Dealing With Cylinders
of Different Capacities
When team members use cylinders of varying capacities, the problem is that pressure is no longer an accurate indicator of actual volume. For example, an aluminum 80 filled to 3,000 psi actually contains 16 percent less gas than a steel 95 filled to 2,640. To accurately determine gas turnaround points, divers using dissimilar cylinders must take this factor into account.
It is possible to determine turnaround points among divers using dissimilar cylinders by solving any of a variety of complex mathematical formulas. The problem with these highly complex approaches is that, the more math involved, the greater the likelihood of error. Fortunately, there is a simpler way to deal with this situation. It involves consulting a table that compares the actual capacity of common cylinders at various pressures. (Click here to make this table appear in a separate window.)
It is interesting to note that, if we so chose, we could obtain the same information dive tables provide us by working a series of complex, multi-compartment equations. Using dive tables to obtain the same data, however, is not only easier and more convenient, it is also safer, in that the possibility of mathematical error is reduced or eliminated.
It is largely the same situation here: The simpler we keep dive-planning procedures, the safer and more reliable they tend to be.
Determining Turnaround Using Tables »