Gantt chart analysis to improve shipbuilding panel line assembly

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Gantt chart analysis to improve shipbuilding panel line assembly Author name(s): Damir Kolich(M), Vanda Brandic(SM), Doroteja Jaki(SM), Lino Novak(SM) University of Rijeka, Faculty of Engineering,

1 Gantt chart analysis to improve shipbuilding panel line assembly Author name(s): Damir Kolich(M), Vanda Brandic(SM), Doroteja Jaki(SM), Lino Novak(SM) University of Rijeka, Faculty of Engineering, Naval Architecture and Ocean Engineering Department, Rijeka, Croatia. Over 60 percent of a typical commercial ships interim products consists of stiffened steel panels. Modern shipyards continually strive to improve their assembly processes. The panel assembly line is one such process which lends itself well to automation in order to reduce man-hours thereby, enabling profit to a shipyard. In this paper, Gantt chart analysis in compliance with a product work breakdown structure (PWBS) methodology is used to map the process of the assembly of a typical panel from a self-unloading bulker vessel. Then, through the combination of lean principles of reducing waste and the utilization of one-piece flow in complement with adaptation of advanced hybrid laser arc welding technology, yields a new and improved panel assembly line proposal. The improvements in the reduction of man-hours through Gantt chart analysis are found to be a significant 86%. This means that a shipyard, by applying these changes could significantly cut its production costs, while maintaining or even improving the quality of its interim products. KEY WORDS: Gantt chart analysis, shipbuilding, Product work breakdown structure (PWBS), lean principles, hybrid-laser arc welding INTRODUCTION Gantt chart analysis is used in many industries. The shipbuilding industry uses it extensively in most levels of its functional analysis. However, whereas shipyard planning offices create Gantt charts that show yearly, monthly and weekly plans, rarely do shipyards have Gantt charts for each type of interim product that is assembled in its premises. In this paper, the most common interim product, a steel panel is analyzed using Gantt chart analysis. This is in compliance with a product work breakdown structure (PWBS) which has proven to be essential in developing an efficient shipyard production system according to the SNAME Design for Production (DFP) Manual (1999). A functional system is based on analysis of different systems throughout the ship and is very practical in the contract stage of shipbuilding. For instance, for the development of the general arrangement plan, the midship section, and outline specifications which are used for price estimation of work, materials and also includes a makers list. Once the contract is signed, the shipyard designers start developing all of the required classification society drawings. When the classification drawings receive stamp approval, then the ship detail designers prepare production drawings. The workers in the workshop are exclusively interested in the detailed production drawings, which define how, where and what to fabricate and assemble. When a PWBS system is successfully integrated with these production drawings, this allows for a very clear breakdown of jobs and interim product development. Likewise, it is possible to identify areas where production could be improved through decreasing unnecessary bottlenecks and replacing outdated tools and assembly methods with avante garde technology. In this paper, the panel assembly line is analyzed utilizing the proper PWBS method, which illustrates the breakdown of both the assembly methods, the corresponding tools, technology, the number of workers and the trade that they belong to. Then through the use of lean principles, a new and better improved panel assembly line is proposed and demonstrated to yield a more efficient panel assembly system, which results in reduced man-hours, thereby yielding increased savings for the shipyard. BACKGROUND The panel assembly line has been analyzed using value stream analysis and lean terminology (Kolich et al 2015a, 2017a). Likewise, the built up panel assembly was also analyzed using value stream mapping (Kolich et al 2016, 2017b). The conclusion is that value stream mapping helps identify losses and through implementing lean methodologies, it is possible to reap savings of up to 80 percent in panel assembly, 50 percent in built-up panel assembly, and finally 50 percent in large erection block assembly (Kolich et al 2017c). Whereas, value stream mapping allows for a very efficient way of viewing the assembly processes in a shipyard, the Gantt charts are able to define more detail which will additionally help production engineering to identify specific tasks that could be improved. SHIPYARD PANEL ASSEMBLY CASE STUDY The case analyzed in this paper is a typical shipyard panel of a self-unloading bulk vessel with a length of 198 meters, a beam of meters and a deadweight of tons (See Figure 1). Fig m self-unloading bulk carrier vessel at 3. Maj shipyard

2 The typical panel is represented by an isometric view in Figure 2. It consists of four steel plates butt welded on both sides, along with a total of nine longitudinal Holland profile stiffeners. The total mass of the stiffened panel is kg (3. Maj 2015). Fig.2 Panel P110 In Figure 3, there is a plan view of the Figure 2 panel, which illustrates how many longitudinal profile stiffeners there are on each plate. Since panel P110 is eventually transformed to a built-up panel, this is why it is labelled as KP which is the symbol for built-up panel in the shipyard analyzed in this paper. Each steel plate has a workshop number. For instance the numbers in squares represent the workshop numbers of each steel plate, 184, 191, 200, and 207 respectively. The thickness of each steel plate is 12.5 mm. Each longitudinal stiffener has its own workshop number, 1727, 1726, Likewise, consecutive numbers of all nine stiffeners from 1 to 9 are embedded in a triangular symbol, which represents each stiffener. Fig.4 Panel assembly line First workstation panel assembly At the first workstation (Figure 5), the first steel plate (workshop number 207) is placed and centered in place. Then the second steel plate (workshop number 200) is placed and centered alongside the first steel plate. The two steel plates are tack welded by ship-fitters. Afterwards, the third steel plate (number 191) is placed alongside steel plate number 200 and tack welded to it. The fourth and final steel plate (workshop number 184) is tack welded to steel plate number 191. This is all demonstrated in the first 16 activities of workstation number 1 Gantt chart (See Figure 6). Since there are four steel plates that means that there will be a total of three seam welds using submerged arc welding technology located on the semiautomated welding gantry. This is illustrated in the final five activities of the first workstation. Five workers multiplied by 3.1 hours yields a total of 15,5 man-hours at this workstation. Fig.3 Panel KP11 In Figure 4 below is a plan view illustration of the panel assembly line. There are four workstations plus the fifth workstation which serves for interim storage before the panel is transported to the built-up panel assembly line. Fig.5 Panel assembly line Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 2

Second workstation panel assembly At the second workstation, once the butt welded panel with four steel plates gets transported to the second workstation along the rollers, then it is connected to

3 Second workstation panel assembly At the second workstation, once the butt welded panel with four steel plates gets transported to the second workstation along the rollers, then it is connected to clamps on a crane and turned over to the other side (See Figure 7). Then each seam is butt welded on the other side one by using the same gantry crane fitted with automatic submerged arc welding technology as was at workstation number one. This can be viewed on the Gantt chart in Figure 8. The duration time is a total of 2.83 hours. There are a total of 5 workers which translates to man-hours. Fig.6 First Workstation Gantt chart Fig.7 Panel assembly line Fig.8 Second Workstation Gantt chart Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 3

Third workstation panel assembly The butt welded panel on both sides is now ready to be prepared for tracing the positions of the nine stiffeners.

This is because there is primer paint which needs to be removed so that the longitudinal stiffeners adhere better to the butt welded panel.

4 Third workstation panel assembly The butt welded panel on both sides is now ready to be prepared for tracing the positions of the nine stiffeners. In order for the welds to be of acceptable quality and efficiently performed, it is necessary to first grind down the positions of the longitudinal stiffeners on the steel panel. This is because there is primer paint which needs to be removed so that the longitudinal stiffeners adhere better to the butt welded panel. In case this would not be done, the welding would take longer and be of a poorer quality. Therefore at this workstation, there are two operators who use the grinding machines and two tracers who trace out the exact positions of the longitudinal stiffeners. Since there are a total of 4 operators and the duration time is 2.83 hours, there is a total of man-hours at this workstation. Figure 9 shows an illustration of the grinding paper used at this workstation. Figure 10 shows the Gantt chart of the third workstation with all relevant activities, duration times and corresponding trades. Figure 9: Grinding paper Fourth workstation At the fourth workstation (Figure 11) each of the nine longitudinal stiffeners are fitted one at a time. Then the welding bridge moves in place and starts welding using submerged arc welding technology. Since there are pins pressing down on the longitudinal stiffeners, it is not necessary to tack weld as in the earlier assembly stations. The welding is performed at a rate of 1500 mm per minute, which means that a stiffener of 9800 mm length will take 6.5 minutes to weld. The total duration time is 2.83 hours. There are four operators for a total of man-hours. This is illustrated in detail by the Gantt chart of workstation number 4 (See Figure 12). Man-hours At the first workstation there were 15.5 man-hours; man-hours at workstation number 2; man-hours at workstation number three and man-hours at workstation 4 for a total of 52.3 man-hours for the assembly of the panel in this case study. The total duration time when the values of the corresponding workstations are summed up: 3.1, 2.83, 2.83 and 2.83 yields a total of 11.6 hours. Fig.10 Third Workstation Gantt chart Figure 11: Welding Gantry for profiles at workstation number 4 Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 4

5 Fig.12 Fourth Workstation Gantt chart LEAN TRANSFORMATION OF PANEL ASSEMBLY Using the principles of one piece flow (Koenig et al. 2002) and reduction of excessive movements (Liker and Lamb 2002), it becomes logical to analyze methods in improving and making panel assembly more efficient. Therefore, considering one-piece flow, the idea is to assemble the stiffeners simultaneously on each unit panel, prior to them being butt welded. Then, once all four unit panels are stiffened, through the use of hybrid arc laser technology (Kolich et al. 2015b), it is possible to butt weld the three seams without having to flip them over. This way, the flipping over of the panel is eliminated. Likewise, the longitudinal profile stiffeners are welded simultaneously, since it is possible to do so which would not be the case for welding all nine stiffeners simultaneously. Lean workstation number one At lean workstation number one, one stiffener is tack welded to unit steel plate number 207; then four stiffeners are tack welded to unit steel plate 200; one stiffener to unit plate number 191; and finally three stiffeners to unit plate number 184. (See Figure 13) Since, there is an automated system, a maximum of two workers are located at this workstation, when multiplied by the duration time of 1.33 hours results in a total of 2.67 man-hours. Fig.13 Lean workstation number 1 Gantt chart Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 5

6 Lean workstation number two At this second lean workstation, the unit panel with tack-welded stiffeners are now fully welded (See Figure 14). The duration time is over one hour and 15 minutes or 1.25 hours. There are two workers which when multiplied by the duration time of 1.25 hours yields a total of 2.5 man-hours. Fig.14 Lean workstation number 2 Gantt chart Lean workstation number three At workstation number three, the unit stiffened panels are then butt welded using one-sided hybrid laser arc welding technology. It lasts 1.1 hours and since there are two workers at this station, there are also a total of 2.2 man-hours. The total man-hours of the three lean workstations by summing up 2.67, 2.5, 2.2 which yields a total of 7.37 man-hours. In comparison to the 52.3 man-hours of the classical panel assembly line workstations, 7.37 man-hours represents an improvement of 86% in man-hours. Since over 60 percent of ships interim products are made up of straight panels, the savings in ship production costs could be very significant The duration time of the classical panel assembly line is 11.6 hours in comparison to ( ) or 3.68 hours in the lean panel assembly line which represents 68% decrease in duration time, which is likewise significant. Fig.15 Lean workstation number 3 Gantt chart CONCLUSIONS. The duration time of assembling one typical panel with nine stiffeners on a classical panel assembly line is 11.6 hours. There are a total of 52.3 man-hours. The lean transformation utilizes laser arc welding and one-piece flow. This in turn yields simultaneous fitting and welding of multiple longitudinal stiffeners, up to four pieces simultaneously to unit plates. The stiffened unit plates are then welded using one-sided hybrid laser arc welding technology which is faster and does not require the panel butt seams to be welded on the other side. Therefore, there are significant savings in duration time of 68% and man-hours of 86%. The argument for transforming classical shipbuilding processes into lean ones is very strong and requires understanding and mapping the present system, and by applying lean principles and appropriate technologies thereby creating a transformed and significantly improved system. This means that shipyards that are presently non-competitive in the international shipbuilding market can become competitive and compete with world-class shipyards both in price and quality. REFERENCES Koenig, P. C., Narita, H. and Baba, K Lean Production in the Japanese Shipbuilding Industry?, Journal of Ship Production 18,3, Kolich,D., Storch, R.L., Fafandjel, N. 2015a Optimizing shipyard interim product assembly using a value stream mapping methodology, Proceedings, World Maritime Technology Conference Papers Society of Naval Architects and Marine Engineers, November 3-7, Rhode Island, Kolich, D., Yao, Y.L., Neuberg, R., Storch, R.L. and Fafandjel, N. 2015b Data mining to predict hybrid laser arc welding improvements in ship interim product assembly, Proceedings, The International Conference of Computer Applications in Shipbuilding, Royal Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 6

Institute of Naval Architects, September 29 October 2, Bremen, 137-168. Kolich,D., Storch, R.L., Fafandjel, N.

Engineers, November 1-5, Bellevue, Washington, 1-10. Kolich,D., Storch, R.L., Fafandjel, N.

2017b Lean built-up panel assembly in a newbuilding shipyard, Journal of Ship Production and Design, 0, 0, 1-9. Kolich,D., Storch, R.L., Fafandjel, N.

Liker, J. K. and Lamb, T. 2002 What is Lean Ship Construction and Repair?. Journal of Ship Production, 18, 3, 121-142. 3. Maj.

7 Institute of Naval Architects, September 29 October 2, Bremen, Kolich,D., Storch, R.L., Fafandjel, N Lean transformation of built-up panel assembly in shipbuilding using a value stream mapping methodology, Proceedings, SNAME Maritime Conference Papers Society of Naval Architects and Marine Engineers, November 1-5, Bellevue, Washington, Kolich,D., Storch, R.L., Fafandjel, N. 2017a Lean methodology to transform shipbuilding panel assembly, Journal of Ship Production and Design, 33, 4, Kolich,D., Storch, R.L., Fafandjel, N. 2017b Lean built-up panel assembly in a newbuilding shipyard, Journal of Ship Production and Design, 0, 0, 1-9. Kolich,D., Storch, R.L., Fafandjel, N. 2017c Lean IHOP transformation of shipyard erection block construction, Proceedings, SNAME Maritime Convention Papers, Society of Naval Architects and Marine Engineers, October 24-28, Houston. Liker, J. K. and Lamb, T What is Lean Ship Construction and Repair?. Journal of Ship Production, 18, 3, Maj Shipyard Archive, Rijeka, Croatia SNAME Design for Production Manual Design for Production Manual, 2 nd edition, Bethesda MD: Naval Surface Warfare Center, National Shipbuilding Research Program, U.S. Department of the Navy Carderock Division, Vol Vanda Brandic, Univ. Bacc. Ing. Nav. Arch. earned her bachelor s degree in 2016 from the Faculty of Engineering, University of Rijeka, and is presently enrolled in the second and final year of the Master s Degree program in Naval Architecture and Ocean Engineering. She presented the paper PWBS Best Practice Analysis of Two Shipyards at the Seventh Conference on Marine Technology - Winkler in November, 2017, which received high acclaim from top shipyard management. and is also Vice- Chairperson of the first SNAME Student section in Croatia; a very active member who among many other things prepared the SNAME student By-Laws for the University of Rijeka. AUTHOR BIOGRAPHIES Prof. Damir Kolich, PhD., Nav. Arch., is an assistant professor at the Faculty of Engineering, University of Rijeka. He is a member of SNAME since 1992 and was graduated from Webb Institute in New York in After working in the sales and design departments of various Croatian shipyards, he enrolled in the University of Rijeka Naval Architecture Department as a Teaching Assistant in 2008, where he earned his PhD in His specialties are lean manufacturing, design for production and data mining in shipbuilding. He is the Faculty Head of the SNAME student chapter at the University of Rijeka, and actively works with the parent Greek section of SNAME. He also assists the student RITEH Waterbike Team. Doroteja Jaki, Univ. Bacc. Ing. Nav. Arch. earned her bachelor s degree in 2017 from the Faculty of Engineering, University of Rijeka, and is presently enrolled in the second and final year of the Master s Degree program in Naval Architecture and Ocean Engineering. She is the Secretary/Treasurer of the first SNAME Student Section in Croatia. Involved in a plethora of SNAME activities, she significantly contributes to the promulgation of the SNAME student chapter at the University of Rijeka, such as Poster development and expert advice. Josip Lino Novak, Univ. Bacc. Ing. Nav. Arch. earned his bachelor s degree in 2016 from the Faculty of Engineering, University of Rijeka, and is presently enrolled in the second and final year of the Master s Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 7

8 Degree program in Naval Architecture and Ocean Engineering at the University of Rijeka. As Chairperson of the first SNAME Student section in Croatia, he attended the SNAME Maritime Convention held in Houston in 2017, where he networked with other SNAME student members, especially with those of the parent SNAME Greek section. Kolich, Brandic, Jaki, Novak Gantt chart analysis to improve shipbuilding panel line assembly 8

Lean Built-Up Panel Assembly in a Newbuilding Shipyard

Journal of Ship Production and Design, Vol. 00, No. 0, Month 2017, pp. 1 9 http://dx.doi.org/10.5957/jspd.170007 Lean Built-Up Panel Assembly in a Newbuilding Shipyard Damir Kolich,* Richard L. Storch,