DRY- DOCK HULL INSPECTION OF NILE CRUISERS

Transcription

1 18 th International Conference on Ships and Shipping Research 2015, June 24 th 26 th, Lecco, Italy M. Altosole and A. Francescutto (Editors) DRY- DOCK HULL INSPECTION OF NILE CRUISERS Arwa. W. HUSSEIN 1, M. M. MOUSTAFA 2, M. T. ELSHERBINY 3 1 Port Said University, Pot Said, Egypt, 2 Port Said University, Pot Said, Egypt, 3 River Transportation Authority, Upper Egypt, Egypt, ABSTRACT Dry-docking of Nile cruisers is a complex, expensive, time-consuming and stressful activity. Time spent in dry-dock is time spent out of service and above all subject the ship to undesirable high docking stress. Consequently, dry-dock hull inspections effectiveness is being challenged by the ever decreasing time that these vessel remains in dock. Most of the inspections rely on the experience of the inspectors to identify the potential problem areas, critical areas and the conditions of the hull. This paper introduces a simple and quantifiable methodology to implement the inspection which is not only based on checklists but also scoring system which can be analyzed to view the condition of certain critical areas, and the condition of the whole vessel. The inspection criteria and a list of target inspection areas are defined based on statistics of data gathered from 44 Nile cruisers docked in the previous 5 years in Upper Egypt. The main benefit behind this methodology is to reduce docking time, increase the value of the ship hull inspections, maintaining a uniform standard across all Nile Cruisers and being able to document the ship s condition. 1. INTRODUCTION To perform hull inspections one needs an efficient methodology which tells what to inspect, when to inspect, where to inspect and how to inspect. Traditionally ship owners and vessel managers have their in-house hull inspection schemes and programs to track, assess and maintain the hull structure. It is usually performed by many agencies such as classification societies, insurers, coastal state and flag state authorities. All inspection data is collected in various forms, check sheets and reports. Classification societies and most of the other agencies perform inspection in a prescriptive manner or on an as-needed basis to assess the hull condition. The hull is inspected based on the experience and work instructions provided to the inspector by their respective agencies. The presence of critical areas in a compartment may or may not be highlighted by the inspection agencies. Some classification societies have their own programs for hull inspection. The DNV proposed the Hull Inspection Manual (HullMan) which is a practical tool for increasing the value of hull inspections, (see for inst. DNV, 2009). The inspection manual provides clear guidance on how to carry out hull structure inspections and helps the technical personnel to focus on critical inspection areas, evaluate findings and report consistently on the hull s condition. The ABS introduces Hull Inspection and Maintenance Program (HIMP),( see for inst. ABS, 2007). This 1091

2 program identifies six different criteria to be addressed during the inspections. These are to be documented based on a traffic light point rating; green, yellow or red, (see Kalghatgi et al, 2009). This paper proposes a hull inspection system for Nile Cruisers. The most critical areas are defined and scoring system is introduced which gives an indication about the condition of each area using color coding. This system will enable the surveyors to get an easy assessment of the hull condition and also will give a rating for the ship which might be used by insurance companies or vetting agencies. 2. NILE CRUISERS CHARACTERISTICS Like any restricted waterway there are some constrains which have to be taken into consideration when designing a ship crossing that waterway. The shallow water of the Nile, the bridges and the locks built along the Nile put some constrains on the design of Nile Cruisers. Due to the restricted depth of the Nile, the maximum allowable draft of the ships is 1.65 m. The presence of bridges along the Nile River restricted the height of the ships to 11.5 m; this usually corresponds to 4 floors. The breadth of ships is restricted due to the presence of locks by 14 m. Table 1 shows the maximum allowable dimensions for Nile Cruisers. Table 1. Maximum allowable dimensions of Nile cruisers Length 72 m Breadth 14 m Draft 1.65 m Depth 11.5 m 3. DEFECTS COUNTING SYSTEM Defects depend on the ship type and the working conditions. One of the aims of this work is to define the common defects in Nile Cruisers. The work depends of statistical information gathered from 44 Nile cruisers. The cruisers were docked within The dry docking reports were analyzed to show the common defects noticed during dry docking. Table 2 shows all the common defects which might be found in Nile cruisers. These defects were recorded in most ships, yet this does not mean it have all to be recorded together. To calculate the occurrence percentage of each defect, a binary system of assessment was used; if the defect occurs it takes 1, if not no value is written. The total defects counted in the 44 ships were 283 defects. Table 3 shows a sample of the count of the defects in the propelling system for 44 Nile Cruisers (NC1: NC44). It was recorded 72 times in all ships. Defects in the propeller blades were recorded 22 times, defects in the shaft were recorded 23 times and defects in the propeller glands were recorded 27 times. 1092

3 Table 2. Common Defects in Nile Cruisers 1 Propelling system Blades Shaft Glands Plating 2 Rudder Stocks Glands 3 Sea Chest Strainer Plating Side Deck 4 Defects of Shell Plating Outer Bottom Inner Bottom Bilge Transom 5 Cathodic Protection 6 Welding 7 Stiffeners 8 Bilge Bracket 9 Fender 10 Water tightness Bulkheads Man Holes 11 Rust Removing and Tank Coating Under Kitchen Sewage Tanks Ballast Tanks Under Crew Accommodation Under W. C. Steering Room 12 Deck Outfitting Under Water Treatment Unit Bollard, hose pipe, anchor, chain, windlass 13 Non-return Valves Sewage Pipeline 1093

4 Table 3. Defects count in propelling system Propelling System Ship Name Blades Shaft Glands N C N C N C N C N C N C N C N C 8 0 N C 9 0 N C N C N C N C N C 14 0 N C 15 0 N C 16 0 N C N C N C N C N C 21 0 N C 22 0 N C 23 0 N C 24 0 N C 25 0 N C N C N C 28 0 N C N C 30 0 N C N C 32 0 N C N C N C N C N C 37 0 N C N C N C 40 0 N C Count N C N C N C Total count (Total/44) % 50% 52% 61% 1094

5 Table 4 shows the count for all the defects in all the Nile Cruisers. The results presented in Table 4 tell that defects in the propelling system were noticed 72 times. These defects might be related to the propeller blade, glands or propeller shaft. Defects of shell plating ; 68 positions were marked. It is clear that most of the defects occurred in the propelling System, thickness reduction of shell plating due to corrosion and deteriorated coating were recorded. Table 4. Defect occurrence percentage Defect Counts Percent (Count/283) % Propelling System 72 25% Defects of Shell Plating 68 24% Rust & Tank Coating condition 56 20% Fender 16 6% Welding 13 5% Stiffeners 13 5% Rudder 11 4% Water tightness 9 3% Sea Chest 7 2% Cathodic Protection 6 2% Bilge Bracket 5 2% Sewage Pipe lines 5 2% Deck Outfitting 2 1% Total % These were counted to present almost 70 % of the defects. Consequently, these three items are considered common defects in Nile cruisers which have to be cautiously checked. Figure 1 summarizes the results. Figure 1. Defects occurrence percentage 1095

6 4. COMMON DEFECTS As mentioned in previous section, most of the defects recorded were in the propelling System, defects of Shell Plating and deteriorated coating. In this section the percentage of the occurrences of the most common defects is studied. This percentage indicates the probability of occurrence of this defect in the 44 ships. 4.1 Propelling System The defect in the propelling system is usually due to defects in the shaft, blade or the glands. To study the probability of occurrence of these defects in propelling system a count for the three recorded defect is made. Figure 2 shows the percentage of occurrences of the three defects. As shown in the figure, 60% of the ships experienced defects in the propeller glands, while 50% of the ships experiences defects in the blades and shaft. Thus, the propelling system is considered critical area where one has to check its blades, glands and shaft. Figure 2. Defects in Propelling System 4.2 Defects of Shell Plating Defects in the shell plating of Nile Cruisers usually occur due to accidents and grounding which were considered the most common accidents in River Nile (see for inst. Sabit, 2000). Figure 3. Percentage of the occurrence of plate defects The most critical areas which usually experience shell plating defects are the fore and aft region. This is usually attributed to grounding, which occurs by fore and collision between ships near the quays which occurs by aft. It is tolerable to have 10% reduced thickness. Higher values 1096

7 usually require changing the plate where corrosion to place. The condition of the following areas has to be checked: Bilge Strake. outer Bottom, Side shell, transom and Inner Bottom. The count of each item was defined. Figure 3 shows that almost 50% of the ships experienced defects in the bilge strake, while more that 40% of them experienced defects in the outer bottom. About 30% of the ships experienced defects in the side shell plating. These three areas are considered critical areas. 4.3 Rust and Tank Coating Condition The reduction of the thickness of shell plating usually occurs due to corrosion. Besides, the condition of the tank coating is deteriorated in some places. The areas where rust occurred and where the coating condition is deteriorated where checked. The below is a list of the checked areas: Sewage Tanks Ballast Tanks Under Crew Accommodation Under Kitchen Under WC Steering Room Under Water Treatment Unit Deck Plating Figure 4 shows the percentage of occurrence of each item. It was noticed that more than 35 % of the ship recorded deterioration of the coating in sewage tanks. Bad condition of coating was also noticed in ballast tanks, below kitchen and toilets. From this figure, one can conclude that the sewage tanks are the most critical area. Ballast tanks, area under crew accommodation and below the kitchen are second critical areas from the coating condition point of view. Figure 4. Percentage of occurrence of rust and tank coating 5. CRITICAL AREAS Each ship has her own critical areas depends on the working conditions. Due to the shallow water of the Nile, ship usually goes aground by her fore. This causes defects in the plating, 1097

8 stiffeners and welding lines. Sometimes reduction in the thickness occurs due to friction between the shell and the Nile bed. It was noticed that most of the Nile Cruisers do not need sand blasting in this area as it is always clean due to this friction. The aft region of the ship is also considered critical area. Ship usually collides by her aft with other ships especially near the quays; this caused deflection in the plates, stiffeners and welding lines. It is also notice that the area below the kitchen and the sewage tanks has unacceptable level of corrosion. Figure 5 shows a comparison between defects in the fore, aft and mid regions. It is clear from the figure that most of the ships the fore region experienced high defects in plating of the fore region. Defects in the bilge plate was recorded in more that 40% of the ships. More than 30% of the ships experienced defects in the bottom plating in the fore region. Figure 5. Percentage of the Defects in plating Figure 6 shows a comparison between the rust presences in the three regions. It is clear that the aft region experiences high percentage of rust especially in the sewage tanks and below the kitchen. Therefore, the aft and fore region of Nile Cruisers are considered critical areas which need careful survey, and hence will be checked separately. The overall conditions of these areas have to be indicated separately. Figure 6. Rust and coating condition 1098

9 6. INSPECTION SCORING SYSTEM (ISC) The Inspection Scoring System (ISC) is a quantifiable system for identified inspection criteria and a list of target inspection critical areas for the Nile Cruisers. It is Nile Cruisers-specific system; it cannot be used for other ship types or even other ships sailing in the Nile River. It aims to give a unified assessment for all Nile Cruiser which gives an indication about their condition. It also gives a quick report for dry dock inspection. The scoring system gives weight for each defect; this weight depends on the occurrence percentage calculated in Table 4. The weight of each item is given in Table 4. The weight of the defects in the shell plating is 24. As mentioned before, 6 areas are considered in this item. Therefore, each area weighs 4. If a defect is remarked in the propelling system, this takes score 1. Each score is reduced from the total weight of the item; No defects gives rate 24, one defect gives rate 20, two defects gives 16 and so on. The weight of the defects in the propeller system is 25, three items are checked in the propeller area; each weighs (25/3). The Inspection Scoring System ISC for the defects in the shell plating for all the ships under study is presented in Table 5. The rating presented in the last column in Table 5 gives an indication about the condition of the hull plating for each ship. Higher score corresponds to better condition. The scoring system is completed for all defects and the rating at each location is calculated. If the defect exists, it takes score 1. Empty cells indicate No Defects. The rating is presented as percentage from the No-Defects condition. If no defects exist, the condition is 100%. The final results are presented in one table which gives the area where inspection is done in the first column. In the second column the expected defects and the next column is the score; 1 or none. The last column gives the condition of the area, which is a percentage of the calculated rating. The condition percentage is highlighted with traffic light color to indicate the condition. Low rating which indicates poor condition takes degree of red color. Fair condition takes degree of yellow and good condition takes degree of green color, Figure 7. Figure 7. Traffic light assessment 1099

10 Table 5. ISC in the defects` of shell plating Occurrence Percentage = 24% Cell Value = 4 Ship Name Outer Inner Side Deck Bilge Transom Bottom Bottom Count Rating N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C N C Count % 32% 5% 45% 7% 48% 18% Total Count

11 7. DRY DOCK INSPECTION SCORING SYSTEM REPORT An excel file is created for the calculations of the rating and the condition of any Nile Cruiser. The ship is divided to three areas; Fore, Aft and mid regions. The condition of each region is checked in a separate table. The hull outfitting and the propelling system are checked in another separate table. The surveyor has to put 1 for the defect. If no defect exists, the cell is left blank. Once the surveyor records the defects at each location by putting the score, the rating and the condition are automatically calculated. The result of each area appears as a percentage highlighted with corresponding relevant color; red for poor condition, yellow for fair and green for good condition. This file is easy to use and it shows directly where the poor conditioned areas are. It also gives a rating for the ship which is an average of the conditions of all the areas. This ship rating gives a uniform assessment for Nile Cruisers which might be used by classification societies, insurance companies or vetting agencies. Table 6 shows a sample of the Dry Dock Inspection Scoring system for a Nile Cruiser. The selected Nile Cruiser was recorded to have one defect in the propeller baled. No defects were recorded in the shaft or in the glands. The condition of the propeller was 67% which is above fair. The rudder had two defects in the rudder plating and the rudder stock. The condition of the rudder is 33% which is poor condition. After recording all the defects, the ship rating -which appears in the last raw of the file- gives an indication about the global condition of the ship. If the surveyor found more defects which are not listed, another file would be attached. A cell in the report is specified for defining if a file is attached or not. Besides, a summary tables shows the condition of each area is given at the end of the report to indicate poor areas Table 6. Dry dock inspection scoring system Ship's Name : Navigational No. : Ship's Owner : Dry Dock Inspection Scoring System For Nile Cruisers NOTE : Put OK for No Defects Fore Region Plating Welding Lines Stiffeners Defects Condition Side Ok Ok 0 Deck Ok 1 Ok 1 Outer Bottom 1 1 Ok 2 Inner Bottom Ok Ok 0 Bilge 1 1 Ok 2 67% Ballast Tanks 1 1 Rust and Tank Coating Under Crew Accommodation Ok 0 Under W. C. Ok

12 Table 6. Dry dock inspection scoring system: continue Aft Region Plating Welding Lines Stiffeners Defects Condition Side Ok Ok 0 Deck Ok Outer Bottom Ok 1 1 Inner Bottom 1 Ok 1 Transom 1 1 Ok 2 Bilge Ok 1 Ok 1 Sewage Tanks Ok 0 63% Rust and Tank Coating Ballast Tanks Ok 0 Under Crew Accommodation Ok 0 Under W. C. Ok 0 Steering Room Ok 0 Kitchen 1 1 Water Treatment Unit 1 1 Mid Region Plating Welding Lines Stiffeners Defects Condition Side Ok Ok 0 Deck 1 1 Ok 2 Outer Bottom 1 Ok 1 Inner Bottom 1 1 Ok 2 60% Bilge Ok 1 1 Rust and Tank Coating Ballast Tanks 0 Under Public WC

13 Table 6. Dry dock inspection scoring system: continue Hull Outfitting Area Defect comments score condition Blades Propelling system Shaft 1 Glands 1 33% Plating Rudder Stocks 1 67% Glands Sea Chest Strainer 1 Plating 1 33% Bolts Bilge Bracket % Fender Fore 1 Mid 67% Aft Doors 1 Water tightness Windows 67% Man Holes Bollard hose pipe 1 Deck Outfitting Anchor 40% Chain 1 Windlass 1 Non-return Valves Sewage Pipeline 100% 1103

14 Table 6. Dry dock inspection scoring system: continue Summary Table Fore Region 67% Aft Region 68% Mid Region 65% Propelling system 33% Rudder 67% Sea Chest 33% Bilge Bracket 100% Fender 67% Water tightness 67% Deck Outfitting 80% Non-return Valves 100% Ship Rating 68% Other defects in attached file Surveyor Signature Date / /

15 8. CONCLUSIONS This paper introduces a system for dry dock inspection for Nile Cruisers. The most important step of the inspection is what to inspect. A check list for dry dock inspection is prepared for Nile Cruisers; this list is prepared based in statistical data gathered from 44 ships. The critical areas are defined based on the defects recoded in all the ships. The most common defects which were recorded in most of the ships were also defined. The ship is divided to three areas; fore, aft and mid region. Each region is checked separately. An excel file is prepared containing all the expected defects. A scoring system is suggested which finally gives the surveyor a complete picture about the condition of each area and eventually the ship. An excel file is created for the calculations of the rating and the condition of any Nile Cruiser. The condition is highlighted by traffic light color. The proposed system is Nile Cruisers-specific and cannot be used for other types of ships or other ships sailing in the Nile. REFERENCES ABS Guide for Hull Inspection and Maintenance Program (2007), American Bureau of Shipping, Houston, TX, USA, DNV Guide for Hull Inspection Manual (HullMan), (2009), Det Norske Veritas program manual., Kalghatgi S. G., Serratella C., Hagan J. B. (2009) Hull Inspection and Maintenance Systems, ABS technical papers, Sabit A. A., (2000) Inland Warter Transportation,3rd Internationa Conference on Role of Engineering Toward Better Environmnet, Alexandria, Egype,