Damage Control Training
Stability and Buoyancy Lessons

LESSON TOPIC: 4.7 TITLE: PRINCIPLES OF CONTROLLING FLOODING

Contact periods allotted this LESSON TOPIC:

Classroom: 1.5 Test: 0.0

Trainer: 0.0 Total: 1.5

MEDIA: Classroom lecture with visual media

TERMINAL OBJECTIVES:

6.0 EVALUATE shipboard stability by analyzing weight and moment considerations. (JTI 3.2.1, 6.0, 6.1, 6.2)

ENABLING OBJECTIVES:

6.42 DESCRIBE the information available on the Flooding Effects and Liquid Loading DC diagrams.

6.43 DESCRIBE the contents of Section II(a) of the DC Book.

6.44 DESCRIBE the investigative procedures to assess flooding.

6.45 DESCRIBE the effects of progressive flooding.

6.46 STATE initial actions required after damage as outlined in the DC Book, section II(a).

6.47 DESCRIBE the four thumb rules of critical stability and the consequence if each individual thumb rule is approached or exceeded.

6.48 DISCUSS possible consequences of not maintaining required intact stability or following liquid loading instructions.

6.49 Extract information from the ship's DC book to solve common stability problems and DESCRIBE probable consequences of departure from liquid loading instructions.

FLOODING EFFECTS DIAGRAM

1. All lines represent watertight boundaries. Spaces having a heavy outline are unsymmetrical with respect to the centerline of ship.

2. Complete flooding of unsymmetrical compartments will produce inclining moments as indicated in the bottom right corner of the space. An adjustment of this moment should be made if the space is not completely flooded. If a tank contains liquid before flooding occurs, an adjustment shall also be made.

3. Dot-Dash lines indicate steel airtight, fire retarding, or flame tight bulkheads, 5 pounds per square foot and heavier fitted with tight doors.

4. The weight in Long Tons of flooding water at 100% flooding is noted for each particular space in the upper left corner.

 

 

 

 

LIQUID LOADING DIAGRAM

1. The Liquid Loading Diagram is either found at the bottom of DC Plate #1, or as DC Plate #2.

a. The following information is given:

(1) Upper left corner: The capacity of the tank in Long Tons. This capacity shall be 95% full for fuel tanks and 100% full for fresh water tanks. For ballast tanks or voids fitted for ballasting it will be 100% full of sea water, unless it is specified that the ballast shall be fresh water, then the weight is to be 100% full with fresh water. For fuel tanks also used as ballast tanks, the Liquid Loading Diagram gives only the weight in Long Tons of the fuel. To determine the weight of the tank when filled with salt water, look at the same tank on the Flooding Effects Diagram.

(2) Upper right corner: Change in the angle of list caused by filling the tank, given in degrees.

(3) Lower left corner: Change in the draft aft caused by filling the tank, given in inches.

(4) Lower right corner: Change in the draft forward caused by filling the tank, given in inches.

 

DAMAGE CONTROL BOOK

Section I(a) - Principle Characteristics. General information about the various lengths and measurements of the ship. Also includes the frame spacing which often varies in the larger hulls.

Section I(b) - Shoring. General description of shoring for your vessel and what factors are involved.

Section I(c) - Steering Gear. General description of the ship's steering gear and itís capabilities. Lists power supplies as well as each of the locations the ship can be steered from.

Section I(d) - Towing. Lists the towing equipment maintained onboard and their general configurations.

Section I(e) - Ships Ammunition and Miscellaneous Ordnance, Handling and Stowage. Discusses the locations and uses of all magazines and hoists.

Section I(f) - Medical Department. Lists the location of the Battle Dressing Stations, Medical Storage lockers, litters and First Aid boxes.

Section I(g) - Personnel Protection. Discusses the equipment onboard for personnel protection from a CBR attack and itís location. Also indicates the Decontamination space(s) onboard.

Section I(h) - Helicopter Facilities. Lists the fittings associated with the helicopter, what fire protection is located at the landing area and general helicopter equipment and itís location.

 

 

 

Section II(a)- Stability Section

INTRODUCTION - Discusses the guidelines for using the stability section and the requirements to maintain stability.

INTACT STABILITY - Before Damage

1. Righting Arm Curves - Displays the growth of righting arms throughout the shipís range of stability. Accompanying discussion describes the uses of the curves.

INTACT STABILITY (cont) - Before Damage

2. Dynamic Stability - Displays the effect of beam winds and seas plotted on a Righting Moment curve. Also describes the shipís ability to resist capsizing during various design criteria such as full speed full rudder turn, crowding of personnel to one side, and lifting heavy weights to one side.

3. Icing - Some DC Books have a special section which discusses the ships ability to withstand Dynamic forces in an iced condition. This section discusses the forces the ship is capable of withstanding with various thicknesses of ice accumulation.

DAMAGED STABILITY - After Damage

1. Floodable Length - Generally the first topic in the damaged stability section of the DC Book. It specifically outlines what damage the ship can withstand, without sinking, and what damage will have the most adverse effect on survival.

2. Watertight Integrity - Outlines the importance of W/T Integrity and where the watertight boundaries on the ship located.

3. Procedures After Damage - A "cookbook" procedure for what to do following damage. It generally follows the following format:

STEP 1. Isolate the Flooding (Set Flooding Boundaries)

STEP 2. Determine the impact of flooding and prioritize dewatering efforts. Dewater spaces colored pink on the Flooding Effects Diagram first.

STEP 3. Evaluate Critical Stability. Stability is critical when the ship is in immediate danger of sinking or capsizing. Improvement is necessary to avoid loss of the ship. Stability should be considered critical if any or all of the following conditions exist:

STEP 3 (cont)

(1) Small or negative metacentric height (-GM)

The ship is logy, with a slow, erratic roll period, and a tendency to hang at the end of the roll.

(2) Approach or exceed Floodable Length

The extent of flooding approaches or exceeds the maximum amount of flooding tabulated in the Damage Control Book, Section II(a).

(3) Excessive List to the Danger Angle

The ship lists to 15 degrees or more.

(4) Heavy winds and seas coupled with extensive flooding damage.

The ship has sustained flooding damage and heavy winds and rough seas are prevailing or anticipated.

If Stability is Critical

(1) Suppress free surface effect by dewatering or filling partially flooded compartments.

(2) Strike down solid weights, such as ammunition, from upper deck handling rooms to magazines.

(3) Ballast tanks in accordance with the ship's Liquid Loading Instruction.

(4) If freeboard is adequate fill completely those compartments which will improve stability when flooded solid. (Yellow or green compartments on the Flooding Effects Diagram).

(5) Favor stability in the handling and maneuvering of the ship. Limit speed and rudder angle to reduce dynamic forces.

(6) Jettison topside weights if items (1) and (2) are insufficient or impossible. This is a difficult and timely procedure. Concentrate on heavy items and plan ahead considering the effect of removing various items.

STEP 4 ELIMINATE OR REDUCE LIST

(1) List caused by off-center flooding only:

Counter-balance on the high side to reduce the list. Ballast enough to correct for one-half the list, evaluate the effect of this action, and then proceed to correct the list.

(2) List caused by negative Metacentric Height

(-GM) only:

DO NOT add weight to the high side to correct for this list. Take action to lower the ship's center of gravity by ballasting low tanks symmetrically, jettisoning topside weight symmetrically, shifting weight low symmetrically, and by suppressing Free Surface Effect.

(3) List caused by a combination of off-center loading and negative Metacentric Height:

First, take all corrective actions listed above to restore positive GM. Then proceed with corrective actions to correct for the off-center flooding.

 

 

 

LIMITING DRAFTS - Limiting drafts are outlined in Section II(a) of the DC Book. These drafts mark the maximum allowable displacement for the ship prior to damage. Should these marks be submerged the ship will experience;

a. Excessive hull and girder stresses

b. Loss of reserve buoyancy

c. Inability to meet design criteria (i.e. Full speed full rudder turn, Beam Winds and Seas, etc.)

STANDARD CONDITIONS FOR LOADING

Outlined in the DC Book are the various loading conditions for your vessel. All DC Books will outline the Full Load and Minimum Operating conditions. Others will have additional sections, such as the 1/3 consumed and 1/2 consumed stores conditions.

Within the loading section, there are complete outlines of the location and value of all weights onboard the ship. This includes the Crew, Ammunition, Aircraft, Potable Water, Lube Oil, Fuel Oil, Provisions & Stores, as well as several others. The data is summarized to outline each loading condition displacement, trim, mean draft, free surface effect, and various locations of the four stability reference points.

 

Section II(b) - Subdivision and access. This section outlines the location of all watertight and non-tight bulkheads, doors, hatches, manholes, scuttles and cross-flooding openings.

 

Section II(c) - These sections outline all system valves, through their locations, and classifications for the Section II(l) various systems:

Section System

II(c) Drainage

II(d) Tank Stripping

II(e) Firemain, Sprinkler, Foam Washdown and Chemical Fire Systems

II(f) Fuel Filling and Transfer System

II(g) JP-5 Filling, Transfer, Service and Stripping

II(h) Gasoline System

II(i) Ventilation Systems

II(j) Air Conditioning Chilled Water Circulating System

II(k) Compressed Air Systems

II(l) Nitrogen Systems

 

Section III(a) - Potable Water System. Describes the capabilities and basic functions system operation onboard the ship.

Section III(b) - Flushing System. Describes the capabilities and basic functions of system operation onboard the ship.

Section III(c) - Voice Tubes. Describes the capabilities and basic functions of system operation onboard the ship.

 

Section III(d) - Lubricating Oil Fill, Transfer, and Purifying Systems. Describes the capabilities and basic functions of system operation onboard the ship.

 

Section IV(a) - Electrical Systems. Describes operation and setup of the electrical system of the ship.

 

Section IV(b) - Interior Communications. Outlines the circuits and their locations.

TOPSIDE ICING

Reprinted, with permission, from National Fisherman, January 1987. Radio transmissions from the trawler Roderigo, riding out 90-mph winds off Iceland on January 25, 1955, 2 hours after her sistership, the Lucky Lorella, sank under a heavy load of spray ice:

1630 Roderigo: Aerials now icing up. Will call from time to time.

1650 Roderigo: We could do with someone up here now. Having difficulty maneuvering.

1651 Roderigo: Come to us. Position becoming serious now.

1652 Lancella: We are coming to you.

1701 U.S. naval patrol aircraft 5301: Roderigo, Roderigo, transmit on 500 kilocycles.

1702 Roderigo: Unable to transmit 500 kc. Listing heavily to starboard now.

1703 Aircraft 5301: Roderigo, Roderigo, what are your intentions?

1704 Roderigo: No intentions. Going further over. No visibility. Still going over to starboard.

1705 Roderigo: Still going over to starboard. Cannot get her back.

1708 Roderigo: Still going over, going over.

After 4 minutes of repeating "SOS, heeling right over" by Morse code, transmissions from Roderigo ceased. (From "Distant Water: The Fate of the North Atlantic Fisherman," by William W. Warner)

 

Introduction

Spray ice has taken many mariners since Roderigo met her cold fate. The trawler Alert, for example, never even had a chance to issue a brief mayday. Caught in freezing temperatures and gale-force winds, the 100' boat disappeared February 14, 1985 while running across Shelikof Strait toward Kodiak, Alaska. The only trace ever found of the vessel or her crew was a life ring that washed up on a Kodiak beach some 16 months later.

Operating a ship in cold weather means dealing with the combined effects of all cold weather factors. A typical situation might consist of:

- Air Temperatures at or Below Freezing

- Water Temperatures Approaching Freezing

- Moderate to High Sea State

- Winds of 20-30 Knots

- Presence of Sea ice

- Reduced Visibility due to Fog, Freezing Rain, or Snow

The conditions that produce spray icing are rarely combined in more deadly fashion than in the Bering Sea and Gulf of Alaska. The Northern Hemisphere's spray-icing waters also run in narrow bands south of the Arctic Circle, and include portions of eastern Canada, New England, Scandinavia, Russia, and Japan. Further north, pack ice keeps the waves and spray down. Further south, temperatures are generally too warm to freeze the spray.

 

Thick layers of ice can form on decks, sides, superstructures, hatches, masts, rigging, deck mounted machinery, antennas, and combat systems. Ships have reported ice accumulations 3 feet thick on decks, with the guard rail covered completely to form a closed bulwark. Freighters have had to spend several days in port chipping ice accumulation off hatches before they could be opened for unloading.

 

The temperature of both the water and air determine the rate at which spray will freeze to a vessel. Wind determines the height and direction of the waves and thus the amount of spray that will splash over a vessel. Green water does not cause icing and can even warm up a deck enough to wash away spray ice. Low waves will cause shelf ice to build up around a hull, while larger waves can cause icing high in a vessel's superstructure. Shelf ice can be less dangerous, as it tends to break off under itís own weight. Ice accumulation in the rigging is much more detrimental to stability, as it more damaging to a vessel's center of gravity.

 

The U.S. Department of Commerce publication, "Climatological and Oceanographic Atlas for Mariners", Volume I, North Atlantic Ocean (August 1959) is a guide for expected winds in combination with icing.

EXAMPLE: Winds up to Beaufort Scale 9 (41-47 Knots) are very likely to occur off the west coast of Greenland. Heavy to severe icing is expected 5 to 15 percent of the time in February based on simultaneous occurrence of winds equal to or greater than 34 knots and air temperatures equal to or less than 28oF.

NAVY WEIGHT AND MOMENT COMPENSATION PROGRAM

Ships are assigned a Stability Status based on their growth potential as measured by the difference between the current Full Load Displacement and KG and the Limiting Displacement and KG. These differences are commonly referred to as the displacement margin and the KG margin. It is expected that a ship will undergo several modifications and ShipAlts during itís service life.

 

STATUS 1: An increase in displacement and a rise of the center of gravity are acceptable.

STATUS 2: Neither an increase in displacement nor a rise of the center of gravity are acceptable.

STATUS 3: An increase in displacement is acceptable, but a rise of the center of gravity are not acceptable.

STATUS 4: A rise in the center of gravity is acceptable but an increase in displacement must be avoided.

 

 

Stability Status of Surface Ships in Service

Class

Displacement

KG Margin

Status

Class

Displacement

KG Margin

Status

Margin

Margin

AD 37

I

CVN 68,74

I

AD 41

CRITICAL

III

CVN 69-73

CRITICAL

III

AE 26

CRITICAL

III

DD 963

CRITICAL

III

AGF 3

CRITICAL

III

DD 997

CRITICAL

CRITICAL

II

AGF 11

CRITICAL

III

DDG 51

I

AO 177

I

DDG 993

CRITICAL

CRITICAL

II

AOE 1

I

FFG 7

CRITICAL

CRITICAL

II

AOE 6

I

LCC 19

CRITICAL

III

AOR 1

CRITICAL

III

LHA 1

CRITICAL

CRITCIAL

II

ARS 50

CRITICAL

III

LHD 1

CRITICAL

III

AS 31

CRITICAL

CRITICAL

II

LPD 4

CRITICAL

CRITICAL

II

AS 33

I

LPD 7

CRITICAL

CRITICAL

II

AS 36

CRITICAL

III

LPH 2

CRITICAL

CRITICAL

II

AS 39

I

LSD 36

I

CG 47

CRITICAL

CRITCIAL

II

LSD 41

CRITICAL

CRITICAL

II

CGN 36

CRITICAL

CRITICAL

II

LSD 49

I

CGN 38

CRITICAL

IV

LST 1179

CRITICAL

CRITICAL

II

CV 59

CRITICAL

CRITICAL

II

MCM 1

CRITICAL

CRITICAL

II

CV 63

CRITICAL

CRITICAL

II

MCS 12

CRITICAL

CRITICAL

II

CVN 65

CRITICAL

CRITICAL

II

MHC 51

I

CV 67

CRITICAL

III

 

STABILITY REPORT

One of your most important duties is to keep the Captain informed during a casualty or in battle. The Stability Report is designed to inform the Captain about the extent of damage and itís affect on stability. During a casualty, the Captainís hands will be full, so focus on conveying an easy to follow report.

Prior to actual damage, review with the Captain stability limitations specific to the ship. As a minimum, discuss conditions of critical stability, floodable length, danger angle, negative GM, the damaged stability curve, and the heeling effects of beam winds.

 

HINTS: - The report shouldnít teach, it should inform

- Avoid calculations

- Formulate an initial stability or damage report with the Captainís assistance. This way, you will know what information is expected, and unreasonable demands (like calculations) will not be made.

SAMPLE FORMAT

     
 

Compartment name: 5-250-0-E, Main Engine Room

 
 

Casualty: Rupture, Hole, Crack, Flooding, etc

 
 

Location: Port, Stbd, deck, fwd, aft, waterline, etc

 
 

Level of flooding: 4 feet and rising

 
 

Flooding Effects Chart information: Is stability improved, impaired, no appreciable effects

 
 

Stability Critical?: a) Exceed Floodable Length

 
 

b) -GM

 
 

c) List Beyond the Danger Angle

 
 

d) Damage w/ Heavy Seas

 
 

Recommendations and Current Actions: Discuss progress of repair parties. Request the bridge maneuver the ship to best aid the repair efforts.

 
 

Expected losses of firemain services: Fire Stations, AFFF, CMWD, Drainage, Mag Sprink, Aux Cooling, etc

 
     

 

RECOMMENDATIONS

Keep your recommendations practical and to the absolute minimum. If you are faced with a catastrophe and don't feel comfortable with a recommendation, simply report the facts. Don't get reckless, for example: Don't recommend to the Captain to abandon ship, even if stability is critical. That is the Captainís decision, not yours. Keep him/her informed: "Captain, the ship is in danger of sinking/capsizing due to...."

 

NSTM 079 volume II, page 186, contains a graphic display of the flooding rate, in gallons per minute, as a function of the diameter of the hole in the hull and the depth of the hole below the waterline.