NAUI Master Scuba Diver 238 Diving Techniques and Deeper Diving single K-valve to a dual outlet for primary and backup regulators. This valve is for a single cylinder to be used in depths of 18 to 40 msw (60 to 130 fsw). Either regulator may be independently isolated if a malfunction occurs. • Two basic K-valves with crossbar: expands two single cylinders to a dual cylinder configuration with two regulator outlets (primary and backup) for deeper advanced diving. • Two basic K-valves with an isolation crossbar: expands two single cylinders to a dual cylinder configuration with ability to isolate either cylinder for technical diving. It should also be noted that several manufacturers supply a Y-valve (slingshot) to facilitate the use of dual regulators on a single cylinder. As with an H-valve, either regulator may be independently isolated in the event of a malfunction. However, the Y-valve cannot be expanded to a dual cylinder configuration. Traditionally, the American scuba industry has used a standard scuba yoke connector (CGA850 or CGA855 connection). The yoke system is, however, technically limited to 200 bar (3,000 psig) under Compressed Gas Association guidelines. For higher pressures, the DIN447 300 bar connector has become the standard fitting. The DIN connector features a “trapped” O-ring configuration that virtually eliminates the potential problem of blown O-rings that has occasionally occurred with yoke fittings (see “Equipment” chapter). Today, most deep and technical divers use the more dependable DIN valve for both high and low pressure cylinders. Most regulators are now available with either yoke or DIN connectors. Several manufacturers have designed DIN cylinder valves with adapters that also allow the use of conventional yoke regulators (see “Equipment” chapter). Regulator Generally, any well-maintained recreational diving regulator should suffice for shallow water recreational diving. However, if you intend to extend your diving activities to the realm of deep diving, you are encouraged to select a proven high-performance regulator. Periodically, the U.S. Navy evaluates scuba regulators and publishes test results. The results of the U.S. Navy test as well as those completed by other agencies are often published in recreational and technical diving publications. Your first concern is performance. Will the regulator deliver a sufficient gas volume with minimal breathing effort under high demands at the anticipated maximum dive depth? Keep in mind that your gas flow requirements can more than quadruple in a high stress situation. If applicable, will the regulator perform adequately in cold water or will it ice (resulting in free-flow) under high demand conditions? Next, consider reliability. Does the regulator have a proven record of reliable performance within your intended application parameters? A reliable equipment dealer and other divers should be able to assist you in identifying both desirable and undesirable regulators. Avoid regulators that have any history of malfunction and that require frequent repair or adjustment. What safety features are incorporated into the regulator design? Regulator maintainability is another important consideration. Some regulators require complex and expensive maintenance procedures. Others are very simple to maintain. Since regulators used for deep diving must always operate at the highest level of performance, maintainability is an important consideration. A regulator must be physically comfortable. Weight and design characteristics become very important in reducing jaw fatigue. Finally, a regulator must be compatible with your scuba system. Obvious compatibility requirements include such thing as DIN connectors. Less obvious considerations include the physical size of the first stage relative to present and future valve and manifold configurations. Other Equipment Safety support equipment is also necessary for deep diving. Standard equipment including first aid kit, oxygen, backboard, communication equipment (VHF or CB radio or cellular/digital phone), and transportation equipment should be available at the dive site. In addi
20047TC
To see the actual publication please follow the link above