1 - Laser Scanning Introduction

Laser Scanning Introduction Modifying an existing offshore platform (or any facility for that matter) can be a daunting task. Any engineering company, owner operator or construction contractor who has tackled an offshore retrofit is well aware of this challenge. Tight spaces, densely packed equipment and a difficult operating environment combined with a tight timeframe for field construction creates engineering challenges that often carry a high penalty when errors occur. And errors do occur! Most platform owners, engineering firms, equipment vendors and construction companies have experienced significant difficulties with retrofit projects at one time or another. The results are major cost overruns and/or schedule delays as well as ‘field compromises’ required to get the platform back online as quickly as possible. These construction issues and delays can frequently be traced back to either inaccurate or missing as-built information used as critical input to the design and construction/demolition planning of the retrofit. The root causes of the poor quality as-built information lie, in turn, in the traditional methods for gathering as-built information: engineers extract ‘as-built’ information from original design/ construction drawings and supplement this information by taking additional asbuilt measurements manually. Both these techniques are prone to error. Existing drawings are rarely, if ever, accurate, and good manual measurements are extremely difficult to obtain. In addition, even when accurate manual measurements can be taken, many critical measurements may be missed due to oversight or later changes in design/scope. The result is field construction interferences, fit-up problems and costly on-site changes. What is Cyrax Laser Scanning ? Cyrax Technologies, a San Ramon, California-based company and subsidiary of Leica Geosystems AG, introduced Cyrax® laser scanning in 1998 and is the largest supplier in the laser scanning industry with over 300 systems shipped through December 2002. The tripod-mounted Cyrax laser scanner sweeps a pulsing laser over the facility, collecting up to 1,000 individual surface geometry measurements per second. By measuring precisely the time of flight for the laser pulse (distance) and two angles (horizontal and vertical rotating mirrors), a rich, dense ‘three-dimensional (3-D) point cloud’ of facility geometry is created. Each individual point measurement is accurate within +/- 6mm up to a range of 50 metres. By averaging thousands of points on surfaces, a few millimetres precision can typically be achieved when point clouds are processed into as-built models and drawings.

Figure 1: Offshore Platform Scan

To capture full 3-D geometry of the area(s) of interest, the laser scanner is moved around the platform or facility as needed. Once multiple scans of a facility (offshore or onshore) are collected, they are ‘registered’ together and typically tied to a local co-ordinate system using several known survey points. The registration process can utilise both known common points (target registration) as well as matching of common surfaces within the point clouds (cloud-to-cloud registration). Even large structures such as offshore platforms can be scanned easily and the scan data tied together accurately, as shown in Figure 1. This project consisted of 43 scans (roughly 43 million measurements) capturing the areas of critical interest for the retrofit. The scans were collected in less than two days. Since the laser scanner literally ‘blankets’ the scene, designers can easily identify all objects (valves, flanges, strainers, structural elements) they are working with (see Figure 2). The point clouds can be used within Cyra’s Cyclone™ software for rapid creation of accurate, complete as-built models, or, with Cyra’s CloudWorx software, the points can be used directly within the AutoCAD or Microstation design environment to extract measurements or create as-built drawings. This allows designers to model existing piping, structures and equipment easily using familiar design tools while referencing the point cloud as an accurate ‘3-D road-map’. Through CloudWorx, plant design software such as PDS, AutoPLANT, CADWorx and Plant4D can all take advantage of rich point clouds for creation of accurate as-builts for interference-free design.

Figure 2: Point Cloud

The Benefits of Cyrax Laser Scanning and Modelling Rapid, accurate, complete measurements combined with the easy-to-use Cyclone and CloudWorx software allow the designer to create truly accurate as-builts quickly and easily and/or create new designs that are interference-free. The result is reduced cycle time, reduced engineering effort, lower project cost and on-time construction completion. The areas that laser scanning has impacted over the past number of years are many. Elimination of Rework This is an obvious and well-documented benefit. Through the increased accuracy achieved by laser scanning, construction contractors are finding that piping spools and prefabricated structural elements fit right the first time. Reports of ‘zero rework’ are common. This, in turn, means no downtime while trying to make corrections, no expensive standby time for lifting equipment and no delays in plant start-up due to ‘field adjustments’. Interferences have been eliminated in advance. Lower Cost Design When laser scanning is used during the design phase, fewer field trips are required in order to obtain geometric data. In essence, the point cloud data brings the ‘3-D field reality’ right to the designer’s desktop. Rather than relying on surveyor notes and a few point measurements, the designer can now ‘virtually’ navigate through the facility, view, measure and design based on complete data. Direct measurements from the point clouds can be taken quickly and utilised for the design. This not only reduces costly and time-consuming field trips to collect missing information, but also increases the confidence in the design, thus allowing for fewer field welds. In one small project alone, over 40 field welds were eliminated after laser scanning data was incorporated into the design process. Another major saving in the design phase is the ability of multiple disciplines to share the same 3- D point cloud information. Rather than each group (electrical, piping, structural, etc.) collecting and using their own field data, a single set of point cloud data can be utilised. This not only saves money (and time) in the data collection phase, but ensures consistency of the information being used for the design. Since everyone can view the same data, numerous potential conflicts can be avoided in advance. Reduced Cycle Time

Due to the rapid collection of field data and minimal ‘post processing’, a reduction in project design cycle time can be achieved. Since each laser point is already a 3-D measurement, the raw point clouds can be used directly for design once they are registered and tied to the appropriate co-ordinate system. No interpretation or translation of field notes is required and there is no need to process 2-D drawings into 3-D. Improved Safety Rather than climb ladders and piping or deal with lifting devices and safety harnesses, a Cyrax laser scanner allows the data to be collected remotely from a distance of up to 50 metres. This also enables the field crew to obtain accurate measurements safely and quickly even in inaccessible or otherwise hazardous locations. Flexible Work Flow A full suite of software products allows the user to select the work flow that is appropriate for the project. If a basic geometry model is required for use within computer-aided design (CAD), the Cyclone software can be used to create and export the required model quickly. In addition, if desired, object intelligence can be added through the use of a ‘Piping Mode’, which incorporates Alias SKEYs terminology. Once the piping is created with the SKEYs, it can be output into the Alias pcf format and then translated into AutoPLANT, PDS and PDMS formats using Alias products. An accurate, intelligent as-built can also be created directly by combining a 3-D design system such as AutoPLANT with CloudWorx for AutoCAD application. CloudWorx 2.0 Pro automatically fits point clouds to pipe centrelines directly in the CAD environment, thus enabling the designer to model existing piping elements quickly and accurately using familiar tools. Figure 3: CloudWorx with AutoPLANT

If the objective is simply a new, interference-free design, CloudWorx can be used within the CAD environment to view the raw points and create the new design around them. Since the plant modelling tools are typically familiar to the designer, and the learning curve for CloudWorx is minimal, high-level production can be achieved quickly. In addition, very little ‘organisational resistance’ is typically encountered since no-one is being asked to make a major change in work practices and deliverables. Now, instead of reviewing surveyor notes, they simply pull the point data directly into their CAD station. Where/How Cyrax Laser Scanning is Being Used

Service providers who own laser scanners and software are often contracted to provide sets of registered point clouds or as-built drawings and models. Today, the technology is available worldwide. Typical costs for services are comparable to costs of as-builts done manually (sometimes less), but the results are far more accurate and complete and the deliverables are available sooner. Cyrax laser scanning and software are being used in the offshore and onshore petrochemical industries and manufacturing facilities of many types. Initially considered a tool for only large-scale projects, it has evolved rapidly to prove cost-effective for small-scale modifications to major revamps. Projects ranging from several hundred million dollars to a few hundred thousand dollars have all been able to reap the benefits of 3-D laser scanning technology. 3-D laser scanning technology was originally focused on the design phase, but it has also proven beneficial during the construction phase. Plants under construction have been scanned (and sometimes modelled) for use in developing crane placements and 3-D rigging plans. Construction verification and deviation analysis (quality control) are additional areas that have benefited from this technology. In some cases, contractors have been able to resolve difficult field issues more quickly by having the 3-D point cloud data available to them.