A series of short, semi-technical, articles covering the
functions, limitations and basic maintenance of the vital parts that, together, make modern SCUBA diving equipment
so easy to use, reliable, and safe.
1. Your Regulator... by Dave Gledhill (Club Nautique Nerja's Proprietor and Chief Instructor)
Your regulator is the most crucial part of your underwater life support system and should be cared-for accordingly. In training, the skills you learn enable you to cope with buoyancy control, regulator replacement, mask clearing etc., but how would you handle the
sudden and total loss of air at depth? No equipment failure could be more
frightening, panic-inducing, or potentially life-threatening.
A diving regulator is like any other pneumatic valve in that it regulates high pressure gas down to a usable lower pressure. In
diving, the gas is either air or a derivative of air, and the usable pressure is the ambient pressure at whatever depth the regulator happens to be at.
Fully compressed cylinder air is at approximately 200 BAR, which is nominally 200 x the air pressure at sea level
or 3,000psi. A correctly functioning diving regulator system reduces this extremely high pressure to whatever the ambient pressure is, at any given depth.
e.g. 1
BAR, or 14.7 psi at the surface.
In addition to regulating pressure, the system is required to provide an adequate air flow to meet the varying requirements of
the diver, at any time, and at any depth within its specified operating range.
To reliably achieve this dual function, the regulator system requires two stages. The first stage
connects directly to the high-pressure cylinder and has only one aim in life: to provide a reliable outlet pressure of between 8 and10 BAR
above ambient.... regardless of how much pressure remains in the cylinder; regardless of depth; and regardless of the rate of air flow through it.
This is achieved by a surprisingly simple, but ingenious arrangement of a spring, a piston or diaphragm and a control valve. The valve is allowed
to open until the pressure in the outlet chamber reaches 8 to 10 BAR above ambient, when it closes to prevent further increase.
The second stage is connected to the first stage by a flexible tube and its outlet feeds the diver's mouthpiece. It doesn't have the wide range of inlet
pressures to contend with but, in addition to having to regulate from 8 to 10 BAR above ambient, down to ambient, the second stage must also sense
and supply the diver's air demand and have a purging facility to expel water.
Second stage regulators are invariably diaphragm based (rather than piston). They work in a similar fashion to first stage regulators but also
serve as air demand valves.
The valve is activated by a lever connected to the diaphragm. As the diver breathes in, the pressure in the outlet chamber drops. This causes the
diaphragm to move the lever which then opens the valve to admit more air. The valve closes again when the diver breathes out. The increased
pressure from the diver's outgoing breath then opens the exhaust valve to expel the depleted air and the cycle repeats.
The purge control is a simple mechanical device that opens the control valve when it is operated. The influx of air at 8 to 10 BAR forces any
water out of the low-pressure chamber.
Taking Care of your Regulator
Diving regulators are generally used in salt water and should therefore be rinsed after every dive. However, even in fresh water, it is a good
habit to rinse regulator after every dive. N.B. Chlorine can be as harmful as salt.
It is extremely important to keep your regulator system sealed during rinsing because if water enters, it can cause many
problems later.
Before rinsing, most divers correctly fit the dust cap on the first stage but we have found that some tend to forget about another important water
entry point.
When the air supply is connected and turned on, it is safe to activate the second stage purge valve because air pressure prevents water entry.
However, this is not the case during rinsing.
Accidentally operating the purging mechanism opens the second stage air inlet valve and allows water from the rinse tank to freely flow up the
connecting hose into the low-pressure chamber of the first stage.
To rinse your Regulator safely and properly:
- Re-fit the dust cap after drying thoroughly. A cloth will do, but
fashion dictates a blast of air from your cylinder.
- Hold regulator system by its hoses and place in a tank of fresh water.
- Give it a swirl.
- Remove and hang up (optionally, re-connect to the cylinder and purge to absolutely ensure internal dryness).
Beyond basic cleaning, there is no additional user-level maintenance to do. Professional servicing involves inspection, lubrication,
adjustment and careful testing. This should be done at least annually unless the manufacturer's instructions dictate otherwise.
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