Straightness tolerance

[Mohamed Elshamy]

Dear all ;
According to ASME B31.3 what is the tolerance of piping straightness for a welded c.s. pipeline 1 km long
Thanks in advance

 

[LittleInch]

31.3 is a piping code not a pipeline one. There are specs for individual pipes but I don't recall one for the pipeline per se. Usually written in the construction specification. Maybe 1m horizontal from the straight line?

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[BigInch]

The beginning and the end.
Two points make a straight line.

Reaction to change doesn't stop it

 

[LittleInch]

Like beauty, "straightness" is in the eye of the beholder.

Some locations and pipes will accommodate significant horizontal shifts and zig zags, others will be laser line straight.

Not everything is written in codes....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Mohamed Elshamy]

Thank you so much, but how can you accept or reject?

 

[LittleInch]

What is written in the construction specification??

If nothing then it becomes a judgement call. As said, for a line of that length, I would place a maximum of 1m away from a notional dead straight line or a maximum of 1 degree at any one point in terms of deflection.

What have you got?

do you have any pictures you can share?

you give us very little to go on here.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

I have not seen any specification on alignment tolerance in the lateral dimension, as generally anywhere within the trench, as long as it is with clearance sufficient for construction between pipe and trench sidewall and as long as the trench is within the right of way, is acceptable. However in the vertical dimension tolerance can be critical for gravity flow lines. Tolerance, if not defined specifically, can be inferred by the dimensions shown on the drawing. If an invert elevation is given as 100.05 ft, then the actual measured elevation would be made to one more decimal place and the value would have to fall within 100.045 ft and 100.055 ft, any of which would round off to 100.05 ft.

Reaction to change doesn't stop it

 

[LittleInch]

The best one I liked was when someone tried to convince me that he could use 3 degree mitre bends instead of cold bends because 3 degrees wasn't officially considered a mitre bend.... So if someone wasn't good at cutting pipe ends it could look rather jagged. ...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Mohamed Elshamy]

Thank you so much for responding but to be more specific the line is rested on supports and these supports must be on the same level but actually some of intermediate supports where fallen due to the fall of soil beneath it resulting in deferent levels in the horizontal direction causing like a small zig-zag shape in the horizontal direction as mentioned before because of elasticity so is there any tolerance in that knowing that this line pressure is 15 bar and containing desel fuel
With my respect to all of you

 

[BigInch]

If it's not touching another pipe, or leaking, I wouldn't get too concerned about "snaking" in the lateral direction. Snaking actually lowers the stress.

Loss of support is another problem. Check the stresses in the line, using the deflected shape. Do the lines need to be continuously drained.

Reaction to change doesn't stop it