DIFFERENCE BETWEEN SEAMLESS AND WELDED PIPES 2

[jellyko]

Can anyone help me I am in the following situation.

I am now considering the piping material as ASTM A53 gr.B and STAINLESS STEEL 304L.
It can be made both seamless and welded type.
I prefer welded type because it costs less money and some of them are as large as 32 inches.
But I am not sure whether it can be applied in a hydro power plant cooling water supply pipes.
If it can be applied, tell me about their durability or difference between seamless and welded.

Cooling water condition are as follows.
- sort : river water
- fluid temperature : 20 ~ max.40 centigrade.
- water supply velocity : 1 ~ 2.5 m/sec.
- pipe diameter : 1 ~ 32 in.
- pressure of water in the water supply circuit : max. 16bar

please feel free to contat with me if you need more data.

Koh.

 

[ElderX]

In order to know whether seamless or welded pipe can be used in your application you should consult the governing code for the construction. The difference between welded and seamless pipe as far as performance is basically none from a practical standpoint. There are two primary means of manufacturing welded pipe there is Electric Resistance Welding (ERW)small and large diameter and Double Submerged Arc Welded(DSAW)mostly large diameter. There are some issues involved with the quality of welding that can come into play with both welding processes and should be considered when making the purchase. Theses issues can be addressed with the mill if you are purchasing a large order. (Mechanical testing and NDT, third party monitoring of manf.) There are also quality issues with seamless pipe that can be addressed the same way. The key to knowing if the pipe you are purchasing is of good quality is to test it. There are third parties that can perform testing of welded and seamless pipe that you may purchase from a supplier's "on the ground" stock. Let me know if I can give more info.

 

[ksuengrng]

I agree with ElderX in that you need to check the governing code and then also what the client is expecting. They may have had experience with welded pipe that failed and may only accept seamless.

In the design of the piping, seamless is considered stronger. A way to look at it is while they both may be welded pipe; seamless pipe has gone thruough a 100% x-ray and no impurities have been found, or those found fall within the aceptable limits. In the design of the pipe, the joint efficiency factor for seamless pipe is 1.0, while for welded pipe it is 0.70, and in some case you may be able to use 0.85.

I would also request MTR's (material test reports) on the pipe you buy to ensure it falls within the parameters set forth for each type, whether you are using SA53-B, SA106-B or SA312-304L. While the "seamless" is more expensive, on critical lines and lines exposed to the human factor, we would use "seamless".

Hope this helps

 

[gthomas]

I just happened to come across this post and have similiar questions about ERW vs. seamless SST piping that you might be able to help me with. We currently use seamless piping for duct burners and would like to switch to ERW due to cost savings. There is some question to ERW piping having problems due to the heat from the welding reducing the ability of the chrome in the steel to resist going into the carbide phase when heated. Basically they are saying that welded pipe does not perform as well as seamless at very high temperatures. I can seem to get a definate temp. limit or what "performance" means. Any help is appreciated

 

[MJCronin]

jellyko,

Is your question about selection of materials or cost or what ? If you have a raw water system, without chlorides, either the carbon steel (A53 gr.B) or stainless would be acceptable. The cost for the stainless would be about double (or more) of that for the carbon steel.

If sufficient chlorides are present,the stainless may pitt and eventually fail...

At 16 bar (~240 psig) a schedule 10 pipe should be OK up to 32 inch diameter for either material.

I may be wrong, but with these modest design conditions for a raw water system, your real question should be about materials, possible coatings and installed cost?

Good Luck !!!..................................MJC

 

[jellyko]

Thanks for your all reply.

Above matters we will use welded pipes(ERW) on you guys help.
Because governing code is ANSI B31.1 POWER PIPING and there are no rules confining seamless or welded as I know.
There joint efficiency factor is 0.85 for (ERW).

But I can't handle the corrosion factor.
Therefore if I consider 20 years of warrenty, how much do I consider for their additional thickness?
See my first question for application details.
PH of river water is 7.5 average.
Should I contact corrosion engineer for this matter?
Let me know the related document or specification if any.
Painting protection may not be allowed in this application(inner part).

Our application are both stainless and carbon steel depends on their function(separated lines).
I am doing this job to minimize the installed cost for sure.

Regards, jellyko

 

[AlanD]

Gthomas, unfortunately it's not quite that simple. The welding process does change crystal structure, the composition of the metal and hence the mechanical and physical properties of the metal. These changes mean that at various locations across the weld and heat effected zone, you are dealing with effectively different alloys and different grain sizes etc.

Your specific application also needs to be investigated, as a result, as temperature is not the only restraint, you also need to know which gasses are involved, etc. Possibly the best idea, is to start seeing how the welded tube performs for situation, by replacing a section of the existing tube.

I hope this helps.

 

[tedg]

I'd like to add two brief cautions to the excellent information you have already received:

1. Corrosion testing versus open natural source water can't be done out of textbooks. As a couple of colleagues have already stated, "suck it and see" testing (ie actual trials) is necessary.

2. The corrosion resistance of some stainless steels depends on the ability of their chromium content to form a self-healing skin on the surface of the alloy. When the steel is heated, the chromium reacts with carbon to form a carbide, thereby depleting the amount of chromium that is available to resist corrosion. That reaction is one of the reasons why certain stainless alloys lose much of their corrosion resistance when they are improperly heat treated or welded. This is a rough explanation. A more accurate one would be available in a textbook on stainless teels.

 

[RichardH]

When considering weather to use seamless or rolled and welded plate, you should check the tolerances in the material specification. I think the material specs you referenced have a plus or minus 12 1/2% tolerance for seamless pipe whereas the rolled and welded plate will have a much lower fabrication tolerance. These tolerances must be considered in your design calculations.

 

[bobn]

Welded stainless pipe can be restored to full passivity by proper heat treating. This usually involves heating austenitic SS to about 2000F and water quenching. Ferritic stainless is heated to about 1650F and quenched. HOWEVER, if the SS is an "L" grade (low carbon, ie, under about .04%) there is usually no need to heat treat the pipe since there is very little carbon available to form chromium carbides.

 

[rustbuster1]

Carbon steel will corrode internally and externally and will require internal coating and external corrosion protection. The latter may be cathodic protection (CP) or wrapping (with or without CP.

Common, austentic stainless steels at the conditions you mention - especially if the lines run full and are not left to "stew" for many weeks at a time - will not require internal or external corrosion protection under most circumstances. This is especially true if the welds - circ and long. - get proper post weld cleaning to prevent localized corrosion (and reduce chances of MIC). At todays prices for 304L or 316L stainless steel welded pipe I'd be surprised if this option is not the winner.

 

[MarkMark220]

ElderX gave you some good info and I hope I can add a little to it. One other thing to consider is that welded pipe whether EFW (Electric Fusion Welded) or ERW (Electric Resistance Welded) will have specific joint factors (again considering applicable codes.) When considering allowable working pressures pipe that has the welded joint 100% x-rayed and approved will have a joint factor of 1.0 making it equivilant to seamless pipe. If the x-ray tests are not performed it will have a joint factor of .85 so allowable pressures would have to be reduced by that factor.

 

[mcguire]

The quality of both welding and non-desrtuctive testing has advanced so much that any consideration of welded pipe being inferior to seamless is quite obsolete. Besides, making seamless stainless steel pipe is an onerous, defect-plagued process while producing welded pipe is a very robust process. There are numerous quality producers.
Just be sure that you specify very low sulfur content, i.e.less than 0.003%. In the past many welded pipe producers used high sulfur ( >0.008% )to facilitate welding, but this results in greatly diminished pitting corrosion resistance.
Welded pipe is made from flat-rolled steel which gives it much better wall uniformity than seamless.
Laser-welded pipe is best, but erw is also fine.
Welding does not diminish corrosion resistance. In heavier sections, low carbon stainless is used to ensure that carbides do not precipitate during cooling from welding temperature.

 

[prvessel]

I am assuming you do not have a preferred site practice; in that case if you decide to go for welded pipe, be extra vigilant in verifying manufacturing quality. This can be done by 1) placing stringent conditions on the PO to avoid liability issues later and, 2) inspection and tests (hardness, x-ray, MPI, UT, MPI). This may seem over the top, but can save embarrassment later.

 

[tedg]

This thread gets a prize for going on forever, but the
messages are certainly useful and interesting.

Japanese engineers have many years of experience with
stainless pipe in water supply service, including high-
pressure and superheated service.

You might find references in their literature (much of
which is in English) about differences in performance
between welded and seamless pipe.

Neverthelesss, you would want to test actual supplier
samples before committing to specifications or bulk purchase.

 

[rkg]

I would like to make the following recommendation:
- For sizes larger than 14", go for welded pipes anyway. You may choose A672 (for CS)and A358(for SS)which are fusion welded pipe specifications. These can be used in all applications where seamless pipes are used for lower sizes.
-For sizes <14", consider both seamless and ERW. For conditions stated, welded pipe would do just fine.At times, seamless pipes can be procured with very little cost differential which must also be considered.

 

[robsalv]

LOL @ Tedg. The initial post was in 2000! This is an aged thread/

For what it's worth, our process chemical plant would not use ERW for hazardous pressure services regardless of codes.

ERW CS pipe in a water service is used though, knowing that preferential corrosion at the weld seam will probably see the ERW requiring replacement well before the seamless equivalent.

We've only ever used ERW SS pipe in air-conveyor services.

5 year thread... and going strong!

 

[eyec]

seeing the age of this thread and hoping that jellyko is still reading it, he will let us know the results of his selection.

i would like to offer that SS is also suseptable to micro-biological attack from river water. we had used SS for a similar service and after a couple of years all of the welded joints started leaking from pinholes caused from pitting due to the attack.

hope this is not the case for jellyko.