The Art of Equipment Configuration

Diver 1

1. Accessibility:

The single most important concept in scuba equipment configuration is accessibility. A diver should be able to deploy, use, and stow dive gear easily and efficiently. Any configuration that makes accessing a piece of dive gear difficult or complicated should be re-thought, even if it fulfils all the other tenets of optimized equipment placement. Whenever possible, configure all dive gear so that it may be deployed and operated with one hand. This ensures that a diver can use his other hand for emergency management, such as maintaining physical contact with an out-of-air buddy.

2. Durability:

The manner in which a diver configures his gear should ensure that it will stay in place for an entire dive. A common equipment configuration failure is the alternate air source regulator coming free of its quick release.  The first time a piece of gear comes loose, the diver should reconfigure his gear to prevent the problem from reoccurring.

If it happened once, it will happen again!

3. Streamlining:

All dive gear, including accessories and hoses should be streamlined. In no circumstance should a piece of dive gear dangle more than a few inches below a diver’s horizontal body line . Hoses should be adjusted so that they do not loop above or beside the diver. Keep in mind that regulator hoses are available in a variety of lengths. Proper streamlining reduces the chance of entanglement, damage to the environment, and drag.

A common failure of streamlining in standard recreational scuba diving is the octopus-style alternate air source, which necessarily must be attached to a longer hose to facilitate donation to an out-of-air diver. The hoses on octopus-style regulators typically loop out to the side of the diver, presenting an entanglement hazard and creating drag. As far as streamlining goes, integrated alternate air sources and long hose/necklace regulator configurations are both preferable.

All types of diving require some level of redundancy in the gear. Recreational open water diving requires that a diver carry at least one redundant second stage for his buddy to use in an emergency. More advanced or technical types of diving may require additional redundant gear for safety. A diver should carry the minimum amount of accessories and gear that allows him to dive safely. At a certain point, additional gear no longer increases dive safety. The trick is to balance redundancy and simplicity when configuring dive gear.

5. Trim and Comfort:

Once a diver has optimized his equipment configuration, he should test it in a forgiving environment such as a pool or shallow water dive site. When evaluating changes to his gear configuration, a diver should notice whether the changes upset or improve his trim and whether or not position of the gear is comfortable. No matter how fantastic it seems on the surface, the final test of an equipment configuration is whether or not it is comfortable and functional underwater.

Evaluating and adjusting your scuba diving equipment configuration can make diving easier, safer, and more comfortable.

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How Does a Regulator Work? A Beginner’s Guide to Scuba Regulators By Matt Dunne, Regulator Nerd and Enthusiast

 

Regulator
Scuba diving regulators may seem complicated, but they are surprisingly simple devices.

Few pieces of sporting equipment carry more mystique than scuba regulators. Regulators are sold with a dizzying array of choices, features, and often hype, and there may be a fierce loyalty to brands among experienced divers. But is all the hype justified?

What Does a Scuba Diving Regulator Do?:

Obviously, a scuba diving regulator allows a diver to breathe from a tank underwater. But how does a regulator transfer the high pressure air from the scuba tank to the diver’s lungs at a pressure that will not injure him?

The purpose of a scuba diving regulator is to reduce the high pressure air in a scuba tank to a breatheable pressure on demand.
Scuba regulators are simple devices, and the method in which they reduce high pressure tank air to a breathable pressure is easy to understand. Even the simplest scuba regulators do this adequately, at all recreational diving depths and with remarkable reliability.

Regulator Terminology:regs

To understand how scuba diving regulators work, it is important to become familiar with some basic regulator vocabulary and concepts.

First Stage: The first stage of a scuba diving regulator is the part of the regulator that attaches to the tank valve.

Second Stage: The second stage of a scuba diving regulator is the part that the diver puts into his mouth.

Tank Pressure: The pressure of the air in a scuba tank. Air inside a tank is compressed to a very high pressure in order to carry an adequate supply of breathing gas for a scuba dive. A full scuba tank is often pressurized to 3000 psi.

Intermediate Pressure: The pressure of the air output from the first stage and sent to the second stage. Common intermediate pressures are around 125 – 150 psi above ambient pressure.

Ambient Pressure: The pressure surrounding a diver. Ambient pressure underwater is greater than pressure at the surface because pressure increases with depth. A scuba diving regulator delivers air to a diver’s lungs at ambient pressure. Since the ambient pressure changes as a diver changes depth, scuba diving regulators must adjust the air delivered to ambient pressure as a diver ascends and descends.

How Do Regulators Work?:

Scuba regulators reduce tank pressure in two steps. The first step of pressure reduction is from tank pressure to intermediate pressure, and the second step of pressure reduction is from intermediate pressure to ambient pressure.

The Regulator First Stage:First Stage

The first stage reduces air at tank pressure to intermediate pressure, and releases the intermediate pressure air into a hose which feeds into the regulator’s second stage. The way the regulator first stage reduces tank pressure is ingenious.

1. A first stage consists of two air chambers separated by a valve. When the regulator is not pressurized this valve is open. When connected to a tank, air from the scuba tank flows into the first chamber, through the valve, and into the second chamber. The valve between the two chambers stays open until the air in the second chamber reaches intermediate pressure.

2. Once the air in the second chamber reaches intermediate pressure, the valve between the two chambers closes, preventing the high pressure air from the tank from flowing into the second chamber.

3. When a diver inhales, air from the second chamber is released to the second stage.

4. As the air in the second chamber is released, the pressure in the second chamber drops, allowing the valve between the two chambers to open. Air flows from the first chamber into the second chamber until the pressure in the second chamber rises to intermediate pressure and once again forces the valve between the two chambers closed.

The Regulator Second Stage:800px-Scuba_regulator_2nd_stage_animation

The second stage reduces air from intermediate pressure to ambient pressure so that a diver may safely and comfortably breathe. Another important feature of a second stage is that it allows air to flow to the diver’s mouth only when he inhales. This is a vital feature of scuba diving regulators as a constant flow of air would deplete the tank very quickly.

1. The second stage consists of a single air chamber with a valve in the inlet fitting for the hose from the first stage. This valve stays closed except when a diver inhales, and separates intermediate pressure air in the hose from ambient air in the second stage.

2. The second stage uses a flexible silicone diaphragm to seal water out and air inside. There is a lever that rests against the diaphragm on the interior of the second stage. This lever operates the valve in the inlet fitting.

3. When a diver inhales, he lowers the air pressure inside the second stage by taking some of its air into his lungs. This allows water on the outside to push the diaphragm in slightly, which pushes on the lever, opening the valve, and allowing air to rush in until the pressure equals the outside water pressure, which is ambient pressure.

The simple genius of this design is that the water pressure surrounding the regulator creates the ambient pressure. The result is that the second stage automatically adjusts to the diver’s depth.

 

Aluminium vs. Steel Scuba Cylinders

 

What is the difference between steel and aluminium scuba tanks?  Divers never give much thought to what their air cylinder is made of, but it can affect your dive.

Cylinders are made out of two types of material: steel and aluminium

Aluminium is softer than steel.   Aluminium tanks must have thicker walls than steel tanks to hold air at a comparable pressure.   Aluminium is softer than steel, it scratches and dents more easily.   An aluminium cylinder is larger and heavier than a similar capacity steel cylinder.  They also don’t handle overfilling nearly as well.  Aluminium tanks are far more tolerant of corrosion from salt water.

Steel tanks may rust in the presence of moisture.   They are more likely to be damaged by improper fills containing moisture than aluminium tanks, and may require periodic tumbling (a process which removes oxidation from the inside of the tank).

Buoyancy Characteristics of Steel and Aluminium Tanks

The type of cylinder you use only has one major effect on your diving: your buoyancy.

As a diver empties his tank by breathing from it, the tank becomes lighter.   Aluminium has a particularly annoying characteristic; it becomes positively buoyant as they are emptied while steel tanks only become less negatively buoyant as they are emptied.   Whether a diver dives with a steel or an aluminium tank, he must compensate for the increased buoyancy of his tanks near the end of a dive.  A full aluminium cylinder will sink while an empty will float. This makes it harder to pin down a perfect weighting for the entire length of a dive.

This is why during a proper buoyancy check it is recommended to use a near-empty cylinder, or add weight to compensate.  The usual recommendation is to add about 2 kg to your base weighting to compensate for an aluminium cylinder.

Durability of Steel vs Aluminium Tanks:

When properly cared for, steel tanks generally last longer.   Steel is a harder metal  than aluminium, and is less likely to pit or dent.   Steel may rust, but with proper care most rust can be avoided. Any rust discovered during a visual inspection can be removed by tumbling the tank.

Aluminium tanks may develop cracks or fractures in the tank neck threads where the valve screws into the tank. These cracks can cause  gas loss, and a tank with a cracked thread is unusable. The tank neck threads of aluminium tanks are inspected during the standard visual inspection, and this problem is usually caught before it becomes dangerous

Steel tanks weigh less, are smaller and more durable, and require that a diver use less weight than standard aluminium tanks. However, aluminium  tanks are so much cheaper than steel tanks that they have rapidly become the industry standard.