SOUNDING AND SECURITY PATROL WATCH

The sounding and security patrol watch is also known as the damage control patrol watch. It is essential that only those who are well indoctrinated be assigned this watch. As the sounding and security patrol, you will follow an irregular route while conducting a continuous security inspection of all spaces. Some spaces will have a watch posted within them or be designated as a limited or exclusive area. In such cases, you will not enter the space, but you will inspect the surrounding areas. While making your rounds, you will inspect all watertight airports, doors, hatches, scuttles, and other closures to ensure that there are no violations of the material condition of readiness that is set. You will also be checking for fire hazards, fire, flooding, theft, sabotage, or other irregularities that would affect the physical security of the ship. You will check for leakage of the firemain, fresh water, and other piping systems. If you find a hazardous or potentially hazardous condition, report it immediately to the OOD and to DCC. To help determine whether voids or tanks are flooded, you will take soundings and you can compare each day's draft report with the draft report of the preceding day.

SOUNDINGS

One of your duties as a Damage Controlman is to determine the amount of liquid in certain compartments, tanks, and voids. You do this by taking soundings at regular intervals when standing the sounding and security watch. You must know where all the sounding tubes are located and also follow the correct procedures for taking soundings.

A sounding tube is usually made of 1 1/2-inch pipe. The lower end of the tube is located near the lowest point of the compartment, tank, or void that the tube serves. The upper end of the tube is usually located on the main or second deck and is secured with a threaded plug or cap.

If the tube extends above the deck, it will have a gate valve installed in the pipe. These tubes normally serve spaces under the machinery spaces. The sounding tubes are normally straight, but they may have a slight curve because of obstructions.

Soundings are taken with either a sounding rod or a sounding tape, whichever is provided. The sounding rod is 2 feet long and is made of 6-inch lengths of 1/2-inch steel rod. The rod is

lowered down the tube by either a chain or a line. The sounding tape is a steel tape that is coiled on a reel. The reel can be held in your hand while you lower the tape. The tape is weighted at the end so it can easily be lowered into the sounding tube.

Soundings are taken in specified peak tanks, ballast tanks, cofferdams, voids, storerooms, and other similar spaces. Although soundings are taken on a regular schedule, they may also be taken at any other time when considered necessary for the safety of the ship.

Before taking a sounding, dry the rod or tape and coat it with chalk. Then lower it down the tube until it touches bottom. Do not drop the rod or tape to the bottom. Lower it slowly so it hits the bottom without being damaged. Then bring it back up immediately. If the ship is rolling, try to lower and hoist the rod or tape rapidly while the ship is on an even keel.

Immediately after taking a sounding, replace the cap or plug and tighten it with a wrench. If a gate valve is installed, close the valve. Next, record the depth of the liquid on the sounding record sheet. If a normally dry compartment shows any liquid, immediately notify the OOD and either the DCA or the engineer officer.

You must use certain precautions when taking soundings. Carefully remove the plug or cap from the upper end of a sounding tube in such a way that the cap is always under control. Back it off slowly and listen for the hiss of escaping air. If a rush of air escapes around the threads while the cap is still under control, STOP REMOVING THE CAP. The escape of air is a sign that the compartment is partially flooded. A trickle of water around the threads indicates that the compartment is completely flooded. In either case, secure the cap and report the situation immediately.

DRAFT AND DRAFT MARKS

The Displacement and Other Curves are a set of curves that shows the various properties of the shape of the underwater body of a ship. The Displacement and Other Curves are also referred to as Curves of Form. The curves are made up by either NAVSEA or a design activity, from the design lines of the ship. The stability officer uses the Curves of Form to calculate and maintain stability. In order to read the Curves of Form, it is necessary to obtain the averaged mean draft periodically. The mean draft of a ship is the average of the drafts at the forward and aft

perpendiculars. All ships have at least two sets of marks (one port, one starboard) at the bow and two sets of marks (one port, one starboard) at the stern. Some ships have two sets of marks (one

port, one starboard) at the amidships point. The amidship marks give a direct reading of the mean draft. All of these draft marks are known as CALCULATION draft marks. They indicate the distance from the bottom of the keel to the waterline.

Ships having projections below the keel are usually provided with additional sets of NAVI-GATIONAL draft marks. These marks indicate the distance from the lowest projection of the hull to the waterline.

Calculation draft marks and navigational draft marks are shown in figure 3-14.

Calculation draft marks are used to determine displacement and other properties of the ship for stability and damage control purposes. Calculation draft marks are marked on the hull with Roman numerals. The marks are 3 inches tall. The bottom of the mark indicates the number of feet of the draft in feet. The top of the mark indicates the number of feet of the draft plus 3 inches. A horizontal bar is inserted between each Roman numeral. The bottom of the bar is the half-foot mark. The bar is 1 inch tall. Therefore, for a draft of 13 feet, the waterline will be at the bottom of the Roman numeral XIII. For a draft of 13 feet 7 inches, the waterline will be at the top of the horizontal bar that is between the Roman numerals XIII and XIV.

Navigational draft marks are used primarily by the ship's navigator. Navigational marks are located on the hull and are Arabic numbers that are 6 inches tall. The bottom of an Arabic number

Figure 3-14.-Draft diagram.

indicates the number of feet of the draft in feet. The top of an Arabic number indicates the number of feet of the draft plus 6 inches. Navigational draft marks greater than 9 feet are indicated by the last digit only. Therefore, for a draft of 25 feet, the waterline will be at the bottom of a 5. For a draft of 25 feet 6 inches, the waterline will be at the top of a 5.

Taking the Draft

The draft is taken daily, before getting under way, upon anchoring, mooring, or entering drydock, before and after fueling, and at any other time when required by the commanding officer. A considerable error can be made if the draft readings are taken when the sea is choppy or when the ship is under way.

The draft is read in feet and inches and is entered on a form provided for that purpose. Inches of draft must be estimated as closely as possible. To obtain an accurate reading that will not be affected by a list, the mean draft is calculated as follows:

1. Read the draft at the bow on the port and the starboard sides. Average these readings and record the results.

2. Read the draft at the stern on the port and the starboard sides. Average these readings and record the results.

3. Obtain the mean draft by adding the average draft forward to the average draft aft and then dividing the sum by 2.

Limiting Draft Marks

When a ship operates at excessively heavy displacements, there are adverse effects on speed, cruising radius, stability, strength, and freeboard.

Limiting draft marks are installed on the ship's hull near the draft numerals or amidships. These marks indicate the draft that is not to be exceeded without endangering the ship's ability to survive damage or heavy weather. Under extreme circumstances, however, the limiting draft mark may be exceeded if the commanding officer decides that the circumstances warrant the risk. Figure 3-15 shows the limiting draft mark used on naval ships.

Plimsoll Marks

_{The Plimsoll} mark (fig. 3-16) is a standard _{marking painted} on the sides of merchant ships

Figure 3-15.-Limiting draft mark.

and some naval auxiliary ships. These marks indicate the maximum draft allowed by law in various waters. The load lines indicate the drafts at which the ship will have a safe reserve of buoyancy. The circular symbol with the horizontal line is usually placed amidships. The horizontal line indicates the same draft that the S line of the symbol to the right of the circle indicates. The abbreviations used in figure 3-16 stand for the following:

TF-Maximum draft, tropical (freshwater)

F-Maximum draft (freshwater)

T-Maximum draft, tropical (salt water)

S-Maximum draft, summer (salt water)

W-Maximum draft, winter (salt water)

WNA-Maximum draft, winter, North Atlantic (salt water)