×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pipeline Transition Piece
2

Pipeline Transition Piece

Pipeline Transition Piece

(OP)
I'm doing a pipeline project. Only my second one. Been a piping designer in shipbuilding and various plants for over 30 years. I have a situation where I have 10" STD wall (.365") pipe going to an 8" SCH80 wall (.500") pipe. I am told I need a transition piece. I just figured this would be a reducer, but I am not sure. Usually when going from a large pipe to a smaller pipe the wall gets thinner. In this case the wall thickness is greater. What exactly is a transition piece in the pipeline world, and how to I transition in my situation? This is a 1200 psi system. The wall thicknesses I state above are required at this location in the system by the client. So I have no options. I have to make the transition.

Thanks,
CAD

RE: Pipeline Transition Piece

You should be able to get a reducer that does this if you specify it on the data sheet as it is not unusaul for wall thicknesses to change as you change sizes, normally thicker, but in your case thinner. This could be however because of the grade of steel or material, e.g. 8" Grade B to say 10" X60. You need to supply this information.

A transition piece in pipeline terminology is normally the same size, but "transitions" from a higher grade material to a lower grade material, made out of the higher grade material. E.g. a 10" X60 pipe of 10mm wall thickness (wt) transitioning to a 10" Grade B pipe of 18mm wt would be a short pup piece (say 500mm long), made of X60 18mm wt, with one end machined down at an internal angle of at least 1:4 or better to a wt of 10mm.

In the pipeline world, material strength of pipe is the thing to look for as this is directly inversely proportional to the wall thickness allowed.

My motto: Learn something new every day

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

RE: Pipeline Transition Piece

An additional consideration is that someone will always regret you burying a pipe-size transition. I've never seen a buried reducer that did not create some (often many) problems for operations. Most common problem is running pigs, but water collection and associated corrosion is right up there. If I have to change pipe sizes, I do it on the surface with a launcher/receiver pair. Usually when I run the economics of a single pipe size vs. launcher/receiver pair the apparent savings vanish and I run the big size from the beginning to the end.

I've inherited problems on several system that the Engineer got "clever" and ran 5 miles of one size then transitioned to the next bigger size because of the velocity increase due to the friction drop. I've frequently said really ugly things about the clever Engineers.

If you must do it, then like LittleInch said it is often possible to transition the pipe wall thickness in the reducer.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Pipeline Transition Piece

(OP)
This is located at a meter station, outside of the pigging limits. I am going to do it with a reducer. The client has agreed to this method. No custom transition piece required. Thank both of you for your invaluable input.

CAD

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources