Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)
66

Increasing speed of Ship Repair throughThree-Dimensional Laser Measurementin Compliance with Environmental Regulations

YUSUKE WATANABE*1NOBUYUKI YAMAGA*2

In recent years, to prevent or mitigate atmospheric/marine pollution, regulations overvessels are being applied and tightened. And further technical innovation to preserve our beautiful
sea and sky as well as enhanced development of diversified environmental equipment for vessels
has also triggered a change with such a trend in engineering needs to repair vessels currently inservice. Mitsubishi Heavy Industries, Ltd. (MHI) has integrated the 3D plant measurement
technology practicalized at its nuclear power sector with the 3D CAD vessel design technique,actively promoting the engineering to repair vessels currently in service. This is an engineering
method based on as-built 3D CAD models of established piping plants reproduced as is on CAD,
using a 3D laser scanner. This report explains specific efforts for implementation of the above.

|1. Introduction
Discharge regulations for ballast water (seawater used for attitude control of the vessel) andthe emission control of air pollutants including SOx are expected to be put in force or tightened instages within the next few years, favoring greater engineering needs to repair in-service vessels incompliance with such environmental regulations. In terms of ballast water regulations, it isexpected that several tens of thousands of ships currently in service will need additional
installations of ballast water management systems. Generally, such repair work often requires large
amounts of materials, complicated pipe arrangements and the troublesome installation of electricequipment.
At ship repair worksites, on the other hand, repair work has been carried out conventionallyrelying on freehand drawings for the repair or on workers’ arbitrary procedures without referring todrawings. The remote cause of this situation is the poor availability of detailed piping drawings ordiscrepancies between the actual state of the onboard plant and drawings for construction.
However, if large-scale repair work is carried out in such a situation as mentioned above,problems could occur such as quality deterioration and difficulty in reflecting the customer’s needsin the repair results as they are not foreseeable, thus leading to not only a loss of the customer’s
trust but also schedule delays.
It is, therefore, becoming indispensable for quick repair work to tightly follow a series ofrepair engineering processes from creating precious “value” that customers expect, to discussing
the “value” with customers and delivering the “value” to them. The method we practiced in giving
shape to this was as-built 3D CAD modeling of onboard plants with a 3D laser scanner.
We successfully constructed as-built 3D-CAD models from the measurement data acquiredby a 3D laser scanner and loaded them not only on general-purpose CAD but also on MATES(Mitsubishi Advanced Total Engineering System of Ships), our proprietary CAD system that
supports engineering from design to production in an integrated manner. In this manner, it has
become possible to create drawings for repair work. This report presents the series of approaches
we have implemented along with several example applications.
*1 Ship & Ocean Engineering Division, Shipbuilding & Ocean Development*2 Submarine Department, Shipbuilding & Ocean Development

Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)
67|2. Workflow of repair engineering
The workflow of repair engineering is outlined as follows:(1) Master plan and investigation(2) Onboard inspection and 3D laser measurement(3) Measured data processing and construction of as-built 3D CAD model(4) Modified piping diagram and detailed production drawings

2.1

Master plan and investigation

First, from customers are heard their needs to be suitably blended with our ideas into a
concurrent base on which conceptual designs for the piping system, pipe arrangement, a piping
diagram, etc. should be put into force for their realization. In parallel, the range of 3D laser
measurement is also determined for actual onboard inspection.

2.2

Onboard inspection and 3D laser measurement

Into the target vessel of repair work, a 3D laser scanner and other equipment are brought formeasurement.
The 3D laser scanner irradiates laser pulses continuously within a hemisphere having its
radius of dozens of meters around the scanner and calculates the distance from a measurementtarget such as hull part, piping, and auxiliary equipment located within the hemisphere bycomparing in terms of phase difference the irradiated wave with the reflected one coming backafter hitting and then reflected by the target. Using the angle derived from the direction in whichlaser was irradiated, the reflection point is identified. A single measurement (scan) obtains tens of
millions of point cloud information pieces.
At the end of measurement, the 3D laser scanner is moved to a different place for anothersimilar measurement. Huge volumes of multi-point cloud information thus obtained can be merged
into a complementarily compounded piece of location information to view the measurement target
as a three-dimensional object.
We have so far completed engine-room 3D laser measurement such as at pure car & truckcarriers, container ships, very large crude carriers, and bulk carriers as well as even accumulated avariety of knowledge and knowhow about how point cloud information can be obtained fromsupposedly hard-to-measure narrow sections of an engine room. It is usually possible with 20-point
and some 2.5-hour measurement to obtain necessary point cloud information for the construction ofa some 100-m2 as-built 3D CAD model.

2.3

Measured data processing and construction of as-built 3D CAD model

The point cloud information measured at multiple points, using a 3D laser scanner, isprocessed in the following procedure:(1) Merging the point cloud information(2) Noise filtering(3) Measurement target modeling by referring to the point cloud data
The accuracy of the above works determines the quality of fresh drawings for repair, thereby
gravely affecting the actual process of ship repair works. This is, therefore, the most importantstage in a series of engineering processes.
We have been actually engaged for about five years in nuclear power plant reform works,
taking advantage of 3D laser measurement. Skilled experts in charge were mobilized to customize
the method or knowhow for vessels, enabling high-accuracy as-built 3D CAD models to be built.
Achievable data processing through as-build modeling process completion in some 15 days
is another important aspect for quick digestion of repair work schedules.

2.4

Modified piping diagram and detailed production drawings

The constructed as-built mode is loaded on general-purpose 3D CAD software or MATES ina universal 3D CAD format. Pipes and equipment to be added are arranged within the space of the3D model.
Particularly, in the case of repair work implementation by our company, MATES can attach
the manufacturing information to each pipe/equipment and also facilitate delivery of information to
the production process, thereby permitting engineering as well as repair works to be executed
efficiently without disruption.

Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)68|3. Examples of repair engineering
3.1

Example of examined ballast water management system installation to a pure
car & truck carrier

Figure 1 shows an example of how we examined an additional installation of a ballast water
management system in the engine room of a PCTC. The initial idea was to add an intermediate
deck with a hull structure in the vicinity of the ballast water pump at the ship bottom and place theballast water management system on this added deck. Through reviewing the as-built 3D CAD
model, however, we confirmed that it could be installed in the recess along the broadside of theship. As a result, the layout as shown in Fig. 1 was proposed. Using as-built models in this manner,extensive modifications of existing pipe arrangements or large-scale hull construction can beeliminated for available additional installation of a ballast water management system.
As for additional installation of a ballast water management system, it is important to selectthe right type of system, but of equal or greater importance is how to cope with the restricted space
for the installation, which would have a significant impact on the cost and period of the repair
work. Therefore, it is of great use in expediting the execution of repair works to obtain a swift andaccurate grasp of an actual ship’s spatial information for continual development of an optimum
system through as-built 3D CAD models-based communication with customers.

Figure 1 Example of repair engineering - Ballast water management
system installation

3.2

Example of MGO Chiller System Installation on a Very Large Crude Carrier

Using MGO (Marine Gas Oil) as engine fuel, the SOx concentration of combustion exhaustgas can be reduced because of the fuel’s low sulfur content. The utilization of MGO is one of thesolutions to meet the SOx emission regulations likely to be tightened in stages.
However, MGO has low viscosity compared with Bunker C, which has been conventionallyused as fuel oil. The low viscosity can be the cause of engine trouble or problems with otherauxiliary systems. The MGO chiller system cools down MGO to increase its viscosity for thereduction of failure risk and a lot of vessels are considering its installation on themselves.
3D laser measurement was carried out to examine how the MGO chiller system could beadded to the engine room. The obtained point cloud information is shown in Figure 2.
And a repaired portion-added image obtainable from the above point cloud
information-based as-built 3D CAD model is shown in Figure 3.
In this ship, since the piping system concerned had a 4-layer structure, requiring 3D laser
measurement of an extensive area, two 3D laser scanners were arranged for respective use by eachof two teams to measure its own preset range. There being numerous pipes running throughbetween upper and lower decks as well as inside and outside the purifier room, the measured point
cloud information was merged into a composed as-built 3D CAD model.
Measured sections were wide in area but relatively uncongested with equipment and the riskof interference was low because the pipes to be added were of a small diameter. This is why the 3D
CAD model was coarser than usual. Depending such as upon characteristics of the system to beadded and the installation area, the degree of elaboration of as-built 3D CAD modeling or“granularity” of the model, so to speak, can be flexibly regulated for available quality-preserved
shortening of the engineering period.

Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)
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In this way, we could also provide customers with the value of a shorter engineering period
in meeting their needs to expedite the execution of repair works as scheduled for the vessel.

Figure 2

Point cloud data acquired by 3D laser scanner

Figure 3 As-Built 3D CAD model with the repair area appended(starboard side of VLCC)|4. Conclusions
Mitsubishi Heavy Industries, Ltd. (MHI) has measured engine rooms of pure car & truckcarriers, very large crude carriers, bulk carriers, etc. by a 3D laser scanner and established methodof constructing as-built 3D CAD models.
We arranged and laid pipes and auxiliary equipment in the space of these as-built 3D CAD
models to prepare fresh drawings for repair works and verified that such 3D information can beused on the detailed design level.
Not to speak of technical innovation, the importance in expediting the execution oflarge-scale ship repair works in compliance with environmental regulations is to obtain an accurate
grasp of the needs customer seek through as-built 3D CAD model-based communication with themfor continual proposal of an optimum system.
MHI will carry on this process of customer value creation in the future through our repair
engineering.