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immediately, without interrupting operation of the ventilators, and the bulkhead closures and registers for the entire submarine ventilation system carefully checked. Charging may not be resumed until the causes of the unsatisfactory ventilation are determined and eliminated.

If it is impossible to ventilate a storage battery through the battery ventilation (exhaust) shaft, and with the diesels charging and boost charging, the battery must be ventilated in the engine room.

If it is necessary for the submarine to crash dive, ventilation of the storage battery is discontinued and greater control over hydrogen concentration maintained.

If, with all of the hydrogen oxidation instruments operating, the hydrogen concentration in one of the battery compartments reaches the maximum permissible level, the battery tanks and compartments must be immediately ventilated in the atmosphere. If this is impossible, the following steps must be taken:

1) carefully secure the battery tanks;

2) secure all closures, registers and plugs and pipes leading to and from the bottom tanks;

3) isolate the battery compartments and discontinue switching electrical equipment on and off in these compartments, before ventilating the compartments and tanks in the atmosphere;

4) with a decrease in hydrogen concentration in the battery compartments due to operation of the hydrogen oxidation equipment, transfer small quantities of hydrogen from the tanks into the battery compartments, in no case permitting an increase in hydrogen concentration in the compartments beyond the maximum permissible level;

5) check the hydrogen content (%) every 15 minutes. In order to prevent accumulation of a dangerous concentration of hydrogen in the battery tanks and compartments, the battery must be ventilated in the atmosphere every 3 hours for 15 minutes. This periodic ventilation is carried out each time by special order of the Commanding Officer of the submarine or officer of the watch if the conditions under which the submarine is fulfilling its mission and the situation permit opening of the shaft to ventilate the battery in the atmosphere.

If before ventilation of the battery in the atmosphere has begun the hydrogen concentration in one of the battery compartments exceeds the maximum permissible level, the conning tower access hatches, bulkhead doors and ventilation shafts must be opened and the submarine ventilated using natural means in order to decrease the hydrogen concentration. Only then should the ventilators be turned on.

5. Explosion of a Storage Battery

If established regulations for the operation and maintenance of submarine storage batteries are not observed, the battery could explode, rupturing the tanks, causing a fire and resulting in seepage of electrolyte.

Explosion of a storage battery results from detonation of the explosive mixture accumulating under the battery tank covers, and in the battery ventilation tubes, battery tanks and compartments. The explosive mixture could ignite anywhere on the submarine if the hydrogen content there exceeds the maximum permissible level.

If a storage battery explodes and fire breaks out in the compartment, personnel must take the following measures:

1) if the storage battery exploded during charging, the latter must be immediately discontinued;

2) if at the moment of explosion the battery and ship ventilating system were operating, they must be immediately shut off and the appropriate closures and registers secured;

3) if the explosion did not involve all of the storage battery groups, the entire load must be immediately shifted to the undamaged groups and the compartments in which these groups are located must be isolated.

In fighting fire, personnel must wear self-contained breathing apparatuses. In extinguishing burning plywood, cork, etc. in battery compartments, foam and carbon dioxide extinguishers may be used, but in such a way that the liquid they discharge will not come in contact with the batteries.

Sea water may not be used to extinguish a fire in the battery compartments. Only distilled or fresh water may be used for this purpose.

When a compartment is opened after a fire, all precautionary measures should be taken to prevent sparks. Neither the battery ventilators, lights or any other electrical equipment may be turned on until the compartment has been naturally ventilated for at least 12 hours.

Personnel first entering a damaged compartment should be wearing selfcontained breathing apparatuses and carrying flashlights.

6. See page of Sea Water into Storage Batteries

If sea water has penetrated one or several storage batteries and this fact is observed immediately, the following steps must be taken:

1) immediately turn on the battery ventilation and disconnect the flooded battery group from the entire circuit, then disconnect the damaged batteries from the circuit;

2) remove the water which has penetrated the battery tank;

3) remove the upper layer of electrolyte from the flooded storage batteries to the level of the upper edges of the plates;

4) carefully fill the batteries with distilled water. If sea water has simultaneously penetrated a large number of storage tanks, the following steps must be taken:

1) immediately cut off the flooded group from the overall circuit and disconnect it at several points;

?) remove water from the battery tank;
3) tum on the battery and ship ventilation;

4) draw off the electrolyte. A gas mask must be worn in working with a storage battery filled with sea water.

SECTION 12. VISUAL AND ELECTRONIC OBSERVATION

1. Use of a Periscope

A periscope has two eyepieces, one of which is used for observation and the other to measure distances.

In using the eyepiece for observation, the position of the observer's head must be such that his eye will take in the entire field of the eyepiece without cutting it off at the edges. One of the important factors in good observation is accurate focusing of the eyepiece. To accomplish this, the periscope is focused on a clearly visible distant object and, in the absence of such an object, on a bright, uniformly illuminated background (for example, the sky). The eyepiece is adjusted by rotating the knob until the image of a distant object (or the reticle if there is none) becomes sharp and clearly visible, after which a reading is taken from the scale and recorded so that subsequently the eyepiece can be focused directly from the scale.

Periscopes have two types of magnification: a small 1.5-power magnification and a large 6-power magnification. In selecting a magnification, it should be borne in mind that in observation using a periscope with 1.5-power magnification, the visibility of the objects observed appears to be about the same as in observation with the naked eye. The greater the magnification, the greater and more visible the dimensions of the target. This makes it possible to examine the target in greater detail and permits accurate focusing. However, with an increase in magnification the field of view of the periscope is reduced. Considering this fact, in searching for the target when observation is begun, when it is necessary to have a large field of view, a 1.5-power magnification must be used. If the target or some other observed object must be examined in greater detail and a large field of view is not required, it is recommended that a 6-power magnification be used.

At night and twilight, as well as with bad visibility, a large magnification must be used.

Distances to the target can be measured using the range-finding reticle on the periscope eyepiece, located in the field of view to the left of the vertical cross hair (Fig. 17), and also by using the range finder.

The range-finding reticle is divided into mils (1 mil = 3.6'). Each small graduation on the range-finding reticle is equal to 5 mils.

In measuring distance to the target using the range-finding reticle of the periscope, the following steps must be taken:

1) focus the periscope on the target in such a way that the cross hairs on the range-finding reticle are superimposed over the target;

150100 50 0 50100

Fig. 17. Periscope reticle.

2) determine and record the number of graduations on the reticle encompassed by the image of the target height;

3) determine the height of the target;

4) determine the distance to the target from the table. The table used to determine distances to the target using the range-finding reticle (Table 4) was compiled for use with a small (1.5-power) periscope magnification.

If we know the actual height of any object and the distance to it, the accuracy of calculations using a range finder can be verified from the table. The table was calculated from the equation:

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where H is the height of the target in meters;

n is the number of graduations on the reticle; and 1.1 is the conversion factor.

In order to determine the distance to the target using the range finder mounted on the periscope, one must:

1) turn the ocular disk and engage the eyepiece in order to measure distances in the optical system of the periscope;

2) use a large (6-power) magnification;
3) focus the image through the eyepiece from the eye of the observer;

4) determine the height of the target from the handbook or silhouette and record the selected value on the lower fixed scale of the range finder, graduated from 5 to 50 m (Fig. 18);

5) looking into the eyepiece and rotating the measuring knob, raise both halves of the target image, which should be equally sharp and clear (Fig. 19);

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