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Cold Cut of Existing Buried Gas Line
4

Cold Cut of Existing Buried Gas Line

Cold Cut of Existing Buried Gas Line

(OP)
We are going to install a 56"x42" barred tee on an existing gas line. I am wondering, from experience point of view, how much ovality can we expect, on the buried 56" line, when it is unearthed. The thickness of CS line is estimated to be about 0.78" and approximately one meter soil is covering the pipeline.
If it is considerably high, what's your suggestion for fabrication/erection of barred tee.
Thanks in advance.

RE: Cold Cut of Existing Buried Gas Line

2
up to 5% of OD, maybe 10

weld pups on the tee. take along some extra pipe joints.
if ovality is too much, cut pipe in a different place.

Learn from the mistakes of others. You don't have time to make them all yourself.

RE: Cold Cut of Existing Buried Gas Line

I love that video.

Ovality is not the most huge problem, I'm usually more concerned with getting the two ends to match the fitting (watch the video, the pipe is always in some amount of a bind and it will move).

BigInch's advice addresses this in the only way I've ever found that works. Pipe above 20" I like to put a full joint on both sides of the tee. Requires a big hole, but it lets you address ovality and pipe jumping issues.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

RE: Cold Cut of Existing Buried Gas Line

Bi = 5 to 10% ovality?? I've seen a lot of misalignment in my time once you cut it and fully agree you need to allow for as long a section to replace as you can, but that sounds way too much to me. You can never know until you dig it up and cut it and it may easily get to the point where the wall thickness is not lined up, but 10% is 5 inches (!).

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Cold Cut of Existing Buried Gas Line

Since it apparently requires cutting out and replacement, I'd tend to expect that there could be far more than the usual, even supposing that a gauging pig did not pass, so that could be 5% right there.

Learn from the mistakes of others. You don't have time to make them all yourself.

RE: Cold Cut of Existing Buried Gas Line

(OP)
Thanks everybody for responses.
What about using Tirfors to achieve alignment, instead of extra pub?

RE: Cold Cut of Existing Buried Gas Line

BI- It doesn't need cutting out and replacing - he's putting a new tee on it.

You can use all sorts of devices to achieve alignment - digger buckets, cranes, tirfors etc. The key is to have as long a section of pipe (15m at least) able to flex as you can or else you're welding in a high level of bending stress.... The extra pup is for when you check the location of your tee and discover laminations, excess ovality (which was your original question), reduced wall thickness etc etc but can't move your tee location very much or at all.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Cold Cut of Existing Buried Gas Line

No practical difference. Whether it's 1% or 10%, he should still bring pups and a joint of pipe to the party, or risk delaying everyone when he goes calling back home for a special delivery. Alternatively he could go out, dig it up and measure it first, but pups are still a good idea, if the welders screw up the tee weld-in. On a pup, you can cut some off and do it again.

Either way.

Learn from the mistakes of others. You don't have time to make them all yourself.

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