Note From seahunt...
Look in any scuba magazine and you will see lots of up to the minute gear reviews.
What you won't find is a gear analysis. Calling on his many years in the industry,
Jim has created a description of dive gear that won't be found anywhere else. This
tells what a diver should know about the development and nature of the gear they use.
It also tells the weak points in that gear and how they can be avoided.
There are 2 parts to this:
Part 1. - BC Failure Points
Part 2. - Regulators
One of the safety issues that many divers fail to recognize is the potential of
Failure Points in their life support equipment.
When buying Diving Equipment, divers seem to be looking more at the features,
price, and color then anything else. Instead, maybe they should be looking at
the design and the practically of the product.
After diving for over 30 years and taking care of Scuba Toys rental department for the last 26 years, I have seen lots of equipment failure points. This is a discussion of the potential failure points with BC Systems.
BC's have the potential for the lots of failure points.
Rapid Dump Valves on the elbow joint of the oral inflation hose has a high
potential for failure. I have seen many of the "RE" values fail (when they fail
you can't get any air in the BC) this is a high maintenance accessory that you
don't need.
Overpressure Relief Valves also has a high potential for failure. Most
have failed because of poor maintenance. You need a relief valve on your BC,
but you don't need 3 of them like some of the new BC's have (the less holes in
the bladder of your BC the better off you are).
Power Inflators have always been one the weakest points in our life support
equipment. They have a high failure rate and need lots of maintenance. Most
cannot be fixed. When they start leaking or self-inflating, you need to buy a
new one.
Poorly designed integrated weight release systems.
These seem to
fall into two catagories either the weights fall-out to easily or you can't
get them out at all. This is something that the diver needs to try out before
they buy the product.
Quick release buckles on your shoulder harness. I have seen many plastic
buckles stepped on and broken. Most of todays BC have Quick release buckles,
the only way to eliminate this potential failure point is to go to a back-plate
with nylon webbing.
There are potential Failure Points in all of our gear, but what we need to do is
to recognize that they are there and eliminate them.
The color, features, and price makes little difference when a piece of Life
Support Equipment fails on a dive.
One of the key pieces of life support equipment is our Scuba regulators.
I don't think that any discussion of Scuba Regulators can be done
without some regulator theory.
The First Stage
There are three types of First Stages on the market today, a balanced piston, a balanced diaphragm, and an unbalanced piston. Almost all the balance piston regulators today are copys of the Scubapro Mark 5, almost all balanced diaphragms we see today are copys of US Divers Conself. The unbalanced regulators are copys I think of an old Healthways design (1960's?).
I have always liked the balanced piston 1st stages, they have fewer moving parts (2) and seem to give more volume then the balanced diaphragm. The balance diaphragm is easy to repair and tune, but has up to 10 moving parts and doesn't give the same volume. The unbalance piston has 2 moving parts. It's simple and works good in shallow water at high tank pressures.
Failure Points:
Almost all the 1st stage failures I have seen have
been from poor maintenance or bad parts from the manufacturer. There
is nothing you can do about the manufacturer , but you can keep
the maintenance up on your regulator. Here are some things to look
for on your regulator:
What does your filter screen look like (is it
green, red, white, if they are, have the reg. checked) I have seen
filters so plugged up with rust that they froze the 1st stage.
Is your 1st leaking air (you and your Buddy should do a bubble check in
the water before you make your dive). If it is, where is it leaking
from and how much? This may be a reason to terminate your dive (I know
that most Sherwood 1st Stages leak air out of their one-way bleed value,
but that is not what I'm talking about).
Take a look at your low pressure and HP hose fittings. The LP and HP
hoses are potential failure points.
If you have hose protectors, you should pull them away from the hose
fitting so this area can dry out. You should never have a hose protectors
on your HP hose. The HP hose will usually balloon at the fitting before
it blows, (and they all blow). If you have a hose protector on this hose
you can't see it.
Your pressure guage spool is another potential failure
point (this is the hollow tube that goes in-between the HP hose and the
pressure guage. It has O-rings on both sides of the tube and seals off the
HP hose and guage). If this not maintained it will seize and break off (if
this happens UW you will lose lots of air, fast).
One last thought on
this, I think that the DIN connector is a better fitting then the Yoke.
The DIN captures the tank valve O-ring better then the yoke and is more
streamlined.
Second Stages:
There are two categories of second stages the downstream
balanced and downstream unbalanced. The pneumatically balanced downstream
second stage was developed by Scubapro in 1985 (G250) and has become the
standard for easy breathing regulators. The balancing is accomplished by
the incoming air pushing equally on both ends of the poppet. With the air
balanced a lighter spring can be used for response smoothness and minimum
breathing effort.
The unbalanced downstream 2nd stage are simple lever and poppet assembles. When inhalation vacuum begins, the diaphragm is drawn inward, depressing the lever and opening the poppet against the spring. Air then flows through the aspirator into the breathing chamber as long as the inhalation continues. The unbalanced downstream 2nd stage has been around for a long time. But they don't give you anywhere near the volume of gas or the smoothness of breathing that the balance units do.
The term downstream indicates that the valve opens in the same direction as the air flow for the first stage.( there are also upstream second stages and tilt valves, we can discuss them at another time).
Failure Points:
I think that 2nd stage failure points fall into 3
catagorys; too much air, not enough air or water leaking in the 2nd stage.
If your regulator is free flowing (to much air) there could be a number of
things wrong: to high of a IP (reg. needs an overhaul), sand, salt build-up
(you need to clean you reg. better take it to a dive shop and have them show
you how to open it up and clean it). If you have a viva system on your reg.
it may cause the regulator to free flow on the surface when it's out
of your month (turn it off).
If your regulator is hard to breath it could be happening because the regulator is poorly tuned or maybe that just the way it breaths. There are alot of poorly engineered regulators on the market today, some just don't breath good when you put a load on them. You should buy the best breathing regulator on the market. Price should not make a difference with your breathing machine).
If your regulator is leaking water, it could be caused buy one of five
reasons.
There is more but I think I'm going to quit, this has gotten way to long. I hope that this post helps some of you understand a little bit about how your regulator works and helps you to recognize some of the potential failure points (so you can do something about them).
So which regulator should I get then?
I like the ScubaPro G250/Mark 20 better than the G500. I always felt that
the G500's were made more from a marketing stand point than an engineering
one (Scubapro's answer to the Atomic regulators).
For a smaller light weight second stage, the Atomic B1-T2 would be my
choice. If you look at the engineering of the G250 and the T2 you would find
that they are almost the same. This is not surprising since both were designed
by the same guys.
One other note about Atomic: Atomic is the only regulator
manufacturer that I know that test the breathing resistance of each regulator
they sell (at a depth of 150 ft. and records it).
If you look at price, the
B1-T2 is about $50 more then the G250/Mark20. The G250 and the T2 are two of
the best Regulators on the market today. Either one would be a good choice.