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35 Cards in this Set
- Front
- Back
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What is a burst disk? |
A think copper disk located in the tank valve designed to blow if over-pressurized.
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Where is a burst disk located?
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In the tank valve.
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Which kind of valve will fail into freeflow, downstream valves or upstream valves?
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Downstream valves.
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Does a downstream valve open with the air flow or against the air flow?
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With the air flow - the pressure is trying to open the valve.
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In a balanced regulator, does the air pressure resist, assist, or neither, the opening of the valve?
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Neither. A balanced regulator breathes the same regardless of tank pressure.
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What is the downside of a balanced regulator?
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More complex mechanisms.
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Which kind of SPG is a clear tube open at one end?
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Capillary tube. Accurate down to 30 feet.
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What are characteristics of a capillary depth gauge?
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Made from clear tubing open at one end; accurate down to 30 feet; rugged; reads theoretical depths at altitude.
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Which kind of SPG is a spiral shaped tube open at one end?
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Open Bourdon Tube Gauge.
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What are characteristics of a Bourdon tube gauge?
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Very common; very accurate. At altitude, reads shallower than actual depth.
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Which kind of SPG is a series of levers and gears that move the needle?
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Diaphragm gauge.
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What are characteristics of a diaphragm gauge?
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Very accurate, but expensive.
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Which kind of SPG uses a transducer?
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Digital gauges.
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What are characteristics of a digital gauge?
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Easy to read, integrated into computers, may adjust for altitude automatically, expensive.
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Which gauge reads theoretical depths when at altitude?
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Capillary depth gauge.
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How often are hydrostatic tests done in the USA?
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Every five years.
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How often are hydrostatic tests done in the UK?
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Every four years.
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What temperature requires a tank to be hydrostatically tested?
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180F.
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A tank marked:
DOT/CTC 3AA 2250 12345 PST 6*96+ Is made from what metal? |
Steel - 3AA = steel, 3AL = Aluminum.
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A tank marked:
DOT/CTC 3AA 2250 12345 PST 6*96+ has what working pressure? |
2250 PSI.
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A tank marked:
DOT/CTC 3AA 2250 12345 PST 6*96+ Has what date of last hydro inspection? |
6/96
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A tank marked:
DOT/CTC 3AA 2250 12345 PST 6*96+ What does the plus sign mean? |
Tank is allowed a 10% overfill.
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A tank marked:
DOT/CTC 3AA 2250 12345 PST 6*96+ What is the serial number? |
12345.
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What are the tank markings for aluminum and steel?
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Aluminum = 3AL
Steel = 3AA |
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Aluminum vs. steel - which has thicker tanks?
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Aluminum.
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Aluminum vs. steel - which is stronger?
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Steel.
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Aluminum vs. steel - which corrodes less?
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Aluminum.
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Aluminum vs. steel - which require more weight when diving?
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Aluminum - require bigger cylinders = more displacement = more buoyant.
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Aluminum vs. steel - which has greater capacity?
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No clear winner. Steel has thinner walls so more cubic feet volume, aluminum has greater pressure, so AL has same or slightly higher capacity.
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What are the steps in hydrostatic testing of tanks?
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- 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 |
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In hydrostatic testing, what is actually being tested?
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The elasticity of the tank.
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What are the benefits of DIN valves over yoke valves?
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DIN valves make better seals since o-rings are trapped between two valves
The connection to the tank is stronger due to threads |
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How many atmospheres are in a typical AL80 tank pressurized to 3000 PSI?
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Roughly 200. One atmosphere at sea level is roughly 14.7 PSI, so 3000 / 14.7 = 204 ata.
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What is the PSI to ATA conversion factor?
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1 ATA = 14.7 PSI.
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How much does the air in a scuba tank weigh?
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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.
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