Most common open-circuit equipment malfunctions leading to problems?

[fuzzybabybunny]

I'm wondering what the most common equipment malfunctions are that can lead to serious problems. I can see the following being possible, but not sure how common they are.

- O-ring failure between the tank and first stage
- Stuck inflator mechanism on the BCD and/or drysuit

First stages are very reliable, right? Is it very rare for a first stage to suddenly stop delivering air or to leak air catastrophically?

Same story with a second stage as well, right? And if it does happen, you've got your backup.

Gauges don't suddenly stop working, right?

I'm thinking that the vast majority of accidents originate from the diver, not the equipment failing. Things like heart attacks, medical conditions underwater, not checking the SPG regularly enough, surfacing too fast, not making sure all threads and connections are tight, panic, not paying attention, too much exertion, etc.

 

[runsongas]

1st stages can fail at the hp seat, any number of orings, and the diaphragm. also the ACD/DVT if you have one of those

second stage freeflow failure means you have the choice of surfacing directly, performing a valve shutdown onto a fully separate redundant source, or valve feathering. gauges can blow out (that is why you point the gauge away from you when you first pressurize).

a bcd failure either at the dump valve or inflator can mean becoming very negatively buoyant if you are deep and diving wet. better drop those weights quick.

 

[GJC]

In my experience, the most common equipment failure is tank o rings on rental tanks. Most often it is a small leak you don't notice until you get in the water and your buddy sees a little stream of bubbles.

Second is regulator free flow on the first dive after servicing. This is caused when the seats have settled in and either the first stage IP is a little too high or the second stage seat needs a slight adjustment.

 

[KeithG]

Not looking at your spg?

 

[Lorenzoid]

. . .
I'm thinking that the vast majority of accidents originate from the diver, not the equipment failing. Things like heart attacks, medical conditions underwater, not checking the SPG regularly enough, surfacing too fast, not making sure all threads and connections are tight, panic, not paying attention, too much exertion, etc.

Yep. Properly serviced, gear is amazingly reliable.

 

[MaxBottomtime]

The common problems I have seen and/or encountered are the O-ring failure between the tank and first stage which can be resolved by using a DIN valve, sticking BC inflator which can be solved by either turning the inflator knob or disconnecting the hose. Routine maintenance helps to avoid these problems. Now drysuit leaks...they happen any time for no apparent reason!

 

[GJC]

Not looking at your spg?

Yep, operator errors are the biggest cause of injury and fatalities.

I also consider lack of maintenance and poor maintenance in the operator error category

 

[2airishuman]

I'm wondering what the most common equipment malfunctions are that can lead to serious problems. I can see the following being possible, but not sure how common they are.

- O-ring failure between the tank and first stage
- Stuck inflator mechanism on the BCD and/or drysuit

Stuck inflator is probably the largest source of accidents

Valve clogged by foreign material from cylinder
Burst disc blown even though overpressure does not exist
O-ring failure between cylinder and valve, usually due to corrosion of the cylinder or attempts to use a cylinder with a damaged o-ring seating area
Valve rolled off and broken by contact with wall or overhead

First stages are very reliable, right? Is it very rare for a first stage to suddenly stop delivering air or to leak air catastrophically?

Rare but it does happen, failure modes vary depending on design.

Diaphragm rupture
Diaphragm pulls out of clamping ring area
HP seat delaminates from opening mechanism
HP seat pin breakage
Freeflow due to accumulation of ice
Loss of air delivery due to main spring breakage

Same story with a second stage as well, right? And if it does happen, you've got your backup.

Diaphragm ripped by foreign object or inherent defect
Broken lever causing complete loss of airflow
Mouthpiece separation from regulator body
Diaphragm jammed open by mud or foreign object
Regulator separation from hose because it wasn't attached wrench tight
Rupture of hose

Gauges don't suddenly stop working, right?

Rupture of bourdon tube causing spg to explode
Gear train corrosion causing needle to stick. Usually not sudden (can affect digital also)
O-ring failure at spg swivel or 1st stage
Flare nut not tightened down causing spg to be lost and leak to ensue
Rupture of hose
Battery failure (digital)

I'm thinking that the vast majority of accidents originate from the diver, not the equipment failing. Things like heart attacks, medical conditions underwater, not checking the SPG regularly enough, surfacing too fast, not making sure all threads and connections are tight, panic, not paying attention, too much exertion, etc.

Probably. The equipment failures happen as well though

 

[scubadada]

In 1600 dives, have not had a serious gear malfunction. Extruded O ring on an SPG x1, extruded O ring on a transmitter x1, leaking spool on an SPG x1, nothing else.

 

[eelnoraa]

a bcd failure either at the dump valve or inflator can mean becoming very negatively buoyant if you are deep and diving wet. better drop those weights quick

If you have a BC what does not have shoulder dumps, losing a butt dump basically doesn't effect much. You don't want to keep diving, but making a safe and control ascent without touching the weight is very doable