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35 Cards in this Set

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What is a burst disk?
A think copper disk located in the tank valve designed to blow if over-pressurized.
Where is a burst disk located?
In the tank valve.
Which kind of valve will fail into freeflow, downstream valves or upstream valves?
Downstream valves.
Does a downstream valve open with the air flow or against the air flow?
With the air flow - the pressure is trying to open the valve.
In a balanced regulator, does the air pressure resist, assist, or neither, the opening of the valve?
Neither. A balanced regulator breathes the same regardless of tank pressure.
What is the downside of a balanced regulator?
More complex mechanisms.
Which kind of SPG is a clear tube open at one end?
Capillary tube. Accurate down to 30 feet.
What are characteristics of a capillary depth gauge?
Made from clear tubing open at one end; accurate down to 30 feet; rugged; reads theoretical depths at altitude.
Which kind of SPG is a spiral shaped tube open at one end?
Open Bourdon Tube Gauge.
What are characteristics of a Bourdon tube gauge?
Very common; very accurate. At altitude, reads shallower than actual depth.
Which kind of SPG is a series of levers and gears that move the needle?
Diaphragm gauge.
What are characteristics of a diaphragm gauge?
Very accurate, but expensive.
Which kind of SPG uses a transducer?
Digital gauges.
What are characteristics of a digital gauge?
Easy to read, integrated into computers, may adjust for altitude automatically, expensive.
Which gauge reads theoretical depths when at altitude?
Capillary depth gauge.
How often are hydrostatic tests done in the USA?
Every five years.
How often are hydrostatic tests done in the UK?
Every four years.
What temperature requires a tank to be hydrostatically tested?
180F.
A tank marked:

DOT/CTC 3AA 2250
12345 PST 6*96+

Is made from what metal?
Steel - 3AA = steel, 3AL = Aluminum.
A tank marked:

DOT/CTC 3AA 2250
12345 PST 6*96+

has what working pressure?
2250 PSI.
A tank marked:

DOT/CTC 3AA 2250
12345 PST 6*96+

Has what date of last hydro inspection?
6/96
A tank marked:

DOT/CTC 3AA 2250
12345 PST 6*96+

What does the plus sign mean?
Tank is allowed a 10% overfill.
A tank marked:

DOT/CTC 3AA 2250
12345 PST 6*96+

What is the serial number?
12345.
What are the tank markings for aluminum and steel?
Aluminum = 3AL

Steel = 3AA
Aluminum vs. steel - which has thicker tanks?
Aluminum.
Aluminum vs. steel - which is stronger?
Steel.
Aluminum vs. steel - which corrodes less?
Aluminum.
Aluminum vs. steel - which require more weight when diving?
Aluminum - require bigger cylinders = more displacement = more buoyant.
Aluminum vs. steel - which has greater capacity?
No clear winner. Steel has thinner walls so more cubic feet volume, aluminum has greater pressure, so AL has same or slightly higher capacity.
What are the steps in hydrostatic testing of tanks?
- Immerse tank in water and measure volume

- Fill tank mostly with water, over-pressurize, measure expansion of tank

- Release pressure and see if tank returned to normal size
In hydrostatic testing, what is actually being tested?
The elasticity of the tank.
What are the benefits of DIN valves over yoke valves?
DIN valves make better seals since o-rings are trapped between two valves

The connection to the tank is stronger due to threads
How many atmospheres are in a typical AL80 tank pressurized to 3000 PSI?
Roughly 200. One atmosphere at sea level is roughly 14.7 PSI, so 3000 / 14.7 = 204 ata.
What is the PSI to ATA conversion factor?
1 ATA = 14.7 PSI.
How much does the air in a scuba tank weigh?
6.5 pounds. Since you never breathe a tank dry, you can expect to be five pounds lighter at the end of the dive, or, five pounds more positively buoyant.