TECHNIQUE OF DIVING

Heat. Heat. I love you. [Music] The little fellow once remarked to Skippy, "The ocean's mighty big." To which Skippy answered, "Yes, and don't forget, we're just looking at the top." "The man who, unlike Skippy, is going to do more than look at the top. The man who is going to adventure into the waters below the top, who is going into a new world, the strange element, must learn how to behave in that element for the sake of his own safety. Not that the techniques of diving are difficult. They are not. But the consequences of disobeying the few simple rules are serious. A man can be made ill, can be killed by such disobedience. Consequently, he must be sure of himself, certain that he understands how to dive. To dive, a man has only a few things on which he can rely. The first is his dress. The second are his tenders, who watch his lifeline and air holes, and with whom he communicates by hand signals on the lifeline. His third aid is the telephone, the cable of which is in his lifeline. The fourth is his descending line, a 3-in cable laid rope, which is his guide for ascent or descent. And the fifth and most important is his knowledge of the conditions of diving and how best to behave. When the diver is dressed, he sets his exhaust valve two and a half to three turns if he's going to work under normal conditions. Once he is on the ladder, the signal to descend two taps on the helmet is given. As he descends, the weight of the water presses the dress tightly against his body. When the water reaches helmet level, he experiences difficulty in breathing because he must expand his ribs against water pressure around his chest. So he opens the control valve to increase the air pressure in his helmet until it equals the water pressure at his lower rib. The air pressure in his lungs is now equal to the water pressure at his chest, so he breathes easily. The upper portion of his dress is inflated just enough to buy the weight of the breastplate, helmet, and belt off his shoulders. The diver swings over to the descending line and stops to make a final survey of his dress. He adjusts his air control valve to maintain the buoyancy of the dress. A turn toward him increases the pressure. A turn away decreases it. More air to me, less air away. More air to me, less air away. The air control valve is in the actual process of diving the divers's chief aid in maintaining a balance of pressure. Consequently, the relationship between it and the exhaust valve is most important. For clearly too much or too little air in the suit can be most dangerous. Should for any reason the pressure of the air inside the helmet become materially greater than the pressure of the surrounding water, the dress will be distended. As a result, the divers's buoyancy increases because of the increased displacement. When he no longer has negative buoyancy, he will begin to float to the surface. The soft twill of his dress will become rigid so that he will not be able to move his extended arms either to reach the air control valve or the exhaust valve. The cause of this condition can be either too much tension on the exhaust valve springs or a supply of air too rapid for the exhaust valve to dispose of since it has an orifice of fixed size. Blowups can also be caused by improper adjustment of exhaust valve or faulty springs, by an over supply of air through the air control valve, or by the loss of weight, as well as shoes or belt or by a broken jock strap. If the diver is lucky, he will float on top of the water until hauled in by his tender, and if blown from sufficient depth, will be let off with only an attack of the bends. If he is unlucky, his dress will burst and drag down by its weight, he will be subjected to a squeeze and possible drowning, or he may come up under the diving ship or other surface objects, in which case he might well be injured. Conversely, if he lets too little air inside his dress, the lack of sufficient buoyancy will force him to carry more of the weight of his equipment, tiring him out quickly. The lack of air in his helmet will cause the carbon dioxide to increase, a dangerous condition made known by the fogging of the lenses and by labor breathing. A sudden change in depth with its resultant increased in water pressure will force the air from the flexible suit into the rigid breastplate and helmet if the volume of air going into the suit is not increased since the pressure of the surrounding water is greater than that within the helmet. A slight negative pressure inside the helmet will cause a mild squeeze. A negative pressure as low as 2 L pounds will produce bleeding from the nose and mouth by rupturing the blood capillaries in the lung. In an extreme case such as complete loss of air in the dressing helmet, the upper portions of the body are forced into the helmet. And so the diver, aware of the necessity for his precautions, makes absolutely certain that all is in proper working order before he gives the signal two pulls that tells the tenders he is ready to go down. Nor does he ever descend, regardless of any signals made by the tender, until he is certain that all well. Then he is the one who makes the signal. To descend, the diver holds onto the descending line with his right hand and grasp the control valve with his left. Remembering more air to me, less air away. He wraps his legs about the descending line and begins his descent, always with his back to the current. His grip on the descending line, however, is not too tight, since if it is, the lay of the line will tend to rotate him, and so put turns of his air hose and lifeline around the descending line, fouling them. In a strong tide or swift current, he can obtain a firmer hold by cradling the line in his right arm and holding onto his breastplate with his fingers. As he descends, he adjusts his air control valve to meet the increase of pressure. More air attuning, less air away. He makes his descent at a speed which permits equalization of pressure between the inner and outer ear. For the first 30 or 40 ft, this speed is necessarily slow since the pressure upon him is increased 100% from the sea level pressure of 14 and 7/10 pound per square in or one atmosphere absolute to 29 and 4/10 per square in at 33 ft or two atmospheres absolute. Having passed that mark, he gradually increases his speed until he reaches approximately 75 ft per minute, controlling the rate by his hold on the descending line and by acquiring buoyancy through manipulation of his air control valve. Though it is desirable to make reasonably good speed and so increase the time available for work on the bottom, 100 ft a minute should be considered the safe limit. For a diver shouldn't get ahead of his ability to equalize pressure. A higher rate of descent means that the body has not adequate time to adjust to the altered pressure and the diver may become dizzy, suffer pain in the ears or sinuses, or show other ill effects. Should any of these symptoms appear, particularly pains in the ears, the diver can find relief by slowing down or stopping or even reasscending a few feet. Time taken in descent to make sure a perfect physical condition will increase the working time at the bottom. Three conditions influence descent. The first of these is water temperature. In cold water, the diver circulation is slowed and so he does not equalize pressure as well. As a consequence, his descent may also be slowed. The second is visibility. If the light is bad, the diver will have to proceed more cautiously, if for no other reason than to avoid meeting any obstruction which may be in his path. The third is the most serious of all, current. His bulky dress presents a large surface of resistance to the flow of current, and should he be unwearing, he can easily be swept away. Having found out the direction of the current while still on top side, the diver descends with his back to it so that it pushes him into his descending line, making his position on that line more secure. Obviously, the divers's progress is by this state of affairs. Not only must he work against the force of current but also against the extended bite which the current produces in the line. Eventually he reaches the bottom. Bur pauses a half minute before starting on his job. This pause enables him to become adjusted to the new pressure level. At the same time he resets his air supply, regulating both his air control valve and his exhaust valve. until he feels that the proper balance and ventilation has been obtained. Then he looks about him to locate his position. For a diver must always keep his sense of direction. He observes the direction of the light, of the current, the position of any object in the vicinity, the tend of his lifeline and air hole. the slope and characteristics of the bottom. Should that bottom be muddy, he must keep moving or he will bog down and justify the old poem, the saddest word from a diver bud is, "Pull me out. I'm in the mud. When he is properly oriented and when he is certain that all adjustments are made, he goes about his work. But while on topside, he and his tenders have studied everything known about the job. The diver is nevertheless on his own. For conditions below cannot be predicted, and none knows them but the diver. There are certain rules for behavior, however, which will fit any situation. A diver should conserve his strength by making all his movements very deliberate. He must at all cost avoid getting nervous or elated. If he is in a tight spot, he should stop to rest and try to figure an easy way out. For if he moves too quickly or by excitement increases his circulation, he will require more air and may exhaust himself without becoming aware of his condition. Confidence in himself and his tenders is essential. The tenders were always in position to pull in the lifeline and hose, watch the divers's bubbles, and look out for his signals. Though the telephone is a very valuable means of communication, reliance should be placed on the standard signals made by pulling on the hose and lifelines. The rush of air through the helmet often makes it difficult for either tender or diver to hear. And in any case, the human voice is difficult to understand at high pressures for the resonating mechanisms are set for sea level pressure of 14 and 7/10 pound and consequently do not vibrate. naturally in the denser air below the surface. Okay, on the bottom bottom good about 2 and 1/2 knots as far as propeller. Okay, what position is it lying in an upward position? Okay. What material do you need? Two and five inch tackle wire strap and four inch line. Okay, line coming down. The standard signals form an easy instantaneous method of communication and enable the diver to feel himself a part of the world which he has left. In the meanwhile, our diver has been hard at work and by now it is possible that he may not have sufficient ventilation since his body produces more carbon dioxide as a result of his exertion. So he opens wider his air control valve and kicks his chin button with his chin, so ventilating the dress. Or perhaps his work necessitates his being in other than an upright position and as a consequence his center of buoyancy is shifted. To close the control valve too far will reduce needed ventilation, thus increasing the amount of carbon dioxide present. And so he kicks his chin valve to increase his weight and change his center of buoyancy. It is also possible to affect a change of buoyancy by opening the spitcock. It sometimes occurs when the diver is in this position that the exhaust valve will become clogged with silk. If so, the spitcock should be immediately open. But of all the accidents that can occur below the surface, nothing is more common than fouling the telephone lifeline and air hose. Though the diver should always try to keep his lifeline and air hose clear, should he become foul, he can usually untangle himself by retracing his steps. Of course, he must remember each of the movements he has made in order to go back over them. Sometimes, however, he may become so completely fouled that he is unable to free himself. In this case, it would be necessary to send down a second diver who in all extended diving operations is kept dressed waiting for such an emergency. [Music] The second diver. passes a manila lifeline under the foul divers's arms and cuts the telephone lifeline cable. [Music] Then he fills the foul divers's dress as full of air as possible to give him a reserve supply. Closing the exhaust valve and then the control valve. When finished, [Music] he removes the valve hose from the control valve. and connects the clear hose which in the absence of a valve is kept free of water by maintaining the air pressure at that of the divers's level. [Music] [Music] And so the diver is free. Most dives, however, are not so eventful. And after an ordinary job completed in an ordinary way, the diver prepares to come up in the usual manner. He is quite likely saturated with nitrogen since he has probably been working at a depth of over 100 ft for a considerable period breathing compressed air. to release this nitrogen from his body and so to protect him from bends that condition caused by the sudden release of pressure and the subsequent formation of nitrogen bubbles in the blood and tissue of the body he must be decompressed. Decompression is accomplished by regulating the speed of ascent and by holding the diver on his way up at certain depths for certain periods of time using a diving stage to make his long weights easier. These certain depths are determined as the points at which the nitrogen forced into solution in the body by the greater pressure of the lower depths can be released by the lungs from the body without the formation of bubbles. and the time allotted at each stop is that sufficient for release of excess nitrogen at that pressure. The procedure for decompression is set forth in the Navy's standard decompression table. Let us say that our diver left the surface at 1000 and descended to 150 ft. At 10:30, he starts his ascent. The table informs us that he must have a total decompression period of 40 minutes. Six of which are to be used in ascending at a standard speed for all depths that does not exceed 25 ft per minute. 13 minutes of which are to be spent pausing at 20 ft, 21 at 10 ft to make the actual ascent. If no diving stage is available, it is mandatory for the diver to use his descending line, clinging to it at the stipulated depth and being held at the various points by his tender. However, the use of the stage is recommended whenever available. It is lowered to the first stop, having been shackled to the descending line. on it. The diver may rest and be drawn up through the water. The stage has the further advantage of permitting the tenders to control the speed of ascent. It must be remembered that except in emergencies, the speed from the bottom to the first stop and between stops must not exceed 25 ft per minute, regardless of the depth at which the diver has been working. As he ascends, the diver relaxes. If he wishes, he may move his legs and arms leisurely to ensure proper circulation. He is held at the proper depths for the correct length of time. Eventually arriving on shipboard free under any normal circumstances from the danger of bends. If there is a recompression chamber aboard ship, a diver who has been submerged under such adverse conditions as extreme cold, great depth, and so forth, then it is advisable to shorten his ascent may, according to the approved surface decompression tables, be brought out more quickly and then rush to the chamber for further decompression. Finally, it must be remembered that if a diver is required to dive more than once a day, he must be decompressed on returning from the second dive for the time on the bottom of both exposures combined. But except in emergencies, a diver shall not make more than one dive in a day. On protracted operations, he should have every third day off. for his job is not an easy one, requiring a relaxed mind and steady nerves. Even though no shark will bite him, no octopus grasp him, he has to be constantly on the alert, thoroughly schooled in what to do and not to do in the deep waters underneath the top. [Music] Hallelujah. [Music]