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.
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.
