joining seamless pipes

[trish129]

The very thought of having a joint in seamless pipes seems absurd but what if the required length of seamless pipe is not available and the only option is to join two pipe pieces such that the joint sustains a particular operating pressure.?is welding recommended in this case?

 

[SnTMan]

trish129, pipe is butt-welded all the time using proper procedures.

BTW seamless pipe has no longitudinal seam but is joined with a circumferential seam. Doubtless you recall longitudinal stress is one-half of circumferential (hoop) stress.

Regards,

Mike

 

[trish129]

thank you for that insight Sntman..are there any examples of this? any published evidence? does any standard purport such a method to obtain this joint?

 

[SnTMan]

ASME & numerous international piping Codes, ASME & numerous international boiler and pressure vessel Codes, doubtless there are others. What (material, diameter, wall thickness, etc) are you joining?

Rgards,

Mike

 

[marty007]

Here's a question, how do you join a seamless pipe to anything else?

It gets welded with a circ seam...

 

[XL83NL]

Have you ever wondered how e.g. forgings are made? Or do you perhaps believe there are trees in the amazones onto which groups of valves or flanges grow, produced by mother earth ;-)? And that these same forests produce complete plants without human intervention? Oh no, its the other way around, people make plants that destry the forests ...

 

[TomBarsh]

"...are there any examples of this? any published evidence? does any standard purport such a method to obtain this joint?"

See the ASME Boiler and Pressure Vessel Code, and the ASME Piping Code B31.

 

[trish129]

thank you all for your replies..

let me lay down the specifics of my problem...

Operating conditions: water for jet washing at normal temperature and a operation duration of 14 hours subjected to a working pressure of 260 bar
Seamless pipe material: ASTM A 106 Grade B
Pipe schedule: 160
¾” (the nominal pipe size)

Important consideration:1) this pipe travels horizontally between circular supports/guides.so the weld beads should be flush with the outer surface of the pipe so as to avoid interference/jamming with the circular guides.

2)alignment..the tolerances and alignment issues are of paramount importance because any mis-alignment would inhibit smooth travel through the circular supports

circumferential butt welding of seamless pipes must be somewhat different from butt welding of welded pipes .what weld procedure should be adopted? What are the considerations for butt weld specific for seamless pipes like proper selection of filler metal


what would be the testing plan for the welded joint to ensure integrity at such operating pressures?what should be the possible configuration of test samples?

 

[SnTMan]

trish129, first, you need to determine whether such work is legally required to be designed / fabricated to a Code of construction, such as a piping code. Following a piping code whether required or not will insure sound welds between the joints.

Seccond, if your piping is moving around as well as under high pressure I suspect extensive analysis will be required to insure adequate life.

As for the interference with guides, is the length of travel so long that the welded joints need travel thru a guide, i.e. travel is longer than a stick of pipe? Maybe you need hose rather than pipe.

I suggest you hire an experienced piping engineer.

Regards,

Mike

 

[metengr]

This original thread is a duplicate of whats in forum330

 

[SnTMan]

its all over the place

 

[GenB]

This requiremNt. Just give thr job to an ASSME PP holder.

 

[trish129]

can i have videos demonstrating welding of seamless pipes..?


SnTMan:
you need to determine whether such work is legally required to be designed / fabricated to a Code of construction, such as a piping code. Following a piping code whether required or not will insure sound welds between the joints.---->can you guide me to those codes?

Seccond, if your piping is moving around as well as under high pressure I suspect extensive analysis will be required to insure adequate life.
---->what sort of analysis? how do i go about it ?


As for the interference with guides, is the length of travel so long that the welded joints need travel thru a guide, i.e. travel is longer than a stick of pipe? Maybe you need hose rather than pipe.--> why do i need a hose? it is a pipe with the specifications i mentioned previously...yes..the length of travel is such that the joint travels thru the guide..


there must be some laid down procedures/standards for circumferential butt welding of seamless pipes..where can i find them?..

and after that how do i test them..the operating time is about 14 hours...how do i plan the testing of this joint?

 

[marty007]

Assuming ASME codes... (you still haven't mentioned your code of construction)

The typical codes are:
ASME B31.3 (Process Piping)
ASME B31.1 (Power Piping)
ASMB B31.5 (Refrigerant Piping)
...
There are a few more.

Piping flexibility is normally addressed via a stress analysis, as required by the codes above. There are many commercial software packages for this (I am most familiar with one named CAESAR).

The welding procedure is typically no different between welded pipe and seamless pipe. The procedure is based on P-number/Group-number.

Regarding your discussion of interference with guides above, what kind of process are you working with that could result in a longitudinal movement in the pipe of over 20ft!

Cheers,