It?s not magic, but it?s more than just a neat lightshow

The 3D laser scanning system captures, visualises and models complex structures and sites with an unprecedented combination of completeness, speed, accuracy and safety.

Provide Solutions, based in Scottsdale, Arizona, is developing 3D scanning system technology for use in the marine industry and has conducted a pilot test in partnership with ConocoPhillips Marine and Northrop Grumman Ship Systems Avondale Shipyard.

The 3D laser scanning technology uses multiple laser pulses to measure the surface geometry of objects to a 1-5mm accuracy up to a distance of 50 m. The scanner sends out laser pulses to the object being scanned and measures how long it takes for each pulse to return to the scanner. Complete surface geometries of exposed surfaces can be remotely captured in minutes in the form of dense, accurate ?3D point clouds?, ready for immediate use. As soon as the scan of the structure is complete, the 3D point clouds can be used in a wide variety of applications, including those that require export to CAD and rendering software.

Scott Cedarleaf, president of Provide Solutions told The Motor Ship, “we had originally presented the technology to their [ConocoPhillips Marine?s] maintenance department to help them with their CAP inspections. Although the company was impressed, they said we intrinsically had safety issues to be concerned with when operating a ship carrying petroleum.” The company has since addressed this concern and has recently found a scanner that is intrinsically safe as far as the actually scanner head and power source is concerned. “So that might open up some new avenues for us in doing maintenance checks and scanning around the manifold and midship areas especially on oil tankers,” says Cedarleaf.

Four areas of application were developed for the Avondale Shipyard pilot test, i.e. fabrication, pre-erection, post-erection and general accuracy control.

The yard was having alignment problems with internal frame structures when it came to fitting hull blocks together. “They would find that the webbings and the attachments would not match,” says Cedarleaf. Provide Solutions took measurements and produced scan clouds that could be rotated in any direction. He went on to say “we isolated it with all the other data around it ? we just cleaned it up to give that specific unit.” The company then took the scanned cloud information for that particular unit and overlaid it into an AutoCAD file. This allowed the yard to find out if they had built the hull block to the design or within tolerance. Although there were variances, they were found to be very minor.

Mixed reactions

However, when the drawing was originally overlaid it highlighted that the turn of bilge was a long way out from the actual shape, but it was pointed out to Provide Solutions that the section of the drawing was forward of the scanned data.

Cedarleaf said that the next stage was where it really became a powerful tool for Conoco. “However, we divided the ranks at Northrop Grumman ?unfortunately, the guys in the field are ?gung ho? with this and making all kinds of noises to get this stuff in the field but the accuracy control guys are not as eager to jump in because they feel it is threatening what they do now as far as systems and processes.”

The company used x, y, z coordinates and least squares to find the best fit for the two blocks. He explains, “we basically did a virtual fit to see how these two units were going to match.” Initially there was a problem with the fit caused by a bottom plate being missing from one of the blocks but once it was replaced it provided a closer fit. “That shows the purpose of the scanner,” says Cedarleaf. “If you have units in different areas miles away, you can scan this data and do a virtual fit and then you can correct problems before it is taken out of an area it is easy to work on. So, the whole goal was to be able to minimise rework and man hours.”

Although Northrop Grumman is divided over the its use, Cedarleaf says that Bender Ships down in Alabama and Verreault up in Quebec have taken a keen liking to this kind of technology for working on double hulls. He explains, “they are adapting it and seeing the value of the tool.”

Virtual fit

Provide Solutions did another virtual fit when the Avondale yard was having problems aligning a ship?s rudder. The company took scans of the rudder and skeg from two locations although more could have been done if required. Cedarleaf says “we took the two scans that we did from the two angles, we registered them together using the software so we were able to catch at least a lot of what the rudder looks like and then we can manipulate that.”

The company then put everything into its correct orientation and obtained an x, y, and z coordinate for the engineers to find out the position of the z-axis alignment, which was the centre of the pintles and gudgeons for both the rudder and the skeg. A 60mm clearance was added which was maintained all the way down.

He says, “they were thrilled with the outcome of this being able to confirm that, based on this information, we know we built these within tolerance and are not going to have issues like we have in the past.” It verified that the shipyard had corrected the problems it was having with the fabrication process.

Powerful tool

The system is also a powerful tool when used for fairness and deformation. ConocoPhillips had huge concerns about the aft deckhouse on one of its ships being built. Cedarleaf said that the yard commented it was a great tool to find out what they had done wrong.

Provide Solutions agreed but told the yard that it wanted to introduce the system in the pre-process to help it solve the problem. Seven or eight scans were taken from different directions and a reference plane was inserted on the scan cloud. Different colours were then used to represent the varying distances the surface was from the reference plane. Targets were used to register all the scans together accurately. “You have to keep in mind that the scan is line-of-sight ? it?s not going to go through anything, or give any information behind ? it?s all line-of-sight,” explains Cedarleaf.

This highlighted that the deckhouse sides were way out of tolerance and the company told the yard that if it scanned after placement of every two panels it could prevent the yard getting any deformation. These are just applications that are specific to ConocoPhillips ? there are hundreds more that yards are dealing with everyday. The president of Provide Solutions says, “we are at the evangelistic state getting this technology out there ? we are not marine engineers ? we just know that if you can see what this stuff can do then you guys can qualify what applications you can use this on.”

“When a company enquires about 3D laser scanning the first question that usually gets asked is how much does it cost? We tell them $160,000 for the scanner and software but we can do one of three things. We can come in and just be your sole service provider ? you call us in when you need us because you?re not going to need this everyday, or we can be your service provider ? you buy the scanner and we operate it for you and as you get comfortable and prove that it is a value add we shake hands and call us when you need us kind of thing. Or we could just sell the scanner and software and we or some other company can train them and they?re up and running.” The system is also not just limited to scanner the outside of ships but can be used to scan the inside as well.

Jumboisation

One application that The Motor Ship can see for this technology is in the jumboisation of ships. The exact measurements of the outside of a vessel can be taken very accurately while a ship is in drydock before the jumboisation takes place and be used to fabricate the block instead of using the ship?s GAs which, as earlier demonstrated, might not always be accurate.

As Cedarleaf explains, “drawings are the perfect world ? you don?t have temperature variations, you don?t have the sun going behind a cloud and all of a sudden the steel wants to move. It gives you a good representation of what is actually going on.” If there are heavy fluctuations of weather the company or yard can just quickly scan it again. He says “as far as where members are, cross sections, attachments for structure, critical pieces to tie into, you can map this out and put it straight into an AutoCAD or micro station drawing. The engineers can then design from that knowing there is going to be some margin of movement or error but, although it?s not going to eliminate errors, it will definitely minimise them.”

One huge advantage is that the equipment can be out of everybody?s way and doesn?t impede those working on the ship. “There will be some noise flashed back but for the most part you capture the data; it?s like a total station on steroids, it captures millions and millions of points of data and we can capture it from two different sides to get outside and inside edges of steel so then they can pull dimensions and extrapolate the data and put it into a file and off they go.”

Quick field test

The company has also done a quick field test for Bender and have since completed an outside hull for a petroleum push-barge. The yard were fitting the barge with a double hull on the outside and Provide Solutions provided the yard with the positions of existing frames and the locations of the existing surface of the outside of the hull.

Based on the pinpointed data the yard supplied, the company isolated where the attachment frames would be. “Then we just did a line through our data and they transferred it straight out of our scan cloud information and put it into their lofting software, which then gave them an outside line section of the hull within millimetre accuracy of the deformation, the dips and the dings, explains Cedarleaf. It is basically taking an image of the outside of the hull and slicing it in half where they need to connect. To try and do that with a total station would be painstakingly unaffordable, whereas we were able to scan the entire bow to stern in two days.”

Proven technology

To get to that stage, the company had to do a field test for Bender Ship and Mobil to prove the technology. The company inserted a small piece of steel in the ship?s bow thruster and scanned it to produce a line drawing of the surface of the hull and how it moulded around the curves of the inside of the bow thrusters and would notch around the small piece of angle iron and continue towards the keel. Two scans were registered together and the company isolated the bow thruster and laid a line along the surface of the cloud data, which was then exported into an AutoCAD file.

This was given to Bender?s engineers, who took the design and used it to fabricate steel for a test fitting. It produced an impressive fit for a minimal scan, which proved to Bender the accuracy of the system, which is 2-3mm when overlaid into AutoCAD. This can be further improved if a design coordinate system is used.

Cedarleaf says “we?re compiling more data now from the double hull we did up in Canada as well as the one we did for Bender ? they?re going to be fitting pieces on the one in Alabama in the next two weeks and the one in Quebec is on sea trials right now.”

Potential applications

Another potential application is to use the system to investigate the damage caused by a collision between two ships. He explains, “we scan both of them and give whoever is manipulating the data an entire 3D, x, y, z coordinate document of these two ships and they can re-enact it.”

The speeds of each ship, point of impact and damage assessment could be determined and this information would help on the litigation side says Cedarleaf. This information could also be used to repair the vessel and save man-hours to such an extent that it could affect the decision as to whether to scrap or repair the ship. He jokes, “it?s not magic, but it sure is neat what you can do with it if it?s used correctly.”

Cedarleaf says, “The last ship that ConocoPhillips had delivered from Avondale was six inches out from bow to stern; you wouldn?t think that was a big deal on a ship that was over 900 feet long, but to them it was huge and just unacceptable.”

Another study that the company carried out at Avondale was to scan the pin jigs used to make the plate sections around the bulbous bow area so that it could create a surface based on the tops of the pin jig plates. The company could then do a polycurve surface or any fabricated surface that would show where the pin jigs were out so the yard could get its pin jigs fixed prior to bending the steel. They were using huge counterweights to bend this steel and it was holding up the other pieces that were meant to follow behind it, which held up the entire schedule.”

Cedarleaf says that while a survey crew can capture critical points, “they can?t capture existing conditions plus we can quickly collect any extra data that the yard might need in the future.” This could negate the need for the company to come out again. “It?s thinking two steps ahead that really saves the yards a lot of money.”

Cost-effective tool

The company is currently holding talks with NASSCO but is having trouble convincing them of the value of the system but, as ConocoPhillips told Provide Solutions, you have to show it to them because “when they see the data coming in real time and after a 13 minute scan you can then pull dimensions and you can find clearances and do volumes and you can create surfaces and cylinders based on 20% of data it?s just remarkably powerful.”

Cedarleaf concludes by saying “we would love to get into the extension of ships and barges because literally within hours you can have a design document. We want to make an impact on the industry; if we can?t save money and make a value add to a client, we?re wasting everybody?s time. It?s kind of a neat lightshow but we want to take it a lot deeper than that because we really believe it can make a huge impact if used correctly.”