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Part B
EM202 Advanced Naval Architecture
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ROPAX and Tankers_Theory Specimen Questions and Answers

ROPAX and Tankers_Theory Specimen Questions and Answers

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① Inherent Strength of Design: Oil Tanker vs. Dry Cargo Ship

A. Structural Strength Advantages of Tankers

1. Double Hull Design (MARPOL Annex I, Reg. 13)

  • Tankers:

    • Mandatory double hull (or double bottom + double sides) for oil tankers > 5,000 DWT (post-Exxon Valdez, 1989).
    • Reduces oil spill risk in grounding/collision.
    • Increases structural redundancy (two layers of hull plating).

  • Dry Cargo Ships:

    • Typically single hull (except bulk carriers > 150m, which may have double sides for ballast tanks).

2. Longitudinal Strength

  • Tankers:

    • Continuous longitudinal bulkheads (centerline or side) reduce hogging/sagging stresses.
    • Cargo tanks act as structural members, contributing to longitudinal strength.
    • Higher section modulus (due to deep, box-like tanks).

  • Dry Cargo Ships:

    • Open cargo holds (no longitudinal bulkheads) → lower section modulus.
    • More prone to hogging/sagging (especially in bulk carriers with large, empty holds).

3. Transverse Strength

  • Tankers:

    • Transverse bulkheads (every 2–4 tanks) resist racking stresses.
    • Wing tanks and double bottoms add transverse rigidity.

  • Dry Cargo Ships:

    • Fewer transverse bulkheads (typically at 1/5 ship length intervals).
    • Higher racking stresses in open holds.

4. Fatigue Resistance

  • Tankers:

    • Smoother stress distribution due to liquid cargo (no point loads).
    • Corrosion protection (coatings, cathodic protection) mandatory in cargo tanks.

  • Dry Cargo Ships:

    • Point loads from grain, ore, or containers → higher fatigue stress concentrations.
    • Corrosion in cargo holds (e.g., bulk carriers carrying salt, ore, or coal).

5. Stability Advantages

  • Tankers:

    • Lower KG (Vertical Center of Gravity): Liquid cargo (oil) fills tanks from the bottom up → lower VCG.
    • Free surface effect minimized (tanks are subdivided).
    • Higher GM (Metacentric Height) → stiffer ship (less rolling).

  • Dry Cargo Ships:

    • Higher KG: Granular cargo (e.g., grain) can shift, raising VCG.
    • Free surface effect in partially filled holds.
    • Lower GM → tender ship (more rolling).

B. Freeboard Assignment Under ILLC (International Load Line Convention, 1966)

  • Tankers:

    • Assigned lesser freeboard than dry cargo ships of the same dimensions because:
      1. Lower KG → higher stability (less risk of capsizing).
      2. Double hull → better damage survivability (reduces risk of flooding).
      3. Subdivision (tanks act as watertight compartments) → better buoyancy after damage.
      4. ILLC Type B Freeboard: Tankers are classified as Type B (lower freeboard) due to higher stability and subdivision.

  • Dry Cargo Ships:

    • Assigned higher freeboard (Type A or B-60) due to:
      • Higher KG (less stable).
      • Open cargo holds → higher risk of flooding if damaged.
      • No subdivision in cargo holds → less damage survivability.

② Freeboard: Tanker vs. Bulk Carrier (Same Dimensions)

A. Why Tankers Have Lesser Freeboard

  1. Stability:

    • Tankers: Lower KG (liquid cargo) → higher GM → more stable.
    • Bulk Carriers: Higher KG (granular cargo) → lower GM → less stable.

  2. Subdivision & Damage Survivability:

    • Tankers:
      • Double hull → reduces flooding risk.
      • Cargo tanks are watertight → limits progressive flooding.
    • Bulk Carriers:
      • Single hull → higher flooding risk if damaged.
      • Open cargo holds → no subdivision → faster flooding.

  3. ILLC Classification:

    • Tankers: Type B (lower freeboard).
    • Bulk Carriers: Type A (higher freeboard).

B. Role of Pump Room Double Bottom & Cargo Pumps in Survivability

  1. Pump Room Double Bottom (MARPOL Annex I, Reg. 13G)

    • Mandatory for tankers > 5,000 DWT.
    • Prevents oil leakage in case of grounding or collision.
    • Acts as a secondary barrier → improves damage stability.

  2. Cargo Pumps

    • Located in pump rooms (separate from cargo tanks).
    • Submersible pumps (in each tank) reduce risk of oil spill in case of hull breach.
    • Remote-controlled valves → faster emergency shutdown.

  3. Survivability Benefits:

    • Reduces risk of oil pollution (environmental protection).
    • Enhances damage stability (fewer compartments flooded).
    • Compliance with SOLAS II-2 (Fire Safety) and MARPOL Annex I.

③ Stability Failures in Al Salaam Boccaccio 98 ROPAX (2006)

A. Incident Overview

  • Date: 3 February 2006.
  • Location: Red Sea (near Safaga, Egypt).
  • Casualties: ~1,000 deaths (one of the deadliest maritime disasters in peacetime).
  • Ship Type: ROPAX (Roll-on/Roll-off Passenger Ferry).
  • Cause: Fire + Stability Failure (capsizing due to loss of transverse stability).

B. Stability Failures (With Diagrams)

(a) Fire Fighting Operations

  • Fire Origin: Engine room (electrical fault or fuel leak).
  • Spread: Fire traveled through ventilation ducts to car deck and passenger areas.
  • Stability Impact:
    • Water used for firefighting accumulated on car deck (not drained properly).
    • Free surface effect → loss of GM → increased rolling.
    • Asymmetrical flooding (water on one side) → heeling moment.

Diagram:

  +---------------------+
  |   Passenger Deck    |  ← Fire spreads upward
  +---------------------+
  |   Car Deck          |  ← Water accumulates here (free surface)
  +---------------------+
  |   Engine Room       |  ← Fire origin
  +---------------------+
  • Result: Heeling → Capsizing.

(b) Passengers Running to One Side

  • Human Behavior: Passengers rushed to one side (starboard) to escape fire.
  • Stability Impact:
    • Sudden shift of KG to starboard → large heeling moment.
    • Reduced GM → ship became unstable.

Diagram:

  Before:          After:
  +----+            +----+
  |    |            |    |← Passengers
  | KG |            | KG→|  rush here
  +----+            +----+
  △ GM △             △ GM→0 (Unstable)

(c) Wide Turn at Speed

  • Maneuvering Error: Ship was making a wide turn at high speed (15+ knots).
  • Stability Impact:
    • Centrifugal force → outward heeling moment.
    • Combined with fire water and passenger shift → excessive heel angle.
    • Loss of transverse stability → capsizing.

Diagram:

  +---------------------+
  |       Turn          |← Centrifugal force → Heel
  |   (High Speed)      |
  +---------------------+
  △ Heel Angle Increases △

C. Root Causes of Stability Failure

  1. Poor Subdivision: No watertight bulkheads on the car deck → flooding spread rapidly.
  2. Inadequate Drainage: No scuppers or pumps on the car deck → water accumulated.
  3. High KG: Passenger decks and car decks were high above the keel → low GM.
  4. No Damage Stability Compliance: Did not meet SOLAS-90 standards.

④ SOLAS-90 Standard for ROPAX Ships

A. SOLAS-90 Standard

  • Applies to: ROPAX ships (Roll-on/Roll-off Passenger Ships) built after 1 July 1990.
  • Key Requirements:
    1. Damage Stability:
      • Must survive flooding of any single compartment (including car deck).
      • Final GM ≥ 0.05 m after damage.
      • Maximum heel angle ≤ 15° in damaged condition.
    2. Subdivision:
      • Watertight bulkheads must extend to the freeboard deck.
      • Car decks must have watertight doors (automatically closed in case of fire/flooding).
    3. Fire Safety:
      • Fire-resistant divisions (A-60 class) around car decks and accommodation.
      • Fixed fire-extinguishing systems (e.g., water mist, CO₂).

B. SOLAS-90+ (50) Standard

  • Definition: An enhanced version of SOLAS-90, introduced after the Estonia disaster (1994).
  • Key Improvements:
    1. Increased Damage Stability:
      • Must survive flooding of any two adjacent compartments (not just one).
      • Final GM ≥ 0.10 m (higher than SOLAS-90).
    2. Stricter Subdivision:
      • Additional watertight bulkheads on car decks.
      • Higher freeboard (to reduce flooding risk).
    3. Enhanced Fire Safety:
      • Automatic sprinklers in car decks.
      • Improved ventilation control (fire dampers).

C. Stockholm Agreement (1996)

  • Context: After the Estonia disaster (1994), the IMO and EU agreed on stricter rules for ROPAX ships.
  • Key Decisions:
    1. Retrofitting Existing Ships:
      • All ROPAX ships (even pre-1990) must comply with SOLAS-90+ (50) by 2010.
    2. A and Amax:
      • A: Permissible damage length (maximum length of a single compartment that can flood without capsizing).
      • Amax: Maximum allowable damage length (based on ship’s dimensions and stability).
      • Compliance Requirement: A ≤ 0.5 × Amax (ship must survive flooding of half the maximum allowable damage length).
    3. Lines of Defense:
      • Primary: Watertight bulkheads.
      • Secondary: Fire-resistant divisions.
      • Tertiary: Improved evacuation systems (e.g., lifeboats on both sides).

⑤ Structural Alterations to Comply with SOLAS-90 / SOLAS-90+ (50)

A. SOLAS-90 Compliance (For Existing ROPAX Ships)

Modification Purpose Diagram
1. Additional Watertight Bulkheads Divide car decks into smaller compartments to limit flooding. ```
+———+———+
Car Car
Deck 1 Deck 2
+———+———+ 
| **2. Watertight Doors on Car Decks** | Prevent water spread between compartments. Automatically close in case of fire/flooding. | ```
+------+------+
|      |      |
| Door | Door |← Watertight
+------+------+
``` |
| **3. Increased Freeboard** | Reduce risk of water ingress on car decks. | ```
+-----------------+
|   Higher        |← Freeboard increased
|   Freeboard     |
+-----------------+
``` |
| **4. Fire-Resistant Divisions (A-60)** | Contain fires in car decks and accommodation. | ```
+-----------------+
|   A-60 Bulkhead |← Fire-resistant
+-----------------+
``` |


---

### **B. SOLAS-90+ (50) Compliance (Enhanced)**

| **Modification** | **Purpose** | **Diagram** |
|------------------|-------------|-------------|
| **1. Double Hull or Side Shells** | Improve damage survivability (e.g., side shells on car decks). | ```
+---------------------+
| Outer Hull | Car Deck |← Double side shell
+---------------------+
``` |
| **2. Automatic Sprinklers in Car Decks** | Extinguish fires early to prevent spread. | ```
+---------------------+
|   Sprinklers       |← Automatic
|   (Car Deck)       |
+---------------------+
``` |
| **3. Improved Ventilation Control** | Fire dampers to prevent smoke/fire spread through ducts. | ```
+---------------------+
|   Fire Damper      |← Closes automatically
+---------------------+
``` |
| **4. Additional Lifeboats** | Ensure evacuation from both sides of the ship. | ```
+---------------------+
| Lifeboat | Lifeboat |← On both sides
+---------------------+
``` |
| **5. Enhanced Drainage Systems** | Remove water quickly from car decks (scuppers + pumps). | ```
+---------------------+
|   Scuppers        |← Drainage
|   + Pumps          |
+---------------------+
``` |

---

---

## **⑥ Design Philosophy & Rulemaking for ROPAX Safety**

### **A. Multi-Pronged Approach to Safety**
The IMO and classification societies (e.g., DNV, LR, ABS) use a **layered approach** to improve ROPAX safety:

| **Layer** | **Objective** | **Examples (Rules & Regulations)** |
|-----------|---------------|------------------------------------|
| **1. Prevention** | Avoid accidents (fire, flooding, collision). | Fire-resistant materials (SOLAS II-2), Navigation equipment (SOLAS V), Training (STCW). |
| **2. Containment** | Limit damage if an accident occurs. | Watertight bulkheads (SOLAS II-1), Double hulls (MARPOL Annex I), Fire doors (SOLAS II-2). |
| **3. Mitigation** | Reduce consequences of accidents (e.g., flooding, fire). | Damage stability (SOLAS II-1, Reg. 8-4), Fixed fire extinguishing systems (SOLAS II-2, Reg. 10). |
| **4. Evacuation** | Ensure safe escape of passengers and crew. | Lifeboats on both sides (SOLAS III), Emergency lighting (SOLAS II-2, Reg. 13), Muster stations (SOLAS III). |
| **5. Survivability** | Improve chances of survival after an accident. | SOLAS-90+ (50) standards (enhanced damage stability), Stockholm Agreement (retrofitting). |


---

### **B. Rulemaking Process**
1. **Incident Analysis**: Investigate disasters (e.g., Estonia, Al Salaam Boccaccio 98) to identify weaknesses.
2. **Risk Assessment**: Formal Safety Assessment (FSA) to evaluate hazards and mitigation measures.
3. **Regulation Development**: IMO Sub-Committees (e.g., DE, FP, SDC) draft new rules. Class Societies provide technical guidelines.
4. **Implementation & Enforcement**: SOLAS amendments (e.g., SOLAS-90, SOLAS-90+ (50)). Port State Control (PSC) inspections to ensure compliance.

---

---

## **⑦ Fire Safety Design for Ro-Ro Ships (SOLAS Requirements)**

### **A. Definitions**
1. **Ro-Ro Space**:
   - A **cargo space** with **roll-on/roll-off access** (e.g., car decks, vehicle decks).
   - **Characteristics**: Large, open areas (no permanent subdivision). High fire risk (vehicles with fuel, batteries, etc.).
   - **SOLAS Definition**: "A space not normally subdivided in any way and extending to either the full width or the full length of the ship" (SOLAS II-2, Reg. 3.44).

2. **Special Category Space**:
   - A **cargo space** that is **not a Ro-Ro space** but has **similar fire risks** (e.g., spaces carrying dangerous goods, vehicles with fuel).
   - **SOLAS Definition**: "A space intended for the carriage of vehicles with fuel in their tanks for their own propulsion" (SOLAS II-2, Reg. 3.45).


---

### **B. Fire Safety Goals (SOLAS II-2, Part C)**

| **Goal** | **Ro-Ro Spaces** | **Special Category Spaces** |
|----------|------------------|-------------------------------|
| **Prevention** | No open flames in cargo areas. Hot work permits required. | Same as Ro-Ro spaces. No smoking in cargo areas. |
| **Detection** | Automatic fire detection (heat/smoke detectors). CCTV monitoring. | Same as Ro-Ro spaces. |
| **Containment** | A-60 class bulkheads around cargo spaces. Fire doors (A-60) on access points. | Same as Ro-Ro spaces. |
| **Extinction** | Fixed water-based fire-extinguishing system (e.g., water mist, sprinklers). Portable extinguishers (CO₂, dry chemical). | Fixed CO₂ or water mist system (for dangerous goods). Portable extinguishers. |
| **Structural Integrity** | Non-combustible materials (SOLAS II-2, Reg. 3). Thermal insulation to delay fire spread. | Same as Ro-Ro spaces. |
| **Ventilation Control** | Fire dampers in ventilation ducts. Automatic shutdown in case of fire. | Same as Ro-Ro spaces. |


---

### **C. SOLAS Requirements for Ro-Ro & Special Category Spaces**
1. **Fire Main System**: Hose reels and hydrants must cover **all Ro-Ro spaces**.
2. **Fixed Fire-Extinguishing Systems**:
   - **Water mist or sprinklers** (for Ro-Ro spaces).
   - **CO₂ or foam** (for special category spaces with flammable cargo).
3. **Fire Doors**:
   - **A-60 class** (fire-resistant for 60 minutes).
   - **Self-closing and remotely controlled**.
4. **Ventilation**:
   - **Fire dampers** in **all ventilation ducts** serving Ro-Ro spaces.
   - **Automatic closure** in case of fire.
5. **Structural Fire Protection**:
   - **Bulkheads and decks** around Ro-Ro spaces must be **A-60 class**.
   - **Insulation** to prevent **heat transfer** to adjacent spaces.

---

---

## **⑧ Corrosion in Tankers (or Bulk Carriers) & Regulatory Solutions**

### **A. Corrosion Problems in Tankers**

| **Area** | **Type of Corrosion** | **Causes** | **Impact** |
|----------|-----------------------|------------|------------|
| **1. Cargo Tanks** | General Corrosion (uniform thinning). | Sulfur in crude oil (forms H₂S, which reacts with steel). Water in cargo (electrolyte for corrosion). | Reduced plate thickness → structural failure. Leaks → oil pollution. |
| **2. Ballast Tanks** | Pitting Corrosion (localized deep pits). | Seawater (high chloride content). Poor coating maintenance. | Holes in tanks → flooding risk. Reduced structural strength. |
| **3. Double Bottom** | Crevice Corrosion (in gaps between plates). | Stagnant water in ballast tanks. Poor drainage. | Cracks in welds → leaks. Loss of watertight integrity. |
| **4. Deck & Superstructure** | Atmospheric Corrosion (rusting). | Salt spray (marine environment). Lack of paint maintenance. | Aesthetic damage. Weakened superstructure. |
| **5. Pipelines & Valves** | Erosion-Corrosion (flow-induced wear). | High-velocity oil/water flow. Abrasive particles (sand, scale). | Leaks in pipes → cargo loss/pollution. Valve failure. |


---

### **B. Regulatory Solutions to Corrosion**

| **Regulation** | **Requirement** | **Impact** |
|----------------|-----------------|------------|
| **1. MARPOL Annex I, Reg. 13G** | Double Hull for Tankers (>5,000 DWT). | Reduces oil spill risk in grounding/collision. Corrosion in one hull does not affect the other. |
| **2. SOLAS II-1, Reg. 3-11** | Corrosion Prevention in Ballast Tanks: Coatings (e.g., epoxy, zinc-rich). Cathodic Protection (sacrificial anodes or impressed current). | Extends tank life by 15–20 years. Reduces pitting corrosion. |
| **3. IACS UR Z10.4** | Enhanced Survey Requirements for Tankers: Close-up surveys every 5 years. Ultrasonic Thickness Measurements (UTM) for cargo/ballast tanks. | Early detection of corrosion. Prevents sudden structural failure. |
| **4. SOLAS II-2, Reg. 4.5.5** | Fire-Resistant Coatings in Cargo Tanks (for crude oil tankers). | Delays structural failure in case of fire. |
| **5. IMO PSPC (Performance Standard for Protective Coatings)** | Mandatory high-quality coatings for ballast tanks (resolution MSC.215(82)). | Reduces corrosion rate by 50–70%. |
| **6. Class Society Rules (e.g., ABS, DNV, LR)** | Corrosion Margins: Additional plate thickness (e.g., 2–3 mm extra in high-risk areas). | Compensates for expected corrosion over the ship’s life. |


---

### **C. Tanker Losses Due to Corrosion**

| **Ship Name** | **Year** | **Incident** | **Corrosion-Related Cause** |
|--------------|----------|--------------|-----------------------------|
| **1. Erika** | 1999 | Broke in two off Brittany, France → 400,000 tons of oil spilled. | Severe corrosion in cargo tanks (thickness reduced to 1–2 mm in some areas). Poor maintenance (no proper coatings). |
| **2. Prestige** | 2002 | Split in half off Spain → 77,000 tons of oil spilled. | Corrosion in single-hull design (no double hull). Brittle fracture due to low-temperature corrosion. |
| **3. Sea Empress** | 1996 | Grounded off Wales → 72,000 tons of oil spilled. | Corrosion in ballast tanks → structural weakness. Hull breach in grounding. |
| **4. MT Haven** | 1991 | Exploded and sank off Italy → 144,000 tons of oil spilled. | Corrosion in cargo tanks → leakage of volatile gases. Static electricity + corrosion → explosion. |

---

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## **Summary Table for Quick Revision**

| **Question** | **Key Points** |
|--------------|----------------|
| **① Tanker vs. Dry Cargo Strength** | Double hull, longitudinal bulkheads, lower KG, higher section modulus, better fatigue resistance. |
| **② Freeboard (Tanker < Bulk Carrier)** | Lower KG, double hull, subdivision → Type B freeboard. Pump room DB + cargo pumps improve survivability. |
| **③ Al Salaam Boccaccio 98 Stability Failures** | Fire → water on car deck (free surface), passengers rushing to one side (heel), wide turn (centrifugal force). |
| **④ SOLAS-90 / SOLAS-90+ (50)** | Damage stability (1/2 compartments), A ≤ 0.5 × Amax, Stockholm Agreement (retrofitting). |
| **⑤ Structural Alterations** | Watertight bulkheads, A-60 doors, increased freeboard, sprinklers, double side shells. |
| **⑥ Design Philosophy** | Multi-pronged: Prevention, Containment, Mitigation, Evacuation, Survivability. |
| **⑦ Ro-Ro Fire Safety** | Ro-Ro space = open cargo space for vehicles; Special Category = dangerous goods. Fixed water/CO₂ systems, A-60 bulkheads. |
| **⑧ Corrosion in Tankers** | Cargo/ballast tank corrosion, MARPOL double hull, PSPC coatings, IACS surveys, Erika/Prestige cases. |
Passenger Ship Safety sample question answersROPAX and Tankers-Sample Questions and answers