Welded Segment Placed On Skid Jumping Like Fox

I couldn't follow all the details and and this is way out of my field.

If I wanted to make this happen I would...

1. Lay the pipe on supports that corresponds close to a length of the natural frequency of the pipe for a distance.

2. Shortening (or lengthening) the gap for a stretch. (an induced vibration would start a harmonic vibration at one end and the motion would be transmitted like a wave down the changing lengths)

3. Look up Von Karmon vortex, figure out the wind speed, and gap required around the pipe for your pipe size and calculate the wind speed to create the vortices that match frequencies of your pipe.

4. Lay the pipe an open area and wait for the wind to match the speed in the stretch of pipe set up with supports at the nodes.

5. When the wind speed was right by watching the galloping pipe, lift the free end and cause the kinetic energy of the vibrating pipe to do jumping stuff.

And I still can't find my slide rule to figure it all out but someone with Finite Element Analysis can do this is seconds.

I hope I am close, any other ideas out there?

I'm thinking along much the same line. As a welder/boilermaker ive seen structures move as you describe many times. There is a correction however. As the pipe was hopping about but reseating accurately each time I expect the wavelength was equal too or an even multiple of the pipes natural frequency. The mounting points were at the nodes and the system had no wave travel - similar to a helicopter rotor. When you lifted one end you changed the neutral point to the end of the pipe, shifting the node. in order to return to neutral the wave runs down ther pipe. thepipe is then forced to Whip because the wave runs down the pipe bending it till it lifts off the ground. When the wave gets to the far end it reverses and runs back up. You then have two opposing waves which will double the amount of jump. Any off centre in the lifting apparatus will cause the wave to rotate around the pipe, twisting it. this is why it didn't stay in position.

repkly to guest idea is smack on, he does have a major problem though in finding the best way to anchor the skids and support struts in the constantly moving sand. that is a real bear to do baybe instead of using the wooden skids he could lay a few sheets of plastic diamond patttern cloth on the sand put extra long and wide skids on them then use flxistrap tpo anchor the ppe to the whole pile at about a 8" cl.?

I once used a fixing system for soil and loose surfaces. It consisted of a pointed spade that you drove into the ground with a hydrualic rock hammer (jackhammer but driven by oil) it had a cable mounted at the rear of the spade and a folding flange behind the mount, like one of those 'through the wall' plasterboard anchors. When you loaded the cable the flanges popped out and dug in. You then just need to tie teh cable to the pipe lengths at the nodes to anchor them.

It sounds to me that you had too long of length of pipe up on the skids. If it was on sand and had hills or vallys it was laid on then the problem of not being well supported in certain places could have started the vibrations. When I worked as a welder on laying pipe lines we would try to x-ray as we welded but would stay back enough not to expose the welding crew. As soon as we got the shots accepted we would immediately set the pipe off the skids on the ground because we would be needing the skids way before the crawler came along to bury the pipe. I never seen what you are talking about but I do not believe it is a common occurrence. I work with steam piping these days and it moves constantly from thermal expansion. I have seen steam pipe get in a bind where it should be free to move and cause it to wreck structural members, electrical conduit/wiring other piping and move sideways out of the roller supports.

pipewelder

Yes! It is true that the section was too long for 24" dia pipe. The ground surface was hard clay (gatch) and evenly smooth from one end to other. The velocity of wind was not changing at any moment. We have learned the lession. Now we have started breaking segments in smaller sections. It is true that it is not a common occurance, but precaution has to be taken to for an accident to come once in thousands. Had I not thought of possible accident, the segment might have fall over the workers engaged to remove the skid underneath. My idea to put on CR-4 to let know the pipeliners the reason and preventions for accident to come once in life time.

I agree and commend you for your foresight in preventing the accident that could have happened. You are one hundred percent correct in saying that the precaution has to be taken no matter the chances of an accident occurring. The main and first thing is to prevent it from doing it again and preventing the accident and getting someone hurt.

pipewelder