Part of traveling’s lure is exposure to different cultures, from sampling new cuisine, to learning foreign languages, to observing weird and wonderful local traditions. It’s exciting to get out of your comfort zone and see something different, but when it comes to our sport, differences in scuba equipment can be confusing. If you have ever traveled abroad to dive, you might have experienced these subtle differences that exist between countries when it comes to gear. Here we aim help to explain the differences in scuba equipment so that you can be fluent in the language of diving wherever you go.
Aluminum vs. steel tanks
In some places (like the U.K. and South Africa), scuba cylinders are most commonly made from steel. In other places (like Southeast Asia and Central America), dive centers are more likely to stock aluminum cylinders. Although the two cylinders may look similar, using one or the other can significantly affect your diving experience, which is why it’s always a good idea when renting a cylinder to find out what it’s made from. When it comes to renting rather than owning a cylinder, the most important difference between steel and aluminum is how each one affects your buoyancy. Both types become lighter, and therefore more buoyant, as the user empties the cylinder of air. However, while a steel cylinder starts the dive negatively buoyant and ends the dive only slightly less negatively buoyant, an aluminum cylinder goes from negatively to positively buoyant, as it gets lighter. If you’re used to diving with an aluminum cylinder, this is no problem; you will have learned to weight yourself to compensate for this added positive buoyancy at the end of the dive. However, if you’re used to steel cylinders, you’ll have to wear considerably more weight than usual to prevent becoming overly buoyant at the end of the dive and on your safety stop.
Although the other differences between aluminum and steel cylinders don’t necessarily affect you as a one-time renter, it’s always wise to know a bit more about your dive equipment. Aluminum cylinders are typically larger and heavier than steel ones, since they are constructed with thicker walls. This is because aluminum is softer than steel, and so the walls of an aluminum cylinder must be thicker in order to hold a comparable pressure. Because aluminum is so soft, these types of cylinders typically dent or scratch more easily, and are therefore not as durable as steel cylinders. Steel is more susceptible to rust than aluminum, however, and therefore more likely to become damaged as a result of constant exposure to salt water if not rinsed thoroughly after every dive. Because steel is more expensive than aluminum, many dive centers favor aluminum cylinders, particularly in less affluent, tropical areas where there is no need for steel’s durability.
To determine whether your cylinder is steel or aluminum, note that steel cylinders are usually stamped with an “AA” in the ring of markings found at the top of the cylinder, while aluminum cylinders should have an “AL.” Aluminum cylinders are almost always flat-bottomed, while round-bottomed steel cylinders usually come with a plastic boot that keeps them upright. There are exceptions to these rules, of course, so if you’re unsure, just ask.
Yoke vs. DIN
Yoke and DIN configurations refer to the way in which your regulator first stage attaches to your cylinder. DIN regulators screw directly into the cylinder valve, and the O-ring necessary to make the seal between the two is part of the regulator, rather than part of the cylinder. Yoke regulators (or A-clamp regulators as they are called in some countries) fit over the cylinder valve and clamp onto it via a tightening screw, and the O-ring is part of the cylinder. DIN regulators are usually used in technical dive centers and in certain parts of Europe, whereas yoke regulators are most commonly used at recreational dive centers, particularly in North America and the tropics. While it is generally accepted that the DIN system offers higher performance in terms of a more secure fit and a better ability to handle high pressures, you’ll most likely encounter the yoke system when diving abroad recreationally.
If you’re renting equipment, your dive center will likely offer one configuration or the other, in which case, your choice is made for you. If the style that you are given is unfamiliar to you, ask for your divemaster’s help when assembling your gear for the first time. Whichever style you use, it is imperative that you make sure your O-ring is in good condition in order to create a solid seal before diving. If you travel with your own regulator but hire cylinders on arrival at your dive destination, you may find that your configuration does not match the cylinders available for rent. It is possible to buy adaptor kits that can turn your DIN regulator into a yoke regulator and vice versa, or you can take your equipment to a certified scuba technician who will be able to convert your regulator into whichever system you require. Another easy way to make sure that your regulator will be compatible with the cylinders in your destination is to travel with a set of Allen keys and a yoke-regulator insert. That way, if you have a DIN regulator and the cylinders are set up for the yoke configuration, you can simply use the Allen keys to remove the valve insert and render the cylinder compatible for DIN use. Conversely, if you have a yoke regulator and the cylinders are set up for DIN use, you can use your Allen keys to screw an insert fitted with an O-ring into the opening of the cylinder valve, which will make it appropriate for use with a yoke configuration.
Different methods of measurement
Different methods of measurement are often a source of confusion when traveling abroad, whether it’s converting miles to kilometers or Fahrenheit to Celsius. The same differences appear in the diving world, most notably when it comes to measuring weight and air pressure. In terms of weight, some countries (like the U.S) use the imperial system, measuring weight in pounds; others (like Australia) use the metric system and measure weight in kilograms. This can get confusing when your dive guide asks you how much weight you need, and given that there are roughly two pounds to the kilo, it’s important that you get it right. Make sure to ask whether they want your answer in pounds or kilos, and make sure that you know the conversion, so that you don’t suddenly find yourself wearing half the weight you’re used to (or double, as the case may be).
The other common difference in measurement comes into play when looking at your air-pressure gauge. Air pressure can be measured either in bar or in psi, and your gauge will read 200 or 3000 respectively when your cylinder is full. Bar and psi are just two alternative ways of measuring pressure, with bar relating to the atmospheric pressure at sea level and psi representing pounds of force per square inch. It isn’t important that you know the conversions for bar to psi and vice versa, only that you understand what each unit as it is written on your pressure gauge means in terms of how much air you have left.
If you find yourself confused about any unfamiliar aspect of your dive equipment when traveling, don’t be afraid to ask for clarification. It is vital that you feel confident in your equipment underwater — after all, your enjoyment and safety depend upon it.