Sunday I had a pool session planned with some technical students. I was planning to do a little fun session to break things up with some odd or vintage regulators. I had an old Healthways tilt-valve regulator that I thought might be fun to play with, so I got it out and put it on a full tank to check it out. The o-ring at the hose to second stage was leaking so I stopped and did a quick repair. I opened up the regulator, replaced the o-ring and tightened the connection.
Now, this Healthways regulator had a second stage that was an old tilt valve design. A tilt valve is an upstream valve and an upstream valve will not relieve excess pressure that builds up in the intermediate pressure hose in case of a first stage freeflow. For this reason, there must be an overpressure valve installed.
After making my quick o-ring repair I replaced the regulator on the tank and slowly turned the air back on with my left hand as I held the second stage by the hose in my right. *BANG* The hose ruptured with the force and sound of a firecracker right where I was holding it. My ears were ringing and my hand stung like crazy. Those of you who have ever had a firecracker go off in your hand know what it felt like - multiplied by about two. Three days later my hand is still sore.
What happened, apparently, was that the first stage was leaking so that the intermediate presssure went up to a pressure that was more than the hose could handle. (Low pressure hoses are rated to something in the range of 350 to 450 psi and will burst at 3 or 4 times their rated pressure.) The overpressure relief valve (which was installed) failed to operate.
I have seen (and heard) low pressure hoses burst on at least three occasions in the past. This was the first time I sustained an injury. I am just glad it was nothing serious. It is a reminder that compressed air can be dangerous.
Now, this Healthways regulator had a second stage that was an old tilt valve design. A tilt valve is an upstream valve and an upstream valve will not relieve excess pressure that builds up in the intermediate pressure hose in case of a first stage freeflow. For this reason, there must be an overpressure valve installed.
After making my quick o-ring repair I replaced the regulator on the tank and slowly turned the air back on with my left hand as I held the second stage by the hose in my right. *BANG* The hose ruptured with the force and sound of a firecracker right where I was holding it. My ears were ringing and my hand stung like crazy. Those of you who have ever had a firecracker go off in your hand know what it felt like - multiplied by about two. Three days later my hand is still sore.
What happened, apparently, was that the first stage was leaking so that the intermediate presssure went up to a pressure that was more than the hose could handle. (Low pressure hoses are rated to something in the range of 350 to 450 psi and will burst at 3 or 4 times their rated pressure.) The overpressure relief valve (which was installed) failed to operate.
I have seen (and heard) low pressure hoses burst on at least three occasions in the past. This was the first time I sustained an injury. I am just glad it was nothing serious. It is a reminder that compressed air can be dangerous.
