Failure of a swivel O-ring causes an emergency ascent.
Reported Story
We were six minutes into the dive at a depth of 14 meters when the dive guide spotted a stingray. I followed him down, and within three minutes we reached a depth of 20 meters. I filmed the stingray for one minute, then I ascended to 17 meters for three minutes and to 15 meters in another three minutes. At that point (total dive time 18 minutes) I heard a loud bang and some screaming. I looked around and saw my buddy above me at about 10 meters taking pictures. We had an arrangement that if I followed the dive guide when he showed us underwater objects, the dive guide would become my temporary dive buddy and my buddy could stay behind.
Photo 1: Swivel leaking air, front view (Photo by David Blackmon)While I was looking around for the origin of the screaming, a stream of bubbles came up from my regulator: It was the source of the “screaming” (see Photo 1). When I took the regulator out of my mouth to check the problem, I saw that all the air was coming out of my swivel. I started finning toward our dive guide.
The dive guide saw me swimming toward him with my regulator in my hand. He finned fast toward me and immediately gave me his own regulator. My cylinder was becoming buoyant and pulling us toward the surface. The dive guide spread his fins to slow down the ascent. This whole incident took less than two minutes. I was calm and had taken a deep breath of air just before all this happened.
I was concerned about the buoyancy of my aluminum 15l-cylinder. Unfortunately, my cylinder was positioned lower than normal because I was filming, so I knew I could not reach it. I should learn to film with a first stage close within my reach.
Photo 2: Swivel leaking air, side view (Photo by David Blackmon)The zodiac of the liveaboard was waiting for us at the surface. It took me back to the boat, and the guide went back down to assist other divers. I rested by lying down for the first half-hour and drank small sips of water. After that, I looked at my diving gear. I removed the swivel right next to my regulator. The O-ring was sticking out of the swivel.
I tried to think back to what might have been the cause of this equipment malfunction. My equipment was serviced before my trip by the best diving store in Holland. I am careful with all my diving gear and always check each item before the buddy check. The only thing I can think of is that at one moment during the last dive the swivel turned without resistance. I did not realize this should cause concern. The online report form required some equipment details. I could not provide any because there were no labels on the swivel whatsoever. I do not recollect receiving any documentation about the swivel when I bought my diving equipment.
I removed the swivel and will not use it again. Currently, many brands of regulators are sold with attached swivels. Incidents like this may occur in the future, and divers need to be warned about this hazard. I am writing a diving blog about this for a Dutch diving magazine. I hope this will spread the warning that a diver should check the swivel rotation friction. If it is too smooth, there is a chance for an O-ring to blow out.
I was using the minimum amount of lead. I have measured the weight so that by an almost empty tank I could still be able to stay below the surface, but it was not enough for a completely empty tank. I should have taken some extra weights.
Comment
Photo 3: The swivel connects the second-stage regulator and low-pressure hose. (Photo by David Blackmon)A swivel is a piece of equipment that is supposed to make it easier to keep the mouthpiece in the mouth. It is a kind of hollow joint that is implanted between the second-stage regulator and the low-pressure supply hose. It enables rotation up to 360 degrees. Any interpolation of this kind introduces additional potential failure points. Failure of early models was not uncommon.
Improvements in design and quality of materials used contributed to near eradication of swivel failures. However, the potential is always there. Not all failures can be prevented, and thus divers must be ready for emergency procedures. In a case like this, closing the tank valve and receiving air from a buddy would do for a safe ascent. However, as stated in the report, the tank valve was out of reach, and the diver could not prevent the tank from getting empty. As a result, the empty tank caused buoyancy problems and a faster than optimal ascent. Fortunately, this incident did not cause any injuries.
It is always a good practice to make sure that all vital equipment is unobstructed and within easy reach.
Dr. Petar J. Denoble, MD. D.Sc