ERW or Seamless pipe for steam service? 1

[mfowler]

I have been tasked with developing a piping specification for steam lines in our plant. We have two on site boilers generating steam at ~90psig. Our plant uses this steam for various heating operations including pipeline tracing and reactor heating. Most of our lines are 2" or less with our main trunk line being 6".

My questions is really a two-part one? What is an appropriate schedule of pipe to use and should it be seamless or is ERW acceptable? I have seen other specifications calling for both Sch40 and Sch80 depending on size and both ERW and seamless. We plan to use either ASTM A53 or A106 pipe.

In my research so far, the only argument against ERW pipe I can find is the creep phenomena at the heat affected zone. This seems to only apply to high pressure steam lines where the temperature is in excess of 800F. Being that our steam is only ~330F (90psig), I don't see that this is an issue.

Please help.

MFowler

 

[JohnBreen]

Hello,

There is no problem with ERW pipe for your application.

The steam and condensate piping is often made schedule 80 just to have additional corrosion life (especially the condensate piping where the water chemistry is not well controlled).

I suggest that you read the ASME B31 Code for Pressure Piping, B31.1, Power Piping. While the Code is not a design textbook it will provide guidance in your spec writing.

Regards, John.

 

[LSThill]

mfowler (Chemical)

PIP.ORG has Piping Classification Specification for STEAM SERVICES.

http://WWW.PIP.ORG

 

[TBP]

Check the safety valve settings on your boilers. You run at 90 PSIG, but the safety valves likely lift at 125 or 150. A53B ERW will likely be fine for your applications. Sch 80 should be used for condensate lines. Many plants buy all of their pipe as sch 80, for 2" and under, which is where most screwed fittings are used. By the time sch 40 pipe in this size range has a thread cut into it, you don't need to take much of a corrosion allowance before it's no longer rated for any kind of pressure. Watch what gets purchased for nipples. Pipe nipples either come in A106B, or junk like A53F. I'm not aware that I've ever seen an A53B ERW nipple. If I have seen them, they weren't identified very clearly. I like the seamless nipples, because they've got the grade and sch # stamped right into them - "A106B Sch 80". Nobody has to wonder what they're looking at. As a general observation, we find that while seamless pipe costs more, it's usually FAR nicer to work with. It will routinely cut, weld and thread better than the lower grades. There's a LOT of junk pipe being sold out there.