since the first pipe line was installed offshore, major developments are happening in deep waters. As the oil reserves are slowly getting depleted in shallow depths, major oil companies are exploring and investing in deep offshore projects, which are highly complex and very expensive when compared to fixed platforms functioning in shallow water depths. In early days of offshore industry, 80-100 meters water depth was considered as deep, but now floating production facilities are being installed in 1500-2000 meters water depth or more. As demand for fuel is growing every day, more and more deep water projects are lined up in the coming years.

 Deep water projects:

In the past 10 years, deep water projects such as Semi submersibles and FPSOs (Floating Production, Storage & Offloading vessel) have been commissioned in many Oil producing countries around the world. As per recent surveys, there are more than 150 FPSOs in operations in various water depths. Brazil leads the FPSO count with as many as 31 vessels producing as on date. It is expected that the FPSO count in Brazil will increase further in the next couple of years when the new projects which are under various stages of design and construction will be ready for production. Also, as announced by Petrobras (the National Oil Company of Brazil) its plans to expand the Floating Production Storage and Offloading systems to increase production in the Pre salt region Brazil will keep its dominance as the world’s leading FPSO user in the next decade.  

Design of FPSO facilities is extremely challenging, but very interesting. The criteria for FPSO piping design are comparatively different from other offshore projects, wherein many additional factors and guidelines have to be considered.

 Typically based on the crude oil properties, the process team defines the process which would determine the engineering design, materials, fabrication, assembly, inspection and testing etc.

The design has to comply with specified codes and standards and follow various Class and International regulatory bodies like ABS, ILO, API, NFPA, ASME etc. Also, many projects have to follow the local Government regulations and statutory requirements. Marine piping design criteria should meet the applicable rules of the Certifying Authority.

 Piping Design:

The FPSO system and associated equipment & components would be usually designed for 20 years life-cycle with minimum in-field maintenance and a maximum operation. Sometimes, due to various reasons, the life might come down and vessel has to relocate to a new field. This necessitates to replace/modify/upgrade a few equipments, pipes and systems to suit the new well fluid properties.

In the FPSO piping design, Topsides and Mooring system are more critical compared to vessel piping. Most of the process lines have to be stress analyzed for various characteristics like Motion (Transit and In-field condition),  acceleration, roll, pitch, wind velocity, seismic etc., and necessary flexibility has to be provided. This is a real challenge in the whole module design due to space constraints and process demands.

FPSO with Turret mooring system will comprise Process and utility pipes for Manifold and Gantry and number of risers for Crude Oil inlet, Water, Gas & Chemical injection, Utilities & Electrical.

The topsides and deck layout is primarily determined by Process requirements and safety considerations, i.e., to maximize the production and ensure safety of personnel on board.  Topside equipment is arranged in such way that hazardous equipment is far away from the accommodation block.

Topsides piping design includes various modules like HP separation, LP separation, Gas compression, Gas treatment, Sea water treatment, Water Injection, Power generation, Lay down /chemical injection etc. Among these modules, Separation and Compression modules are more critical in nature.

During conceptual design and front-end engineering phases of a project, a sound asset lifecycle knowledge and best design practices and efforts have to be in place to do an optimum design in terms of layout, material, safety, accessibility, maintenance etc.

Detailed engineering, due to its complexity, requires a good knowledge in process, safety, maintenance, constructability, stress analysis and supports.

In an offshore detail engineering project, usually Piping has more than 40% scope which plays a major contribution in the overall project cost. Hence, during detailing, an optimum design has to be made for expensive materials like Duplex steel etc. which could reduce the cost considerably.

Unlike previous design approach, such as material selections and plant layout that were typically handled during the detailed design phase, are now planned at the front-end engineering and design (FEED) phase to have a better estimate on the project cost. In fact, detailed P&IDs and 3D models are developed at a much earlier stage, so that essential decisions based on cost implications can be made. This also ensures that major maintenance or constructability issues do not arise during the engineering, procurement and construction phase.

 Challenges in piping design:

As the offshore projects are always limited in terms of space, piping design is a tough task throughout the detail engineering. In reality, on a FPSO project, a lot of information would not be available during the initial phase. The adaptability to change at the shortest time due to lack of inputs is the most critical aspect during the detail engineering phase. Design team has to work on certain assumptions in terms of equipment sizing & maintenance, instruments, valves and special components. Due to lack of space, the permissible reserves are minimal and if the final component varies in geometry, size, orientation etc., to a large extent from the assumed, it will pose as a major challenge to the design. Also, unanticipated process updates sometimes cause a major rework on the design which impact on Stress analysis and pipe routing. This would impact on the phase wise progress and final deliverables.

It requires highly skilled resources to handle the complex design. The ability to produce quality deliverables in the agreed time is very essential and is always a challenging job in reality. Adapting to changes or in better terms, the ability to use previous experiences to assume most suitable equipments and other necessary inputs would be a major difference between a good design and a design that needs correction on the yards.  In spite of these challenges, a clash free and consistent piping design with good flexibility and appropriate supports are to be achieved within the project duration. A superior design with lesser re-work will always reduce the project cost to a large extent and plays an important role in the project success.

Cost is one of the major challenges in an offshore project. The use of exotic materials and special components is inevitable with the varying nature of Crude extracted. The geological nature of the seabed also necessitates expensive materials to be used. The recent cost escalations coupled with the increasing demands due to the complexities requires design to be accurate and optimal. 

 A Good piping design is one, which accomplishes all above difficulties in spite of uncertainties and limitations, but finally delivers the quality product with better productivity. The modern competitive world expects all projects to be cost and time effective, which obviously looks for a continual improvement in the project strategy and execution methodology.

It’s been a practice to effectively use latest tools and techniques available in plant design engineering to overcome the complex nature and strict demands of projects. Using latest 3D tools, these projects could be built to a real scale model for better visualization and checked for integrity, consistency, clashes, access, safety, mechanical handling, maintenance etc., and all major deliverables like Plot plans, Piping Isometrics, GA Drawings, Supports, MTOs could be extracted directly from the software. This would help in minimizing the errors, improving quality and reducing project duration.

 Points to focus during piping design:

• Understand the complete process of modules before detailing and go through all process requirements (like Slope, upstream/downstream lengths, drains/vents, instructions on hazardous area, process controls etc)
• Always select the correct material/components as per Specifications to avoid rework.
• Procurement, erection/fabrication sequence and yard priorities must be kept in mind during detailed design and Material take off.
• Understand the pipe support philosophy as per project/client requirements and follow throughout the project
• Document/Drawing Checking procedures as per project requirement must be followed strictly to achieve desired quality.
• Always keep alternative plans in case of crisis.
• Use project management tools to have better planning, monitoring and control.

 Conclusion:

Having been associated with Piping design for nearly two decades, I have been a witness to technology progressing rapidly to assist the piping engineers and designers across the world. Globally with land based and shallow water Oil and Gas explorations maturing, the future requirements will have to be met by deep water explorations. The latest technologies, where the production depths have touched or crossed 2000 meters and future targets of 3500 meters below sea level, the challenges in technology will increase. The coming decades will provide engineers and designers better techniques and technologies as they strive to address these challenges.

Present generation engineers and designers have access to various tools and technologies that allow simulation of the complete system to avoid many fabrication errors while providing quicker deliverables. Tools like intelligent 3D modeling that can detect clashes between various items, 2D drafting tools that allow quicker and accurate drawing production and simulation tools that can generate flow patterns, provide termination details, identify loops etc enhance effective engineering practices.

The digital connectivity across the globe has also made it possible for the various simulation tools to be shared across locations helping improve quality, minimize errors and instant collaboration with all stake holders of a project. 3D models that are being designed in engineering offices can be viewed by construction engineers and immediate points that can reduce material and improve efficiency based on construction requirements can be notified to the engineering offices.

Effective Engineering best practices are being adopted by many organisations across the globe to reduce the project completion timeline. The initial investment in technology may seem a bit high compared to the traditional engineering practices but the Total cost of the project is reduced considerably. The total savings of effective engineering practices are multiple and to list a few

1. Design team members need not be present on the yard at all times to guide the construction teams.
2. Quicker time to completion will ensure earlier commissioning of the project and quicker time to market of the final product.
3. Yard clash resolution is minimal resulting in considerable saving in terms of time and cost.
4. Accuracy of the drawings is very high resulting in better construction.

Sidvin is one of the engineering companies that follow effective engineering practices to help its customers to save on time and cost.  At Sidvin it is a policy to evaluate all the latest best practices to ensure its customers get the best services at the best price.

Effective Engineering is the way forward for all engineering activities.

So watch this space for releases and updates of services by Sidvin.