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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 as-

built 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 shippedthrough 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 flightfor 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.

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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 Cyras Cyclone

software for rapid creation of accurate, complete as-built models, or, with Cyras 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.

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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 inadvance.

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 designers 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

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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

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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.