Failure of back-plate single tank adapter (Bolts)

[apivonka]

Hope this helps someone else.

Spent the wknd in Florida's east coast and had a great time, until.

Last of five dive wknd and this happened as I was getting back into the boat on the ladder.

Single Tank Adapter separated from back-plate and tank also had 4.00 lbs extra weight in pockets. I run a long hose setup and had clipped off the primary to my d-Ring and use my snorkel to swim/wait for the boat.

As I climbed up the ladder, the tank separated from the back plate and fell back into the water, which pulled me back into the water. Entire system was separating and the tank was going down/floating away and dragging me via the short hose (bungee'd to my neck).

Got the short hose off my neck (lost snorkel and mask in process) and grabbed the attached long hose primary back in my mouth. I got back to the boat (After dropping weights) and with the help of others got all the pieces back on the boat including the tank.

Back-plate, harness still attached to me, single tank adapter and tank cam bands attached to the tank and my wing floating around in the water like a life vest.

Come to find out both single tank adapter bolts were gone and no signs of stress on the back-plate.

Ok, I see and have experienced a point(s) of failure with a single tank adapter.
1) Two stainless steel bolts with wing nuts (how they failed is beyond me this was dive 30 on this setup)
2) All the load was on the two bolts. Failure was the tank separated from the back-plate.

I'm going to research a way to route the cam-bands through the back-plate and use the adapter (instead of through the single tank adapter) and have the adapter also attach to the back-plate.
This will put all the weight of the tank on the back-plate + cam-bands and not on two bolts.


Thoughts/suggestions

 

[Ghetto Diver]

I have had mine loosen, but that's it.
If your plate is a DR/copy..ditch the adapter. I don't use one on my SS plate, only on an old ABS plate.

Eta: Heaviest tanks I use are Faber 117s

 

[Diver below 83]

What rig are you using? Are you sure your plate even needs the STA?

 

[apivonka]

HOG Wing & Stainless Steel BP

 

[Landau]

Were there lock nuts of some type on the wing nuts? (Nylon inserts in the nuts, lock washers, locktite etc) Could they have just loosened over time and fallen off?

Time to switch to a BCD, no bolts to fail

 

[saxman242]

I had a similar thing happen in the pool when I first got my bp/w. The wing nuts decided to work their way loose and fall off. I've found that adding some lock washers and being sure to check and tighten the bolts every time I change tanks has cured the problem.

I also agree with others that if your wing allows to go without an sta and you don't need it for other reasons, get rid of it and go without.

 

[johndiver999]

Does it make sense that the wing nuts or nuts backed off and fell out?

I rig my single tank BP/W by always running the tank cam bands through the plate itself. The STA is held by bolts and they serve to primarily hold the plate wing and STA in one fixed unit at all times. I think I recall, taking a drill, jig saw and file in order to make new or place slots in revised locations. I'm pretty sure I wanted to avoid double tank cam bands on one rig, so I had to make a new, centrally located slot location on that plate.

It is pretty easy to work with aluminum plate, SS would be a pain to work with if you have just rudimentary skills and tools like me.

 

[Marie13]

Mine loosen after dives but I just tighten them.

 

[JMBL]

Were there lock nuts of some type on the wing nuts? (Nylon inserts in the nuts, lock washers, locktite etc) Could they have just loosened over time and fallen off?

Time to switch to a BCD, no bolts to fail

I use that kind of nuts on my rig as well, and I check them also. So far, never got loose.

 

[rhwestfall]

are lock washers being used?