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The Regulator or "first stage", probably the most important part of any dive equipment.
Regulators
There are four main types: Piston and Diaphragm and each of these can be balanced or unbalanced:
Unbalanced Piston Valve
- HP spring
- Ambient water pressure
- Intermediate chamber
- Valve and HP seat assembly
- HP air
- Air to second stage
- First stage unbalance piston
How it works
This valve operates by the opposing forces of the intermediate pressure and the main high pressure spring of the regulator. When the diver inhales, the intermediate pressure drops, causing the main spring pressure to move the piston towards the low pressure side. When the piston moves, it takes the valve off its seat, allowing air from the tank to enter and causing the intermediate pressure to rise. This pressure increase overcomes the main spring pressure, causing the piston to move to the closed position, thus closing the valve so no more air can enter from the cylinder.
Since this valve is still unbalanced, the valve is affected by the pressure change in the air entering from the tank. As tank pressure decreases the valve will alter its sensitivity and breathing actually becomes more laboured toward the lower pressure. This is because as the cylinder pressure drops, the intermediate pressure increases but due to the small orifice sizes dictated by the design of unbalanced valves, air flow is decreased so much that even with the higher intermediate pressure, breathing resistance is increased. Although these types of first stage valves are gradually being replaced with balanced valves there are still quite a few of them around today in numerous types of regulators.
Balanced Piston Valve
- Air to second stage
- Intermediate chamber
- HP spring
- Ambient water pressure
- HP air chamber
- Valve and HP seat assembly
- HP air
- Balanced piston assembly
How it works
This type of valve operates in the same manner as the unbalanced piston except that when the piston moves causing the valve to open, the valve is not influenced by the high pressure air coming from the tank. Thus the valve will open and close unaffected by the change in the tank pressure. This will provide a more consistent and smoother flow of regulated air to the second stage. With piston valves, two vital O ring seals inside the first stage are subject to malfunction if damaged by sand or salt crystals.
Unbalanced Diaphragm
- HP air
- HP air chamber
- Intermediate chamber
- Diaphragm
- Diaphragm balance spring
- Ambient water pressure
- Air to second stage
- Valve & HP seat assembly
- HP spring
How it works
This is also called an upstream first stage, since the valve seat is located on the upstream or high pressure side of the valve. As the diver inhales, a diaphragm flexes inward, pushing on a rod which causes the valve to open. Air flow is thus provided to the diver. The valve closes when the diaphragm is returned to it's relaxed position as the pressure builds up in the intermediate chamber and reaches a predetermined level.
A major disadvantage of this type of valves (as in all unbalanced first stage valves) is that the high pressure air acts directly on the valve, effecting the opening and closing of the valve.
To compensate for this effect, the valve opening is often made smaller but this in turn results in a reduced flow of air. This type of valve may be found in some older type regulators but has largely been phased out.
Balanced Diaphragm Valve
- Air to second stage
- Valve balance spring
- Intermediate chamber
- Diaphragm
- Balance spring
- Ambient water pressure
- Valve & HP seat assembly
- HP air
- HP air chamber
How it works
The operation of the balanced valve is essentially the same as the balanced piston valve, except that a flexible diaphragm is used to push the air valve open, instead of a metal piston. This valve was developed to eliminate the effects of the changes in the high pressure cylinder air on the first stage. Since the valve stem extends through the high pressure chamber into the intermediate air chamber that flows through the hose, the high pressure air from the cylinder cannot exert a closing force on the valve stem. The air pressure in the intermediate chamber acts to help balance the forces acting on the valve stem.
Second Stage Regulators
Most regulators manufactured today incorporate the use of downstream valves in second stages. This means that the valve seat is situated in the down-stream or after-side of the valve assembly and opens with the flow of air rather than against it. This is an important design feature since it allows the intermediate air pressure to assist in opening the valve. Thus if the first stage valve should malfunction the high pressure air would not damage the hose or the second stage. Instead it would force the open the second stage valve and cause the regulator to free flow while still providing air to the diver.
A Venturi can be found in the second stage of a demand valve and is used to reduce inhalation effort by operating the diaphragm with a servo effect.
Testing Second Stage Regulators
To inhale from a regulator, it would lift 20mm to 40 mm of water in a U tube, called a Manometer. A Magnahelic gauge is the same as a manometer, but is diaphragm operated, is expensive and needs calibrating regularly. A manometer on the other hand is self calibrating and cheap, but not as fast as the magnahelic gauge in getting results if mass testing.
Cold Water Regulators
Some regulators have been designed to resist the effect of jammed valves caused by cold (Free Flows). The idea of environmentally sealed first-stages is to keep water out. Examples of regulators with this advantage are the Apeks TX100, Aqua-lung Titan D and Cousteau Supra D, Dacor 360XP AER Pacer, Ocean Reef Polar Enterprise and Oceanic Delta II Sub Zero.
Some regulators, like the Poseidon Cyklon 5000 and Jetstream, and Beuchat VS8 and VS10, can be adapted with cold-water kits that use silicone grease.
Certain second-stages have specially coated moving parts to stop any ice from sticking. Examples include the Beuchat VS8 and VS10, Dacor 360XP AER Pacer, and Spiro Cousteau Arctic. Some plastic regulator second-stages such as the Apeks TX100, Spiro Cousteau Arctic, Aqua-lung Cryo, Mares V16 SCS-XTR and Sherwood Blizzard have additional metal heat-sinks.
It is strange to think that what might feel like very cold water is, in fact, warming up the much colder air coming from the scuba cylinder, but regulators with plenty of metal in their design to conduct this small amount of heat to the air tend to be less prone to freezing. Examples include the Mares Ruby and Dacor 960XLE.
Other manufacturers say their regulators are designed not to freeze. Scubapro says its Thermal Insulation System works, and that the cold air never cools down any water that might enter the regulator. TIS is fitted to all the latest Scubapro designs.
You never know how close your regulator comes to failing because of icing, even if it has the latest cold-water technology, because the cir-cumstances that make that subtle difference are so varied.
The only regulator now approved by the US Navy for cold-water use is the Poseidon Jetstream, which is quite an old design.
It's a good idea to practise the technique of making an ascent, breathing from a free-flowing regulator. This is a technique routinely taught by many training agencies.
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