Leaky Solenoid and high PPO2

Padipro · October 13th, 2008, 10:44 PM

I originally posted this on RBW but thought it was relevant to post it here as well now that the rebreather thread seems to have taken off. It's an example of how proper training can help you make it out of what could be a bad situation. Thanks Jill.

Hello Kitty (Netmage) and I were diving the Capt Dan on Saturday morning when I had to thumb the dive because of a creeping PPO2.

My assembly set point checks the night before were perfect. The rig maintained set point with no creep. The predive checks went just as well with no indication of anything abnormal. Even during the descent there was no indication of anything wrong. When we made it to the wreck I changed the set point to 1.2, confirmed that the solenoid was firing and then headed toward the bow following Hello Kitty. I checked the PPO2 about 20 to 30 seconds later and it was at 1.3 on all three cells. At first I figured that I had just descended a little to far and had over run the set point so I watched it figuring I'd just breath it down but instead it continued to rise. At 1.4 I did a Dil flush bringing the PPO2 down to about 1.0 and watched it rise back to 1.3. I did another Dil flush when I noticed a barely audible hiss. At first I thought it was a boat passing over head but soon realized, as the PPO2 was again rising, that it was the solenoid stuck open. I immediately shut down the O2 tank valve and the hiss quickly faded. By this time Hello Kitty had returned to see what was keeping me. I signaled to him that I had a problem but I was able to manage it by feathering the tank valve and told him my dive was over and I was headed back to the line. I felt comfortable enough to ascend on my own so I ascended slowly feathering the valve until I reached the surface. Once there I just opened the O2 tank valve, monitored the PPO2 and climbed back on the boat.

When I got home I tore down the solenoid and found the cause of the problem. Check out the picture below. That little black rubber hose shaving on the left was right in the middle of the valve seat keeping it from closing completely.

Looking on the bright side I now know I can handle a stuck solenoid and feather the valve to control the PPO2.

almity1 · October 13th, 2008, 11:07 PM

Glad you made it OK and thanks for sharing...

Not just Good Training, a level head as well.

Helps that the Meg has a loud hiss as well.

How do you think the offending material got in????

Padipro · October 13th, 2008, 11:15 PM

I had the O2 injection hose shortened so it would run straight up the side of the can to the quick disconnect. I added a 90 degree elbow so the hose wouldn't bow out like it does from the factory and I figure that when the new end was crimped on the small shaving was stuck inside the hose and it finally worked it's way out.

Here's a picture of the mod I did to the O2 QD.

almity1 · October 13th, 2008, 11:38 PM

Wow!!!!

So the infringing item was blown through the 02 Nozzle - Connection, through the coiled piping into the solenoid.

It was the solenoid that caught it...

Padipro · October 13th, 2008, 11:56 PM

Yes, it was stuck on the seat of the solenoid and wouldn't allow it to seal and shut off the gas flow. Even turning the gas supply off and on during the ascent and after surfacing wouldn't dislodge it. I had to remove the solenoid and take the entire thing apart to remove it. There is an inline filter that can be installed by ISC that is supposed to prevent this but I don't have that filter installed. It's on my short list of things to have done right along with the latest software update. I'm also going to install an inline shutoff on the O2 injection hose, like the one on the ADV, so if something like this ever happens again I won't have to mess with feathering the tank valve. I just shut off the slider and use the manual add button.

RebreatherPro · October 15th, 2008, 08:12 PM

Hey, I'm glad everything worked out. That is interesting "detritus" in the solenoid. Most leaks I've seen over the years have been from rust build up... especially from connecting the oxygen supply when it is wet with salt water. At first I thought you were going to tell us it was a hair ball from Hello Kitty!
Jill

Padipro · October 15th, 2008, 08:54 PM

I was surprised myself, I figured it was rust as well. After diving in saltwater for over a year and half I fully expected it but when I pulled the solenoid apart that there wasn't even the slightest bit of rust anywhere. Just that little shaving of rubber stuck to the seat.

Thanks again Jill for the great training that allowed me to deal with the problem in the appropriate way and walk away from what could have been a bad situation.

I wish I had thought of blaming it on Hello Kitty, Lord knows we blame everything else on him.