Oct-2008

Process design benefits of 
laser scanning

The effectiveness of laser scanning and 3D modelling is considered from lessons learned in the field, providing better ways to capture process data

Julie Martin, Foster Wheeler South Africa (Pty)

Article Summary

Two projects were executed on the same chemicals site, each with the objectives of increasing production and upgrading control and safety. Although the plants produced different products, there were the same concerns: toxic substances, poor plant records and non-standard equipment.

Pre-laser scanning era
The first project was executed in the pre-scanning era and commenced with a team of engineers and designers being dispatched to the site. The process engineers had to generate the process documents by following the lines on-site, while the other disciplines did the same for the various engineering documents. The summer ambient temperatures were around 36°C with high humidity levels, the plant layout was tight and cramped, and the personal protective equipment (PPE) requirements included full hazard suits in certain areas. This exercise took six months and the conditions were reflected in the quality of the information gathered, resulting in regular subsequent site visits to recheck information or get additional data.

The second project was executed using laser scanning and again commenced with a team of engineers and designers being dispatched to the site. However, the team was a third of the size of the previous project’s team and the process engineers could concentrate on confirming the process requirements, knowing that the additional data required was being captured with a combination of laser scanning and digital photographs. The time taken to gather the necessary data was reduced to three weeks and the quality of the information was significantly better. The entire project team benefited from using laser 
scanning, not only from a health and safety aspect, but also from having good-quality information available to start the design.

Selection criteria
Whether and how to use laser scanning must be a project-specific decision and focus on achieving the overall project objectives. Having clear selection criteria avoids the temptation to use laser scanning as a default and sets guidelines for the decision-making process. The selection criteria used by Foster Wheeler South Africa are:
•    Safety   
•    Contract type
•    Schedule
•    Complexity
•    Location
•    Personnel.

The safety section takes into account the risks to personnel on the specific plant, including the process hazards and the probability of exposure. The contract type section considers the project phase and the contracting strategy and is linked to the project schedule constraints. The complexity section requires evaluation of both the design and construction complexity. The location of the site relative to the engineering office is also considered together with the experience level of the project team. Each of these criteria is allocated a score and the decision is based on the weighted overall score.

Process and safety benefits
Generally, process engineers see the scan as a tool to be used for detailed engineering and design that brings no benefits to them. If applied correctly, there is a wealth of data available for the process design and real benefits for the process engineer. These include health and safety benefits, as demonstrated in the introductory example, design benefits such as project schedule improvements, accuracy of data and availability of information, and finally commissioning and operational aspects such as system definition and safe-making.

Safety is an often under-estimated benefit of using laser scanning. It is possible to substantially reduce the time personnel are exposed to potentially hazardous environments, and Foster Wheeler has specifically used laser scanning on several projects for this reason. Also, for projects in remote or dangerous locations, information that would take weeks of site work to gather can be scanned within days. Accessibility within the plant itself is another consideration: scanners can now scan up to 300m from the scan position, accurately to 70m and visually to 150m, and the equipment can be used in live plants.

The process design benefits result from having the plant information available in the engineering and design office. Revamp projects often involve reiteration to find the optimum solution in terms of process optimisation and constructability. Project layout affects everything on a revamp. Options can be explored and checked for accessibility, clashes and constructability, and the process engineer can take these aspects into account from the start of the project. The use of laser scanning and 3D models is a more recent aspect to the process and piping partnership that is so critical to revamp project success.

The old-fashioned approach usually means information is initially gathered based on the first-pass solution. This solution is evaluated, changes are made and the team returns to site to get additional information. Laser scanning, combined with 360° photographic bubble views, gives quick and easy access to the entire plant, with potentially significant time-savings. Not only is the information readily available, but laser scans also allow line sizes, control valves, flow meters, equipment dimensions and nozzle information to be checked and confirmed against existing documentation. This gives the process engineer accurate and reliable data to proceed with the process design. For example, for critical hydraulic circuits such as reactor circuits, the exact lengths and fittings can be extracted either directly from a 3D model built and verified against the scan or by utilising a combination of scan, photographs and available isometrics. Laser scanning with modelling provides the necessary information within a similar time frame, but with much improved accuracy.

For revamps, safe-making prior to shutdowns is a critical activity. The process systems will extend beyond the modified or worked-on sections into the existing plant, and an accurate picture of the existing plant makes system definition easier. Isolation points can be identified, engineers can verify that lines can be drained and made safe, and equipment can be correctly spaded. The same approach can be followed for pre-commissioning and commissioning activities with the integration of new and existing plant in the 3D environment. This can be extended further to assist in planning for phased execution on revamp projects. The combination of the new and existing plant can be modelled and linked to plans for a visual and very effective check of the proposed sequences that can be easily reviewed by both design engineers and operations engineers.