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Gear Miester answers your gear questions about REGULATORS...

Life Support

As the spring/summer season approaches, a diver’s heart turns to thoughts of … breathing underwater! (What did you think I was going to say??) This month, we’ll begin a discussion of the gear that allows us to breathe underwater - our regulator. This is perhaps the most important piece of gear. Think of it as your underwater life support system.

Be informed

A regulator is neither as simple nor as complicated as most divers think. For most of us, our regulator does its job, and we are content. But, when it’s time to shop for a regulator, a good understanding of how it works will help you to make a more informed decision.

First things first

In general terms, the regulator consists of a first stage which attaches to the tank and a second stage which goes in the diver's mouth. The first stage takes the high pressure gas from the tank, reduces it to an intermediate pressure and sends it to the second stage. The second stage takes the intermediate pressure air and reduces it to slightly above the surrounding water pressure. Voila! We're breathing underwater.

 

 

 

To begin our discussion, let’s dive into some of the design terminology of the first stage – stuff  that maybe you have heard but aren’t really sure what it means. Here goes:

 

Breathing Resistance refers to the amount of diver effort involved in getting air from the regulator. It is often depicted in a series of complicated looking graphs for inhalation and exhalation. Put simply: the lower the resistance, the easier the diver finds it to inhale and exhale. However, there is a point where too little resistance can be a problem leading to free flows. These “work of breathing” curves also change with depth. So when you’re comparing regulator performance, make sure you’re comparing them at similar depths.  All that being said, most modern regulators will breathe comfortably for most divers in most situations. However, at deeper depths, you will definitely notice a difference between a high performance and a low performance regulator.

Diaphragm or Piston addresses the basic design of the first stage. When you take a breath from your second stage, it lowers the pressure in the first stage. That lower pressure allows a valve in the first stage to open, allowing air from the tank to enter the first stage and replenish the air that you breathed. When the system is back in equilibrium, the valve closes and the airflow stops until you breathe again.

The mechanism that opens and closes the valve to allow replenishment of air is either a piston or diaphragm. Does it really matter to you? Probably not. Both piston and diaphragm designs are used in the entire range of regulators from the low end to the high end. In general, piston regs have fewer moving parts and may be easier to work on. Diaphragm regs are less prone to corrosion since the internal parts are separated from contact with the water. This might be a plus if you spend a lot of time in salt water

Balanced or Unbalanced No, this does not refer to divers as opposed to nondivers (at least in this context!) This refers to whether the effort of breathing changes as the tank pressure decreases during the course of a dive. Unbalanced first stages use the air pressure from the tank to help open the valves in the first stage. As the tank pressure gets lower, breathing resistance increases. (Back in the day before submersible pressure gauges, this was an indicator that your tank was almost empty!) Nowadays, most modern first stages use a balanced design where tank pressure has no effect on the breathing resistance. In other words, a balanced regulator breathes roughly the same at any tank pressure.

Ports are either high pressure or low pressure and allow for the attachment of the various hoses and equipment that divers use. High pressure ports are used almost exclusively for attachment of the submersible pressure gage (or hoseless transmitter.) Low pressure ports are for most other equipment - second stages, low pressure inflator, and dry suit inflators. Worried about hooking a low pressure hose to a high pressure port? Don’t worry – the ports and hoses are different sizes so you can’t make that mistake!

Environmentally sealed means that the interior parts of the first stage are not open to the water. This helps to prevent contamination, corrosion, and icing. If you plan on diving in really dirty water or extremely cold water, you might want to consider an environmentally sealed first stage. Otherwise, it’s not really needed.

 

Yoke and DIN are two ways that the first stage attaches to the cylinder.

Yoke 1st stage reg systems are commonly seen in the United States and on rental tanks. They fit over the cylinder valve and use a large screw to pull the first stage into place.

 

 

 

 

 

 

 

 

 

DIN regs are more prevalent in Europe.
A DIN system has a male threaded end that screws into a female threaded end in the cylinder valve. Although a little more complicated, DIN systems do have some advantages over yoke systems. First, a DIN system can easily be adapted to fit on a yoke cylinder valve. The opposite is not usually true. Second, DIN systems come in 5 thread and 7 thread variations - the 7 thread version can be used with cylinder pressures above 3000 psi (200 bar). Most regulators come in a yoke and DIN version depending on your needs.

 

Coming up next month...

We’ll put our money where our mouth is and talk about second stages.