kjpwong:
g'day fellas,
i m looking to get my regs soon. there are just a few questions hope you guys can help me out.
i) what are diaphram/ piston?
ii) balanced/ unbalanced?
iii) are metal regs more reliable and durable than plastics?
iv) do most regs come with a backup reg?
v) if not, are there specified backup regs or simply get a cheaper one?
cheers
Wow. The answers to your questions could fill a book. Actually they have. I'll try a thumbnail.
i) The diaphragm or piston is the main pressure sensing element of the regulator. It is also what provides the power to make the valve work. A diaphragm regulator is generally more resistant to freeze-ups in cold water but is more temperamental, requires more careful service and has many more parts. A well designed piston regulator can deliver more air flow and is much more simple in design. Some piston regulators have as few as one moving part. Service is very straight forward. The downsides for piston regulators is that they tend to freeze up more easily, suffer from contaminants in the water mucking up their insides and some of the older designs may not perform as well when used with high pressure cylinders.
ii) An unbalanced first stage regulator will allow the intermediate pressure (in the hose to the second stage) fall slightly (about 12 psi) as the tank pressure drops during a dive. This reduction of intermediate pressure makes the second stage slightly harder to breath on as the dive progresses. A balanced first stage keeps the intermediate pressure constant throughout the dive. Balanced second stages use a balancing chamber to reduce the effort of breathing. With regulators with very small diaphragms, the use of a balance chamber partially makes up for the fact that small diaphragms cannot produce enough force to adequately operate the regulator valve.
iii) Virtually all first stage regulators are metal. Most second stages today are made of plastic. Plastic is lighter and therefore reduces jaw fatigue. There is a difference, however in the plastics used. Some are prone to breakage. Care must always be taken with plastics (and soft metals) not to tighten connections so hard as to break or strip threads.
iv) Virtually no regulators come packaged from the manufacturer with a back-up regulator. The regulator is usually sold as a first stage with one hose and one second stage. You must purchase your SPG and back-up regulator separately and assemble them to your regulator. The BC inflator hose comes with the BC.
v) You can put just about any second stage regulator on your first stage to use as a back-up. I recommend that you use a good-quality, extra-reliable unbalanced second stage, such as the ScubaPro R190. Put the back-up on the short hose that came with your original regulator and put your primary first stage on the longer hose that comes with the "octopus."
Hope this helps.
