EMERGENCY REPAIRS TO THE FIREMAIN

Firemain systems are designed so that damage to one section does not necessarily affect the operation of the entire system. Fire pumps and cutout valves are installed throughout the system so that a damaged section can be isolated. Isolating a damaged section allows firemain pressure to be maintained in the remainder of the system.

However, a section of firemain piping could be ruptured as in view A of figure 5-1. If that happens, the cutout valves on each side of the break can be closed to isolate the break. The ruptured section can then be removed. Service can be temporarily restored by inserting hose adapters and connecting a length of hose between the adapters (view B of fig. 5-1). Hose flange adapters are provided to repair parties so temporary connections or jumper lines can be rigged. These

Figure 5-1.-Providhg temporary firemain service by using flanges and fire hose.

hose flange adapters can be bolted (or clamped with C-clamps) into place quickly and easily.

If the ruptured section of piping cannot be removed, you can provide temporary service by joining together the fireplugs that are nearest the closed cutout valves on each side of the break. In this case, you would use hose and a double female coupling, as shown in figure 5-2. Then open both fireplugs to restore the pressure. This method of emergency repair is effective, but it does eliminate the availability of two fireplugs.

No matter which method of emergency repair you use, repair the damaged section of firemain as quickly as possible.

TESTS AND INSPECTIONS ^OF THE FIREMAIN SYSTEM

Various tests and inspections for the firemain system are prescribed by the 3-M Systems. These tests and inspections are conducted on the firemain piping, fireplugs, valves, operating gear, remote control operating equipment, and other components.

You will need to flush the firemain system on a quarterly basis. However, if the ship is operating in tropical waters, you must flush the firemain system more often. By flushing the firemain, you help to minimize problems such as fouling of valves. When flushing the firemain, use freshwater whenever possible. Freshwater will help to destroy

Figure 5-2.-Providing temporary firemain service by using hose and double female coupling.

marine growths within the firemain system. Use a minimum pressure of 60 psi to flush the firemain.

FIRE STATIONS

The numerous fireplugs aboard ship are served by branches from the firemain system. Fireplugs have outlets either 2 1/2 or 1 1/2 inches in diameter.

On small ships, fireplugs are located so that any point on the ship can be reached with 50 feet of fire hose from each of two or more fireplugs. On large ships, any point can be reached with 100 feet of fire hose from each of two or more fireplugs. On aircraft carriers, any area of the flight deck can be reached with 150 feet of hose from at least two fireplugs.

Fireplugs below the weather decks are normally set 5 to 6 feet above the deck. The outlets face downward. If these outlets are 2 1/2 inches in diameter, they are reduced by w ye-gates to two 1 1/2-inch outlets. Fireplugs on the weather decks are normally set 13 to 18 inches above the deck with the outlet in the horizontal position.

A quick-cleaning strainer is normally attached directly to each fireplug outlet, as shown at the top of figure 5-3. Sometimes the strainer is attached to a short length of hose. The other end of the hose will connect to the fireplug outlet. This type of installation is shown at the bottom of figure 5-3. It is used only when it is not practical to install the strainer as a direct attachment to the fireplug outlet. Clean out the quick-cleaning strainer by turning the handle as far as it will go. This will discharge the contents of the strainer onto the deck. After the contents have been discharged, place the handle back in its original position. The strainer serves a very important purpose-it allows for rapid removal of marine growths, scales, incrustations, and other foreign matter that could clog the nozzles or nozzle tips.

FIRE HOSE AND FITTINGS

The standard fire hose used by the Navy in the past was a double-jacketed, rubber-lined, cotton hose. Now, when you order either the 1 1/2-inch or the 2 1/2-inch fire hose, you will receive an orange polypropylene-jacketed, rubber-lined hose. The orange hoses will phase out the older hoses. The standard length for both the 1 1/2-inch and the 2 1/2-inch fire hoses is 50 feet. A 50-foot length of hose is normally referred to as a length; longer runs are described in terms of how many lengths they contain. Thus, a 100-foot run of hose is described as two lengths, and a 200-foot run of hose is described as four lengths, and so on.

There are two fittings on each standard length of hose-a male fitting at one end and a female fitting at the other end. Double female couplings are available to connect two male fittings. You will use a double female coupling when you make up a jumper line assembly to bypass a damaged section of firemain. Double male couplings can be used to join two female fittings. Reducer couplings are used to connect the female end of a 2 1/2-inch hose to a 1 1/2-inch outlet.

Figure 5-3.-Normal method of connecting quick-cleaning strainer to fireplug outlet (top view) andunusual or inaccessible locations (bottom view).

Hoses should be handled and stowed with care. Figure 5-4 shows properly rigged hoses at a fire station. When you roll up a hose, ensure that the male fitting is on the inside of the roll. This method will protect the threads on the male fitting.

After a cotton-jacketed fire hose has been used, it should be thoroughly drained and properly dried. If the hose is not drained properly, a weak solution of sulfuric acid may form inside the hose. The sulfuric acid is produced by a reaction between the water and the sulfur contained in the rubber lining of the hose. It can deteriorate the fire hose. Check the fire hoses weekly, in accordance with PMS, to be sure that they contain no moisture. Once a month, in accordance with PMS, remove the hoses from the racks and restow them. This ensures that the folds in the hoses are not in the same place all of the time.

At least once a year, in accordance with PMS, hydrostatically test the fire hoses to 250 psi for 5 minutes. If you suspect a hose of being damaged or deteriorated, conduct a hydrostatic test on it even if it has not been a year since the last test. The test date must be stenciled on the hose after it has been tested. To stencil the hose, use black paint, MIL-P-2856, on the double-jacketed, rubber-lined, cotton hoses. Use yellow paint, TT-E-489, class A, to stencil the orange, synthetic

Figure 5-4.-Fire hose properly rigged at fire stations. 5-4

rubber hoses. Conduct the hydrostatic test only in such a manner that the ship is not left without fire protection. You may test a third of the hoses at a time. You can do this by removing the hoses from every third fire station on each side to test them. Make sure that no two of the fire stations selected are directly across from each other. You might prefer to conduct the test when your ship is alongside a tender or during a shipyard availability. These two activities can provide your ship with fire protection while you test all of your hoses.

In general, low pressure can be attributed to friction losses through the hose, excessive head pressure, overtaxing of the firemain system, or clogging by foreign matter. Also, such things as breaks in the line, kinks in the fire hose, or partially closed fireplug valves can seriously decrease the pressure available at the nozzle. Be alert for low pressure and know how to locate the cause and correct it.

The pressure delivered at the nozzle is always lower than the pressure at the fireplug because of friction losses. The amount of friction loss depends upon a number of factors, These include the length of the hose; the diameter of the hose; the number, size, and design of the fittings; and the velocity of the stream of water. Because friction loss depends upon so many different factors, it is quite complex to calculate. However, you will learn through experience how friction loss varies with different sizes and lengths of hose.

Excessive head pressure can cause low pressure at the nozzle when water must be forced up through risers. This pressure loss also occurs whenever the nozzle is at a higher level than the plug to which it is connected. There is a decrease of 0.433 psi per foot of elevation. Simple arithmetic indicates that a rise of 20 feet will decrease the pressure by about 8.7 psi.

Overtaxing the firemain can cause low pressure at the nozzles. If too many hoses are in use at the same time, the pressure will drop in all hoses. The only remedy for this is to secure some of the hoses in order to maintain pressure in the most vital ones. A few properly charged hoses are more effective than many undercharged hoses.

If the hose is clogged with foreign matter, pressure will drop. Fortunately, you can quickly correct this trouble by flushing the quick-cleaning strainer at the fireplug.