On Friday, my local gas/electric utility decided it was time to replace the gas meter and 40-year old steel gas pipe between the street and my house. I had a chance to chat with the guys a bit while they were working and I learned about a small little innovation that not only makes their work easier, it provides better uptime for natural gas customers, and most likely saves lives.
It all started when I looked out the window and saw the large hole they’d jackhammered into my driveway. At first I was a little worried about the jackhammer hitting the gas line but I they do 2-3 of these a day so I figure they must know what they are doing. Then I saw them welding–in the hole! And it turns out that they were literally welding ON the gas line. So I naturally asked, “so you had to turn off the gas to whole street to do this?” to which they replied “nope, the gas is still flowing in there.” Now some of you may know how this is achieved without large fireballs in peoples’ front yards but I was a little stunned at first. So they explained the whole deal. It turns out that the little innovation that allows them to weld a new pipe onto an in-service gas line is called a hot tap. Actually a hot tap is made with several components– a flange, a valve, a few other accessories, and a hot tapping machine.
I couldn’t find a picture that showed the same hot tapping valve they used on my gas line but the following picture from http://www.flowserve.com gives you an idea of what it does…
Flowserve "NAVAL" Hot Tapping Valve
One line shows a completed hot tap in service, and the other shows the hot-tapping tool inserted with a hand drill to drive the cutter.
Basically, they weld the valve onto an existing pipe, along with a flange to better match the contours and add some “meat” to the fitting. In the case of this picture, the hot tapping machine is inserted through the valve, sealing the opening in the valve itself, and the drill turns a magnetic cutter to cut into the working gas line. The magnetism helps to retrieve the metal shavings from the cut.
Once the hole is complete, the hot tapping machine is backed out a bit, the valve is closed, and the machine is completely removed. After that, you can attach a new pipe to the valve and open it up whenever you are ready.
The Pilchuck crew that was working on my line had an even fancier valve with a knob on top and a built-in cutter. So after they welded it on, they just screwed it down to cut the hole and unscrewed once they attached the branch line. Pretty slick since they didn’t need a separate tool to do the cut.
I was thinking about this whole process the next day and it occurred to me just how dangerous it would be to tap live gas lines. And how the idea of a hot tap is really pretty simple, but it probably saves lives. It also keeps service up for every other customer who shares the main pipeline while maintenance is performed, and I’m pretty sure it speeds up the work significantly over shutting down a gas line to cut it and inserting a T-fitting.
While I was looking for a suitable picture I found out that they do this same thing with large continental pipelines as well. There are companies that will hot yap pipes over 100″ in diameter.
This is totally unrelated to storage but I thought it was interesting.